A Study on the Reduction Strategies of Stack Effect in High-rise Residential Buildings

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1 A Study on the Reducton Strateges of Stack Effect n Hgh-rse Resdental Buldngs Dongryul Park, a, Joonghoon Lee 2, b, and Doosam Song 3,c Graduate School, Sungkyunkwan Unv., 300 Chunchun-dong, Suwon , Korea 2 Samsung Corporaton, Seohyun Bldg., Seohyun-Dong, Sungnam 0-, Korea 3 Dept. of Archtectural Eng., Sungkyunkwan Unv., 300 Chunchun-Dong, Suwon, , Korea a knoknd00@skku.edu, b jh6.lee@samsung.com, and c dssong@skku.edu ABSTRACT The stack effect n hgh-rse buldngs n wnter causes many problems such as dffculty n openng or closng doors, nfltraton, energy loss, nose n lobby and fre protecton. The man purpose of ths study s to analyze the feature of stack effect n hgh-rse resdental buldngs and nvestgate the effect of reducton strateges wth network smulaton method. The smulaton has been conducted for 2 hgh-rse buldngs under the constructon whch have 36, 3 stores above the ground level and 2 basement stores respectvely by CONTAMW. In ths paper, the results of pressure dfference, the locaton of the neutral plane and ar-flow between spaces for analyzed cases wll be presented. Further, the control method to mnmze the stack effect wll be dscussed. Keywords: stack effect, arflow, hgh-rse resdental buldng, CONTAMW, smulaton. INSTRUCTION Recently, the resdental buldngs are becomng hgher and more luxurous due to the ncrease of urban populaton and betterment of qualty of lfe n Korea. In urban renewal projects, tearng down low-rse buldngs and re-constructng as hgh-rse buldngs can afford to supply more green space and can be secured the urban envronment n healthy. Furthermore, hgh-rse buldngs have many benefts n terms of effcency and envronment-frendlness such as centralzng facltes to maxmze convenence of the resdents. For ths reason, hgh-rse resdental buldng s popular n advanced countres where renewal projects are actvely undertaken. However, hgh-rse buldngs arouse a seres of new problems such as stack effect. A hgh-rse buldng nevtably contans a lofty vertcal shaft, and stack effect occurs because of pressure dfference between the nsde and outsde. The temperature dfference between nsde and outsde of buldngs causes a dfference n ar densty, whch leads to pressure dfference and arouse ar-flow. Especally, the stack effect become conspcuous n wnter accordng to the temperature gap between nteror and exteror of buldng wdens. Compared to offce buldngs, resdental buldngs usually have a larger number of openngs, n other words, the ar-tghtness of exteror skn s relatvely nferor. Also, the probablty s hgh that some openngs are lkely to be open at any tme. Thus resdental buldngs are more subject to the stack effect. To reduce the stack effect, buldng envelope needs to be tghten to mnmze nfltraton of outsde ar. Another way s to nstall a wnd-screenng room at the entrance of the ground and the basement, whch helps to dstrbute pressure at the entrance. As a more progressve soluton, the 3

2 archtectural strateges such as parttonng a vertcal shaft and mechancal soluton such as coolng shaft space and pressurzng the vertcal shaft space to dscourage nfltraton of outsde ar should be consdered. Researches on the stack effect have begun n the North Amercan snce 60s. Tamura and Wlson (6) measured a pressure dstrbuton n hgh-rse offce buldngs and they examned the effect of an artghtness of exteror wall and archtectural elements of the nteror on ar flow through the numercal smulaton. Tamblyn (3), Lovatt (4) reported nfluence of the stack effect on openng and closng an elevator, and ventlaton system performance. Hayakawa and Togar (88) suggested a modfed TDC(Thermal Draft Coeffcent) as target offce buldngs. In Korea, the ssue of the stack effect has begun to attract attenton from 2000s as a number of hgh-rse buldngs constructed. Researches on the stack effect mostly depend upon feld research and network smulatons, and the topc were restrcted to the archtectural solutons n most cases. Based on the prevous researches, n ths study, the mpacts of the stack effect of a hgh-rse buldng wll be analyzed through network smulaton method. Moreover the reducton strateges of stack effect such as enhancement of ar-tghtness of buldng envelopes and doors or coolng vertcal shaft spaces wll be analyzed. 2. SIMULATION OUTLINE 2. Buldng Descrpton The analyzed buldng s hgh-rse resdental buldng located at A-san cty n Korea, that s under constructon. As shown n Fgure (a), the analyzed buldng s conssts of two resdental buldngs (buldng A: two-story underground, 36-story hgh; buldng B: two-story underground, 3-story hgh) and a utlty complex that connects the two buldngs. The analyzed buldng s arranged n a typcal composton of a large-scale hgh-rse resdental complex. As for buldng A, three unts surround each core respectvely. In buldng B, fve households are arranged around the center core for each. Both buldngs have separate elevators for general use and emergency use and there s no shuttle elevator. The elevator shaft s n one unt from bottom to the top of the buldng, therefore a probablty of stack effect s farly hgh. Heatng s expected durng the wnter n elevator halls, whch further aggravates the stack effect. 2.2 Smulaton Outlne The network smulaton method was used to examne the stack effect of a hgh-rse buldng n ths (a) Buldng layout Fgure. Buldng Layout and Floor Plan (b) Floor plan 32

