NUMERICAL SIMULATION ON AIR DISTRIBUTION OF A TENNIS HALL IN WINTER AND EVALUATION ON INDOOR THERMAL ENVIRONMENT

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1 Engneerng Revew, Vol. 34, Issue 2, , NUMERICAL SIMULATION ON AIR DISTRIBUTION OF A TENNIS HALL IN WINTER AND EVALUATION ON INDOOR THERMAL ENVIRONMENT X. Su 1* G. Han 2 F. Chen 3 1 School of Envronmental Scence and Engneerng, Chang an Unversty, X an , Shanx, Chna 2 X an Muncpal Commsson of Urban-Rural Development, X an , Shanx, Chna 3 Chna Unted Northwest Insttute for Desgn and Research, X an , Shanx, Chna ARTICLE INFO Artcle hstory: Receved: Receved n revsed form: Accepted: Keywords: Tenns hall Ar dstrbuton Numercal smulaton Thermal envronment Thermal comfort 1 Introducton Stadums are large space buldngs whch have large space, large heat transfer of envelopes, large staff, ntensve lghts, and large ar-condtonng load. Therefore, desgnng ratonal ar dstrbuton to meet the requrements of games and audences on the premse of low energy consumpton of arcondtonng system has great sgnfcance. For the Abstract: Supplyng ar wth ball spout ar dffusers s a common ar-condtonng system for ar dstrbuton n large space stadums. When supplyng hot ar wth ball spout dffusers n wnter, the phenomenon of hot et upturnng may appear, so the desgn should consder adustng the spout angle so as to control the rsng arflow. The purpose of the paper s to predct and optmze the ar dstrbuton of a tenns hall n wnter for the purpose of gudng the desgn and regulaton of ar-condtonng system. Based on the optmal scheme of summer condtons, usng computatonal flud dynamcs (CFD) technque, the ar dstrbuton and ndoor thermal envronment of a tenns hall n wnter were numercally smulated. Two condtons were consdered dschargng ar wth spouts downwards wth a 30 degree slope and dschargng ar horzontally. Indoor thermal envronment was evaluated from two case studes ncludng the protecton of the movement of the ball and thermal comfort of the human body, and consequently, the optmal desgn was then proposed. The results can provde some gudance for ar dstrbuton desgn and spout regulaton n wnter condtons of ar-condtonng systems n smlar tenns halls. ar dstrbuton desgn of large space stadum, the dffculty s how to predct ndoor ar dstrbuton quckly and accurately to develop a reasonable ar dstrbuton scheme. The stadum s a typcal type of a large space buldng, and ts nternal arflow s more complcated than the one of offce buldngs. The method of tradtonal et analyss cannot be appled to a varety of complex stuatons such as varous dstrbutons of nternal heat sources, and * Correspondng author. Tel.: ; fax:

