NUMERICAL EVALUATION ON FLOOR COOLING CAPACITY IN AN AIRPORT AH, Nijmegen, the Netherlands Tianjin, China

Transcription

1 ceedings: Building Simulatin 07 NUMEICAL EVALUATION ON FLOO COOLING CAACITY IN AN AIOT 3,3, Bing Yu, J.. uchti and.g. Luscuee Divisin Building Sevices, yal Haskning Gup, stbx AH, Nijmegen, the Nethelands Delft Univesity f Technlgy, stbx 5043, 600 GA, Delft, the Nethelands Tianjin Univesity, Schl f Envinment Science and Technlgy, 9 Weijin ad 007 Tianjin, China UABSTACT In the mden achitectual design, lage space pen aea is idely used, f example, atium, aipt, pen ffice, etc. adiatin heat tansfe pvides bette ind themal cmft and makes it pssible t apply high tempeatue cling and l tempeatue heating. This ill lead t high enegy efficiency. Wate caying adiatin systems, e.g. cling ceiling and fl heating system, becme an applicable slutin f a gd ind climate design. The fl cling is less effective than fl heating and can pvide usually limited cling capacity. In de t make a gd design f fl cling system, a theetic methd is descibed and the numeical evaluatin f the cling capacity is dne. The influence paametes f the capacity, f example the distance beteen pipes, the length f ne lp, the ate fl ate and the supply ate tempeatue, etc, have been analysed. It can be used f the cect estimatin duing the design phase. UKEYWODS Fl cling, Capacity, Numeical evaluatin, Aipt UINTODUCTION Lage space ith pen aea is idely used in the mden achitectual design, t ealize such as atium and halls. Especially, thee is a lt f lage pen space in the aipt. In the past, a le ceiling ill be placed t hide all the technical installatins, such as pipes, ducts, cables, etc. Nadays, steel stuctue is inceasing ppula. This means a vey high f in the space. Taditinal cnditining methd ith hunded pecent f ai is nt efficient in this situatin. Fl heating ks pefect f the lage fl aea in the aipt. adiatin heat tansfe pvides bette ind themal cmft. In de t make use f the existed fl heating system, the cncept f fl cling is lgically aised. It is suppsed t k ith supplied chilled ate. Sme f the aipts, such as Suvanabhumi aipt, the ne Bangkk Intenatinal Aipt, Thailand and the Intenatinal Aipt f Jeddah, Saudi Aabia applied fl cling system t cnditin the ind climate. A pevius eseach (Nissn, 97 shs adiant fl piping can be used t cl a huse, but it is nly apppiate f dy climates. The fl tempeatue is held at C by using eithe a small cling machine (chille cnnected t the fl piping the steady 3 C tempeatue f the gund by means f an eath lp. In mst climates, the cl fl can be used t supplement eplace standad ducted ai systems. Heve, in humid climates, pblems ith vecling the fl culd lead t et slippey sufaces and fungus gth. Agiiu et al (05 applied TNSYS pgam t study the pefmance f a building ith Absptin Heat ump ith fl heating/cling system. The eseach as fcussed n the applicatin as ell and used standad mdel f fl cling hich is integated in TNSYS. A validatin n the fl cling mdel ith test chambe as dne and a cnclusin as dan that the TYE 60 mdule that as used in de t assess the pefmance f the ttal system seems t have systematically undeestimated the paticula expeimental esults. Anthe eseaches lk at the applicatin f fl cling system in the esidential building as ell (Hamada, et al. 0, Lim, et al. 03, Lim, et al. 06. Nmally, fl heating ill geneate a gd tempeatue gadient vetically because the ame ai ill fl upads. In cetain applicatin, fl ill be used f bth heating and cling pupse due t the lage space, e.g. at aipt. The fl cling ill less effective than fl heating and can pvide usually limited cling capacity. This is due t the cld ai ill stay le and clse t the fl and theefe, the cnvective heat tansfe is eake than fl heating. This can be pved fm the data f heat tansfe cefficient f hizntal plate as ell (ASHAE handbk, 05. In this study, the auths build up the physical and mathematical mdel f the hall f Eindhven aipt. Based n the cnsevatin equatins, a simulatin mdel is built ith Matlab. The influences ith the ttal length, distance beteen s, supply ate

