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Passive cooling methods for mid to high-rise buildings in the hot-humid climate of Douala, Cameroon, West Africa
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Passive cooling methods for mid to high-rise buildings in the hot-humid climate of Douala, Cameroon, West Africa
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PASSIVE COOLING METHODS FOR MID TO HIGH-RISE BUILDINGS IN THE HOT-HUMID CLIMATE OF DOUALA, CAMEROON, WEST AFRICA by Lucy-Bertha Mai Nkuo A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF BUILDING SCIENCE August 19 88 UMI Number: EP41418 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI EP41418 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 -1 3 4 6 UNIVERSITY O F S O U T H E R N CALIFORNIA T H E G R A D U A T E S C H O O L U N IV E R S IT Y P A R K L O S A N G E L E S . C A L IF O R N IA 9 0 0 0 7 This thesis, written by under the direction of hfz&^.Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillm ent of the requirements for the degree of ^ — - tfe " ^ & N738 Dean Date....... COMMITTEE UNIVERSITY O F S O U T H E R N CALIFORNIA T H E G R A D U A T E S C H O O L U N IV E R S IT Y PA R K L O S A N G E L E S . C A L IF O R N IA 9 0 0 0 7 This thesis, written by ........ under the direction of h£&^.Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillm ent of the requirements for the degree of Dean ACK NOW LEDG EM EN TS I would like to thank my thesis advisor, Pierre Koenig, for his guidance and use of the wind-tunnel. I am very grateful to Marc Schiler for his support, encouragement, and guidance throughout my graduate study, particularly in this thesis. Many thanks to Michele Galloway of U.S.C Student Information Systems for the many hours she spent helping me to format and make it through this study. Thanks to Fon Akenji for obtaining, from Cameroon, the climatic data I used for my wind-tunnel tests. Special thanks to my parents, Thadeus and Catherine Nkuo, the entire Nkuo family, the Ngeh family, and Samoh Wallang for always cheering me on. TABLE OF CONTENTS 1. CAMEROON 1-1 Present Energy Conservation Needs 1 1-2 Presentation of the Country 2 1-3 Prevailing Winds in Cameroon 3 2 . CLIMATIC ANALYSIS 2-1 Climatic Data 4 2-2 Analysis of Climatic Data 12 2-2.1 Incoming Radiation 12 2-2.2 Diurnal Temperature Swing 14 2-3 Wind Rose 15 3 . THERMAL COMFORT THROUGH PASSIVE COOLING 3-1 Ventilation 18 3-2 Human Comfort 19 3-2.1 Human Comfort Chart 23 3-2.2 Comfort Chart Analysis 24 3-3 Air Distribution 25 3-4 Clothing 25 3-5 Humidity and Dehumidification 28 3-6 Air Movement 31 3-7 Emissivity of Materials 32 3-8 Staying Cool 33 3-9 Vertical Distribution of Wind 35 4 . HISTORICAL PRECEDENTS 4-1 Use of the Wind-Scoop in Hot-Arid Climates 38 4-2 Wind-Scoop Orientation 41 4-3 Principles of Cooling and Ventilation in Hot-Humid Climates 44 4-4 Roofs and Floors 57 i v 4-5 Vegetation 58 4-6 Principles to Promote Interior Air Flow 59 5 . WIND-TUNNEL TESTS 5-1 Hypothesis 69 5-2 Goals 69 5-3 Ventilation Requirements in Hot-Humid Climates 69 5-4 Wind-Scoop Test Methodology 76 5-4.1 How does Shape Of Wind-Scoop Affect Flow Rates? 77 5-4.2 How does Size Of Wind-Scoop affect flow rates? 91 5-4.3 How does Scale Of Wind-Scoop affect flow rates? 105 5-4.4 Interior Air Distribution. 127 6 . Results and Observations 153 7 . R eferences 154 8 . Bibliography 159 V LIST OF FIGURES 1 .1 Cameroon in the African Continent 2 1 .2 Prevailing Winds in Cameroon, 3 2 .1 Climatic Data Analysis #1 4 2 .2 Climatic Data Analysis #2 5 2 .3 Monthly Average Insolation 6 2 .4 Heat Exchange at Noon for Summer Days 7 2 .5 Wind Rose: Douala Annual - Direction 16 3 .1 Heat Balance of the Human Body Interacting With its Environment 20 3 .2 Human Comfort Chart 23 3 .3 Examples of a Range of Clo Values 26 3 .4 Clothing Levels Necessary for Comfort at Different Operative Temperatures 27 3 .5 Solar Cooling System 30 3 .6 Global Circulation 33 3 .7 Vertical Distribution of Wind 35 4 .1 Temperature Variation Curve 38 4 .2 Examples of Wind-Scoops 39 4 .3 Wind-Scoop in Hyderabad, Pakistan 41 4 .4 Wind-Catchers in Hot-Arid Climates, p. 43 4.5 - 4.12 Examples of Vernacular Adaptations to Hot-Humid Climates 45 - 47 v i 4 .1 3 Use of Horizontal Louvers in Muscat 49 4 .1 4 Operation of Louvers 50 4 .1 5 Operation of Louvers 51 4 .1 6 Elevating Buildings Off-Ground for Free Flow of Breezes 52 4.17 - 4.20 Examples of Building Principles for Hot-Humid Climates 54 - 56 4.21 Single-Room Ventilation in Hot-Humid Climates 56 4.22 Pressure Zones Around A Building 59 4.23 Average Air Velocity as a Function of the Free Wind Speed for Various Wind Directions 60 4.24 The Effect of the Size of the Inlet and Outlet on the Efficiency of Ventilation for Cross-Ventilated Spaces, p. 61 4.25 Shows how Average Indoor Velocity Increases by Increasing the Width of the Openings 62 4.26 Relationship of Average Indoor Velocity With Window Area 64 4.27 Effect of Inlet and Outlet in Cross-Ventilated Spaces;Openings on Adjacent Walls 65 4.28 Vertical Positioning of Apertures 66 5 .1 Analysis of the Subjective Responses Concerning Uncomfortable vs. Modified Temperature 71 5.2. Wind Box 72 5.3. Experimental Plan 7 2 5.4. Voting Scale 73 5 .5 How Does Shape of Wind-Scoop Affect Flow Rates? v i i Experiment #1: Preliminary Test Shaft 78 5 .6 Experiment #2: How Does Shape of Wind-Scoop Affect Flow Rates? Scoop #1 82 5 .7 Experiment #2: How Does Shape of Wind-Scoop Affect Flow Rates? Scoop #2 83 5 .8 Experiment #2: How Does Shape of Wind-Scoop Affect Flow Rates? Scoop #3 85 5 .9 Experiment #2: How Does Shape of Wind-Scoop Affect Flow Rates? Scoop #4 87 5.10 Experiment #2: How Does Shape of Wind-Scoop Affect Flow Rates? Scoop #5 89 5.11 Wind-Scoop Inlet Depths Tested 92 5.12 Wind-Scoop Inlet Widths Tested 93 5.13 Graphic Results of "How Does Size of Wind-Scoop Affect Flow Rates?" 97 - 102 5.14 How Does Size of Wind-Scoop Affect Flow Rates? - Model 103 5.15 Pictures of Models Tested at Different Scales 106 - 107 5.16 - 5.17 How Does Scale of Wind-Scoop Affect Flow Rates? 109-110 5.18 How Does Scale of Wind-Scoop Affect Flow Rates? 114 5.19 How Does Scale of Wind-Scoop Affect Flow Rates? 119 5.20 - 5.21 Graphic Results of "How Does Scale of Wind-Scoop Affect Flow Rates? 124 - 125 5.23 Distribution Studies: Wind-Scoop #1 129 5.24 Distribution Studies: Wind-Scoop #1 130 5.25 - 5.44 Air Distribution Studies: Wind-Scoop #2 131-150 v i i i LIST OF TABLES 2.1 Temperature: Monthly Average 6 2 .2 Temperature: Maximum Monthly 7 2 .3 Winds: Monthly Maximum Average 8 2 .4 Insolation: Monthly Average 9 2 .5 Relative Humidity: Monthly Average- % 10 2 .6 Relative Humidity: Maximum Monthly Average- % 11 2 .7 Wind Rose Values 15 3 .1 Factors influencing the Heat Balance Equation 19 3 .2 Human Responses to a Range of Air Movements 32 3 .3 Reflection Coefficient Values of Materials 33 3 .4 Beaufort Scale of Classification of Winds 34 3 .5 Comparative Range of Wind Speed Measured Vertically 36 4 .1 Solar Control Devices 48 4 .2 Heat Storage Capacity of Different Constructions 53 4 .3 Range of Temperature Variations Over Different Surfaces 58 4 .4 Average Velocity at Various Levels for Different Values of Window Height 63 5 .1 Experimental Conditions 73 5 .2 Preferred Air Velocities by the Subjects 75 5 .3 Preferred Air Velocity 7 5 5.4a - 5.4b How Does Size of Wind-Scoop Affect 5 .5 5.6 - 5.9 - 5.13 5 .1 7 i x Flow Rates? - Results 94 - 95 How Does Size of Wind-Scoop Affect Flow Rates? - Results 104 5.8 How Does Scale of Wind-Scoop Affect Flow Rates? - Results 111-113 5.12 How Does Scale of Wind-Scoop Affect Flow Rates? - Results 115 - 118 - 5.16 How Does Scale of Wind-Scoop Affect Flow Rates? - Results 120 - 123 Interior Distribution Studies 151 X ABSTRACT The purpose of climatic design is to improve human comfort or minimize the energy cost of maintaining thermal comfort within building interiors. To accomplish this, the building envelope should respond to and work with the natural forces of sun, wind, and temperature. The purpose of this thesis is to investigate how people can stay cool through good building design in mid to high-rise buildings which respond effectively to the hot- humid climate of Douala, Cameroon, West Africa. The study examines how natural ventilation can be used to effectively cool occupants in interior spaces. The climatic data for this area is enclosed and shows that ventilating the interior environment is essential year-round for this climate. 1 1-1 PRESENT ENERGY CONSERVATION NEEDS In July of 1987, a very significant economic change took place in Cameroon, when it was announced that the national budget is being cut from 800 million francs to 600 million francs. This drop in national spending has affected every area of life in Cameroon, including the building industry. One of the major prob lems faced by architects in tropical areas is^overheating in interior spaces. Now with a national energy and economic crises, designers and builders, more than ever, need to site, orient and construct buildings to take full advantage of natural ventilation to cool spaces. 2 1-2 PRESENTATION OF THE COUNTRY The Republic of Cameroon is situated to the NE of the Gulf of Guinea. It lies between longitudes 8° and 16° East of the Greenwich Meridian and between latitudes 2° and 13° North of the Equator. Douala is located on Latitude 4° N and Longitude 9° 44' E. * 2 1 Cameroon in the African continent 201 M A U R I T A N IA C H AO IPE R OJIBOUTJ , GUINEA CENTRAL AFRlCi REPUBLIC R E N VA (Rw a n d a ICABlNOA TAN Z AN ;b u r u n o: iSO U T H -W E Sl \ AFRICA M A M I8IA ] ► 2 D :s w a 2i l a n 5~ Scale l /4 0 000 000 iLtBO TH O I S O U T H A F R I C A ? c r 4 < f Fig 1.1 Cameroon in the African Continent. [1] 3 1-3 PREVAILING WINDS IN CAMEROON The flow of air masses in Cameroon are controlled by the anticyclone of the Azores in the northern hemisphere and that of St. Helena in the southern hemisphere. These two air masses converge in a low pressure zone called the Intertropical Convergence Zone (I.T.C.Z). The anticyclone of the Azores causes the dry season Harmattan and the St. Helena anticyclone causes Monsoon. Figure 1.2 shows that Douala has a typical warm and wet climate throughout the year resulting from the S.W. Monsoon winds. a) SITUATION IN JANUARY b) SITUATION IN JULY Strong N-E Trade Winds (cold and dry) Strong S-W Monsoon Winds (warm and wet) ------------ ^ Weak S-W Monsoon Winds (warm and wet) ^ Weak N-E Trade Winds (cold and dry) / / •Ikousseri •Jkousseri Approximate position of rrcz in January Approximare position of ITCZ in July NGAOUNDERE NGAOUNDERE BAMENDA BAMEND DOUALA YAOUNDE DOUALA YAOUNDE / / Fig 1.2 Prevailing Winds in Cameroon. [1] 4 2-1 CLIMATIC DATA The climatic data included here was gathered over a period of nine years (1976 - 1985) from the meteorological station at Douala International Airport. The data shows monthly values for temperature, humidity, wind velocity and insolation. "CLIM ATIC DATA AN ALYSIS #19 9 1 00 -i---------------------------------------------------------------------- 5 0 - J J d I I * I E 6 0 ' i I ! ! ! I I ! ! ! ! 4 0 ; | j L |t j | | | | | | 20 - I ] i f j ! j ! | ! j | i l |j j i 1 1 | | |_ || || || i; || ij |j || || j | |j II 0 , 11 1 , B B , HI , Ki , m , Kl , Ml , Bi , m u , w t\ , B J JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV OBC MONTHS ■ HUMIDITY (MONTHLY AVERAGE - %) E3 TEMP (MONTHLY AVERAGE-°F) M WINDS (MONTHLY AVERAGE MPH) FIG. 2.1 Climatic Data Analysis #1 INSOLATION 5 "CLIM ATIC DATA A N ALYSIS #2 " 100 ---------------------------------------------------------------------- I I I I i 80 - 60 - 40 - 20 " o , . ■ , , . . ■ ” . . . . JAN FEB MAR APR MAY JUN JUL AUG SEP OCTNOVDBC MONTHS ■ HUMIDITY (MONTHLY MAXIMUM - %) E3 TEMP (MONTHLY MAXIMUM - °F) M WINDS (MONTHLY MAXIMUM MPH) Fig. 2.2 Climatic Data Analysis #2 "M O N T H LY A V E R A G E IN SO L A T IO N " 200 00 - JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTHS Fig. 2.3 Monthly Average Insolation TEMPERATURE: MontMy Average MlNISTERE DES TRANSPORTS DIRECTION RE L A M ETEOROLOGIE NATIOHALE SERVICE D E L A CLIMATOLOGIE DES D O N N EES ET DES PUBLICATIONS REFUBLIQUE W C A M E R O U N P aix - T ra v ail - P a tr ie Bureau des P u b lic a tio n s , Renscignements e t dos A rchives < = ;__ STATION D E : PA RA M ETK ES : PERIODS : A C u A L A ~ -/V Sif____ .1 AlfNEES J JAI'JV. EEV. : L IA R S AVRIL mai JUIN : JUIL, : A O U T : SEPT OCT. * 1 r" . O 0 ^ 3 > 4 6 S ’ NOV. - ? 4 \6 DEC. ! 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V ' 1 /t 1 - J O 1 AO 7 4 7'' 73 6: 7 C > : .7 ^ '/7 '7t~ 7 ► ■ /S ' JO 0 X J 0 1 •J6-7-1.J5 i-.lU-S ■■Atf? -ZS-i MS'? •■ Z e .'C , -.Z6'9 x iU 'i -.X6-i Table 2.1 TEMPERATURE: Maximum Monthly °C Jey/ l s j. - U lN IS T E R E D E S T R A N S P O R T S REPUBLIQUE DU CAMEROON Paix - Travail - Patrie DI/JOT O N D E L A H E T E O R O L O G I E M T I O N A L E S E R V IC E D E L A C L I M A T O L O G I E D E S D O N N E E S E T D E S P U B L IC A T IO N S Bureau des Publications, Rensoignements et des Archives S T A T I O N E E : P A R A M E T K E S i P E R IO D S : do U A LA T t u - I J ) C 4 u . C u s < . y O l A M H E E S ! J A N V . E E V • : M A R S A V R IL IIA I J U IN JU IL . A O U T : S E P T O ct. N O V . E E C . T O T A U X :M or. A A J- 6 j '64'A 3^* 4 . 3 4'2 3 f L ^ • 9 .?s-l o T 6*7 2 4 A 6 0-0 6 4 • 0 35*6-^ .^9*7- A . 3 4 -3 U ! 3 i - T 3 4'S 3A-0 ^£•.2 i l o -T ,- ^ M 3 0 7 64 ' 5 3 . 6 2'U 3 3 L t 3^-3 6 4 -Q 60-2 2~l-b 24 A . ■ ? fr ■ o 2 7 2 IQ'I 6-f‘b 36-/-^ 3C?-4 4 . 62- > 33- 7 6 4 -q 64 -S' 3 4 7 44-5 i i-o 2 1-0 : ■ ? 1 ' o 2 4 7 6 O'L 3.1-5 . 3 C>-^ ^ '( 0 . 33 0 33,' ■ 4 62-4 3 4- 3 3 0-9 I f 3 2 7 -i Z7-1 .£ ?■? Z4*b 6 0-d 3'/ b . 30-2 4 3^-6 33- I . 34-9 34-9 3 0 ^ 2b-9 3J-4 .<2?* j o - z IA-4 $7L. 363^> , 30-3 C ) " O . 64 b 33- 3 . 3*- 4 34*£ 30-3 ^■3 1 1 2 J.b'% ,1%'U .14-4 3 0-2 x34'k 36 0 0 . 3 0-c 5 . U - s 3 3 *u . .U -'l 3 * * 3 4 6 49*0 1 1 1 . t2l>-U . 1 1 0 M - ? 3 lQ% IQ'U b6 4'5 j 3 cm ..... ....Jif...* 64' ? ,3A- %, 3 * 0 34*9 3 3 0 30-6 W f .<2<f:2 .1 7 2 .JWI'9 ZJ'O >3*'? 3 W4- t 3^1-D i S .34 Z u . 3 * 4 3 4*3 3 0 ’9 W .it-9 .2,4-Z . w h 3 f i .31-6 ^ i £ i £ . 30*5* 4o- Vi ’ 'H v -f-A v. 3? " i ■ ' ’? a ■ r> t> s74- si_ T O T A U X l s32/f 6 *3<0-£ 346-4 307-9 X ^-3 .-2T-CS' t W ' l xlVW 3oj'Z 3^3-7 3632-^ .30^-7 N om b re d’ - Annees : 0 /f 0 : 4 0 4 0 4 0 .4 0 ^ 0 JO ! 4 0 40 4 o ^ 0 0 : A 0 M o ism n s ; 3H =32-5- : ll-o ■ 3+6 ! 3 D '% 'IVl' 2l-T'*T~3 > VI-? ' Ifl-S' 3 O? « l+k » 3iVZ' 3 0} -o Table 2 .2 WINDS - Monthly Maximum in mVsec Jet/ l s j. - 1'iXNISTERE DES TRANSPORTS DIRECTION D E L A M ETEOROLOGIE RATIONALE SERVICE D E IA CLIM ATOLOGIE DES D O N N EES ET DES PUBLICATIONS REFUBLIQUE DU CAMEROUN Paix - Travail - Patrie STATION D E : SJo - uqJ) CL Bureau des P u b lic a tio n s , Renseignemen'ts e t do3 Apciiives PA RA M ETH ES : PERI O D E : A < 1 > < o - ■{% g t f e ™ a^/s AlfNEES ! JA W V . ■ I* M I L . £ l i / t e n \A lS > W ■ - & } ± Z L l l .. A ag.Q_^ - g — _ ja £ A _ !