2 110 X.M. Su, G.H. Han, F. Chen: Numercal smulaton on varous layouts of ar nlets and outlets [1]. CFD smulaton has some advantages such as beng quck, economcal, ntutve, and easy to conduct [2]. It has ncomparable superorty n predctng the ar dstrbuton of the large space buldngs as well as human thermal comfort [3-5]. Supplyng ar wth ball spout ar dffusers s the common ar dstrbuton form n a large space Stadum [6,7]. Due to a large nozzle secton, large ar supply velocty and long ar et, the supplyng ar strongly mxes wth ndoor ar to form a larger recrculaton zone. Therefore, settng several dffusers can meet the requrements of the ar dstrbuton n such a large space. Also, t has some advantages such as a smple layout, convenent nstallaton and low nvestment costs. Supplyng ar wth ball spout dffuser s smlar to the ar supply from the sde wall, and the arflow pattern belongs to lmted et. The ar dstrbuton of lmted et depends on buldng geometry, mountng heght of the ar nlet and other related factors. If the mountng heght of the ar nlet s too low, the et wll drectly come nto the personnel actvty area; f the mountng heght of the ar nlet s too hgh, the thckness of recrculaton zone wll ncrease and the ar velocty of return ar wll decrease. Both of the napproprate mountng modes mentoned above can affect thermal comfort of a human body. When supplyng hot ar wth ball spout dffusers n wnter condton, the phenomenon of hot et upturnng may appear, so the desgn should consder adustng the spout angle so as to control the rsng arflow. The ndoor ar dstrbuton and thermal envronment n a tenns hall of Shangha cty n wnter was numercally smulated by usng Arpak2.1 software based on the optmal ar supply scheme and ball spout ar dffusers n summer condton. Two condtons were consdered ncludng dschargng ar wth spouts slopng 30 degrees downward and dschargng ar horzontally. Indoor thermal envronment was evaluated from the aspects of protectng the movement of the ball as well as the thermal comfort of a human body, and the optmal desgn was then proposed. The results can provde some gudance for ar dstrbuton desgn and spouts regulaton n wnter condtons of ar-condtonng systems n smlar tenns halls. 2 Ar dstrbuton desgn requrements n stadums The man tasks of ar dstrbuton desgn n large space stadums are to control ar velocty n the playng area, meet thermal comfort requrements and provde the acceptable ndoor ar qualty. The man desgn ponts are as follows [8]: 1) Indoor arflow should meet the requrements of sports compettons. For varous ball sport venues, controllng the ar velocty n a playng area s the key pont. For tenns halls, the ar velocty n the range of tenns actvtes should not be greater than 0.5 m/s. The heght of tenns actvty range generally s less than 4 m. 2) The arflow should form a unform temperature feld and velocty feld n the audence area, and cold draft should be avoded. Cold asymmetry should be also avoded, and the temperature dfference between human head and foot should not exceed 3 C. For the desgn of the ar velocty n a workng area, the current desgn code GB Desgn code for heatng ventlaton and ar condtonng of cvl buldngs prescrbes that the ndoor ar velocty should not be greater than 0.2 m/s n wnter and should not be greater than 0.3 m/s n summer [9]. 3) Based on meetng the above requrements, the flexble adustment of a system should be acheved for the purpose of energy-savng. 3 Numercal smulaton 3.1 Physcal model The physcal model of ths tenns hall s shown n Fg. 1. The tenns hall s a large space buldng wth a ptched roof. It has a length of 50.7 m and a wdth of 38 m. The heght of exteror wall s 7.9 m and the total heght s 13 m. There s a fabrc wall wth a 3 m heght at the dstance of 1.5 m from the surroundng walls. The total area of ths tenns hall s 1932 m 2, and the total volume s m 3. There s no audence. The total number of sportsmen, referees and caddes s 27. There are sx all-ar systems n the tenns hall, and the ar volume of each unt s 6480 CMH (m 3 /h). Ball spout ar dffusers are employed and arranged on both sdes. The ar ets are dschargng to each other. The

3 Engneerng Revew, Vol. 34, Issue 2, , geometrc dmensons of return ar outlets are 800 mm 1200 mm. The return ar outlets are located at the same sde wth the ar nlet system at the bottom of the room. Its hemlne s 0.5 m away from the ground. The outdoor desgn ar temperature s -0.1 C. The ndoor desgn ar temperature s 20 C and ndoor desgn relatve humdty s 50%. Fgure 1. Physcal model. 3.2 Numercal smulaton methods In ths artcle, Arpak 2.1 software was employed for numercal smulaton. The flow feld studed n ths artcle belongs to turbulent flow. As far as numercal smulaton methods of turbulent flow, the Reynolds-averagng equatons methods are the basc methods for engneerng turbulent flow calculaton. The Reynolds-averagng equatons methods are dvded nto two categores such as the Reynolds stress equaton method and the turbulent vscosty coeffcent method. Turbulent vscosty coeffcent method s the most wdely used method n numercal calculaton of engneerng turbulent flow, so t was also used n the smulaton of ths study. For the turbulent vscosty coeffcent method and the turbulent flow model, there are some relatonshp formulae that lnk turbulent vscosty coeffcent ( t ) to tme-averagng parameters of the turbulent flow. Dependng on the numbers of dfferental equatons determnng turbulent vscosty coeffcent, the turbulence flow models can be dvded nto the zero-equaton model, oneequaton model and two-equaton model. Based on a lot of tral calculaton smulaton result analyses, the k two equaton model was used as the mathematcal model combned wth the standard wall functon. The two-equaton model needs to solve two turbulence parameters n order to make the equatons of turbulence model be closed. In the k two-equaton model, k s the knetc energy per unt mass of the pulsatng turbulent flow, whch s defned as follows [10]: k u w (1) s the dsspaton rate of pulsatng knetc energy per unt mass of flud, and t s defned as follows: u u (2) xk xk The turbulence equatons are as follows. The contnuty equaton s: u x The momentum equaton s: u t uu x u eff x x 0 p x u T T x The energy conservaton equaton s: 0 g (3) (4)