2 ceedings: Building Simulatin 07 tempeatue, themal adiatin and ate fl ate ae analyzed by simulatin. A peliminay design ppsal ith a fl cling system is chsen as the efeence. This has been evaluated and bette slutin is pesented. UMODELING A typical hydnic adiant fl system is usually placing the ate pipe beneath the finished fl sceed fl. The pipe laye is shn in the Figue. The heat tansfe pcess ccus ith the fl cling system ill invlve seveal aspects: heat cnductivity ithin the cncete fl; heat cnvectin ith the suunding ai; adiatin fm the fl t the the sufaces; and sla lad falling n the fl suface. The geneal scheme f the fl piping system is shn as Figue 3. The pipes ae placed unde the cncete laye ith cetain distance beteen diffeent lines. Sla lad m abve Ind suface adiatin cnvectin d d d δ d x m bel Figue. Example layut f hydnic adiant fl system (pictue fm Ecnst F the applicatin at Eindhven aipt, a peliminay cncept is ppsed ith the sectin vie as Figue. This is a system hich the pipes ae placed abve the pefab bad and then filling sand cncete abve them. Figue 3. Scheme f the fl piping system ith elated t the suunding Enegy cnsevatin: Ta q_sun Ts Tc T The ate pipe is installed inside the cncete laye f 80mm thickness. The cente f the pipe is (47+ = 59mm bel the fl. Outside lng diamete f the pipe is 4mm. The inne diamete is mm. q& = α ( T T + q& = U ( T T ( c t a s sun t s α = 0.7( T T + 4 σεc ( T ( t a s s d U t = ( z + x (3 λb T Ti Ts T = Ts T ln Ts T i UA t mc & p T = T + ( T T ( e i s i (4 (5 Figue. Fl cling system

3 and and ceedings: Building Simulatin 07 C is the cectin fact t cect the influence f the suunding bjects. In this study, C is chsen If much funitue fixed stuctue ith sufaces is placed neaby the fl, the suface tempeatue ill have big deviatin fm the ai tempeatue and the C ill be deceased. If lage atium is applied, C shuld be inceased. Ttal heat tansfe cefficient analysis n distibuted pipes It is assumed that the distibuted pipes ill be simplified as a cntinuus functining (cncete ce laye. Accding t the they by Kschenz and Lehmann (00, the ttal heat esistance fm the ate supply tempeatue t the cncete ce laye includes fu items: x is the heat esistance hich is suppsed the hle plane f the cncete ce is the same as the suface tempeatue f the egiste is the heat esistance fm the ate t the inne suface f the egiste is the heat esistance due t the cnductivity f the all f egiste z is the heat esistance due t the incnsistent tempeatue f the ate in the egiste t = x z (6 Whee x dx dx ln( = πδ (7 πλ b This equatin is a simplified vesin hen d dx > 0.3, d dx > 0.3 and δ dx < 0..F mst situatin, these cnditins ae met. z dx = α ( δ d π (8 δ d x ln( δ d = (9 λπ = m& c sp (0 Heat tansfe cefficient [ASHAE Handbk, 05 Fundamentals] Cnvectin fm hizntal plates facing dnad hen heated ( upad hen cled is a special case. Because the ht ai is abve the clde ai, theetically n cnvectin shuld ccu. Sme cnvectin is caused, heve, by secnday influences such as tempeatue diffeences n the edges f the plate. As an appximatin, a cefficient f smehat less than half the cefficient f a heated hizntal plate facing upad can be used. F lage space fl cling, h 0.33 = 0.7( Δ t ( F fce cnvectin, Nu hl λ = = e ( USIMULATION CONDITIONS The m tempeatue is 5 C and utside tempeatue is C. Wate supply tempeatue is 6 C. The equied cling capacity f the fl pipe system is 5W/m. A peliminay design has been ppsed as: Length f ne pipe: 0m The distance beteen cente f the neighb pipes: cm Wate fl ate: 4 l/h UANALYSIS AND DISCUSSION Evaluatin f the peliminay design Accding t the infmatin abve, the flling esults ill be achieved. F the cnditin f n mvement (n passenge, the natual cnvectin ill be applied based n the equatin (. The eleased cling capacity is appximate 7W/m the etun ate tempeatue is abut C. F the cnditin f 0.5m/s mvement (sme passenges alk elaxedly inside the aipt, the eleased cling capacity is abut W/m the etun ate tempeatue is abut. C; F the cnditin f 0.5m/s mvement (passenges keep mving, the eleased cling capacity is abut

