INDOOR AIRFLOW BEHAVIOR AND THERMAL COMFORT IN A COURTYARD HOUSE IN WARM HUMID TROPICS

Transcription

1 INDOOR AIRFLOW BEHAVIOR AND THERMAL COMFORT IN A COURTYARD HOUSE IN WARM HUMID TROPICS I Rjpksh 1*, H Ngi 2, M Okumiy 3 1 Dpt. of Arhittur, Ngoy Univrsity, Furou-ho, Chikus-Ku, Ngoy , Jpn 2 Grut Shool of Environmntl Stuis, Ngoy Univrsity, Jpn 3 Cntr For Intgrt Rsrh in Sin n Enginring, Ngoy Univrsity, Jpn ABSTRACT This ppr sssss th ffts of inoor irflow hvior moifying th inoor ir tmprtur on thrml omfort onitions in rsintil tropil ourtyr uiling whr ourtyr mintins irt ontts with outoor nvironmnt through opnings foun in th nvlop. Rsults tkn from fil invstigtion n omputr simultion rvl tht givn th mint limti onitions prtiulr inoor irflow hviors r suffiint to lowr th inoor ir tmprturs low th mint lvl in th ourtyr s wll s in surrouning intrnl sps. Thus, thrml omfort onition not orrlt to th numr of opnings ut to th istriution pttrn n volumtri rt of inoor irflow in nhning ht xhng twn wll surfs n ir. Th optimum rng of mint win irtion, whih rquir for optimum istriution n volumtri flow of inoor ir, ws foun within rng of grs to th longituinl xis of th ourtyr n uiling. INDEX TERMS Inoor Airflow Pttrn, Thrml Comfort, Pssiv Cooling, Tropil Courtyr INTRODUCTION In wrm humi limts, whr th omin fft of high lvls of mint ir tmprtur n rltiv humiity rsults in thrml isomfort, lowring of inoor ir tmprtur through rhitturl sign is simpl nrgy onsrving pproh in promoting inoor thrml omfort. In high-mss nturlly vntilt uilings, th fft of ht xhng twn th mss n ir is suffiint in orr to lowr th inoor ir tmprtur thn th mint lvl. Howvr, th ffiiny of suh moifitions n ttriut to th inoor irflow istriution pttrn n orrsponing volum of ir (irflow rts), whih n fft th ht xhng twn th mss n ir. Builings with ourtyrs hv ttr vntiltion potntil through th intrnl sps. With th ourtyr, th funtionl pth of th pln n kpt to minimum for ttr vntiltion potntil thn p pln soli uiling form of th sm r. Whn th ourtyr is surroun y uilt mss n mintining irt ontts with th outoor nvironmnt through opnings foun in th xtrnl nvlop, th sp ov th ourtyr n t s n opning tht ishrgs ir into th sky whil opnings in th nvlop t s inlts. Assssmnts of irflow hviors in uilings with isolt ourtyrs (isolt from outoor nvironmnt xpt from its sky roof opning) hv n rri out using win tunnl xprimnts n omputr simultions (Wlkr t l. 1993, Sho t l. 1993, Alvrz t l n Bnslm t l. 1989). Thrml hviors in hot ry ourtyr uilings hv n invstigt using fil xprimnts (Mir, 2000). Howvr, tul irflow hviors n onsqunt fft on inoor ir tmprtur in opn tropil ourtyr uilings whr th * Contt uthor mil: inrik_r@hotmil.om 1072