4 112 X.M. Su, G.H. Han, F. Chen: Numercal smulaton on T t u T T t S x x P r T x The k -equaton s: k u t u t x u x The -equaton s: k t k x x k x u t T g x T x t u t x x xk 2 c1 u u u t c 2 k x x x k t T c 1c3 g k T x (5) (6) (7) The turbulent vscosty coeffcent s calculated by Eq. (8): 2 cμk t (8) Where s the ar densty; u s the velocty n the x drecton; v s the velocty n the y drecton; w s the velocty n the z drecton; x and x are the drectons (=1,2,3; =1,2,3); u s the velocty n the x drecton; u s the velocty n the x drecton; p s the ar pressure; eff s the effectve vscosty coeffcent; t s the turbulent vscosty coeffcent; s the lamnar vscosty coeffcent; s the thermal expanson coeffcent; T0 s the reference temperature (K); T s the ar temperature (K); g s the gravty acceleraton n the -drecton; s the molecular vscosty of flud. As mentoned above, the contnuty equaton, momentum equaton, energy equaton, k -equaton, -equaton, and the Eq. (8), consttute the basc flud flow and heat transfer equatons of ndoor ar. The two-equaton model coeffcents are shown n Table 1. The Boussnesq assumpton was adopted to reflect the nfluence of buoyancy force [10]. The couplng between pressure and velocty was calculated by SIMPLE algorthm. The constant heat flux boundary condton was adopted for the sold wall accordng to load calculaton results. The velocty nlet boundary condton was adopted for the ar supply nlet, and the pressure outlet boundary condton was adopted for the return ar nlet. 3.3 Smulated condtons The tenns hall s located n Shangha cty; ts arcondtonng load n summer s larger than n wnter, the desgn and selecton of the ar condtonng system depends on the summer condton. Concernng the summer condton, the author has conducted optmzaton desgn on ar dstrbuton [11]. Accordng to the smulaton results, n the double sde drectons, the desgn should respectvely arrange three ball spout dffusers wth the dameter of 400 mm, the dstance from ts center to ground s 5.95 m and the ar supply velocty s 4.78 m/s. The supplyng volume of summer condton s equal to that of wnter condton. Accordng to the load calculaton results, the supply ar temperature should be 22.5 C. When the ball spout dffuser s used to supply hot ar for heatng, the desgn usually adopts the downward blowng ar supply mode to solve the hot ar rsng problem due to thermal et floatng. Table 1. Coeffcents of the Coeffcent k two-equaton model c c1 c2 Value k T