^'L do_ - J A I L . A<6%5 t s IO T A U X t FEV. >12. ( X x / t 4C L s s t: KARS S c IN 4£L _ d £ AVRIL L ± l . ±J3. JUHJ : JUIL, -4- I1AI ■ r - ^ 1 — — » ,! » • ' ■ —:— 1 — ^ g . > 10 . (7- f it ' Z i e J * A b ., ± JL L AL IMA- P a -'L ^ . r - 'H iwd i _ s l ^ A O U T i SEPT : OCT. S -tfi [ *'!■< L d £ L ^ ± L , t l A . L “*" 3 e ^ . i L ^ j ^ 9 NOV. i dec. t s g m g ^ i U e s t i .1---------- * D t V w LUtiL Nombre d 1 - Annees : AO _ _ i . .'! 'N 4 0 W S »V wa,- u < v u O tlrv /L - IMO. 0 * n >v5w g, vevx. 40 i 40 ISOLATION: Monthly Average 9 Table 2.4 o p *H p h 0 -H w d p - q p - i 1 * a | a ? J h t- H s 3 i F P p M W rf H a. EH Ph O fH c o J z ; E H I * s - p P I I C O P I O u I § 3 a s £ o F 3 2 v d | r*- O Q c S © o H !f) Tl ^ [ C tf eft' <d j g d ^ " I ^ ^ ^rl o ! O m i lo cT)j ^ rj Cpj - ij « 0 - 3 Ph w w o o m C * ' i< 3 M Sq J a £ - s i £ j § S i § i^! 5 ^ , ^ ^ i i i C 3 W o ra C S * RELATIVE HUMIDITY: Monthly Average - * Jet/ l s j. - 1'iINISTERE DES TRANSPORTS REPUBLIQUE DU CAMEROUN Paix - Travail - Patrie DIRECTION D E L A M ETEOROLOGIE H A TIONALE SERVICE D E L A CLIM ATOLOGIE DES D O N H EES ET DES PUBLICATIONS Ol Bureau des P u b lic a tio n s , Renseignementst e t d6s A rchives - FEV. STATION D E : P A R A M E T E E S ft uWrti-J* PERIODE I'Wtj % A I1N EES ! JA 17V . W n \ 7 3 . 5 9 J 1 2 . 3r-L l i m . J-2 31 lA . 2 1 . S £ _ . j m . . . .1123 A 3.il .1311 13S± -A 3 1 1 1 3 1 1 A 3M 7 m , g i - . . n : >> . ?,o - I O - . S jO _1S s L _ ,_ £ 1 M A R S : AVRIL : mai : JUHJ : JUIL. : A O U T : SEPT s OCT. NOV. s DEC. 2 1 . 8 1 . . £ £ . 32 . S 3 . i?JT . SiT 2 4 -. . ? > . S I . 2 1 .. HL.-J&& . S> , . SJ J i ____ li. 21 . 2 1 . 2} 85 .26. lit- -ILL-*. >7- . _>3 tomux . 1 2 1 1 v g S i Norabre d ’- Aimees : 40 40 : AO 1 L Z Z A l X X _ £ H _ . 3 J A A O l h 11 1 1 8 < ¥ 1 1 m s i m . 10 2U . &A- 23 . 23 g f . S 3 g } I t t i A L . . . A 1 - . 1 X . 28 S3 J L S L H , S i., Sir e g , s c * . s> A -10 ! 1 0 ' ■ 1 0 I S . U ZJk— | — ... & & :— •—S 2 4 .S£_:-1SL_ 3.5L_ < 3 3 - i L L £ 1 , g ^ . S i i AO M oienne J M ) 81 .A 1 — , A L U l 11 & 3 l M . 10 1 IQ 3g,g JSJt. M l M L 1 A £ 3 ^ < 3 .S i h i 4 XX. 3 1 1 . M l 3M 8 : S2H 10 • 10 ftf. : ^ i ! I'iO ■ ■ §-0 Table 2.5 RELATIVE HUMIDITY: Maximum Monthly Average - * J ey/ l s j . - MlNISTERE DES TRANSPORTS REPUBLIQUE DU CAMEROUN Paix - Travail - Patrio DIRECTION D E L A M ETEOROLOGIE N A TIONALE SERVICE D E L A CLEtATOLOGIE DES D O N N EES ET DES HJBLICATIONS Bureau des P u b lic a tio n s , Renseignements e t des A rchives ------- —T STATION D E PA RA M ETEES PERIODE : ANNEES 1 JANV. .1 1 2 £ , _ ! £ . A m . .3 3 ..4221. „12J32_ J « 1 L M & , A m . A i k . A & A M . JL&. A t FEV. 1 1 M . MBS 1 1 n 92 3 1 1 1 A t A m . . A i jmBiux i ; ^IRO N om bre d1 - AO -.AO A rm ees : moyenne _ £ i _ , 2 2 - 3R M . 92 _9_q_ 9 8 JLS. H AO : A V B IL m i . <2» 02 ... 9S 9 8 ! - K 3<? 2 £ . 0 ? 3,? . 3 3 9 9 . aiL. 9 ? ._ 9 9 . . 0 2 . 3 g 9 ? ....92. 9 2 . • Wf : AO 0 0 0 8 JUH : JUIL. - V - 9 2 0 2 JiL 9 g 2 1 M . 3 5 9g 9 2 J .S . . g g ^ 9 8 .12. 9 g a s q >10 i AO 9 g < 0 ? > 9 S : y g : 0 , $ > , <}£ A O U T : SEPT oct. H O V . DEC. TOTAUX sliOY. 3 S .. 3 S’ 95 33 93 A 9 8 , 9 . ? 39 92 . 3.2 M 9,2 A1 % - AS 0.8 ,2 3 33 38 , a m _ ; 6s_ 9g . 02 9? 3a A1l£_. I S 08 , 3 8 9? 3^ 3? A i l £ t 3i~ 9* , 92 38 A m . 3g 3§ -.92. 92 98 9 s Afr> . 95 02 . 9R 92 92 92 . 92 3 92 H U . .91 <3?0 : 3?/ 9«f? 98.1. 4 2 i w t s >Mn > 10 • • - < 0 -<0 aQ i 0 AO * 4 0 9 8 ! 2 8 ! 21# >A1?J> 00 C T 5" N) bt 12 2-2 ANALYSIS OF CLIM ATIC DATA * Monthly average temperatures remain in the upper 70’s to mid-80s ( °F) during the day on a year-round basis. * The monthly average humidity remains between 75% - 85% year-round. * The monthly average high and low wind speeds range between 9mph - 34mph. * At night, the monthly average temperatures are in the upper 70’s ( °F). This indicates a very low diurnal temperature swing, which is typical in hot-humid climates. 2-2.1 Incoming Radiation Douala has one of the lowest rates of insolation in Cameroon: 1,023 hours/year, due to cloudiness, precipitation, and higher relative humidity. Climate and weather is greatly influenced by solar radiation. When the sun is at a low altitude angle, it’s rays have to travel a longer distance through the atmosphere before reaching the earth. The intensity of the solar radiation reaching the earth is greatly reduced because much of the sun’s radiation is absorbed or scattered during it’s journey. The atmosphere traps most of the radiation from the earth’s surface and about 1/5 of the radiation emitted from surfaces escapes back into space. The rest is absorbed by clouds and is radiated back to earth as sky radia tion. The lower the sun, the the stronger the scattering of it’s radiation and the greater the sky radiation as compared to weaker direct radiation. Given the water vapor in the atmosphere, the intensity of the solar radiation is reduced to about 13 half its original strength when it reaches sea level. In the humid climate of Douala where the water vapor content in the sky is high, solar radiation is weak. Clouds also have an effect on incoming radiation because a large amount of the sun’s radiation is reflected from the upper side of the cloud. Part of this radiation is scattered within the cloud and eventually is emitted to the lower side of the cloud as seen in figure 2.4. The width of the arrows corresponds to the amount of heat transferred and the emission rate depends on the water content of the cloud and its thickness. Universal space absorption tn ro ftrm trto l •olor rod lotion reflection / • from clouds diffuse scoffering Solar radiation lo e o flon from sky from ground Surface tom * ground h e r e long wov* outgoing rodtotton Layer close Convection to the surface Radlattvo p*eudo conduction H*at conduction Supplied Heat transport by: Molecular hoot conduction I. ‘ ‘ ‘ • ‘I Short wov* radiation J Convection K & S & f S jj Long wav* radiation Chang*, of th* phyrked clot* of th* water Fig 2.4 Heat Exchange at Noon for Summer Days. [2] 14 2-2.2 Diurnal Temperature Swing Whenever there is even a low cloud cover there is virtually no net outward radia tion from the earth back to the atmosphere. Even if incoming radiation during the day is low, cloudy equatorial regions experience higher night temperatures than drier regions. Since solar radiation varies very little in tropical latitudes, the temperatures remain fairly constant year-round as seen in the graphs for Douala. This applies particularly to Douala which lies on the Atlantic coast. Because of its high heat capacity, even if considerable amounts of heat energy are added or removed from water, its temperature only changes marginally. The values in the graphs and tables above clearly indicate that there is a real need for cooling people in interior spaces on a year-round basis in Douala. Because this need is so great, an efficient passive method of ventilation is ideal because it would lower otherwise high artificial energy costs to keep the spaces comfortable. Since this study will concentrate on the use of wind for natural ventilation, I will be using two “study-months” for high and low velocities. The humidity and temperature of both months are very similar: APRIL: 34mph DECEMBER: 9mph 15 2-3 WIND ROSE The values for the monthly average wind velocity over a nine year period (1976- 1985) are used to make a wind rose for Douala. The percentage of time during which the wind blows within a range of velocities in a particular direction is recorded as shown in Table 2.1 These percentage values are used in figure 2.5 to make the wind rose, which shows the annual direction, velocity, and frequency of wind in Douala. The optimum orientation for a wind-scoop would be SW be cause this would be a cooler breeze coming from the Atlantic Ocean. Winds from the East come from the interior of the African continent and will be hot. MPH WIND DIRECTION 9-13 16-22 25-36 38-49 AVERAGE SPEED %TIME N 0.8 30 0.8 NNE 0.8 30 0.8 NE 1.7 1.7 36 3.4 0.8 38 0.8 E 3.5 6.1 3.5 31 13.1 ESE 2.6 28 2.6 SE " '" 3 3 " 1.6 1 .7 28 7.8 SSE 1.7 1.7 34 3.4 S 0.8 1.7 1.7 21 4.2 SSW 0.8 2.6 17 3.4 SW 2.6 3.5 6.1 18 12.2 wsw 1.7 3.5 2.6 20 7.8 w 0.8 1.7 1.7 21 7.8 WNW 1.7 22 1.7 NW 9.8 25 0.8 NNW CALM 7 10.5 8.7 19 26.2 Table 2.1 16 N NNE NNW NE NW : n e WNW] w 4- 20 /22 p4 ESE WS' SE SW SSE ssw s Fig. 2.5 Wind Rose: Douala Annual - Direction THERMAL COMFORT THROUGH PASSIVE COOLING 18 3-1 VENTILATION Ventilation comes from the Latin word ventus and means the movement of air. It is defined by the air-conditioning industry as the process o f supplying or remov ing air by natural or mechanical means to or from a space, usually through air exchange with the outdoors. [3] Ventilation serves three ends in the environmental control of buildings. It is used: 1) To satisfy the fresh air requirements of the occupants (“health ventila tion”) by removing odors and particles from the air. This is important in hot-humid climates because if the air is left stagnant it will promote the growth of fungi in furniture, walls, ceilings and floors. Also still air can cause lethargy and sickness among the occupants. 2) To increase the rate of evaporation and sensible heat loss from the body (“comfort ventilation”). This is important because air moving over the skin’s surface removes moisture and has a cooling effect even at high temperatures (see Comfort Chart). 3) To cool the building interior by exchanging warm indoor air for cooler outdoor air when conditions are appropriate (“structural ventilation”). 19 3.2 HUMAN COM FORT Through the centuries man has successfully inhabited different regions of the earth from the equator to the poles. Physiologically, man can only comfortably withstand a narrow range of climatic conditions, outside of which daily activities are constricted by heat or cold. The use and adaptation of fire, clothing and shelter are developments to help adjust to local climatic conditions. In order to keep comfortably cool, the body loses heat through evaporation. Evaporation happens easier in a hot-arid climate, hence is invisible. In a hot- humid climate there is already a high moisture content in the air therefore evapo ration is difficult and becomes visible in the form of perspiration. It becomes essential to create air movements across the skin’s surface to assist the evapora tion process and cool the body. Excess heat is also eliminated from the body in three forms of sensible heat transfer: conduction, convection, and radiation. FACTOR ENVIRONMENT HUMAN Metabolism (M) Little Effect Activity Weight Surface Area Age Sex Evaporation(E) Wet-bulb temperature Sweat production Dry-bulb temperature Surface Area Velocity Clothing Radiation(R) Temp, difference btwn bodies S.A Emissivity of surfaces Clothing Convection(C) Dry-bulb temperature Clothing Velocity Surface area Table 3.1 Factors Influencing Heat Balance Equation. [4] 20 The body is in a state of equilibrium with it’s environment when it loses heat at exactly the same rate as it gains. According to Vaughn Bradshaw, the relation ship between the body’s heat production and all its other heat gains and losses can be represented mathematically as: where: M= Metabolic rate E= Rate of heat loss by evaporation, respiration, and elimination R= Radiation rate C= Conduction and convection rate S= Body heat storage rate Heat Production = Heat Loss or M = EiR^C±S Radiation Evaporation M = E + R + C + S Fig 3.1 Heat Balance of the Human Body Interacting With its Environment. [5] 21 Varying with the degree of exertion, the metabolic rate (M) is always positive because the body always produces heat. Excess heat is stored in the body tissue if the environmental conditions are such that the combined heat loss from radiation, conduction, convection, and evaporation is less than the body’s rate of heat production. The body has a limited thermal storage capacity so body heat storage (S) is always small. Therefore, as it’s interior becomes warmer, the body reacts to correct the situation by increasing blood flow to the skin surface and increasing perspiration and body heat loss. This is especially important in hot-humid cli mates. The body can either gain or lose heat by radiation (R) and conduction-convection heat transfer (C), depending on the temperature of the surrounding objects and ambient air. Evaporation however, is exclusively a cooling mechanism. It be comes the predominant factor when ambient temperatures are so high, as in hot- humid conditions, that radiant or convective heat losses cannot occur. There is a steady flow of sensible heat from the skin to the surrounding air at comfortable temperatures. This flow rate depends upon the temperature differen tial between the skin and air. The deep body temperature remains relatively constant but what varies is the skin temperature (between 40° to 105° F) depend ing on the surrounding humidity, temperature, and air velocity. If the ambient temperature rises above the skin temperature, the body gains heat from the envi ronment, and the only way it can lose heat is by increasing evaporation. The evaporation rate and evaporative heat loss from the body is effected by the evapo ration potential of the air. It is dependent to a minor degree on the relative humid 22 ity of the surrounding air. As the moisture is evaporated from the skin surface it is carried away by the passing air current. The heat needed in order to vaporize the perspiration is drawn from the body. Even though the skin perspires only at moderate to high temperatures, evaporative losses of water from the respiratory passages and lungs occur continuously. The air exhaled is saturated (100% R.H.) and even at rest the body requires lOOBtuh of heat to evaporate this moisture from the lungs into the inhaled air. This shows a considerable amount of heat to convert water into vapor, therefore, the evapora tive heat loss from the lungs and skin plays an important role in disposing of body heat. 3-2.1 Human Comfort Chart The chart below outlines the relationship between temperature, humidity, and human comfort. The graph indicates that above the human comfort zone it is necessary to introduce a cooling device such as shading, ventilation or added moisture in order to restore the feeling of comfort. PRYtULB TEMPERATURE F« 23 120 P W M U SUM fcTW OKB 100 7 1 * s o ■ 50 100 -wo ISO. 200 300. 