2 ourtyr mintins irt ontts with outoor nvironmnt through vrious opnings foun in th nvlop, r lss unrstoo ut im t rssing in this ppr. In rnt fil invstigtion, uthors monitor high-mss (rik) singl story tropil ourtyr uiling foun in Colomo, Sri Lnk (Figur1) for thrml hviors. Ltr, inoor ir movmnt ws simult using CFD. Th rtngulr 3D uiling mol (Figur 2 n 3) ws llow to vntilt through opnings foun in th uiling nvlop n lot with th ourtyr on th longituinl n ross xis. It ws foun tht th ourtyr funtions s win show whil othr opnings in th xtrnl nvlop funtion s sution zons inuing irflow n thus optimizing th xposur of high- mss intrnl wlls with inoming ir. Th ir ntring from th nvlop opnings is sn trvling through th inoor sps n finlly ishrgs into th sky through th ourtyr n Up win ir funnl. Th prsnt stuy is im t ssssing inoor thrml omfort onitions in this tropil ourtyr uiling invstigt rlir. Thrml omfort is ssss using nw PMV* whih hs n propos for wrm humi limts. In wrm humi tropis, s ir tmprturs n humiity lvls r high, highr mn vloitis r ssntil for promotion of thrml omfort. Howvr th mol priting th prntg of popl isstisfi y Fngr t l. (1989) is pplil for limit rng of ir tmprturs n ir vloitis, within 20 to 26 C n 0.05 to 0.5m/s rsptivly. Thus nw inx PMV* (Kinngn, 1997), whih hs n propos for hot n humi nvironmnt, rpling th oprting tmprtur (T o ) of Fngr s omfort qution with Stnr Efftiv Tmprtur (SET*) is us in th ssssmnt of thrml omfort. METHODS Th 230m 2 stuy uiling ommots ntrl rtngulr ourtyr msuring 3.7m x 8.1m. Th ourtyr is oun y living r to th wst n rooms to th st. It is visully opn to th outoor nvironmnt through nvlop opnings foun t th ns of two xs pssgs, whih r prpniulr to h othr (Figur 1). Th high-mss rik uiling hving wi roof vs on primtr nsur qut shing to th nvlop opnings throughout th y. Wlls n roofs r not instll with insultion. f N Sky opning Courtyr Courtyr Stion through ross xis Figur. 1 Th stuy uiling Cross xis SW Longituinl xis x Builing mol Win inin t ngl y Cy x Outlt ounry Gomtry of th Gri with inlt n outlt ounris in rsptiv to th mint win irtion z y Inlt ounry Figur. 2 Simult uiling mol S W Thrml hvior of th stuy uiling ws monitor for tn ys uring th April 12 to My 3, 2001 with fiv iffrnt ounry onitions with rgr to omposition twn th 1073

3 ourtyr n othr mjor opnings foun in th nvlop (Tl 1). During ytim (9.00h to 18.00h), ounry onitions of th uiling wr hng through losing n opning th mjor irflow ss points (, 2, 3 n 4). During nighttim (18.00h to 9.00h) qul ounry onitions wr mintin y kping th opning 2 n ourtyr s top opn whil othr nvlop opnings (op1, 3 n 4) wr rmining los. Inoor ir tmprturs, rltiv humiity, wll surf tmprturs n ir vloitis t h opning wr msur t 5-minut intrvls n ltr vrg for hourly vlus. Furthr, flow nlysis softwr α - Flow, n th stnr k-ε turuln mol with isothrml flow n ounry onitions wr implmnt to osrv ir movmnt n vntiltion prformn of h nvlop opning omposition prform in th fil invstigtion (Tl 1). Vntiltion from stk fft ws ignor, s its fft is smll ompr to ytim mint win. Simultions wr rri out for fiv mols of opning ompositions invstigt uring fil invstigtion. Th gomtry ws rlistilly mol for th simultion (Figur 2) utilizing th imnsions of th uiling invstigt on th sit. For h mol, thr-imnsionl orthogonl msh ws rliz with Crtsin oorints. Th totl gri is ompos of 921,100 (119x129x60) non-uniform lls with nsity of mor fin gris t th nvlop opnings, ourtyr voi n wll ounris. Th gomtry of th gri is shown in Figur 2. Eh ir movmnt ws simult with win t to th uiling f. Powr lw gv vrtil win profil. Th trrin roughnss (α) ws riv from on sit win vloity msurmnts of mn vloity of 1.5 n 1.8m/s t th hight of 5m n 10m rsptivly. Th vlu of α is shown s qul to 0.25, n urn onition. RESULTS AND DISCUSSION Th mint wthr pttrn ws osrv s uniform throughout th stuy prio n vn svrl ys prior. Th mximum n minimum mint tmprturs of 32.8 C n 25.5 C wr ror t h n h rsptivly. Dytim (9.00h to 18.00h) n nighttim (18.00h to 9.00h) mn tmprturs wr 29.6 C n 24.5 C. Dytim n nighttim humiity lvls rmin roun 65 n 96%. Mn ytim win vloitis wr ror twn 1 n 1.2m/s from SW with lmost still onitions (or 0.2m/s) t night. Cross xis Courtyr Longituinl xis Tl 1. Inoor thrml moifition n orrsponing irflow rts Opning Air tmprtur moifition- T Air Flow Composition Courtyr Intrior zons Volum Rt Dy Night Dy Night m 3 /h ACH Courtyr -A ,2,Cy. - B ,4,Cy. - C ,2,3,Cy. - D ,2,3,4,Cy- E T = T o T i T o = Dytim mn Outoor T i = Dytim mn inoor tmprtur (Courtyr n Intrior Zons) Figur 3. Thr Dimnsionl form of th uiling mol Moifition of inoor ir tmprtur A positiv T vlu (Tl 1) inits rution of vrg ir tmprtur low th vrg mint lvl whil ngtiv vlu rprsnts n ovrht onition. Eh s monstrts iffrnt ir tmprtur moifition lvls in th ourtyr n intrior zons. Howvr, th iffrn is not sn s orrlt to th mint wthr onitions, whih rmin uniform uring th stuy, ut to th opning omposition of th uiling (Tl 1). 1074