4 cling ceedings: Building Simulatin 07 W/m and.5 C. the etun ate tempeatue is abut ssible adaptatins Seveal adaptatins can be chsen t impve the cling capacity eleased fm the fl piping system. Mdificatin f the length f ne lp; etun ate tempeatue ( C.5.5 n ai mvement Mdificatin f the ate fl ate; Mdificatin f the distance beteen the cente f neighb pipes; Change f the supply ate tempeatue. The flling figues sh the esults ith ne vaiable and the est keep the same as the peliminay design. Evey adaptatin ill sh f thee type f mvement abve the fl. Influence f length The length f ne pipe ill influence the cling capacity fm the hydnic adiant fl system. The lnge the length f ne pipe is, the highe the ate etun tempeatue is and theefe, the mean tempeatue diffeence beteen ai and ate is smalle. It is clealy shn in the Figue 4 and 5 f the change f cling capacity and ate etun tempeatue. fl cling capacity (W/m n ai mvement length (m Figue 4. Vaiatin f cling capacity f diffeent length f ne pipe length (m Figue 5. Vaiatin f etun ate tempeatue f diffeent length f ne pipe Fm the abve shn esults, it is clea that the length f the pipe shuld be deceased t 60 ~ 00m t get a 5W/m capacity f diffeent mvement cnditin. Influence f ate fl ate The ate fl ate ill influence bth the themal pefmance and the hydaulic system. Highe ate fl ate ill lead t a highe cling capacity. This can be fund fm the esult f Figue 6. Heve, attentin shuld be paid f a highe ate fl ate because this might equie a t lage pump and theefe, it is nt cst effective. fl cling capacity (W/m n ai mvement fl ate (l/h Figue 6. Vaiatin f cling capacity f diffeent ate fl ate

5 cling cling ceedings: Building Simulatin 07 etun ate tempeatue ( C.5.5 n ai mvement fl cling capacity (W/m n ai mvement fl ate (l/h Figue 7. Vaiatin f ate etun tempeatue f diffeent ate fl ate Fm the abve shn esults, it is clea that the ate fl ate shuld be inceased t 540 ~ 340l/h t get a 5W/m capacity f diffeent mvement cnditin. This is abut.7 ~ 3 times f the peliminay design. Influence f distance beteen neighb pipes The distibuted chaacteistic f the pipes ill geneate nn-hmgeneus tempeatue distibutin hizntally. Figue 8 shs a esult fm CFD (Cmputatinal Fluid Dynamics n ne sectin alng the pipe f fl cling system. It can be clealy seen that the tempeatue inceases ciculaly aund the pipe and intefees ith each the. If the distance beteen pipes changes, the hmgeneus f the tempeatue at a hizntal level changes as ell. Figue 8. Sectin vie f the tempeatue distibutin alng the pipe f fl cling (an example The h..h (heat f heat epesents the distance beteen the centes f the neighb pipes. It can be seen that the cling capacity inceases hen the h..h deceases. And this ill lead t the decease f the ate etun tempeatue (Figue h..h (m Figue 9. Vaiatin f cling capacity f diffeent distance beteen neighb pipes etun ate tempeatue ( C.5.5 n ai mvement h..h (m Figue 0. Vaiatin f ate etun tempeatue f diffeent distance beteen neighb pipes Fm the abve shn esults, it is clea that the distance beteen the pipes shuld be deceased t 0.5 ~ 0.m t get a 5W/m capacity f diffeent mvement cnditin. Influence f ate supply tempeatue Wate supply tempeatue ill influence the cling capacity as ell. When the supply tempeatue deceases, the tempeatue diffeence beteen the m ai and the ate ill becme bigge and theefe, me cling capacity can be eleased t the m. This is almst a linea pcess (Figue. And the ate etun tempeatue ill decease flling the tend as the supply tempeatue (Figue