3 study. Because the stack effect s hard to generate through an actual experment, and the analyss should be examned at the early desgn stage. A network smulaton tool such as CONTAMW s sutable to analyze for a subject wth numerous analyzng nodes as lke analyss model n ths study. As a result of CONTAMW, the ar features (pressure dstrbuton, temperature, etc) and quantty of arflow at multple nodes wll be suggested. In CONTAMW, the propertes of arflow on each node and among nodes are defned as follows. The ar flow rate from zone to zone j s functon of the pressure dfference along the flow path. The mass of ar F = f ( P P ) j, j (2.) m [kg] n zone s gven by the deal gas law. PV m =ρ V = (2.2) RT 3 where, V s zone volume[ m ]; P s zone pressure[pa]; T s zone temperature[k]; and R s gas constant for ar, 28.0[J/kg K] For a transent soluton the prncple of conservaton of mass states that m V ρ = ρ + V = Fj, + F (2.3) t t t j where, m s mass of ar n zone I[kg]; F j, s arflow rate[kg/s] between zones j and zone; s postve values ndcate flows from j to I; and F s non-flow processes that could add or remove sgnfcant quanttes of ar form the zone. Table llustrates condtons for smulaton modelng. The underground parkng lot was consdered as outdoor, only core sectons were ncluded n the modelng for underground level. Atmospherc pressure of the ground- level was consdered as base and varance s accordngly appled to heght of analyzed node. Each resdental unt, hall and corrdor were regarded as a sngle zone. An elevator shaft and a starwell, whch are vertcal arflow paths, were modeled as ndependent zones for each, and each zone was vertcally connected. Table. Condtons for Smulaton Modelng Category Modelng assumpton Atmospherc pressure Temperature settng Ar leakage data Underground parkng lot Underground levels Starwell Elevator shaft Hall Resdental unt Modelng Condton Consdered as outdoor ar Modelng only core sectons Modelng each story as one node. Vertcal connecton of nodes Modelng each story as one node. Vertcal connecton of nodes Modelng as a sngle zone Modelng as a sngle zone Atmospherc pressure on the frst s set as a base and the varance due to heght s consdered. Interor (household unts, hall): 22, Outdoor ar: -.4 (lowest wnter tme average temperature of the area) Coolng temperature for a shaft s set above a dew pont (shaft temperature/humdty s set at 22, 3% as a ntal condton) CONTAMW Lbrary, ASHRAE (200) Data Measured data from prevous researches; Tamura (4), Jaehun Jo (200)