300 100 20 4 0 RELATIVE H U M IP I T m Fig. 3.2 H um an Com fort C hart. [6 ] 24 3-2.2 COMFORT CHART ANALYSIS This chart, based on the studies done by Olgyay In 1959 is applicable to inhabi tants of the moderate climate zones in the United States at elevations not in excess of 1 0 0 0 feet above sea level, with customary clothing, doing sedentary or light work. This chart, therefore, is used more as a guide than as an absolute rule in its application to my studies of ventilation and human perception of comfort in Douala. Here, the climate is hot-humid, not moderate, and the physiological nature of its inhabitants is more tolerant to higher temperatures and humidities. Generally, insufficient air movement causes stuffiness and air stratification, resulting in an imbalance of temperature between the floor and the ceiling. When air velocities are too rapid, it is perceived as unpleasant by the occupants. The exact limits to acceptable air motion in the occupied zone depend on the overall room conditions of humidity, mean radiant temperature, the temperature and humidity of the moving air stream. The three points on the comfort chart represent the intersection of monthly average temperature and monthly average humidity for three sample months: January (red), February (blue), and March (green). These points are outside of the comfort zone as described by Olgyay and are on the outskirts of the perimeter zone where increase in wind speed can cool effectively. Consequently, higher wind speeds than recommended on the graph would have to be maintained. A noticeable air movement across the body when there is perspiration on the skin may be regarded as a pleasant cooling breeze. Every 15fpm increase in air move ment above a velocity of 30fpm is sensed by the body as a 1° temperature drop. [7] 25 3-3 AIR DISTRIBUTION Based on the distribution of air in an interior environment, occupants perceive cool air in two main ways: 1) they think warm air introduced into the room may cool off before it reaches the occupant, 2 ) or that the air is intended to cool occupants under warm ambient conditions. Hence attention must be given to air distribution as well as velocity and flow rates. To avoid using very high wind speeds indoors, either the temperature or the humidity would have to be reduced. Either of these would require mechanical energy and would no longer qualify as a passive system. The climatic data analysis graphs indicate the average monthly night temperatures are within an acceptable range of the comfort chart. For this reason, the night air can be used to cool the building by adopting an open system of ventilation. By using the wind-tunnel, the building will be flushed of hot air at night and cooler air collected and brought in. This may minimize or eliminate the need for ex change of warmer outdoors air during the day. 3-4 CLOTHING Individual human comfort is also determined by clothing because it is an impor tant modifier of body heat loss and comfort. Clothing insulation is described in terms of its £k> value, a numerical representation of a clothing ensemble’s thermal resistance: 1 clo = 0.88 deg F h ft2/Btu. [8] 26 0.8 Clo 0.2 Clo 1.0 Clo 3.0 Clo Fig 3.3 E xa m p les of a Range of Clo V alu es. [9] 27 In addition, figure. 3.4 shows the conditions that are thermally acceptable for at least 80% of normally clothed occupants under the following conditions: 1) Sedentary, 2) 50%RH, 3) Air Velocity^ 30fpm. Celsius 20“ 25" 2.0 Sedentary, 50%. R H Air Velocity 5 30 fpm, or 1/3 mph, or 0.15 m/s o _ j o z o 5 10 c o z C 3 z X o 0.5 64 " 69" 74 " OPERATIVE TEMPERATURE " F. 79" Fig.3.4 Clothing Levels (in Clo units) necessary for Comfort at Different Operative Temperatures. [10] Adjusting clothing can help satisfy comfort requirements. In the hot-humid climate of Douala energy savings can be achieved if the insulation value of clothing worn by office workers is appropriate to the season. The traditional clothing of Cameroon is made of natural materials which help to maintain comfort in hot conditions. In a hot-humid climate, the lower the clo value, the more comfortable the individual. 28 3-5 HUM IDITY AND DEHUM IDIFICATION Human tolerance to humidity variations is much greater than tolerance to tem perature variations. However, humidity control is also important because high humidity retards human heat loss by evaporative cooling (perspiration and respi ration). Studies on the human response to hot-humid climate have been done by Givoni (1976). According to Givoni, as long as the skin is dry, the rate of sweat secretion and evaporation depends only on the metabolic heat production and the dry heat exchange. At high levels of humidity, a large area of the skin is thickly covered with perspiration. All the perspiration is evaporated from the skin, but part is evaporated at some distance from the skin. The problem with this is that some of the heat required for evaporation is taken from the ambient air and not from the skin, thus the cooling efficiency of the evaporation is reduced. As a result the body has to secrete and evaporate more sweat than that equivalent to the required cooling. [1 1 ] Givoni has established certain boundaries of thermal regions which determine the effect of humidity. These regions depend on the overall requirements for evapo rative cooling, the velocity of the air and the clothing. These ranges are: At air temperatures between 68-77 °F, the humidity level does not affect the physiologi cal and sensory responses, and variations in RH between 30% and 85% are almost imperceptible. 29 According to Givoni, feelings of clamminess and dampness are only perceptible when the air is almost saturated. The human perception of humidity becomes more apparent at temperatures above 77°F. What becomes most effected are; skin temperature, skin wetness, and at even higher temperatures, the sweat rate. [1 2] What is most important to my ventilation studies is the fact that an increase in the air velocity counterbalances the effect of humidity and therefore the lower limit of physiological and sensory response to humidity elevation is raised as the air velocity increases. [13] This principle, coupled with the studies done by Tanabe (see section 5-3) on the human perception of comfort in hot-humid climates as a response to air move ment, is very important in my studies. The study of human responses to humidity is beyond the scope of my thesis, yet these results are essential for me to under stand what velocities I need to maintain in a room in order to keep its occupants comfortable. Research into the use of both dry and liquid desiccants in cooling systems for humid climates indicates that such systems are very expensive. One such system is called the “Imperfect Open Cycle Solar Cooling System Using Liquid Des- iccant” by Ken-ichi Kimura in Tokyo. The basic principles of this study are shown in figure 3.5. 30 *_r HOT WATER SUPPLY Fig. 3.5 Solar Cooling System. [14] This open cycle solar dehumidification system uses lithium chloride (LiCl), a liquid desiccant which is easier to transport within the system and has a lower regeneration temperature than solid dessicants from his previous studies. The system is made up of three circuits: 1) air circuit, 2) dessicant circuit, 3) and domestic hot water circuit. In the air circuit, the room air is is dehumidified and F ig .23 O u t s id e v ie w o f th e sy s te m made in 1 9 8 0 . F ig .22 S y stem d ia g r a m o f th e sy ste m made in 1 9 8 0 . F ig .24 I n s id e v ie w o f th e sy ste m made i n 1 9 8 0 . 31 heated in the dehumidifier, then sensibly cooled by city water and evaporatively cooled by an evaporative cooler, if necessary, before the air enters the room. The liquid desiccant circuit, LiCl absorbs the moisture from the air in the dehumidi fier. The diluted solution then trickles down onto the surface of the collector where regeneration occurs due to the natural upward air current caused by solar radiation. The thick and hot solution is cooled by city water at the heat exchanger in a tank before it is sprayed on the dehumidifier. The city water is brought into the collector before being used as domestic hot water. [15] Further work in this area is beyond the scope of my thesis and I am more inter ested in a completely passive means of cooling and ventilating occupants of interior spaces. 3-6 AIR MOVEMENT Air movements result from natural or forced convection as well as from the occupants’ bodily movements. Such movement significantly affects body heat transfer by convection and evaporation. The faster the motion, the greater the rate of heat flow by convection and evaporation. There is no minimum air movement that must be provided for thermal comfort when ambient temperatures are within acceptable limits because the natural convection of air over the body’s surface allows for the continuous dissipation of heat. However, natural air flow is not adequate when ambient temperatures rise and air flow must be artificially or passively increased, such as by use of fans. 32 VELOCITY PROBABLE IMPACT Up to 50 fpm Unnoticed 50 to lOOfpm Pleasant 1 0 0 to 2 0 0 fpm Generally pleasant but causing a constant awareness of air movement. 2 0 0 to 300fpm From slightly drafty to annoyingly drafty. Requires corrective measures if work and health are to be kept in high efficiency. Table 3.2 Human Responses to a Range of Air Movements. [16] 3-7 EMISSIVITY OF BUILDING MATERIALS Surfaces lose absorbed heat by emitting radiation at a longer wavelength than the incoming solar radiation. Natural and artificial surfaces absorb and/or reflect sun and sky radiation based on the color spectrum of the radiation and the character of the surface. The color, especially black or white, of such parts of the building as the walls and the roof will determine the amount of heat they absorb or reflect. Surfaces with a high reflection co-efficient will remain cooler than others. 33 Material Reflection Level Silver Gray Slates 1/5 Red Clay Tiles 2/5 Uncolored Red Concrete Tiles 1/3 White Cement(fresh) 1 /2 White Cement(after 12 months 3/10 New Galvanized Iron 1/3 Whitewashed Surface 3/4 Very Dirty Objects 1 /1 0 Polished Copper 4/5 Tarnished Copper 1/3 Table 3.3 Reflection Coefficient Values of Materials. [17] I recognize that the Olgyay comfort chart is not specifically for hot-humid cli mates therefore it is possible to assume that the comfort ranges he suggests may not be applied directly in Douala. 3-8 STAYING COOL Where does the wind come from? Below is a schematic of global circulation of winds as they are constantly “looping” in the earths atmosphere: North Pole South Pole Fig. 3.6 Global Circulation. [18] 34 As the sun heats the earth, certain areas (the tropics) are warmed more than others. These temperature differences cause air to rise, resulting in unequal pressures on the earth’s surface which induce winds. The hot air from the tropics rises to the atmosphere above and moves towards the North and South poles, deflecting under the Coriolis force. The air is cooled at the poles and descends, then returns from the poles with a deflected path towards the tropics. Beaufort No. Indications Vel. (mph) 0 Smoke rises verticallv Less than 1 1 Dir. of wind shown by smoke drift but not wind vanes 1 - 3 2 Wind felt on face; leaves rustle; ordinary vane is moved bv hand 3 - 10 3 Leaves and small twigs in constant motion 7 - 12 4 Raises dust and loose paper; small branches are moved 13- 18 5 Small leaves in tree begin to sway; crested wavelets form on inland waters 19-24 6 Large branches in motion; umbrellas held with difficulty 24-31 7 Whole trees in motion; inconvenience felt in walking against the wind 32-37 8 Twigs break off trees; walking on the street is difficult 39-46 9 Trees uprooted; considerable structural damage 47-54 1 0 Slight structural damage occurs to construction 54-67 11 Rarely experienced, accompanied by widespread damage 63-75 1 2 Hurricane force over 93 Table 3.4 Beaufort Scale of Classification of Winds [19] Height (ft) Above G round 35 3-9 VERTICAL DISTRIBUTION OF WIND The diagram below shows that wind velocity increases with building height. The mean velocity of wind decreases the closer it gets to the earth’s surface due to the retarding effects of friction. This principle is important for my studies using the wind-scoop because air will be collected from distances of at least 40 feet above ground. SUBURBAN G radient Wind 1200 OPEN COUNTRY G radient Wind G radient Velocity Wind Velocity b G radient Wind G radient Velocity 1500 CITY a Wind Velocity Fig. 3.7 Vertical Distribution of Wind. [20] 36 Table 3.5 below shows the comparative range of wind speed measured vertically, taking the speed of wind at a height of 32 feet as 100% [21]: Feet Above Ground: 1 3 10 20 32 50 92 197 % of Wind Velocity 50 62 90 95 100 107 125 143 My experiments using the wind tunnel will be based on this fact. To promote cooling by natural ventilation, air can be brought into the building from a level or levels above the ground floor (where the actual pressure and wind velocity will be measured) and circulated through all interior spaces vertically and or horizontally. 