6 cling cling ceedings: Building Simulatin 07 fl cling capacity (W/m n ai mvement fl cling capacity (W/m n ai mvement ate supply tempeatue ( C Figue. Vaiatin f cling capacity f diffeent ate supply tempeatue etun ate tempeatue ( C n ai mvement ate supply tempeatue ( C Figue. Vaiatin f ate etun tempeatue f diffeent ate supply tempeatue Fm the abve shn esults, it is clea that the ate supply tempeatue shuld be deceased t.6 ~ 3. C t get a 5W/m capacity f diffeent mvement cnditin. Influence f the sla adiatin The sla adiatin falls n the fl ill incease the cling demand t the ate pipe (theefe the cental cling machine but elease less cling capacity t the ai. This is because the sla adiatin ill be absbed by the suface f fl and tansfeed quickly t the hydnic system. The ate etun tempeatue ill be highe than the situatin f n sla adiatin. The mean tempeatue diffeence ill be smalle and leads t less effective cling capacity t the suunding ai. Influence f adiatin cectin fact C C is a cectin fact t invlve the effect f the tempeatue distibutin f the suunding sufaces. T explain it in a simple ay, hen mst sufaces ae fa aay fm the cling fl, C is clse t. In case, many sufaces ae clse t the fl, e.g. much funitue stand abve the fl, C is smalle than C (- Figue 3. Vaiatin f cling capacity f diffeent cectin fact C etun ate tempeatue ( C n ai mvement C (- Figue 4. Vaiatin f ate etun tempeatue f diffeent cectin fact C Fm the abve figues, it can be seen that C ill cect a little bit n the cling capacity but nt damatically. The change fm 0.5 t f C ill lead t abut 9% vaiatin n the cling capacity. Influence f the mvement Fm Figue 4 t 4, all the esults indicate the influence f the mvement abve the fl. It is clea that the mving f the passenges ill give a psitive effect t elease me cling capacity. In pactice, hen a lt f peple ae mving, me cling is equied. It happens baely that n mvement ccus hen the cling is equied. UCONCLUSIONS The analytical mdel f the fl cling system f the Eindhven aipt is built based n the cnsevatin equatins. The peliminay design has been simulated and culd nt be able t delive 5W/m capacity as expected fm fl piping system. Seveal paametes can be adapted t impve the cling capacity:

7 αbtb UBtB intenatinal ceedings: Building Simulatin 07 Mdificatin f the length f ne lp; Subsciptins: Mdificatin f the ate fl ate; c cling Mdificatin f the distance beteen pipes (h..h; Change f the supply ate tempeatue. The influence fm the abve paamete as ell as the the facts such as sla adiatin and the mvement f the passenges has been discussed. The intduced cectin fact C has been analyzed and the esult shs that C ill lead t a bit change n cling capacity but nt damatically. It is pssible t ptimize all the paametes ith the simulatin mdel if an bject such as ttal cst is defined. UNOMENCLATUESU q T σ ε δ d λ A Heat flux Ttal heat tansfe cefficient Tempeatue Ttal heat tansfe cefficient f distibuted pipes Stephen-Bltzmann cnstant Black bdy cefficient Diamete f pipe Themal esistance Thickness; distance Themal cnductivity Aea a s i ai suface ate inlet utlet UACKNOWLEDGEMENT The auths acknledge the financial suppt fm Ecnst. UEFEENCE ASHAE Handbk Fundamentals, 05, pp. 3.7 Agiiu, A.A., Balaaa,, C.A., Kntyiannidis, S. and Michel, E. 05. Numeial simulatin and pefmance assessment f a l capacity sla assisted absptin heat pump cupled ith a sub-fl system, Sla Enegy, Vl 79, pp. 90- Hamada, Y., Nakamua, M., Ochifuji, K., Nagn, K. and Ykyama, S. 0. Field pefmance f a Japanese l enegy hme elying n eneable enegy, Enegy and Building, Vl 33, pp Kschenz, M. and B. Lehmann, 00, Themaktive Bauteilsysteme tabs, Siss Fedeal Office f Enegy, July Lim, JH, J, JH, et al. 06. Applicatin f the cntl methds f adiant fl cling system in esidential buildings. Building and Envinment, Vl 4, I-, Januay, pp m h Cp C Δt Nu e Mass fl ate Heat tansfe cefficient Themal capacity Cectin fact Tempeatue diffeent Nusselt numbe enlds numbe andtl numbe Lim, JH, Ye, MS and Kim KW. 03. A study n the applicatin f the adiant fl cling system integated ith a dehumidificatin th system. The 8 IBSA Cnfeence f Building Simuatin, August, Eindhven, pp Mhamad, AA, Sicad, J and Bennace,. 06. Natual cnvectin in enclsues ith fl cling subjected t a heated vetical all, Intenatinal Junal f Heat and Mass Tansfe, Vl 49, Issue -, Januay, pp.08- Nissn, N. 97. "Can adiant Fl Cling Succeed Despite Design Limitatin?". Enegy Design Update, (7:5 pp. 5-8, May