4 Volumtri irflow rts msur n lult Th volumtri irflow rts r proportiont to th r of opnings. It is lso foun tht msur irflow rts r losly gring with lult flow rts tkn from CFD nlysis for ll ounry onitions. Mximum rutions of ourtyr n intrnl ir tmprturs r sn with Css B n D whr th orrsponing irflow rts r foun within rng of 1.5 to 2.0 Air hngs pr hour. Airflow pttrns Most of th nvlop opnings monstrt positiv prssur zon whil sky opning of th ourtyr show ngtiv prssur (sution) zon. This prssur iffrn is sn s th riving for in inuing irflow n thus optimizing th xposur of high-mss wlls to inoming ir. Th ir ntring from th nvlop is sn trvling through th inoor sps (joining xis n ourtyr) for gtting ishrg into th sky through th ourtyr. Thr si irflow pttrns, upwin funnl, horizontl plus upwin n top vortx flows r intifi for ll fiv ounry onitions s shown in Figur 4. Th top vortx flow is visil only whn ll nvlop opnings, xpt th ourtyr opning, r los (Cs A in Tl 1 n Figur 4C). Inoor irflow istriution with top vortx flow is sn s miniml (Figur 5C). Th mximum inoor irflow istriution is sn in ss B n D with upwin funnl flow whr th opnings 1 n 2 on th longituinl xis t s inlts (Figur 5A). A. B. C. Upwin funnl flow Horizontl plus upwin flow Top vortx flow Figur. 4 Diffrnt 3D irflow pttrns, A. Courtyr n Longituinl xis (Cs B n D) B. Courtyr n oth xs (Cs E n similr in Cs C) C. Sky opning of th ourtyr (Cs A) Win inin ngl 2 Op f f 0.05 f A. B. C. Figur. 5 Airflow hviors t humn oy hight (1.1m, ll vloitis in m/s) A. Courtyr n longituinl xis (Cs B n D) B. Courtyr n oth xs (Cs E) C. Sky opning of th ourtyr (Cs A) Wll surf tmprtur A signifint orrltion twn msur intrnl surfs n inoor tmprturs ws osrv. During th rly hours of ytim, inoor surf tmprtur rmins low th

5 lvl of inoor n mint ir ut grully inrss n quls th inoor ir tmprtur y vning (t 16.00h). During th rly hlf of th night, th wll tmprtur rmins highr thn th inoor ir ut grully rss n rhs minimum y rly morning. Th optimum ht trnsfr from ir to mss in ytim is sn in ss B n D, whn th mximum istriution of ir through th inoor sps hs nhn th grtr intrnl wll surf xposur. A mor til invstigtion of th hvior of wll surf tmprtur hs n prsnt in Rjpksh t l. (2002). Thrml omfort onitions Ativity lvls r tkn s 1.1mt (55Wm 2 ), sntry tivity, with tropil lothing of 0.4lo. Sin th PMV* is lult for intrnl rs irtly los to th ourtyr (Zon, n ourtyr zon, rfr to Figur 5.), mn rint tmprtur of wll surfs n lult inoor ir vloity t humn oy hight of ths intrnl sps wr onsir s prmtrs of PMV*. Air vloitis wr tkn from CFD lultion. PMV* % Nutrl Comfortl Dytim Wrm unplsnt Slightly wrm Aptl 14% 6% 5% 5% -1-1 A B C D E A B C D Figur 6. Dytim n Nighttim omfort nlyss for ll ss (PMV* n PPD%) PMV* Wrm unplsnt 50% Nutrl Comfortl Nighttim 5% Slightly wrm 18% Sin th PMV* vlus twn th intrnl zons show un notil iffrn, PMV* vlus wr vrg for nlysis of ss. Diffrns in omfort lvls from wrm unplsnt to nutrl omfortl wr osrv (Figur 6). Cs A, with PMV* vot of 2.2 n 1.5 in y n night ws foun s hving th worst thrml onitions with wrm unplsnt n slightly wrm unptl inoor nvironmnts throughout th y. Howvr ths onitions wr hng in othr ss. Th rst of th ss wr foun within rng of omfortl (0) to slightly wrm ut ptl (1) omfort lvls. Among thm th st thrml nvironmnt throughout th y ws vint in Css B n D. Amint (xtrnl) win irtion 6% E 34% N Win inin ngl 0 Tl 2. Amint win irtion n orrsponing ACH 30 Win inin Airflow Pttrn Flow ngl Courtyr Rt ACH 0 Outlt Inlt Outlt Inlt Inlt Outlt Inlt Inlt Outlt Inlt Inlt Outlt Outlt Inlt Outlt Outlt Inlt Outlt 1.3 Longituinl Axis 90 Inlt Inlt Outlt 1.4 Figur 7. Simult win inin ngls 1076