37 HISTORICAL PRECEDENTS 38 4-1 USE OF THE WIND-SCOOP IN HOT-ARID CLIMATES In today’s society there is a very high expenditure of artificial energy to keep the internal environment of buildings comfortable however uncomfortable the external environment may be. Even in the most adverse climatic conditions, man has adapted a vernacular architecture that responds to natural forces and availabil ity of local building materials. For example, the vernacular architecture of many cultures in climates with a high diurnal temperature swing features buildings with thick exterior walls of brick or stone which act as both insulators during the day and reservoirs of heat at night. This has the effect of lowering the temperature variation inside the building. In light-weight structures, the indoor temperature curve closely follows the out door temperature cycle, but is always above it at maximum conditions and throughout the night. This means that even in light-weight structures indoor temperatures could not be lowered below outdoor maximum conditions without natural or artificial methods. IOO 90 90 80 80 7 0- Outdoor air Heavyweight house Lightweight house Noon 16 20 24 Time of day (hrs) Air temperature °F HOT HUMID CLIMATE 60 — Noon 5 20 24 Time of day (hrs) Air temperature °F Fig. 4.1 Temperature Variation Curve [22] c l i m a t b 39 The development of masonry wind-scoops which extend above the roof line of buildings in the East and Middle-East has a history that is centuries old. These systems, which resemble large periscopes, are oriented in the direction of the prevailing wind and circulate air throughout the building. Because they operate without any input of energy other than that of the natural environment, they are classified as passive systems. Figure 4.2 Examples of Wind-scoops: [23] Egyptian house with wind-scoop Peruvian Wind Scoop Wind-Scoop with Trap Door (West Pakistan- used since the 15009 s): Wind-Scoops on Rooftops (Herat, Afghanistan) Roof scape with wind-scoop (Sind, West Pakistan) 41 4-2 WIND-SCOOP ORIENTATION The wind-scoop resembles a chimney, with one end in the basement or ground floor of the building and the other rising above the roof. Figure 4.3 shows such a system in Hyderabad, Sind, Pakistan where the 120°F outdoor temperatures that prevail from April to June can be decreased to 95° F in the interior environment by using the scoop Fig. 4.3 Wind-Scoop in Hyderabad, Pakistan. [24] 42 The actual operation of the wind-scoop depends on wind conditions and the time of day. When the inlet of the scoop is facing the prevailing wind, it harnesses the wind and forces it to move downward into the rooms to be ventilated, and finally to exit through the windows where there is a negative pressure. The flow of air through different parts of the building is controlled by opening or closing the apertures from the tower and the doors of the spaces off the interior hall. When the prevailing wind is in the opposite direction there is a negative pressure in the front of the scoop which creates a suction effect that pulls warm air from the building below. In Douala, there may be a 10° F drop in temperature at night- the walls of the wind-scoop absorb heat during the day and at night the walls transfer this heat to the cooler air in and around the tower. The pressure at the top of the tower is reduced since warm air is less dense and an upward draft of air results. As this warm air is pulled up through the tower, cooler ambient air is suctioned into the building through doors and windows. This particular mode of ventilation is also known as the “stack effect” which occurs in a tall building when there is a natural temperature gradient; hot air rises and stratifies in layers of increasing temperature on the tops of elevator shafts and stairwells. Cooler air is pulled in from outside of the building at the bottom of the shafts and rises as it warms up and decreases in density. This causes a strong convective upward airflow which ventilates the interior environment. An added effect is that apertures on the top of the shafts and stairwells produce areas of negative pressure when wind flows over them. As the air is pulled through doors and windows on the lower floors of the building, it is pushed through these apertures on the upper levels adding to the stack effect. 43 In his thesis, “A Passive Cooling.System for Residential Building in the Eastern Province Desert in Saudi Arabia”, Turki Haif Al-Qahtani studied the modem application of wind-catchers in hot-arid climates. -ycnjQsiSe j; i i I Fig 4.4 W ind-Catchers in Hot A rid Climates. [26] 44 His studies are based on two thermodynamic theories of cooling in such climates: sensible and evaporative cooling. Sensible cooling occurs when the heat loss from the air results in a lowering of the air temperature without a change in the water vapor content of the air. In evaporative cooling, the warm air comes into contact with water- in Turkis’ experiments this occurs by means of cheezecloth soaked in water. The water absorbs heat from the air thus cooling it. The moist cool air is then circulated throughout the building. By using this system, Turki was able to induce a 30° F temperature difference between the exterior and inte rior. Evaporative cooling can not be used in a hot-humid climate because the air is already moisture-laden. Therefore, in such a climate the cooling potential of the wind-scoop to cause a temperature drop is not as feasible as in a hot-dry climate where there is also a larger diurnal temperature swing. However, I believe that the wind-scoop can be used in a hot-humid climate mainly to ventilate the interior environment and to flush the building of excessive heat, more than to cool or lower the temperature of the air. 4-3 PRIN CIPLES OF COOLING AND VENTILATION IN HOT-HUM ID CLIM ATES In observing the historic adaptation of man to a hot-humid climate, the main principle was to provide shelter and shade against sun and rain as well as to maintain maximum openings to allow the free flow of breezes. Figure 4.5 thru figure 4.12 are examples of these vernacular adaptations to the climate [27] Fig.4.5 This window combines shutters, lattice screens, and louvers for good ventilation and privacy- Jeddah, Saudi A rabia. Fig. 4.6 Horizontally Hinged Shutters Double as Shades (Kavalla, Greece) and allow for a 50-100% opening Fig. 4.7 Placing the screens or louvered shutters away from the windows causes less interference with the air flow through the interior. (San Antonio, Texas) 4 6 Fig. 4.8 Seminole Building, Florida: Open and elevated houses are built in hot-hum id areas partly because they take advantage of the cooling breezes Fig. 4.9 Tree House, New Guinea Fig. 4.10 Air Movement through a Bari Village, Sudan: The open planning of villages is also essential for good air flow. Fig. 4.11 Open Samoan H ut Fig. 4.12 Open Porch, New O rleans (1800’s) There is a strong link between building design, particularly housing, and culture in many tropical areas such as Douala. Generally, there are three types of living spaces: indoor, outdoor, and indoor-outdoor combination such as a verandah, which become social spaces as well as a means for letting breezes into the interior. Shading and sun control should also be used to keep the building’s surface skin from overheating. Otherwise solar radiation alone can increase the temperature of the sunlit surfaces by as much as 300 - 80° F. When the exterior is shaded by use of vegetation or overhangs, its temperature is maintained at or about the 48 temperature of ambient air. This maintains a smaller outdoor-indoor temperature difference to drive heat indoors. However, under predominantly overcast conditions, the sky is the main source of heat, not the sun as discussed in section 2-2.2. In overcast conditions, the clouds diffuse the radiation from the sky so that devices designed to shade from the sun are only partially effective. Type of Control %Reduction in total heat gain ventilation %Efficiency to ensure cross control of control %Natural light resul ting from as means Approx. average efficiency Curtains 10-20 5-25 30-50 35 Metal Venetian Blinds 20-30 5-90 50-75 64 Heat Resisting Glass(colored) 60 70 40 57 Roof or corri dor overhang 75-80 80-100 40 69 Concrete hood and fins 70-80 80-100 45 70 Louvered hood 85 80 -100 77 84 Vertical louvers 70-80 10-50 45-65 53 Horiz. louvers 70-80 15-50 45-70 53 Suspended louvers 8 0 -8 5 80 -100 70-80 82 Table 4.1 shows the types of solar control devices which can be used in a hot- humid climate and their overall effectiveness. The problem of sun control is more one of glare from small openings which are surrounded by darkened areas. Ordinary windows create excessive glare because the degree of contrast they cause is greater than the eye can comfortably tolerate. The best way to counteract this is to cut off direct view of the sky from the build ing interior by use of such devices as grilles and screens in front of the window. Figure 4.13 shows a building in Muscat which uses horizontal concrete louvers on the entire facade which serve as both a shading device and openings to allow the free flow of breezes. Fig. 4.13 Use of H orizontal Louvers in M uscat. [28] In hot-humid areas, adjustable wooden and aluminum louvers, pivoted doors and windows, and pierced screens are also used for controlling glare without hampering air movement. The advantage of louvered windows and doors is that they allow for a 100% opening and while allowing air in they keep the rain out. Examples and principles of the operation of louvers are seen in figure 4.14 [29] and figure 4.15 [30]. 50 LCU VEK3 G 4N C & M tXTD, A major advantage of the jalousie window is the almost unrestric ted free area in the open position. For glass louvers, a free area of up to 86% is obtainable in the open position, 46% at 30°, 22% at 15° horizontally pivoted windows hardwood or asbestos adjustable louvres top hung awning windows “ calorex” glass solid insulated panels horizontally pivoted window top hung awning — windows “calorex” glass solid insulated panels window over solid hardwood pivoted door ^ Fig. 4.14 Operation of Louvers Another major bene fit of jalousie windows is rain control, and with opaque or heat absorbing glass louvers, sun screening is also achieved. 51 h i | j ! | r Fig. 4.15 Operation of Louvers In my studies, the use of the wind-scoop is primarily for use when the major inlets in the building cannot be oriented in the direction of the prevailing wind, because of site conditions or other constraints. Rising above the roof-line, only the scoop would need to be oriented in the direction of the prevailing wind. The use of louvers and elevating the building above ground as in figure 4.16 is most effective when the building is directly oriented in the direction of the prevailing wind and breezes can enter directly into each space. 52 Fig.4. 16 Elevating Buildings Off-Ground For Free Flow of Breezes: View of L ibrary Building of the Indian Institute of Technology, K am pur, India [31] In most hot climates, the optimum building orientation is E-W in order to mini mize exposure of the east-west walls to solar radiation. How'ever, the impact of temperature compared with humidity is not too excessive in hot-humid climates. Therefore freely elongated buildings are advantageous. Because Douala has a reasonable diumal range of temperature, on a building oriented N/S, the sun strikes the east and west walls more directly. Therefore the walls may be of solid construction and the roof insulated, w'hile the north and south walls when properly shaded could be of a light-weight construction which cools quickly when the sun 53 goes down. Even when there is a very slight drop in outside temperature, the light-weight construction cools down rapidly. Table 4.2 illustrates how dense materials such as brick or stone take a considerable amount of time to heat up and cool down again. CONSTRUCTION COEFFICIENT OF TRANSMITTANCE E.T. DIFFERENCE HEAT TRANS. BTU/FT(HR) HEAT TRANS REL. TO l"WOOD 6" Construction 0.69 46 31.7 95 6"Construction with 1" cork 0.21 45 9.5 28.4 6" Construction with 2" cork 0.123 44 5.4 16.2 6"Construction with 2" cork air-space & plastered ceil. 0.107 44 4.7 14.1 1" Wood 0.54 62 333.4 100 1" Wood with 2" cork 0.118 62 7.3 21.9 Table 4.2 Heat Storage Capacity of Different Constructions. [32] In hot-humid regions, to effect optimum cross ventilation, opposite walls in rooms require maximum openable areas which respect the privacy of occupants and layout of furniture. In the interior, privacy can be achieved by the use of louvers and other separating devices which can be made from local materials such as bamboo or opaque materials. However, the basic principle is to minimize walls, doors, and other baffles and dampers to the air flow. There is a problem however, of sound transmission, which is difficult to control in such as open environment. 54 The Northern Australia houses in figure 4.17 thru figure 4.21 illustrate some of the basic principles in a hot-humid environment for any building type. [33]. These are: 1) Openness. 2) Designed to catch every vagrant breeze. 3) High ceilings. 4) Large windows. Fig. 4.17 House at Sturgess, A ustralia. 55 F ig .4 .18 House at D arra. Block screen wall for privacy. Clerestory high lights for w arm air removal. Fig. 4.19 Flats at Toowong. Flats facing west; screening devices- concrete block screens and adjustable external tim ber Venetians on balcony. 1111 52 56 Fig. 4..20 W ilson’s Residence at Toowong. L inear plan for cross ventilation- large areas of floor to ceiling louvers, large overhangs & brcezeway in center of house. Efficient cross-ventilation requires both exterior inlets and outlets in the same room and single-room deep buildings provide good cross-ventilation in such climates. CONTI NUOUS WIND&V &&ND L tv Fig 4.21 Single-Room Ventilation in H ot-H um id Climates. [34] 57 4-4 ROO FS AND FLOORS It is recommended that the “temperature of the underside of the ceiling should never be more than 8° F higher than the dry bulb temperature” in hot-humid areas. Studies have shown that the most efficient roof in a hot-humid region should have thermal and reflective insulation in the ceiling because this is: “By far the most effective means of reducing lower surface of ceiling and room temperature, and that once achieved, natural ventilation of the roof-ceiling space is no longer important.” [35]. The heat load in the building is reduced if the building structure itself decreases heat gain. I believe, however, that ventilation of the ceiling level is important for flushing out the warm air that stratifies there more than for reducing the air temperature at that level. A good example would be the use of aluminum sheets with insulation at the ceiling level to reduce temperatures, and an opening near ceiling level to flush out warm air. Floors may be of concrete or raised timber, or placed on the ground. There is an advantage in raising large buildings off the ground on pilotis since this would not impede air flow at the ground level. Indeed, studies show major drafts result at ground level. 58 4-5 VEGETA TIO N The advantage of natural growth is that it stabilizes or minimizes the surrounding air temperature. Vegetation grows easily and profusely in hot-humid climates and care should be taken to control this growth and plants selected should be a species that would not obstruct air flow indoors. The use of trees goes beyond the practi cal application for shading. They are also used as gathering spaces during work breaks and can act as a substitute for bicycle, car, and bus shelters. Material Temperature (°F) Tar Macadam 91 Sand 79 Earth 77 Gravel 70 Grassy Ground 61 Clay Soil 52 Table 4.3 Range of Temperature Variations Over Different Surfaces on a Given Day. [36] Because plants transpire, it would be expected that their surface temperature would be less than that for clay soil. 59 In a hot climate the daily evaporation from a mature beech tree can provide an air conditioning effect of 1 million Btuh - the equivalent of 10 room-sized air condi tioners operating 20 hours/day. Although this process can occur in a hot-humid climate, it’s effect will not be the same because evapo-transpiration of the plants’ leaves will be reduced due to the high moisture content of the air. [37] 4-6 PRINCIPLES TO PROMOTE INTERIOR AIR FLOW Winds are produced by a difference in pressure and outdoor breezes create air movement through the building interior by the “push-pull” effect of positive air pressure on the windward side and a negative pressure (suction) on the leeward side. Both orientations are important for ventilation. The sides are also low pressure areas. Figure 4.23 illustrates this principle: Fig. 4.22 Pressure Zones around a Building. 