5 Engneerng Revew, Vol. 34, Issue 2, , The author conducted numercal smulaton of two schemes ncludng dschargng ar wth spouts slopng 30 degrees downward and dschargng ar horzontally. The reasonable arflow dstrbuton was determned after analyzng, evaluatng and comparng arflow dstrbuton dfferences of these two schemes. 4 Numercal smulaton results In the analyss of numercal smulaton results, four representatve vertcal sectons were consdered ncludng a vertcal secton through the ar nlet (x=3.4m), a vertcal secton through the return ar outlet (x=8.3m), two sectons through the human body (z=6.6m, y=1.4m) and three sectons (y=4.3m, y=4.5m, y=5.95m) through spouts. 4.1 Supplyng ar wth spouts slopng 30 degree downward (Condton A) The velocty and speed felds of x=3.4m are shown n Fg. 2. The velocty and speed felds of x=8.3m are shown n Fg. 3. As the fgures have shown, the ar s suppled downward, but the upturned phenomenon of thermal et s not obvous, so the thermal et drectly comes nto the staff actvty area. Due to the short range of thermal et and less ar entranment n workspace, the work area cannot form a crcumfluence zone. The arflow forms updrafts n the mddle of the room after fnshng the attenuaton of ts speed, then crosses the cloth obscuraton and dscharges from the return ar outlet. Ths ar dstrbuton form makes the upper non-ar-condtoned area form a recrculaton zone, whle the lower personnel actvty area does not form a recrculaton zone. The ar dstrbuton n personnel actvty zone s uneven, and the speed of partal zone has exceeded 0.5 m/s, whch cannot meet the comfort requrements and the requrement of desgn velocty n the movement zone of the ball. The man reason that the thermal arflow does not rse s that the supply ar temperature dfference s relatvely small and the nfluence of the buoyancy effect caused by the temperature dfference s far less than the nfluence of the ar supply momentum. Fgure 2. Velocty and speed felds of x=3.4m secton n condton A. Velocty feld; Speed feld.

6 114 X.M. Su, G.H. Han, F. Chen: Numercal smulaton on Fgure 3. Velocty and speed felds of x=8.3m secton n condton A. Velocty feld; Speed feld. 4.2 Supplyng ar wth spouts horzontally (Condton B) Fg. 4 shows the velocty and speed felds of the x = 3.4m secton at the ar nlet. Fg. 5 shows the velocty and speed felds of x=8.4m secton at the ar outlet. Fg. 6 and Fg. 6 show the temperature feld through the nlet secton and the outlet secton, respectvely. From Fgs. 4 and 5, t can be seen that the two ets overlap n the mddle of the Z-drecton above the ball movement area, and most of ar flows nto the lower part of ball movement area and forms reflux, whch meets the requrements for fresh ar of the work area. Due to hgher ar supply temperature and rsng of hot ar, the phenomenon of et snkng s not obvous compared wth condton 4.1. There s a lght subsdence phenomenon of warm ar n Fg. 5. It s manly because of the entranment of warm ar due to the recrculaton ar zone formed near the ar outlet. The ar velocty of recrculaton zone s less than 0.3 m/s, and t can meet the desgn requrements. As can be seen from Fg. 6, the temperature feld n the workng area s consstent and ts value s about 22.1 C. Fg. 7 shows the velocty feld of y=5.95m secton. As can be seen from the fgure, several parallel ets ntersect at the et boundary, and then supermpose wth each other. It makes ndoor arflow evenly dstrbute and makes dead ends be avoded n room. The PMV and PPD ndces are wdely used to predct thermal comfort of a human body n steadystate thermal envronment [12]. The PMV (predcted mean vote) s an ndex that predcts the mean value of thermal sensatons of the maorty of persons n the same envronment, based on the heat balance of the human body. The PPD s an ndex (predcted percentage dssatsfed) that establshes a quanttatve predcton of the percentage of people dssatsfed wth a thermal envronment, people who feel too cool or too warm. The GB Standard recommends the values of PMV/PPD ndces to be adopted: -1 PMV 1; PPD 27% [12]. In the calculaton of the PMV and PPD ndces, the average metabolc rate of people s 2.0 met, and the clothng nsulaton value s 0.5 clo. Fg. 8 shows the PMV and PPD values of z=6.6m secton. Fg. 9 shows the PMV and PPD values of y=1.4m secton. (0 to 2 m), and the PPD values are less than 15%. It can be seen from the fgures that the PMV values are between +0.7 and- 0.7 n human actvty range. The thermal comfort ndces meet the specfcaton lmt of GB Standard [9].

7 Engneerng Revew, Vol. 34, Issue 2, , Fgure 4. Velocty and speed felds of x=3.4m secton n condton B. Velocty feld; Speed feld. Fgure 5. Velocty and speed felds of x=8.3m secton n condton B. Velocty feld; Speed feld.