6 By vrying th mint win irtion, uiling mol ws simult in orr to fin out th optimum win irtion, whih oul rsults in n inoor irflow rt within rng of ACH. From th fil invstigtion it ws foun tht mximum rution of inoor ir tmprtur is sn with this irflow rt. Tl 2 (prvious pg) givs th rsults of irflow pttrns n orrsponing irflow rts. Simultion rsults provi vint tht xtrnl win inin within grs from th longituinl uiling xis oul rsults th rquir rng of inoor irflow rt. In ition, sm win irtions promot opnings 1 n 2 s inlts for irflow u to win. Also vritions in win vloity lso hv n impt on irflow rt. For 45 n 60 ngls 25% inrs in win vloity rsults 20% inrs of ACH. CONCLUSION AND IMPLICATIONS Rsults from th stuy rvls orrltion twn thrml omfort onitions n inoor irflow hviors in tropil ourtyr uiling with qut shing on its nvlop opnings. Inoor irflow hvior in trms of irflow pttrns n irflow rts pns grtly on th omposition twn nvlop opnings n th ourtyr thn th numr of nvlop opnings. Also, optimum moifition (lowring) of ourtyr n inoor ir tmprtur n thus thrml omfort onition is sn not orrlt to th numr of opnings ut th istriution pttrn n volumtri rt of inoor irflow in nhning ht xhng twn wll surfs n inoor ir. Ths onlusions hv implitions on limt sign. Thus, th us of ourtyrs for pssiv ooling in tropil limts is possil provi optimum istriution n volumtri flow rt of inoor ir r hiv through uiling sign. Furthr rsrh for othr limti xtrms woul usful. ACKNOWLEDGEMENTS Th uthors xprss thir thnks to Tsutomu Aoygi of Fujitsu Corp., Jpn n Ihiro Tkhshi of Computtionl ntr, Ngoy Univrsity. REFERENCES Alvrz S, Snhz F n Molin JL. 1998, Airflow pttrns t ourtyrs, Pro. of th 14 th Intrntionl Confrn on Pssiv n Low Enrgy Arhittur PLEA 98, pp Lison, Portugl. Bnslm R n Shrpls S. 1989, Nturl vntiltion in ourtyr n trium uilings, Pro. of th 2 n Europn Confrn on Arhittur-1989, pp , Pris, Frn. Fngr PO, Mlikov AK, Hnzw H, t l. 1989, Turuln n rft: th turuln of irflow hs signifint impt on th snstion of rft. ASHRAE Journl. Vol. 31(7), pp Kinngn J Winow n roof onfigurtions for omfort vntiltion, Builing Rsrh n Informtion. Vol. 25(4), pp Mir I Courtyr mirolimt, A hot ri rgion s stuy, Pro. of th 16 th Intrntionl Confrn on Pssiv n Low Enrgy Arhittur PLEA 2000, pp Cmrig, UK. Rjpksh I, Ngi H n Okumiy M. 2002, Inoor thrml moifition of vntilt ourtyr hous in th tropis. Journl of Asin Arhittur n Builing Enginring Intrntionl Journl of Arhitturl Institut of Jpn. Vol.1 (1) Mrh.2002, pp Sho L, Wlkr RR n Woollisroft M. 1993, Nturl vntiltion vi ourtyrs: th pplition of CFD, Pro. of th 14 th AIVC Confrn on Enrgy Impt of Vntiltion n Air Infiltrtion, pp Copnhgn. Wlkr RR, Sho L n Woollisroft M. 1993, Nturl vntiltion vi ourtyrs: Prt I- thory n msurmnts, Pro. of th 14 th AIVC Confrn on Enrgy Impt of Vntiltion n Air Infiltrtion, pp Copnhgn. 1077