60 Good natural ventilation requires locating openings in opposing pressure zones. The greatest volume of air movement occurs when the windows or screened doors are located in the portions of the facade that experience the greatest pressure difference between them. One of the principles which governs air flow through a space is the Venturi Effect. If openings on two opposite walls are arranged to funnel the wind, the velocity increases at the narrowest point in the flow. The flow rate remains constant. This is an important aspect of my ventilation studies because the size of the openings from the wind-scoop into the rooms is based on this principle. Ventilation through a space having only one aperture functioning as both inlet and outlet is poor. 1 Q O % L I \ t 4 .7 7 o U “ * « | 1 00% U A c 1 00%U 1 00%U \ J -3-3»%JL _ , J | 3.6% L I t 1 00%U II 3: tr% u s / Fig. 4.23 Shows the Average Air Velocity as a Function of the Free Wind Speed for Various Wind Directions. Maximum velocity occurs when the wind is perpendicular to the aperture. [38] 61 10 0 7 ^ 477olK- 36% U ' - - , ^ 1 007* U 100%U L 2 h i Figure 4.24 shows the effect of the size of the inlet and that of the outlet on the efficiency of ventilation for cross-ventilated spaces. [39] 62 A popular misconception regarding the proper size of the openings is the belief that a small opening on the exit side of a large opening will faciliate efficient cross ventilation. However, a large inlet and a large outlet is best. Figure 4.25 shows that maximum cross-ventilation is reached when both the inlet and outlet are both at maximum size. The minimum efficiency is attained when the inlet is maximum and the outlet size is minimum. > U J 30 u. 10 0 D UJ O 0 WINDOW WIDTH I W A LL WIDTH Fig. 4.25 Shows how Average Indoor Velocity is Significantly Increased by Increasing the Width of the Openings. [40] The graph begins to level off when the window width is greater than 2/3 of the room width i.e. the possibility of improving ventilation is decreased. Table 4.3 also shows how average indoor velocities increase with a corresponding increase 63 in the size of identical inlets and outlets. The values shown are the percentage of total velocity for various values of window height at various levels above the floor. WINDOW HEIGHT (FEET) l 2 3 3.5 4 4.5 6 Ht. of work plane (ft) r ....."| 1 "1 - r~ :i3 t------- 1 I J 1 ---------1 1 ----------1 2 16 22 24 22 22 24 22 3 14 20 24 26 27 29 26 4 8 17 25 26 26 31 28 5 7 13 25 26 26 30 28 6 8 12 18 19 23 28 28 7 ,: 9 13 15 14 18 20 24 Table 4.4 Average Velocity at Various Levels For Different Values of Window Height. [41] Air movement is increased up to a value of 3.5 feet window height. Beyond this, any increase has a small effect in ventilating the interior. Figure 4.27 shows the variation of average indoor velocity with the window area. “Indoor air motion increases by increasing the window area up to 25% of floor area, beyond which air motion is more or less independent of the area opening.” [42] 15 20 25 30 WINOOW AREA * PERCENT OF FLOOR AREA) Fig. 4.26 Relationship of Average Indoor Velocity With Window Area. [42] If design constraints prohibit the inlets and outlets from being on opposite walls, they can be located adjacently. However, the effectiveness of ventilation is reduced: 65 1 /3L 1/3 U a 1/3L 2/3L 1 /3L 1 00%U 1 /3L Fig 4.27 Effect of Inlet and Outlet in Cross Ventilated Spaces; Openings on Adjacent Walls. [43] The vertical positioning of the apertures above the floor of interiors to be venti lated greatly affects the effectiveness of ventilation: 66 D Fig 4.28 Vertical Positioning of A pertures. [44] 67 A) When both inlet and outlet are near the ceiling, only the warm air that has risen to that level is flushed out of the space and occupants don’t receive any direct relief. B) Conversely, when both inlet and outlet are just above the ground level, layers of warm still air will be left near the ceiling. C) There is a good interaction of air layers when the inlet is higher than the outlet even though this leaves a dead pocket of warm air over the outlet. D) When the inlet is lower than the outlet, the interaction of the air layers is not very effective. These are some of the basic principles that I will be testing and applying in wind- tunnel tests to determine the optimum location and size of inlets and outlets. 68 WIND-TUNNEL TESTS 69 5-1 HY POTHESIS Is it possible for occupants of mid to high-rise buildings in hot -humid climates to be cooled passively by use the of natural air flow? 5-2 GOALS To effectively cool people in interior commercial or office spaces by maintaining a constant air velocity within a “comfortable” range to induce a consistent rate of evaporation of moisture from the skin’s surface. This will be done by inducing air flow in the buildings and the target interior velocities will be those shown in Table 5.2 from experiments by Tanabe. The criteria used to determine this “comfortable” range of wind velocity in inte rior spaces is based on recent studies done by Tanabe as discussed below. Tana- bes’ experiments and results indicate that even though the air may be humid, a comfortable wind velocity can result in efficient cooling. Effectively, this is applying the “chill factor”, commonly associated with cold climates, for ventila tion. 5-3 VENTILA TIO N REQUIREM ENTS IN HOT-HUM ID CLIM ATES My studies for the application of the wind-scoop in hot-humid climates uses the research and testing done by Mr. Shin-ichi Tanabe in his publication, “The Effects of Air Movement on the Thermal Comfort for People under Hot-Humid Condi tions.” My interest in his studies and its’ relevance to my thesis is because the hot-humid climate of Tokyo, Japan is very similar to that in Douala. Also, his 70 work details the human perception of comfort in a humid environment which gives me more pertinent background information to work with than perhaps the bioclimatic comfort charts of Olgyay. Tanabe conducted a series of experiments to determine comfort ranges as per ceived by the 64 college-age Japanese individuals who took part in his experi ments. The experiments were done in two parts: the first part studied thermal comfort under hot-humid conditions, and the second part studies the effects of air movement on thermal comfort. Biologically, the physiology of people living in hot regions makes them more tolerant of warmer conditions than those living in cold regions. For example, individuals in hot regions have more sweat glands than those in colder climates. “Osada postulated (1982) that people who live in hot climates sweat less until a certain temperature is reached, but above that sweat more than those who live in a cold climate when exposed to the same conditions. Hori et al. (1978) concluded that subjects who were bom and reared in a hot and humid region were superior to those who were bom and reared in a temperate region in the efficiency of sweat for cooling bodies. Ellis (1953) also found out similar results in Singapore.” [45] Tanabe uses a Comfort Sensation Vote of “comfortable”, “slightly uncomfort able”, “uncomfortable”, and “very uncomfortable” in order to determine the subjective effects of humidity on thermal comfort. Using the scale, it was found that there is a physiological distinction between thermal comfort and temperature sensation. He found that temperature sensation is more related to a rational experience whereas thermal comfort is related to an emotional experience. 71 In terms of thermal comfort, figure 5.1 shows the percentage of “uncomfortable” in the comfort sensation vote for different relative humidities reported by the Japanese participants who took part in the experiments. It shows that the subjects were most uncomfortable at 80% RH than at 40%RH or 60%RH. Some of the ways to increase thermal comfort would be to increase air velocity, dehumidify the air, or lower the temperature. By using the wind-scoop, my studies involve increasing the air velocity, since this can be done passively, in order to lower the percentage of “unacceptable” and “uncomfortable” assessments as determined by Tanabe. 40%rh 60%rh 80%rh 90 - u S 70 h C C g 50 I 40 o 30 = 5 20 10 °C 29 30 31 28 27 26 MODIFIED TEMPERATURE Fig. 5.1 Analysis of the Subjective Responses Concerning Uncomfortable vs. Modified Temperature. [46] In his studies to test the effects of air movement on the thermal comfort, the 64 Japanese participants wore uniform clothing of a .5clo rating (see figure 3.3). Two subjects at a time were seated in a test chamber containing a wind-box as shown in figure 5.2. The experimental plan is shown in figure 5.3. 72 Fig. 5.2 Wind Box. [47] M T « Fig. 5.3 Experimental Plan. [48] Table 5.1 shows the experimental conditions. All temperature and humidity values were monitored and registered outside of the chamber. There was no set sequence or order in the way the velocities were adjusted during the time each pair of participants was in the chamber. 73 Subject Exposure Time Clothing Activity College-age Female 32 Male 32 Female Total 64 3 hours 0.5clo 1 met (Sedentary) MT(°F 81 84 88 84 Air Temp. °F 82 85 88 84 Humidity %RH 50 50 50 80 Mean Radiant Temp. Equaled Air Temp Air Movement Mean Air Velocity (fpm) 26 87 140 203 264 321 Turbulence Intensity 0.47 0.3 0.31 Table 5.1 Experim ental Conditions. [49] For each temperature, velocity was adjusted until each participant reported “just right” more than three times. Figure 5.4 shows the voting scale used by each participant to indicate their individual thermal and comfort sensation and accepta bility of each air movement: 74 1. How do you fool 7 - 3 - 2 - 1 0 -1 -2 -3 I ........... i-----------------1 ------------------- 1 -------------------- 1 -------------------- 1 -------------------- 1 odd eool — ghly coot aoutral adghtty warm worm Hot L Do you fool this thoonal onvtronmont yncomfortablo 7 0 - 1 - 2 - 3 I------------------------1 ------------------------ 1 ------------------------ 1 oomfortoMo aSgfitty laieomfortabao aneoaifortdbfo uory aneoarfortaMa 3. Do you fool olr movomont 7 □ You □ No 4. • V yoo, do you find tho air movomonl uncomfortaMo 7 □ Yoo □ No • Whoro do you notlco tho air mouomant 7 □ lioad □ nock Q hands □ foot othor p lic u ( ) Fig. 5.4 Voting Scale. [50] Table 5.2 and Table 5.3 show the preferred air velocities for each temperature as registered by the participants. These are the ranges in velocity that I will try to maintain and distribute in the interior environment in my studies using the wind- scoop in order to keep the interior spaces well ventilated and to induce a cooling effect on the buildings occupants. 75 Female Male Male and Female 81° F 50%RH 197fpm 195fpm 195fpm 84° F 50% RH 266fpm 224fpm 244fpm 88° F 50% RH 295fpm 325fpm 31 lfpm 84? F 80% R H 289fpm 246fpm 268fpm Table 5.2 Preferred Air Velocities by the Subjects. [51] 80.6° F 84.2° F 84.2° F 87.8° F 50%RH 50%RH 80% RH 50%RH 190fpm 244fpm 268fpm 31 lfpm Table 5.3 Preferred Air Velocity. [52] The conditions matching the values in italics are closest to the prevailing climatic conditions in Douala. Therefore, in my wind-tunnel studies I will try to maintain an interior velocity between 268fpm and 31 lfpm. Tanabe concluded his studies by saying: “Since at high temperatures mean skin temperature and skin wettedness become higher than those under neutral conditions (0.6 clo, 50%RH), it is considered that air movement has much more cooling effects than predicted by (previous studies).” [53] 76 5-4 W IN D -SCO O P TEST M ETH O D O LO G Y A series of experiments were done to determine four major principles in the use of the wind-scoop in a hot-humid climate: 1) How does shape of wind-scoop affect flow rates? 2) How does size of wind-scoop affect flow rates? 3) How does scale of wind-scoop affect flow rates? 4) Distribution of air throughout the interior spaces. The objective of each set of tests is to determine whether a velocity of 246- 289fpm, as prescribed by Tanabe, (see Section 5-3) can be maintained in each interior space to cool the occupants. Equations used to find velocity and flow rates are: Velocity: V=v /(P/12 x 62.41b/sq.ft/0,00119 = Feet/sec Feet/sec x 60sec/min = Fpm (Feet/min)/88 = Mph Flow R ates (Q): Q= Area ft^ x Velocity ft/min Where: P = Pressure in inches water. Pressure readings on models are measured in the wind tunnel as described below. Where: Q= in cfm Note: This assumes uniform velocity and no turbulence within the ducts. 77 Each model was constructed of 1/8" plexiglass in the USC School of Architecture Model Shop. Plexiglass was used in order to keep the inside air flow smooth and frictionless. All edges were sanded smooth and glued together. The first phase of tests were conducted in the School of Architecture Wind-Tunnel which has a maximum height of 10" and all model testing was done within this constraint. A larger wind-tunnel at the USC Department of Aerospace Engineering, with di mensions 24" x 30" x 10', was used for the studies which test how scale affects flow rates. Pitot tubes were attached at one end to the wind-tunnel's manometer and at the other end to the pitot tubes on the model. This way, pressure readings at different points of the model, such as the inlet and outlet, could be recorded and used to calculate velocity and flow rates. The models were secured to the base of the wind-tunnel with clear tape and the tunnel turned on at the speed simulating outdoor conditions. 5-4.1 How Does Shape Of Wind-Scoop Affect Flow Rates? Experiment #1 Tunnel Conditions: Barometer: 30 Tunnel Temperature: 78° F Tunnel Velocity: 27mph. A preliminary test shaft was constructed of plexiglass as shown in figure 5.5. 