8 116 X.M. Su, G.H. Han, F. Chen: Numercal smulaton on Fgure 6. Temperature feld of sectons through nlet and outlet. x=3.4m; x=8.3m. Fgure 7. Velocty feld of y=5.95m secton.

9 Engneerng Revew, Vol. 34, Issue 2, , Fgure 8. Thermal comfort of z=6.6m secton. PMV; PPD. Fgure 9. Thermal comfort of y=1.4m secton. PMV; PPD. 5 Conclusons The ar dstrbuton desgn of tenns hall should consder ball movement requrements as well as human thermal comfort requrements. Supplyng ar wth ball spout ar dffusers s an approprate ar dstrbuton desgn scheme for ths buldng type. However, when supplyng hot ar n wnter condtons, floatng of hot et may appear. CFD smulaton can predct the ndoor arflow and thermal envronment well to gude ar dstrbuton desgn and spout regulaton. Wth regard to the case n ths artcle, dschargng ar horzontally can meet the desgn requrements. Ths s because the supply ar temperature dfference s relatvely small, and the floatng of hot ar has lttle effect on ar dstrbuton. So, supplyng ar horzontally wth ball spouts s recommended n wnter for ths case. The results can provde some gudance for ar dstrbuton desgn and spouts regulaton n wnter condtons of ar-condtonng systems n smlar tenns halls. 6 Acknowledgments Ths work was supported by the Natonal Natural Scence Foundaton of Chna (Grant No ), the Postdoctoral Scence Foundaton of Chna (Grant No. 2013M532002), and the Constructon Scentfc Proect of X an Cty (Grant No. SJW201202).

10 118 X.M. Su, G.H. Han, F. Chen: Numercal smulaton on References [1] Zhao, B., L, X.T.: The Dffculty and soluton of ndoor arflow pattern desgnng for gymnasum, Refrgeraton and ar-condtonng, 2 (2002), 2, [2] Perčć, M., Lenć, K., Trp, A.: A threedmensonal numercal analyss of complete crossflow heat exchangers wth conugate heat transfer, Engneerng Revew, 33 (2013), 1, [3] Zhang, H., Yang, S.Y., You S.J.: CFD smulaton for the ar dstrbuton n a gymnasum, Heatng Ventlatng & Ar Condtonng, 38 (2008), 3, [4] Wang, G.S., Ln, B.: CFD smulaton and research on arflow organzaton n gymnasum competton hall, Refrgeraton, 29 (2010), 3, [5] Zhang, H.Z., Hou, Y., Chen W.N.: Research on CFD smulaton for ar dstrbuton n tranng gymnasum, Refrgeraton Ar Condtonng & Electrc Power Machnery, 30 (2009), 2, [6] Xe, L.Z.: Applcaton of motorzed nozzle outlets to ar condtonng system of Yanta multfunctonal gymnasum, Heatng Ventlatng & Ar Condtonng, 39 (2009), 5, [7] Zhao, B., Ma X.J., L X.T.: Outlne of Arflow Pattern nsde Gymnasum, Buldng Energy & Envronment, 2 (2002), 5, [8] Beng Insttute of archtectural desgn: Desgn code for sports buldng (JGJ ), Chna Archtecture & Buldng Press, Beng, [9] Mnstry of Constructon P.R. Chna, Desgn Code for Heatng Ventlaton and Ar Condtonng of Cvl buldngs (GB ). Beng: Chna Archtecture & Buldng Press, [10] Tao, W.Q.: Numercal Heat Transfer, X an Jaotong Unversty Press, X an, [11] Su, X.M., Zhang, X., Hu, Y.: CFD forecast on ar dstrbuton n the tenns court and schemes optmzng, Flud Machnery, 36 (2008), 3, [12] Internatonal Standard Organzaton for Standardzaton, Moderate thermal envronments: determnaton of the PMV and PPD ndces and specfcaton of the condtons for thermal comfort (ISO7730), Geneva: 2005.