4 Table2. Smulaton Cases Cases Classfcaton Reducton Strategy Case Basc desgn - Case 2 Mnmal strategy Installaton of a wnd-screenng room n the lobby and underground level -Buldng A: Renforcng ar-tghtness of doors to emergency starwell n the whole buldng, addtonal dvson of an elevator hall n the Case 3 Archtectural measures lobby, nstallng a wnd-screenng room on the roof level -Buldng A & B: Installng a revolvng front door n the lobby -Buldng B: Addtonal dvson of an elevator hall on the lobby, standard and upper levels Basc desgn wth coolng Case 4 the elevator shaft and Coolng temperature: 6 starwell Case Basc desgn wth coolng Coolng temperature: 6 the elevator shaft only The nteror temperature was set at 22. For outdoor temperature, lowest wnter perod average temperature of A-san cty was appled. Shaft coolng temperature was set above a dew pont about 6, the dew-pont temperature was calculated on the condton that the nteror temperature and humdty was set at 22, 3% respectvely. Buldng A and B are connected by Buldng C for workng as a corrdor space and communty space. To examne nteracton among the three buldngs, the three buldngs were modeled smultaneously. Table 2 lsts smulaton cases. In case, the stack effect for a basc desgn was analyzed. In case 2, the effect of mnmal reducton strategy such as nstallng a wnd-screenng room n the lobby and underground level was nvestgated. In case 3, when more archtectural measures such as nstallng a revolvng door n the lobby and underground level, enhancng ar-tghtness n each starwell entrance and parttonng elevator halls were taken, the reducton effect was revewed. For case 4 and, a mechancal method was adopted to reduce the stack effect, the shaft space (elevator hall, starwell) s cooled to mnmze a temperature dscrepancy between the exteror and nteror. By dong so, the outdoor ar whch nflows nto ndoors through shaft space wll be dmnshed remarkably. For case 4, the coolng temperature for shaft space (elevator and starwell) was set at the lowest pont wthout dew condensng. For case, to mnmze problems derved from coolng the whole shaft space, only elevator shaft was cooled. 3. SIMULATION RESULT Ths chapter presents the results of network smulaton under the above mentoned condtons. The results focus on the pressure dfference at man elements and overall ar flow of the analyzed buldng. 3. Basc Desgn (Case, Fg.2) No partcular measure s appled to reduce the stack effect n Case. Fgure 2 shows the result of the smulaton. In comparson wth the allowable pressure standard for entrances(elevator door: Pa, and general doors: 0Pa), the pressure on doors of the lobby, top, elevator and starwells are kept wthn the standard. However, the pressure appled to the entrance door of each resdental unt s rather sgnfcant. Especally, for resdental unts located n the lower levels and upper levels, the stack effect mght brng dffcultes n openng and shuttng the entrance doors. Thus, t s recommended to take approprate measures to mnmze stack effect. 34

5 3 3 3 Lobby door(f) Buldng A Lobby door(f) Buldng B Fgure 2. Basc Desgn (Case ) Lobby door(f) Buldng A Fgure 3. Mnmal Strategy (Case 2) Lobby door(f) Buldng B Lobby door(f) Buldng A Addtonal partton Buldng B Fgure 4. Archtectural Measures (Case 3) 3.2 Mnmal Strategy (Case 2, Fg. 3) Installng a wnd-screenng room n the lobby and underground level contrbuted to decrease the pressure dfference at the lobby entrance. The pressure dstrbuton of the lobby (Fg.) shows that after nstallng a wnd-screenng room, the pressure decreased by half. However, other nodes n buldngs are hardly nfluenced, as results, the volume of arflow s almost same (Fg. ). 3

6 3 3 3 Lobby door(f) Buldng A Lobby door(f) Buldng B Fgure. Coolng Elevator Shaft and Starwells (Case 4) Lobby door(f) Buldng A Lobby door(f) Buldng B Fgure 6. Coolng Elevator Shaft (Case ) Lobby door Lobby door 48. Lobby 38.8 House4..8 Lobby 3.3 House House House2 House House House2 House3 (Unt: Pa) (a) Basc desgn(st, Buldng B) (b) Mnmal strategy(st, Buldng B) Fgure. Pressure Dstrbuton between Basc Desgn and Mnmal Strategy 36

7 3.3 Archtectural Measures (Case 3, Fg. 4) For buldng A, the pressure n the underground level and the lobby substantally decreased. However, due to mproved ar-tghtness of buldng B, more ar flowed nto the less protected buldng A, whch causes a pressure ncrease on the upper s. For buldng B, the pressure decreased generally. However, the based dvson of the elevator hall led to sgnfcant varance n ar pressure for each resdental unt (Fg. 8). 3.4 Basc desgn + Coolng Elevator Shaft and Starwell (Case 4, Fg. ) The vertcal shaft space was cooled to 6 o C. Both buldng A and B showed decrease of pressure by House 2 Addtonal partcle House2 House3 House4 House Fgure 8. Pressure Dstrbuton n Case of Archtectural Measures (Pa) approxmately half compared to the basc desgn. In comparson wth a case of archtectural measures (Case 3), the pressure dropped by more than half n buldng A. Whle, n case of buldng B, the pressure somewhat ncreased for unts where pressure was measured. However, n general, the pressure evenly decreased for the resdental unts. 3. Basc Desgn + Coolng Elevator Shaft (Case, Fgure 6) Coolng the whole shaft space s deal to mnmze stack effect. However, n realty, t can occur addtonal problems such as thermal comfort and ncrease of heatng load, thus t s crtcal to fnd an optmal pont. Takng feasblty nto consderaton, a case where only elevator shaft s cooled was analyzed. The pressure on elevator doors s decreased substantally, yet the pressure on the entrance to a starwell relatvely ncreased. The temperature dscrepancy between elevator shaft and starwell led to ncreased volume of arflow to the starwells. 3.6 Overall ar-mass flow Fgure llustrates the overall ar-mass flow of the analyzed buldng n ths study. By examnng the amount of ar nfltraton, the degree of stack effect reducton could be compared among analyzed cases. Case 2 shows lttle varance of the ar-mass flow compared to the basc desgn(case ). Ths means that wnd-screenng room s not effcent n reducng stack effect on the whole. In Case 3, the arflow reduced by 42% compared to the basc desgn n buldng B, however, the effect was neglgble for the buldng A. As to the Case 4, where whole vertcal shaft space s cooled, the arflow decreased evenly n both buldngs. The stack effect reducton was most outstandng wth all condtons(ar pressure appled on the man elements of the buldng, ar mass flow, pressure dstrbuton) n Case 4. In case, where only the elevator shaft s cooled, stll showed superor case case2 case3 8 case4 6 6 buldng A case 6 6 buldng B (% 2 Fgure. Rato of Ar-mass Flow n Comparson wth basc Desgn (%) 3