78 HOUJ DOES SHAPE OF LUINP-SCOOP AFFECT FLOLU RATES? EHPERIMENT # 1 : PREL1MINRRV TEST SHAFT SIDE UIEUJ Points where pressure readings are taken in the wind-tunnel PREUR1LING WIND IN LE T i i i t i i / V < r i i I l OUTLET Path of air mouernent inside shaft SCALE: 5/4"= 1 0 -P" Fig. 5.5 79 Pressure readings were taken at the inlet and outlet and flow rates calculated. Changes in pressure values at the outlet indicate the velocity and volume of air that may be available for distribution in upper levels.: Inlet(A) Pressure= 0.03 Velocity =A().03/12 x 62.41b/sq. ft) / 0.00119 = 11.4ft/sec 11.4 ft/sec x 60sec/min = 687 fpm 687 ft/min / 88 = 7.8mph Flow Rate (T T ) = A x V = 0.016 ft2 x 687 fpm =10.73 ftVmin Outlet(B) Pressure= 0.25 Velocity =7/0.25/12 x 62.41 / 0.00119 = 33 ft/sec 33ft/sec x 60sec/min = 1983fpm 1983ft/min / 88 = 22.5mph Flow Rate fOl = 0.019ft2 x 1983fpm =37ft3 /min The purpose of this preliminary test model was to determine whether any air would enter into the wind-scoop at all and if so, at what flow rates? The calcula tion results indicate that the volume of air flow in the scoop and its velocity may be sufficient to be branched off into different levels for ventilation purposes. Since the air is to be channeled directly into the spaces from the scoop, the con figuration and dimensions of this particular scoop causes constraints. The width of this model is 1", representing 10', and in order to ventilate spaces larger than this air would have to channelled from the length of the scoop through ducts into the space. This is not ideal because each time the air path changes direction there will be a decrease in velocity. Other models with a broader base were constructed so that air can be fed directly into interior spaces through openings in the length 80 of the scoop. The following series of tests were done on these models to deter mine how shape affects velocity. Experiment #2 Tunnel Conditions: Barometer: 30.1 Tunnel Temperature: 79 F Tunnel Velocity: 27mph The drawings and pictures below are of the different shapes that were tested in the tunnel. Arrows on the diagrams indicate the path of air flow. The corresponding flow rates and velocities were calculated and are included. The dimensions kept constant for each scoop are (scale= 1" = 10"): 1) Length of inlet# 1 was kept constant at 2". 2) Inlet# 1 depth = 1" 3) Inlet# 1 width = 1.25" 81 RESULTS: WIND-SCOOP SHAPE #1 Inlet #1(A) Pressure= 0.04 V=/0.04/12 x 62.41b/sq.ft) / 0.00119 = 13.22ft/sec = 13.22 x 60sec/min = 793fpm = (793fpm) / 88 = 9mph R ow Rate (Q2) = A x V = 0.018ft2 x 793fpm = 14.62ft3 /min Inlet #2(B) Pressure: 0.35 V=y?0.35/12 X 62.4 lb/sq.ft / 0.00119 = 39.1 ft/sec x 60sec/min = 2346 fpm = (2346fpm) / 88 = 26mph R ow Rate (Q2) = A x V = 0.014ft2 x 2346fpm = 32ft3 /min Total Inlet R ow Rate Q1 + Q2 = 47.5 ftVmin Outlet(C) Pressure = 0.3 V=/(0.3/12 x 62.41b/sq.ft) / 0.00119 = 36.2 ft/sec = 36.2 x 60sec/min = 2172fpm = 2172fpm / 88 = 24.6mph R ow Rate (Q3) =.017ft2 x 2172fpm =37ft3 /min 82 EHPERIM ENT # 2 : H01II DOES SHAPE OF 1DIND-SCOOP Path of air movement inside shaft z ^ z . . . . . f r . . . . . . . . . . . . . . OUTLET .Points tvhere pressure readings are taken in the Lvind-tunnel SCALE: 5/4"° 1 Q -Q1 ' INLETS Fig 5.6 SCOOP #1 SIDE DIE1D RFECT FLOUJ ROTES? PR EUR IL IN 83 E H P E R IM E N T * 2 : HOW DOES SHAPE OF t lH N D -S C O O P RFECT FLQIU RATES? SCPPP- * 2 SIDE UIEW PRESJRSLSNS W IN D INLETS \ J r OUTLET -4—i. h / ~ Points inhere pressure readings are taken in the wind-tunnel Path of air mouement inside shaft SCALE: 5 / 4 " = 1Q'-0" Fig. 5.7 84 RESULTS WIND-SCOOP SHAPE #2 Inlet #1(A) Pressure = 0.01 V= /(0.01/12 X 62.41b/sq.ft) / 0.00119 = 6.6ft/sec = 6.6ft/sec x 60sec/min = 396fpm = 396fpm / 88 = 4.5mph Flow Rate (Q1 ) = A x V = 0.018ft2 x 396fpm = 7.3ft3 /min Inlet #2(B) Pressure = 0.016 V = /( 0.16/12 X 62.41b/sq.ft) / 0.00119 = 26ft/sec - 26ft/sec x 60sec/min = 1586fpm = 1586fpm / 88 = 18mph Flow Rate (Q2) = A x V = 0.016ft2x 1586fpm = 25ft /min Total Flow Rate (Q1 + Q2)= 32ft3 /min Outlet(C) Pressure = 0.14 V= 7(0.14/12 X 62.41b/sq.ft) / 0.00119 = 24.7ft/sec = 24.7ft/sec x 60sec/min = 1484fpm = 1484fpm / 88 = 16mph Flow Rate (Q3) = A x V = .007ft2 x 1484fpm = 10.38ft3 /min 85 E H P E R IM E N T # 2 : HOLU POES SHAPE OF W I N D - S C O O P RFECT FLOW BATES? S CQLDEJPJE SIDE UIEUJ PREURILING W IN D OUTLET INLETS Points inhere pressure readings are taken in the luind-tunnei Path of air mouement inside shaft OUTLET SCBLE: 5 / 4 “= 1 O'-O" Fig 5.8 86 RESULTS: WIND-SCOOP SHAPE #3 Inlet #1(A) Pressure= 0.02 V=j/(0.02/12 x 62.41b/sq.ft) / 0.00119 = 9.3ft/sec = 9.3ft/sec x 60sec/min = 558fpm = 558fpm / 88 = 6.3mph R ow Rate (Q l) = A x V= 0.018ft2x 558fpm = 10.04ft3/min Inlet #2(B) Pressure # 2= 0.25 V= 7(0.25/12 X 62.41b/sq.ft / 0.00119 = 33ft/sec = 33ft/sec x 60sec/min = 1983fpm = 1983fpm / 88 = 22mph R ow Rate (Q2) = A x V = 0.014ft2 x 1983fpm = 2.7ft /min Total Inlet R ow Rate (Ql+Q2)= 37.04ft3 /min Outlet(C) Pressure = 0.18 V = /0 .18/12 X 62.4 / 0.00119 = 28.04ft/sec = 28.04ft/sec x 60sec/min= 1682fpm = 1682/88 = 19mph R ow Rate (Q3) = A x V =.007ft2 x 1682fpm= 12ft3 /min 87 EHPERIMENT * 2 : HOW DOES SHAPE OF W IND-SCOOP RFECT FLOW RRTES? SCOOP . * 4 SIDE DIELD P R E U M L tN G W IN D OUTLET INLETS Points where pressure readings are taken in the wind-tunnel Path of air movement inside shaft OUTLET SCBLE: 3 / 4 - - 10 -0 " Fig. 5.9 88 RESULTS: WTND-SCOOP SHAPE #4 Inlet #1(A) Pressure= 0.01 V= y 0.01/12 X 62.41b/sq.ft / 0.00119 = 6.6ft/sec = 6.6ft/sec x 60sec/min = 397fpm = 397fpm / 88 = 4.5mph How Rate (Q l)= A x V= 0.018ft2 x 397 = 7,146ft3/min Inlet #2(B) Pressure= 0.18 V =/(0.18/12 x 62.41b/sq.ft/0.00119 = 28ft/sec =28ft/sec x 60sec/min = 1682fpm = 1682fpm /88 =19mph How Rate (Q2) = A x V= 0.016ft2 x 1682fpm= 26ft3 /min Total Inlet How Rate= 34.05ft3 /min O utlet(C) Pressure= 0.12 V = /0 .12/12 X 62.4 / 0.00119 =22.8ft/sec =22.8ft/sec x 60sec/min = 1368fpm =1368fpm /88 =15.5mph How Rate (Q3) = .007ft2 x 1368fpm= 9.6ft3 /min 89 EXPERIMENT * 2 : HOLU POES SHAPE OF IDIND-SCOOP RFECT FLQUJ RRTE$? .& CPQP * 5 SIDE DIELU PREVAIL ING W IND ft— INLETS Points where pressure readings are taken in the wind-tunnel Path of air mouement inside shaft OUTLET SCRLE: 3 / 4 " = 1 0 -O'1 Fig. 5.10 90 RESULTS: WIND-SCOOP SHAPE #5 Inlet #1(A) Pressure= 0.04 V= v/(0.04/12 X 62.41b/sq.ft / 0.00119 = 13.2ft/sec = 13.2ft/sec x 60sec/min = 792fpm = 792fjpm / 88 = 9mph Flow Rate (Q l)= 0.014ft2 x 792fpm= 11.08ft3/min Inlet #2(B) Pressure= 0.27 V=v 6.27/12 x 62.41b/sq.ft) / 0.00119 = 34ft/sec = 34ft/sec x 60sec/min = 2060fpm = 2060fpm / 88 = 23mph Flow Rate (Q2) = 0.014ft2 x 2060fpm= 28.84ft3 /min Total Inlet Flow Rate= 39.92ft3 /min Outlet(C) Pressure= 0.17 V= y 0.17/12 x 62.41b/sq.ft / 0.00119 = 27.2ft/sec = 27.2ft/sec x 60sec/min= 1632fpm = 1632fpm / 88 = 18.5mph Flow Rate (Q3)= .007ft2 x 1632fpm = 11.4ft3 /min 91 5-4.2 How Does Size O f Wind-Scoop Affect Flow Rates? The shape of the wind-scoop in figure 5.6 was selected for further study for two reasons: The resulting velocities and flow rates are within Tanabes’ recommended values, and the broader base of the wind-scoop, (representing 25 feet full-scale), will allow the air to be suctioned directly into interior spaces of the same width.) The objective of the following tests was to determine the optimum wind scoop inlet depth and width. The inlet length was kept constant at 2" for each study and the tunnel velocity at 27mph. Figures 5.11 and 5.12 show the combination of width and depth that I tested. These are: 3/4", 1", 1.25" and 1.5". Table 5.3 gives the resulting flow rates and velocities for each test. These results were used to make graphs (for each inlet depth: figure 5.13) showing: 1) Inlet Flow Rate / Width. 2) Inlet Velocity / Width. 3) Outlet Flow Rate / Width The objective of the test was to see which scoop induces a high volume and high velocity of air so that sufficient air would be available to be brought into each level. The highest velocity and flow rates were obtained with the scoop measur ing 3/4" depth x 1.25" width so these dimensions will be used for further study as described below. The inlet #1 depth was changed for each of the w idth dimensions shown in figure 5.12. Inlet #1 depth: 1 Inlet # / depth: 1.25” Inlet #1 depth: 1.5” Fig. 5.11 W ind-Scoop Inlet D epths Tested 93 Inlet # 1 width dimensions was changed for each of the depth dimensions shown in figure 5.11. Inlet #1 width: 1 Inlet #1 width: 3 / 4 .1 ^ H , B __ _JB r _ C - " .1 V Inlet # / width: 1.25 " Inlet #1 width: 1.5" Fig. 5.12 W ind-Scoop Inlet W idths Tested TABLE 5-4a HOW DOES SIZE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS 3/4"DEPTH INLET #1 INLET #2 INILET TOTAL O UTLET P V(FPM) V(MPH) Q(F3 /MIN) P V(FPM) V(MPH) (XFI^/MIN) V(FPM) V(MPH) QiFf/MIN) P QCFI^/M IN) 3/4"WIDTH .02 538 6.3 2.17 .33 2278 25 10.2 2816 32 12.44 0.3 36.72 1 "W IDTH .01 396 4.5 2.06 .34 2310 26.25 12.01 2706 30.51 14.07 .28 35.59 1.25"W IDTH .016 501 5.7 3.26 .32 2243 25.3 16.48 2744 31.18 20.74 .33 40.69 1.5" W ID TH .012 432 4.9 3.37 .34 2310 26.25 20.79 2742 .3 24.09 .28 35.5 1" DEPTH 3/4"WIDTH .03 336 7.2 3.3 .33 2394 27 10.77 3030 31.3 14.07 .3 36.72 1" WIDTH .02 516 5.8 3.5 .34 2310 26.25 12.01 2826 32.05 15.51 .29 36.21 1.25" W ID TH .04 792 9 9.6 .35 2346 26.6 11.46 3138 35.6 21.06 .3 36.72 1.5" W ID TH .045 841 9.5 8.7 .34 2310 26.25 20.79 3151 35.75 29.49 .34 39.27 V O TABLE 5-4b HOW DOES SIZE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS 1.25" D E P T l INLET #1 IN LE T #2 INLET TOTAL O U T L E T P V(FPM) V(MPH) Q(FT3 /MIN) P V(FPM) V(MPH) CKFI^/M IN) V(FPM) V(MPH) Q(FT3 /MIN) P 0(F3 /MIN) 3/4"WIDTH .05 882 10 8 .34 2310 26.25 10.39 3192 36.25 18.39 .25 33.71 1"W IDTH .05 882 10 6.1 .34 2310 26.25 12.01 3192 36.25 18.25 .31 37.53 1.25"WIDTH .045 841 9.5 8.41 .36 2379 27.6 17.04 3220 36.5 26.25 .3 36.72 1 .5" W ID TH .045 882 10 10.02 .35 2346 26.6 21.1 3228 36.6 31.34 .3 36.72 1.5" D E P T H 3/4"WIDTH .06 971 11.04 12.6 .33 2278 25 10.25 3365 36.04 23.37 .3 36.72 1 " WIDTH .068 1034 11.7 10.7 .34 2310 26.25 12.01 3344 37.95 22.7 .3 36.72 1.25" WIDTH .08 1080 12.2 14 .32 2243 25.4 16.82 3322 37.68 30.82 .28 35.5 1.5" WIDTH .08 1080 12.2 16.8 .35 2346 26.6 21.14 3426 38.85 37.94 .3 36.72 'O HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? GRAPHIC RESULTS 97 Fig 5.13 G raphic results of "H ow does size of wind-scoop affect flow rate?" HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 3/4" E x a H < 06 £ O fc H W h J 2 5 ]..5' 20 - 1.25 3/4' 1.4 1.6 0.6 0.8 1 .0 1 .2 INLET WIDTH (INCHES) HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 3/4" 2 8 2 0 3/4' 2 8 0 0 - 2 7 8 0 - H U o 2 7 6 0 - i — a E x a > H 2 7 4 0 - E x a 5 1.5 2 7 2 0 - 2 7 0 0 1.6 1.4 0.8 1.0 1.2 0.6 INLET WIDTH (INCHES) 98 HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 3/4” fa H < P i & o fa fa H fa fa H fa O 42 1.25 40 - 3 9 - 3 8 - 3/4' 37 3 6 - :l .5! 3 5 1.2 0.6 0.8 1.0 1.4 1.6 INLET WIDTH (INCHES) HOW DOES SIZE OF WIND-SCOOP AFFECT FLOW RATES? DEPTH: 1" 40 3 0 20 - :L.25! 3/4' 1 .6 0.6 1 .0 1.2 1.4 0.8 INLET WIDTH (INCHES) IN L E T VELOCITY (FPM) 99 HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1" 3 2 0 0 1.5 1.25' 3 1 0 0 - 3/41 3 0 0 0 - 2 9 0 0 - 2 8 0 0 1.2 1 .4 1.6 0.6 0.8 1 .0 INLET WIDTH (INCHES) HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1" 1 w H < £ o p fc H W P H P O 4 0 1.5 3 9 - 3 8 - 3/4’ 1.25 3 7 3 6 3 5 1 .4 1.6 1.2 0.8 1 .0 0.6 INLET WIDTH (INCHES) 1 0 0 WINDSCOOP DEPTH: 1.25" w H < P i £ o J ta H W J 5 40 1.5 3 0 - 1.25 3/4’ 20 - -= & 1.4 1 .6 1.8 0.6 0.8 1.0 1.2 INLET WIDTH (INCHES) HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1.25" 3230 £ 3220 I e 0 32 1 0 O J W > a 3200 3 1 90 0.6 0.8 1.0 1.2 1.4 1.6 INLET WIDTH (INCHES) 1.25 3/4 1 0 1 HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1.25" P V w H < C 4 £ O u < H W 3 9 3 8 3 7 3 6 3 5 3 4 3/4' 3 3 3 2 0.8 1.2 0.6 1.0 1.4 1.6 INLET WIDTH (INCHES) HOW DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1.5" H f e - W H < P C & o H W s 40 1.5 1.25 3 0 - 3/4' 20 1 .8 1.2 1.4 1.6 0.8 1.0 0.6 INLET WIDTH (INCHES) OUTLET F L O W R A T E (FT^MIN) o IN L E T VELOCITY (FPM) 1 0 2 HOW DOES SIZE OF WIND SCOOP AFFECT FLOW RATES WINDSCOOP DEPTH: 1.5" 3 4 4 0 3 4 2 0 - 3 4 0 0 - 3 3 8 0 - 3/4' 3 3 6 0 - 3 3 4 0 - 3 3 2 0 0.6 0.8 1.0 1.2 1.4 1.8 1.6 INLET WIDTH (INCHES) W DOES SIZE OF WINDSCOOP AFFECT FLOW RATES? DEPTH: 1.5 37.0 1.5 36.5 - 36.0 - 35.5 1.25 35.0 1.0 1.8 0.6 0.8 1.2 1.4 1 .6 INLET WIDTH (INCHES) 103 The next level of testing was to construct another model, at the optimum wind- scoop dimensions, which includes different floor levels and openings from the tower to feed air into interior spaces on each level (see figure 5.14). The model shows the points where pressure readings were taken on each level in order to velocity and flow rates. The results are on Table 5-5. Fig. 5.14 Table 5.5: HOW DOES SIZE OF WIND-SCOOP AFFECT FLOW RATES?- RESULTS WIND-SCOOP INLF.T- DEPTH: 3/4" WIDTH: 1.25" In let# !: P= 0.02 Inlet#2: P= 0.45 V= 560fpm V= 2660fpm = 6.3mph =30mph Flow Rate= 560 x 0.22ft2 Flow Rate= 2660 x 0.008ft2 = 12.3ft3/min = 22.8ft3/min Total Inlet Flow Rate = 35.15 ft-/min VELOCITY (FPM) Q(FT3/MIN) Level Outlet 1 Pt. 1 Pt. 2 Shaft Inlet 1 Scoop Shaft Shaft Inlet 2 Pt. 3 Pt.4 Outlet 2 1 V=2600 Q=11.18 2600 2600 V=2806 Q=12.04 2400 2800 Q=12.04 2600 2600 V=2600 Q=11.18 2 V=2600 0=11.18 2600 2600 V=2600 Q=11.18 2600 2700 Q=11.61 2650 2650 V=2700 Q=11.61 3 V=2550 Q= 10.96 2550 2550 V=2550 Q=10.96 2550 2650 Q=11.4 2600 2600 V=2600 Q=11.18 105 The values in Table 5.5 are helpful in that they show that flow rates remain fairly constant on each level and within a small range in different levels. However, the graphs in figure 5.13 indicate that no true conclusion can be drawn on flow rates or velocities because the scale of the models is so small and constricting that air flow inside the scoop is turbulent. 5-4.3 How Does Scale Of Wind-Scoop Affect Flow Rates? The graphs in figure 5.13 show that these wind-scoops are out of the range of the Reynold's number, therefore, I had to establish a scaling factor for further tests and in order to achieve a smoother flow of air within the model, studies had to be done at a larger scale. Because of its larger size, the wind-tunnel at the USC De partment of Aerospace Engineering was used for both purposes. The model con figuration shown in figure 5.14 was reconstructed at three different scales; lx , 2x, 3x, keeping the proportions constant as seen in figure 5.15. Each was tested at four different tunnel velocities: 9mph, llm p h , 27mph, 34mph and the results are shown in the following charts and graphs. 106 Fig. 5.15 Pictures of models tested at different scales Original M odel Twice Original Size 107 Three Times Original Size 108 HOW DOES SCALE OF WIND SCOOP AFFECT FLOW RATES? R ESU LTS Flq . 5 . 1 6 HOUJ DOES SCHLE OF W I N D - S C O O P BFFECT FLOIU BHTES? SCOOP INLET Front Uieiu of Ulind-Scoop #1 (Original Model) Scale: 3/4"= 1Q '-Q ’ niet n l^ - i I Scoop Inlet # I Point 1 I Scoop Inlet # • • Point 1 1 Air In PITDT TUBES Shaf Shaft • Scoop Inlet • Point 2 i Top Level [ • Scoop inlet • Point 2 i Middle Level | Scoop Inlet • 1 Point 1 S haft Scoop Inlet Point 2 Bottom Level J " 1 1 0 Fig. 5.17 HOW DOES SCALE OF W IND-SCOOP AFFECT FLOW RATES? F T A SCOOP TN T,RTS INLETS PR EUR ILING WIND OPENING FROM SCOOP SHAFT INTO SPACES TOP LEU EL MIDDLE LEUEL BOTTOM LEUEL Outlets at ceiling leuel and middle of each floor (50% opening) S IDE. DIEIP P f .illlN IL=S£D. QE..* J ; ALL PANELS AT OUTLET S c ale L. 3M l= _ m iQ : ORIGINAL MODEL SCBLE TABLE 5,6 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Velocitv= 9mph Scale: Original Model Inlet #2 P= 0.05 V= 900fpm Flow Rate= 900fpm x .008 =7.2ft^/min TOTAL INLET FLOW RATE= 17.98ft3/min VELOCITY (FPM) Q(FT3 /MIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SCOOP SHAFT SCOOP INLET 2 POINT 2 O u t l e t 2 1 V=890 890 V=890 890 V=910 890 V=890 Q=3.83 Q=7.74 Q=3.91 Q=3.83 2 V=890 890 V=890 % 9 0 V=910 890 V=890 Q=3.83 Q=7.74 Q=3.91 Q=3.83 3 V=890 890 V=890 890 V=900 890 V=8$ ) Q=3.83 Q=7.74 Q=3.87 Q=3.83 Inlet #1: P=0.015 V=490fpm Flow Rate= 490fpm x .022 = 10.78ft-/min TABLE 5.7 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RF.StH.TS Tunnel Velocitv= llmph Scale: Original Model Inlet #1: Inlet #2 P=0.03 P= 0.0S V=700fpm V=1130fpm Flow Rate= 700fpm x .022 Flow Rate= 1130fpm x .008 = 15.4ft3/min =9.04ft^/min TOTAL INLET FLOW RATE = 24.44ft3/min VELOCITY(FPM) Q(FT3/MIN) LEVEL OUTLET 1 POINT 1 SCdOP INLET 1 SCOOP SHAFT SCOOP INLET 2 POINT 2 Ou t l e t 2 1 V=1130 Q=4.86 1130 V=1170 Q=5.03 1180 V=1130 Q=4.86 llt o v = n io Q=4.86 2 V=1130 Q=4.86 1130 V=1130 Q=4.86 1060 V=1130 Q=4.86 11^0 V=1130 Q=4.86 3 V=1136 Q=4.86 1180 V=1130 Q=4.86 1060 V=1130 Q=4.86 1130 V=1130 Q=4.86 112 TABLE 5,8 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Velocitv= 22mph Scale: Original Model Inlet #2 P= 0.3 V= 2200fpm Flow Rate= 2200fpm x .008 =17.6ft-/min TOTAL INLET FLOW RATE= 45.32ft2/min VELOQTY (FPM) Q(FT3/MIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SCOOP SHAFT SCOOP INLET 2 POINT 2 O u t l e t 2 1 V=2200 Q=9.46 2200 V=2300 Q=9.89 2200 V=2300 Q=9.89 2200 V=2100 Q=9.03 2 V=2200 Q=9.46 2200 V=2200 Q=9.46 2100 V=2200 0=9.46 2200 V=2200 Q=9.46 3 V=2200 Q=9.46 2200 V=2100 Q=9.03 2100 o < n i t V O N > & § 2200 V=220(i Q=9.46 Inlet #1: P=0.1 V= 12600fpm Flow Rate= 12600fpm x .022 = 27.72ft-/min 113 F ig , 5 , 1 8 HOW DOES SCALE OF U JIN D -SC O O P AFFECT FLOW RATES? SCQQP INLET Inlet 1 Front Uieui of Illind-Scoop #1 (Turne the size of original model) Scale: 3/4"= 20'-0“ nlet t 1 • Scoop Inlet 1 • ■ Point 1 1 • 1 • j Point 1 Air In Shaft Shaft tu b e s * Scoop Inlet • Point 2 i Top Level f • • i Point 2 Middle Level | 1 • i I Point 1 Shaft Point 2 , I . . ........................ Bottom Level | TABLE 5.9 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Ve1ocitv= 9mph Scale: 2 x Original Model Inlet #1: Inlet #2 P=0.03 P= 0.07 V=700fpm V= 1060fpm Flow Rate=700fpm x .044 Flow Rate= 1060fjpm x .016 = 30.8ft3 /min =16.96ft3 /min TOTAL INLET FLOW RATE= 47.76ftVmin VELOC3TY(FPM) Q(FT7MIN) LEVEL OUTLET 1 POINT 1 SC 06P INLET 1 SC 60P SHAFT SCOOP INLET i POINT i OtJTLET2 1 V= £ > 8 6 m V=8^0 V=08O V=^80 Q=8.53 Q=7.74 Q=8.53 Q=8.53 1 V=98ti ^80 V=$$6 1060 V=980 i6i6 v=46d Q=8.53 Q=8.53 Q=8.53 Q=8.53 V=980 980 V=1060 1060 V=1060 1060 V=980 Q=8.53 Q=9.22 Q=9.22 Q=8.53 115 TABLE 5.10 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? - RESULTS Inlet #1: P=0.048 V= 880fpm Flow Rate=880fpm x .044 = 38.72ft%rin Tunnel Velocitv= llmph Scale: 2 x Original Model Inlet #2 P= 0.11 V= 1330fpm Flow Rate= 1330fpm x .016 =21.28ft2 /min TOTAL INLET FLOW RATE= 60ft2 /min VELOCITY (FPM) Q(FP/MIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SCOOP SHAFT SCOOP INLET 2 POINT 1 OUTLET 2 1 V=1130 Q=9.83 1170 V=1170 0=10.18 liSO V=1180 0=10.27 1160 V=1200 0=10.44 2 V=1200 0=10.44 1160 o I I I I ><y 1190 V=1390 0=12.09 1260 V=1200 Q=10.44 i V=122ti Q=10.44 12O 0 V=1190 Q=10.35 1200 V=1130 Q=9.83 1200 V=1200 0=10.44 116 TABLE 5,11 HOW POES SCALE OF WIND-SCQOP AFFECT FLOW RATES? - RESULTS Tunnel Velocitv= 22mph Scale: 2 x Original Model Inlet #2 P= 0.3 V=2200fpm Flow Rate= 2200fpm x .016 =35.2fta /min TOTAL INLET FLOW RATE= 114.4ftVmin VELOCTTY(FPM) QtFTTMIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SOoOP SHAFT StOO P INLET 2 PO lN T l O u t l e t 2 1 V=2256 Q=19.58 2400 v=15to Q=20.01 2300 V=25(J6 Q=21.75 Hod V=24O0 Q=20.88 2 V=2200 Q=19.14 2i56 V=23M Q=20.01 2180 V=2300 Q=20.01 15oo V=l300 Q=20.01 3 V=24(to Q=20.88 2400 V=l4$0 Q=21.66 2160 V=l4 ( K ) 0 =21.66 l5b0 v 3 4 d 0 Q=20.88 Inlet #1: P=0.2 V= 1800fpm Flow Rate=1800fpm x .044 = 79.2ft2 /min TABLE 5.12 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES?- RESULTS Tunnel Velocitv= 37mph Scale: 2 x Original Model Inlet #1: Inlet #2 P=0.6 P= 1.3 V=3100fpm V= 4550fpm Flow Rate=3100fjpm x ,044ffi Flow Rate= 4550fpm x ,016ft^ = 136.4ft2 /min =72.8ftVmin TOTAL INLET FLOW RATE= 209.2tf/min VELOOTY(FPM) (XFTYMIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SCOOpSh a f t SCOOP INLET 2 POINT 2 O u t l e t 2 1 V=4000 Q=34.8 4000 V=3900 0=33.93 3900 V=420O 0=36.54 4000 V=4O0O Q=34.8 2 V=3900 0=33.93 400O V=4000 Q=34.8 4700 V=4000 Q=34.8 4000 v =380o 0=33.06 3 V=4000 Q=34.8 4000 V=4000 Q=34.8 3900 V=4000 0=34.8 4000 0=34.8 118 F l a . 5 . 1 9 HOUJ DOES SCBLE OF U J I N P -S C O O P HFFECT FLOW ROTES? SCOOP INLET FRONT IfIEIII O F IVIND-SCOOP #1 (Three times size of original modell Scale: 1/4*. 1Q'-(T Inlet nlet • - Point 1 • Scoop Inlet • I Scoop Inlet 1 • Point 1 Air In Brass tubing for attachment to pitot tubes Shaft S haft * Scoop Inlet Point 2 i Top Level [ • Scoop Inlet • Point 2 I Middle Level [ 1 r I Scoop Inlet Scoop Inlet 1 1 • • • 1 Point 1 Shaft Point 2 i 1 Bottom Level | J - TABLE 5.13 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Velocitv= 9mph Scale: 3 x Original Model Inlet #1: Inlet #2 P=0.45 P= 0.85 V= 840fpm V= 1160fpm Flow Rate=840fpm x .066 Flow Rate= 1160fpm x .024 =55.4fta /min =27.84ft3 /min TOTAL INLET FLOW RATE= 83.28ftVmin VELOCITY(FPM) CXFP/MIN) LEVEL OUTLET 1 POINT 1 S t0 6 P INLET 1 sC o6 p S h a f t SCOOP INLET 2 POINT 2 o u t u S t I 1 V=1060 Q=13.78 1016 V=1110 0=14.43 1010 V=1060 0=13.78 1066 v =i 616 0=13.91 2 V=1060 Q=13.78 i'0'26 V=1030 Q=13.39 1020 V=1050 0=13.65 1620 v= 9to Q=12.74 3 V=1000 Q=13 980 o < i i i i 1060 V=l626 0=13.26 o o v=i666 0=13 TABLE 5.14 HOW POES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Velocitv= llmph Scale: 3 x Original Model Inlet #2 P= 0.13 V= 1440fpm Flow Rate= 1440fpm x .024 =34.5< ?ft^M a TOTAL INLET FLOW RATE= 109.8ft2/min VELOCITY(FPM) Q(FT3/MIN) LEVEL OUTLET 1 POINT 1 SCOOP INLET 1 SCOOP Sh a f t SCOOP INLET 2 POINT i O u t l e t 2 1 V=1330 Q=17.29 1260 V=1330 Q=17.29 1140 V =li60 0=16.38 1260 0=16.38 2 V=1340 Q=17.42 1330 V=1390 Q=18.07 l&O V=1390 0=18.07 1330 v =1330 Q=17.29 3 V=13^0 Q=17.29 1336 V=1366 0=17.68 1370 V=1370 0=17.81 1330 v =i 350 Q=17.55 M et# l: P=0.081 V= 1140fpm Flow Rate=l 140fpm x .066 =75.24ft^/min TABLE 5,15 HOW. DOES SCALE OF WINP-SCOQP AFFECT FLOW RATES? - RESULTS Tunnel Velocitv= 22mph Scale: 3 x Original Model Inlet #1: Inlet #2 P=0.31 P= 0.5 V= 2200fpm V= 2750fpm Flow Rate=2200fpm x .066 Flow Rate= 2750fpm x .024 =145.2ft3 /min =666fta /min TOTAL INLET FLOW RATE= 21L2ftVmin VELOCITY (FPM) Q(FT7MIN) LEVEL OUTLET 1 POINT 1 SCOOP INLfeT 1 SCOOPSHAFT SC 60P INLET 2 POINT 2 Ou t l e t 2 1 V=l540 Q=33.02 2530 V=2560 Q=33.28 25$0 V=2520 0=32.76 2530 V=2540 Q=33.02 2 V =l5i0 Q=32.76 2530 V=2520 Q=32.76 25^0 V=2530 Q=32.89 2530 V=2520 0=32.76 3 V=l4W) Q=31-2. 2500 V=25O0 Q=32.5 2566 V=2500 0=32.5 2500 V=24O0 Q=31.2 122 TABLE 5.16 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? ■ RESULTS Tunnel Velocitv= 37mph Scale: 3 x Original Model Inlet #2 P= 1.43 V= 4800fpm Flow Rate= 4800fpm x .024 =115.2ft^/min TOTAL INLET FLOW RATE= 379.2ft2/min VELOdTY(FPM) Q(FT3/MIN) LEVEL Ou t l e t i POINT 1 SCOOP INLET 1 SOOOp s h a f t IScOOP INLET 2 POINT 2 O u t l e t 2 1 V=4200 Q=54.6 4200 V=4466 Q=57.2 4660 V=4060 Q=52 4360 V=4000 Q=52 2 V=4000 Q=52 4460 Q < N ^ v -j I t I I ><y 4660 V=4600 Q=59.8 4400 V=4406 Q=57.2 3 V=3866 Q=49.4 3900 V=4000 Q=52 46oo V=4006 Q=52 4060 V=3866 Q=49.4 Inlet #1: P=1.05 V= 4000fpm Flow Rate=4000fpm x .066 =264ft^/min AVERAGE VELOCITY (FPM ) AVERAGE VELOCITY (FPM) 124 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? TUNNEL VELOCITY: 9MPH 1 1 0 0 1 ooo - 900 - 800 0 2 3 4 MODEL SCALE Fig. 5.20 HOW DOES SCALE OF WINDSCOOP AFFECT FLOW RATES? TUNNEL VELOCITY: 11MPH 1400 1300 - 1 200 - 1 1 00 3 2 4 MODEL SCALE Fig. 5.21 125 HOW DOES SCALE OF WIND-SCOOP AFFECT FLOW RATES? TUNNEL VELOCITY: 22MPH E > * & u o -J m > w o < 06 0 6 > < 2 6 0 0 2 5 0 0 2 4 0 0 2 3 0 0 2200 2 1 00 0 2 3 4 MODEL SCALE Fig. 5.22 The graphs do not indicate any type of scale factor as initially expected and this can mean one of two things: 1) The graphs may indicate that even at this scale of testing, the models are still outside the range of the Reynold’s number and there is a lot of turbulence inside the spaces, 2) a 9mph wind outside, for example, can actually induce velocities inside the space of over 30mph. As a point of study, it is apparent that if the values for the scales are extrapolated ten times to fu ll scale (the models are 1/10 of full scale) the interior velocities will be in excess of 1350fpm even at a tunnel velocity of 9mph. Though these values are exceedingly high, what these studies indicate is that the wind-scoop can be used to ventilate spaces because air is moving through the interior. It may be a matter of management carefully moni toring the volume and velocity of air allowed into each space. 126 DISTRIBUTION STUDIES 127 5-4.1 Interior Air Distribution It is very important that any air entering the spaces be distributed evenly through out the room as much as possible. In terms of human comfort, this distribution should be within the 2.5' - 6' range so that occupants may be well ventilated while seated and standing up. Based on Tanabes’ studies, in “cooler” weather, it is more important to have a greater volume of air through the space than it is to have high velocities. However, when it is very hot, it is more important to have a higher wind velocity for evaporative cooling than it is to have a large volume of air through the space. Figure 5.23 shows how air is siphoned back into the interior spaces when using wind-scoop #1. From distribution studies, air is drawn into inlet #1 where there is a positive pressure, and exits through the outlets on lower levels where there is a negative pressure. However, because inlet #2 is actually perpendicular to the prevailing wind, as the air passes over the opening, it creates a negative pressure and air is drawn back outside of this inlet from the outlets of lower levels. This is contrary to what was expected when this particular wind-scoop con- figuuration was selected to be tested further in my studies. However this scoop presents interesting architectural possibilities. It is feasible that inlet #1 may be oriented in the direction of the prevailing wind and its flushing effect act as the main source of supply air for ventilating the lower levels. The siphoning effect of inlet #2 can be used to draw air out of the space at different times of the day, also 128 ventilating the space. In either case, this particular wind-scoop may be used effectively whether or not the inlets are in the direction of the prevailing wind. Since the net flow rates at the outlet are greater than the flow rate of the inlet from the scoop, there is considerable turbulence in the room even though the velocities range, the management can close off part or all of the scoop openings. The control of the louvered outlets can be done by the occupants. Because the interior distribution with wind-scoop type 1 was inefficient as de scribed above, I did other distribution studies using one with a completely differ ent configuration as seen in figures 5.25 and 5.26. These studies were done in wind tunnel velocities of 9mph, 1 lmph, and 22mph. The path of interior air flow was followed by using streamers, markers, and tufts as seen in the model in figure 5.15. Also, for each tunnel velocity, different outlet conditions were tested: a) 100% opening, b) 75% opening with a top panel only, c) 75% opening with a bottom panel only, d) 50% opening with a top and bottom panel at the outlet. Diagrams for each outlet condition and tunnel velocity are shown in figure 5.23 Fig. 5.23 Fifl. 5 . 2 5 DISTRIBUTION STUDIES: W I N D - S C O O P # 1 Front View of Wind Scoop S cale: 3/4"= IQ'-O" i flir returns to iniet - v _ Point 1 SCOOP INLET «-r nlet : Air In Brass tubing for attachm ent to pitot tubes Scoop Iniet * , Scoop- Inlet * ^ ' \ Scoop Inlef i w Point 1 I I • • ' i i S h i f t i K I I •! Shqft 9 • « % V Point 2 Top Level u - S^oop iniet «< - ------ v . . - ^ x ^ P o in t 2 « Middle Level , Scoop Inlet, --------------- 1 Point 1 - - • 4 Shqft Bottom Level vjScoop Ini^_______________ | I •— -M a t.2 _________ ) r to V O 130 Fig, 5.24 DISTRIBUTION STUDIES: UJINPSCOOP #1 SCOOP INLETS INLETS OPEN PREUR ILIN6 WIND OPEN TUNNEL UELOCITV: 9MPH. 11MPH. 22MPH B flB ffl MESIU...5 0 j 1 TEMPERRTURE:75 F O Location of Markers • Pita.llU bfil OPENING FROM SCOOP SHAFT ic. INTO SPACES “T TOP LEVEL FLOOR MIDDLE LEVEL FLOOR BOTTOM LEVEL FLOOR Outlets at celling leuel and middle of each floor (50% opening) SIDE UIEIU OF IDIND-SCOOP #1: RLL PANELS RT OUTLET Scale; 3/4"= IQ’-Q " Air SCOOP INLET PITOT TUBES Fig. S .2 5 DISTRIBUTION STUDIES WIND-SCOOP #2 FBONT UI t i ll OF lU IN PSCOO P: UIITH ALL OUTLET PANELS Scale: 3/4"= 1Q'-(T SHAFT IN L IST * y ," • " shaft" im.Fr 1 POINT 1 _...............^ P O IK T .l’ POINT 1 POINT 2 TCF4.EJIEL POINT 2 MIDDLELEDEL POINT 2 BOTTOM LEVEL J - 132 E l f r ^ 5 .2 6 DISTRIBUTION STUDIES; UIINDSCOOP * 2 INLET OPEN OPEN OPEN OPEN OPEN OPEN TUNNEL UELOCITV; 9MPH. 11MPH. 22MPH BAROM ETER; 50 J IEMPEBQIURE;7.S-£ O Location of M a rk e rs • PIT Q .T T U B E S OPENING FROM SCOOP SHAFT INTO SPACES r TOP LEUEL FLOOR M ID D L E LEDEL FLOOR BO TTO M LEUEL FLOOR O utlets a t ceiling leuel an d m iddle o f ea ch flo o r (50% opening) Side View of Wind S c o o p : Tiuo p r n e is at outlet S c a le : 3/4"= 1Q'-0" 133 SCOOP INLET I OUTLET 1 TOP LEUEL U= f 1 5 0 fp m Erratic s t r e a m e r m o u e m e n t !?I L O D M O D O t E Q O P S s Tun n e l UelocLty; 9 m p h BIJ Pan e ls a_t-Outle t Mouement of Markers " ' ' s M ouement of Streamers SCOOP INLET I OUTLET M IDDLE LEUEL U=1 0 9 0 fp m S tr e a m e r s pulled to iu a rd s th e left an d m a rk e r s rem a in s t a g n a n t SCOOP INLET I y OUTLET BOTTOM LEUEL U = 9 9 0 f p m Fig. 5.27 Air D istribution Studies 134 SCOOP INLET SCOOP INLET ♦ J OUTLET ^ TOP LEUEL U-1 4 5 0 fp m IPHfflW O P a H Q D P^S Tunnel Uelocity: l l m p f i Rll P a n e ls a t Outlet ,'l Uibrates OUTLET! MIDDLE LEUEL U-1 5 5 0 fp m SCOOP INLET ♦ f OUTLET BOTTOM LEUEL U -1 4 5 0 f p m Fig. 5.28 Air D istribution Studies 135 SCOOP INLET OUTLET TOP LEUEL U = 2 8 0 0 fp m M ost e rra tic s t r e a m e r m o u e m e n t on all leuels fo r this o u tle t s itu ation [ P f L G D l ^ D J 3 Q [ E D D C ^ s Tu n n e l U elo c ity : 22 m p h fill Panels at Quite! 