8 performance to the archtectural measures. 4. CONCLUSIONS In ths paper, the propertes of the stack effect have been examned through a network smulaton upon a hgh-rse resdental buldng. Followng outcomes were derved from examnng archtectural, mechancal methods to mnmze the stack effect. ) The basc desgn wthout reducton strateges could be problematc because of hgh pressure on the entrance doors of resdental unts located on the lower and upper levels. 2) By nstallng a wnd-screenng room on the underground level and the lobby, the amount of arflow and pressure decreased for the entrance on the same levels. However, other nodes are hardly affected. Thus the effect s evaluated to be rather neglgble. 3) Analyss of archtectural measures revealed that the pressure on the underground and the lobby level for buldng A substantally decreased, however, due to the renforced ar-tghtness of buldng B, the amount of ar nfltraton for buldng A unchanged. On the upper levels of buldng B, the ar pressure slghtly ncreased. Also, uneven dstrbuton of pressure was observed due to based dvson of an elevator hall. 4) As to the mechancal method of coolng a shaft, pressure was evenly decreased by about half compared to the basc desgn. Furthermore, the problem of uneven dstrbuton of pressure was releved. Ths mechancal method was the most effcent for reducng the stack effect among the analyzed cases. ACKNOWLEDGEMENT Ths work was partly supported by grant R from the Basc Research Program of the Korea Scence & Engneerng Foundaton, WAAZ from Samsung Corporaton. REFERENCES Tamura, G. T., Wlson, A. G., 6. Pressure dfferences caused by chmney effect n three hgh buldngs. ASHRAE Transactons Vol. 3, part 2. Tamblyn, R. T., 3. HVAC System effects for tall buldngs. ASHRAE Transactons Vol., part 2. Lovatt, J. E., 4. Stack effect n tall buldngs. ASHRAE Transactons, Vol. 00, part 2. Hayakawa, S. and Togar, S., 88. Study on the stack effect of tall offce buldng(part). Journal of Archtectural Insttute of Japan, Vol. 38. Jo, J. H., Yang, I. H., Yeo, M. S., Km, K, W., A case study on the feld measurement and reducton of the stack effect n hgh-rse buldngs. Archtectural Insttute of Korea, Vol. 8-. Dols, W. S and Walton, G. N., CONTAMW 2.4 user gude and program documentaton. NISTIR, Natonal Insttute of Standards and Technology. ASHRAE, 200. ASHRAE gude and data book-fundamentals and equpment. Amercan Socety of Heatng, Refrgeratng, and Ar-Condtonng Engneers, Inc., Chapter 26. Tamura, G. T., 4. Smoke movement and control n hgh-rse buldngs. Natonal Fre Protecton Assocaton. Jo, J. H., 200. Smulaton of pressure dstrbuton and solvng the pressure dfferentals problem n hgh-rse resdental buldngs. Archtectural Insttute of Korea, Vol. 2-. ASHRAE, 3. Feld verfcaton of problems caused by stack effect n tall buldngs. ASHRAE Research Project 66, Amercan Socety of Heatng, Refrgeratng and Ar-Condtonng Engneers. The fre fghtng law n Korea, Deutsche Industre Normen(DIN). 38