0 -^. M o u e m e n t o f M ark ers - * * - .. M o u e m e n t o f S tre a m e rs SCOOP INLET t OUTLET MIDDLE LEUEL U = 2 8 0 0 f p m SCOOP INLET OUTLET BOTTOM LEUEL U = 2 8 0 0 f p m Fig. 5.29 Air D istribution Studies SCOOP INLET FRONT UIEUI Of UIINDSCOOP- BOTTOM OUTLET PANEL SCALE; 3/4"- 1Q'-0‘ Air In PITOTTUBE Fig. 5.30 DISTRIBUTION STUDIES WIND-SCOOP #2 < • 1 SHAFT INL£,V • ' shaft INLET POINT 1 .................. POINT 2 " " “ “ ?OFtEVfi: 1 POINT 1 POINT 2 MIDDLELEUEL - 1 I - POINT 1 "PO IN T 2' DOTTOM LEUEL ]~ 137 E l 6. 5 .3 1 DISTRIBWTI0 H L S IilH m m -IP »N PSCQQ P _ * 2 SCOOP INLET .TU N N EL UELQCITY; 9MPH,-llJdPH, 22MPH BAROMETER; 50.1 TEMPERATURES F . o Location of Markers • Pitot Tubes OPENING FROM SCOOP SHAFT INTO SPACES OPEN TOP LEUEL FLOOR OUTLET: 75% OPENING Panel at bottom of floo only OPEN MIDDLE LEUEL FLOOR OPEN BOTTOM LEUEL FLOOR Side Uieiu ofLLUirnl - Scoop: BOTTOM OUTLET PANEL ONLV Scale ;, 3/4w = , I Q'-Q " 138 SCOOP INLET OUTLET § TOP LEUEL U = 1 1 6 0 fp m SCOOP INLET 4 i t t OUTLET M ID D LE LEUEL U = 1 1 2 0 fp m SCOOP INLET FLGDM 00[]H O flflgS Tunnel U elo c ity: 9 m p h B o tto m P a n e l Only a t O u tle t M o u e m e n t of M o u e m e n t o f S tr e a m e r s ♦ OUTLET BOTTOM LEUEL U= 1 1 2 0 f p m Fig. 5.32 Air D istribution Studies 139 SCOOP INLET ♦ . i • h r ♦ » i / ; i * i t 0 0 * * 0 0 •2s . « A » 0 1 0 f * / * a ■ A • TOP LEUEL U=1 4 0 0 fp m SCOOP INLET I f MIDDLE LEUEL U=1 4 2 0 fp m SCOOP INLET iptimw qpoegqpss I i m n e l U e lo c ity :1 1 m nh ELpttom P anel Only a t O u tlet M o u e m e n t of M a rk e rs M o u e m e n t of S tre a m e rs OUTLET BOTTOM LEUEL U=1 4 2 0 f p m Fig. 5.33 Air D istribution Studies 140 SCOOP INLET r OUTLET TOP LEUEL U = 2 5 0 0 fp m SCOOP INLET OUTLET MIDDLE LEUEL U = 2 5 0 0 fp m I P OL GE I M Q D O E G B D S s T u n n el U elo c ity : 2 2 m o h B o tto m P an el Only a t O u tle t Mouement of Markers Mouement of Streamers SCOOP INLET OUTLET BOTTOM LEUEL U = 2 5 0 0 f p m Fig. 5.34 Air D istribution Studies SCOOP INLET FMNT UIEU I O F W INDSCOOP; TO P O U TLET PANEL O N LV Scale: 3/4"= 1Q '-Q " Air In Brass tubing for attachment to pitot tubes Fig. 5.35 DISTRIBUTION STUDIES WIND-SCOOP #2 SHAFT INLET*^ SHAFT INLET s . , POINT 2 TOP I f 911- ~ SHAFT INLET 0' SHAFT INLET ~ POINT 1 POINT 2 MIDDLE LEVEL SHAFT INLET POINT SHAFT INLET ----------- POINT 2 BOTTOM LEVEL 142 Fig. 5.56 DISTRIBUTION STUDIES: IUINP-SCOOP #2 SCOOP INLET TUNNEL UELOCITV: 9MPH. 11MPH. 22MPH BAROMETER: 30.1 TEMPEBRTURE:75 F O Location of Markers OPEN OPENING FROM SCOOP SHAFT INTO SPACES 75% Opening: Panel aboue mid-height of space OPEN TOP LEUEL FLOOR OPEN OPEN MIDDLE LEUEL FLOOR OPEN OPEN BOTTOM LEUEL FLOOR Side View of JUind-Scoop: TOP OUTLET PANEL ONLY Scale: 3/4”= 1Q'-0" 143 SCOOP INLET SCOOP INLET 1 I li Uibrates OUTLET i? * TOP LEUEL U=1 1 5 0 fp m Fairly s m o o th s t r e a m e r m o u e m e n t on all leuels (P dG D M GUOIIIM s Tunnel U e lo c ity : 9 m p h Top P a n e l Only a t O u tle t 0 ~ s^.M ouem ent of - * * * .. ^ M ouement of Streamers OUTLET MIDDLE LEUEL U = 1 2 0 0 f p m SCOOP INLET ♦ if I 1 1 ? r OUTLE7J BOTTOM LEUEL U=1 1 5 0 f p m Fig. 5.37 Air Distribution Studies 144 SCOOP INLET I ^ OUTLET TOP LEUEL U = 1 5 2 0 fp m $COOP_ INLET I Uibrates p OUTLET MIDDLE LEUEL U= 1 5 2 0 fp m I P I L U D M O D Q E O G D S s Tunel U e lo c ity : 11 m ph Tod P a n e l Only a t O u tlet 0 — ^ M o u e m e n t of Markers ^ M ouement of Streamers SCOOP INLET I i t * OUTLET BOTTOM LEUEL U = 1 5 2 0 fp m Fig. 5.38 Air D istribution Studies 145 SCOOP INLET I OUTLET ; TOP LEUEL U = 2 5 0 0 f p m IPlLlM G D flH Q O P S s l a p P a n e l Onlu a t Ontypt M o u e m e n t o f M a rk e rs * * * * .. M o u e m e n t o f S tr e a m e r s SCOOP INLET OUTLET MIDDLE LEUEL U = 2 5 0 0 fp m SCOOP INLET I r - \ OUTLET i f f BOTTOM LEUEL U = 2 5 0 0 f p m Fig. 5.39 Air D istribution Studies SCOOP INLET Fig. 5.40 DISTRIBUTION STUDIES WIND-SCOOP #2 ■ f ^ nipt Brass tubing for attachment to pitot tubes Air In fflQNT U IE L U or lillND-SCOOP- N O PANELS A T O U TLET Scale: 3/4"= 10'-0" < ■ - " .............. * -------------* * V ....................... SHAFT INLET < - ^ ....................... • ...............^ ^ / • POINT 2 TOP LEJIEE S *$S5n~INLET*................. POINT 2 M iB B L E U u E L .SHAFT INLET POINT 1 SH A FT POINT 2 s - ............................. f fl/T f O M LEUEL 147 Fiq. 5.41 DISTRIBUTION STUDIES: UlINP-SC0QP_#2 SCOOP INLET RIB IN 31iaMEJL.mQ .C IIY; 9M EikJlM £JHL22MEH BflRflMEIE RL51L.1 TEMPEBATURE;75 F 0 Location of Markers 7 ^ OPENING FROM SCOOP SHAFT i INTO SPACE ON ALL LEUELS OPEN TOP LEVEL FLOOR OUTLET: 100% OPENING OPEN MIDDLE LEVEL FLOOR OPEN BOTTOM LEVEL FLOOR S id e rnew of tUind-Scoop: NO OUTLET PANELS Scale: 3/4"= 10'-0" 148 SCOOP INLET / U ibrates U ibrates OUTLET TOP LEUEL U= 1 0 6 0 fp m Good air distribution I F I L O D I ^ I O P f l E O f l P S s T u a a e i jJelJDCil ^ a m p ii No P a n e ls a t O u tle t 0 '* « ^ > M o u e m e n t of M a rk e rs M o u e m e n t o f S tre a m e rs SCOOP INLET Uibrates MIDDLE LEUEL U= 1 0 6 0 f p m SCOOP INLET 4 U 1 O U T L E T BOTTOM LEUEL U = 1 01 O f p m Fig. 5.42 Air Distribution Studies 149 SCOOP INLET SCOOP INLET I OUTLET TOP LEUEL U= 1 4 5 0 fp m P I L C D N G D O E O Q D S s Tu n n el U elocity: l l m o h No P a n e ls a t O u tle t 0 * ^ M o u e m e n t of M a rk e rs - • * ^ ^ M o u e m e n t o f S tr e a m e r s I OUTLET MIDDLE LEUEL U= 1 41 5 fp m SCOOP INLET I OUTLET BOTTOM LEUEL U = 1 5 2 0 f p m Fig. 5.43 Air D istribution Studies 150 SCOOP, INLET P OUTLET TOP LEUEL U = 2 4 9 0 fp m \P\L\$1M Q D O iE Q flD S s Tunnel U elocity: 22m u h. No P a n e ls a t O u tl e t M o u e m e n t o f M a rk e rs ^ ^ M o u e m e n t o f S tre a m e rs SCOOP INLET I OUTLET MIDDLE LEUEL U = 2 5 0 0 fp m SCOOP INLET I OUTLET BOTTOM LEUEL U = 2 5 0 0 f p m Fig. 5.44 Air Distribution Studies TABLE 5.17 INTERIOR DISTRIBUTION STUDIES Tunnel Velocitv= 9mph 75% Outlet Opening: With A Top Panel Only VELOCITY (FPM) Q(FT3/MIN) LEVEL Ou t l e t i POINT 1 SCOOP INLET 1 SCOOP SHAFT SCOOP INLET 2 POINT 1 Ou t l e t 2 1 V=1110 Q=14 1120 V=1120 Q=10 1110 V=1120 0=10 1120 V=1120 Q=15 2 V=1115 Q=15 1130 V=1120 Q=10 1120 V=1120 Q=10 1140 V=1115 Q=15 3 V=1100 Q=14 1140 V=1115 Q=10 1120 V=1115 Q=10 1130 V=1120 Q=15 152 RESULTS & OBSERVATIONS 153 RESULTS AND OBSERVATIONS This thesis study has been very interesting because it does show that the wind- scoop, traditionally used for purposes of reducing temperature in hot-dry climates, can also be used solely for ventilation requirements within a space. I was able to obtain good results even though they are outside of the Reynold's number. Never theless, the distribution studies clearly showed that wind-scoop type 2 is the most efficient and that the optimum ventilation condition is with a 100% outlet open ing when there is the least resistance to the air flow. However, for security and safety reasons, the outlets cannot be left completely open. The values in Table 5.18 show that the flow rates at the inlet to each room from the scoop (scoop inlet) and at the outlets are very close which indicates that there is very little turbulence inside the space. See figure 5.25. The types of louvers, grilles, and shades shown in figure 4.14 can be used to obtain a maximum opening. My primary suggestion for further study in this topic is that all testing be done in a larger wind tunnel so that the velocity readings will be inside the Reynolds number. I also suggest the following for further study: 1) More information is needed on measuring both velocity and observing direc tion of air flow simultaneously, 2) several measurements of pressure readings at different levels vertically and horizontally should be done inside the space, 3) Include 'furniture' and panels in the tests- it is important to keep furniture as open as possible so as not to impede air circulation and interior screens can be used to direct air flow, 4) several other configurations and aspect ratios of wind-scoop can be tested for many other climatic conditions. 154 R E FE R E N C E S 1. Neba, Aaron, Modern Geography of the United Republic Of Cameroon. Hamilton Printing Company, 1982, p.23. 2. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.10. 3. Watson, d., Labs, K.. Climatic Design. McGraw Hill, 1983, p.53. 4. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985, p .16. 5. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985, p .16. 6. Olgyay, V., Design With Climate. Princeton University Press, Princeton, New Jersey, 1963, p.22. 7. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985, p.29. 8. Givoni, B., Man. Climate and Architecture. Applied Science Publishers Ltd., 1976, p.68. 9. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985, p.25. 10. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985, p.24. 155 11. Givoni, B., Man. Climate and Architecture. Applied Science Publishers Ltd., 1976, p.64. 12. Givoni, B., Man. Climate and Architecture. Applied Science Publishers Ltd., 1976, p.64. 13. Givoni, B., Man. Climate and Architecture. Applied Science Publishers Ltd., 1976, p.65. 14. Kimura, Ken-ich, Studies on the Architectural Planning with Complex Use of Natural Energy. Waseda University, p. 6. 15. Kimura, Ken-ich, Studies on the Architectural Planning with Complex Use of Natural Energy. Waseda University, p.6. 16. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p .88. 17. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p .10. 18. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p.41. 19. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p .n . 20. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p.47. 21. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.21. 156 22. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970, p.26. 23. Taylor, John. Commonsense Architecture. W.W. Norton & Co.. 1983. p.62. 24. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p.339. 25. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.92. 26. Turki Haif Al-Qahtani, Masters Thesis, A Passive Cooling.System for Residential Building in the Eastern Province Desert in Saudi Arabia. University of Southern California, 1987, p.62. 27. Taylor, John. Commonsense Architecture. W.W. Norton & Co.. 1983. pp.53-56. 28. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.42. 29. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970, p.29. 30. Watson, d., Labs, K.. Climatic Design. McGraw Hill, 1983, pp. 193, 198. 31. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.71. 32. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970, p.25. 157 3 3. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970, p.46. 34. Watson, d., Labs, K.. Climatic Design. McGraw Hill, 1983, pp. 193, 141. 35. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970, p.30. 36. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.116. 37. Watson, d., Labs, K.. Climatic Design. McGraw Hill, 1983, pp. 193, 95. 38. Melaragno. Michele. Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p.322. 39. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p. 333. 40. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p .96. 41. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p.96. 42. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978, p .97. 43. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p. 337. 158 44. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982, p. 331. 45. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.7. 46. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.25. 47. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.26. 48. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.26. 49. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.23. 50. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.27. 51. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.23. 52. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p.3 53 Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University, p. 15. 159 B IB L IO G R A PH Y Angus, T.C., The Control of the Indoor Environment. Pergamon Press, 1968. Bradshaw, Vaughn, Building Control Systems. John Wiley & Sons, 1985. Brown, G..Z, Sun. Wind, and Light. John Wiley & Sons, 1985. Brown,Reynolds Ubbeholde, Insideout. John Wiley and Sons Inc., New Tork, 1982. Egan, David, Concepts in Thermal Comfort. Prentice-Hall, 1975. Givoni, B., Man. Climate and Architecture. Applied Science Publishers Ltd., 1976. Henke, Russell, Introduction to Fluid Mechanics. Addison-Wesley Publishing Company, 1966. Kimura, Ken-ich, Studies on the Architectural Planning with Complex Use of Natural Energy. Waseda University. Kukreja, C.P, Tropical Architecture. McGraw-Hill Book Company, 1978. Lin, Hsein, A Simplified Method for Energy Consumption Estimation For Buildings In Hot Humid Climates. Melaragno, Michele, Wind in Architectural and Environmental Design. Van Nostrand Reinhold Company, 1982. Neba, Aaron, Modem Geography of the United Republic Of Cameroon. Hamilton Printing Company, 1982. 160 Nelson, Harold, Area Handbook for the United Republic of Cameroon. Library of Congress, 1974 Olgyay, V., Design With Climate. Princeton University Press, Princeton, New Jersey, 1963. Saini, Balwant, Architecture in Tropical Australia. George Wittenbom Inc., 1970. Shaw, Allan, High Quality Tropical Air Conditioning With Low Energy Consumption. Tamblyn, Getting High On Low Temperature Air. Tanabe, Schin-ichi, Kimura, Ken-ichi, Thermal Comfort Requirements Under Hot and Humid Conditions. Waseda University. Taylor, John. Commonsense Architecture. W.W. Norton & Co.. 1983. Turki Haif Al-Qahtani, Masters Thesis, A Passive Cooling.System for Residential Building in the Eastern Province Desert in Saudi Arabia. University of Southern California, 1987 Watson, d., Labs, K.. Climatic Design. McGraw Hill, 1983.
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Asset Metadata
Creator
Nkuo, Lucy-Bertha Mai
(author)
Core Title
Passive cooling methods for mid to high-rise buildings in the hot-humid climate of Douala, Cameroon, West Africa
Degree
Master of Building Science
Degree Program
Building Science
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
engineering, architectural,OAI-PMH Harvest
Language
English
Contributor
Digitized by ProQuest
(provenance)
Advisor
Schierle, Gotthilf Goetz (
committee chair
), Koenig, Pierre Francis (
committee member
), Schiler, Marc (
committee member
)
Permanent Link (DOI)
https://doi.org/10.25549/usctheses-c20-298999
Unique identifier
UC11259469
Identifier
EP41418.pdf (filename),usctheses-c20-298999 (legacy record id)
Legacy Identifier
EP41418.pdf
Dmrecord
298999
Document Type
Thesis
Rights
Nkuo, Lucy-Bertha Mai
Type
texts
Source
University of Southern California
(contributing entity),
University of Southern California Dissertations and Theses
(collection)
Access Conditions
The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...
Repository Name
University of Southern California Digital Library
Repository Location
USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA
Tags
engineering, architectural