COLLECTOR SELECTION FOR SOLAR EJECTOR COOLING SYSTEM

Transcription

1 Slar Enrgy Vl. 71, N. 4, pp , 001 Prgamn P II: S X(01) Publishd by Elsvir Scinc Ltd Printd in Grat Britain X/01/$ - s frnt mattr lcat/ slnr COLLECTOR SELECTION FOR SOLAR EJECTOR COOLING SYSTEM, * * ** ** B. J. HUANG, V. A. PETRENKO, I. YA. SAMOFATOV and N. A. SHCHETININA *Dpartmnt f Mchanical Enginring, Natinal Taiwan Univrsity, Taipi 106, Taiwan **Odssa Stat Acadmy f Rfrigratin, Odssa 7006, Ukrain Rcivd 1 Sptmbr 1999; rvisd vrsin accptd 7 March 001 Cmmunicatd by BYARD WOOD Abstract Th prfrmanc f a slar jctr cling systm is simulatd using thr diffrnt cllctrs: a cnvntinal flat plat cllctr, a high fficincy flat plat cllctr and a vacuum-tub cllctr. It is shwn that with th prpr slctin f th gnrating tmpratur an ptimum COP can b achivd. Th slar jctr cling systm using th singl-glazd slar cllctr with slctiv surfac and an nhancd air insulating layr can b mst cnmical whn pratd at th ptimum gnrating tmpratur f th jctr cling machin. In this cas, th slar systm cst is arund 1 USD pr watt f cling capacity fr air cnditining applicatins. 001 Publishd by Elsvir Scinc Ltd. 1. INTRODUCTION. DESIGN OF A SOLAR EJECTOR COOLING A slar cling/ rfrigratin systm which cnvrts SYSTEM th slar thrmal nrgy int cling ffct W hav bn invstigating jctr cling has lng bn an intrsting subjct fr intists machins (ECM) using R113 and R14b as th and nginrs. In practical applicatin, a slar wrking fluids (Huang t al., 1985; Ptrnk and cllctr is usd t absrb th slar thrmal Shchtinina, 199; Ptrnk t al., 1997; nrgy first. Th hat is thn usd t driv a Shchtinina t al., 1987a,b). In a rcnt study, w hat-drivn cling machin t prduc a cling fund that a slar jctr cling systm (SECS) ffct. Th ttal cst f a slar cling systm using R141b as th wrking fluid and utilizing a thus includs th csts f th slar nrgy cllct- spcially-dsignd jctr can btain a bttr ing systm and th hat-drivn cling machin. COPECM than bfr (Huang t al., 1998, 1999; Fr a hat-drivn cling machin, th rquird Huang and Chang, 1999). An ECM using R141b gnrating tmpratur may b high (highr than as th wrking fluid is thus chsn fr th SECS 808C). A high-prfrmanc vacuum-tub cllctr in th prsnt study. Fig. 1 is th hmatic f a with high cst is thus rcmmndd and th ttal singl-stag SECS. cst f a slar cling systm bcms unaccpt- A SECS cnsists f an ECM and th slar abl. cllctr systm. Slar thrmal nrgy is absrbd Whthr a chapr slar cllctr lik a flatby th slar cllctr and usd t driv th ECM. plat cllctr can b usd fr a slar cling Th gnrating tmpratur Tg f th ECM is systm still rmains an unrslvd qustin fr usually high (. 708C) in rdr t btain a bttr many rsarchrs. By utilizing a high-quality prfrmanc. Th slar cllctr thus nds t slctiv surfac, gd insulatin dsign and highprat at a highr tmpratur (. 808C). Vacuum prfrmanc glass cvr, th flat-plat slar cltub slar cllctrs hav bn rcmmndd by lctr can b mad with rlativly high fficincy many rsarchrs fr SECS in rdr t hav at lw cst. In additin, th fficincy f hathighr nrgy cllctin fficincy at a high inlt drivn cling machins has als bn imprvd tmpratur. Hwvr, th cst is vry high. Fr a dramatically. Th prsnt study intnds t r- SECS which rquirs th cllctr t prat at a xamin th fasibility f using lss xpnsiv tmpratur in th rang C, a chapr flat-plat slar cllctrs t prvid th nrgy fr a slar cling systm. flat-plat typ cllctr may b usd thugh its nrgy cllcting fficincy is rlativly lw. Fr a SECS, slctin f th dsign pint fr Authr t whm crrspndnc shuld b addrssd. cndnsing tmpratur T c, vaprating tmpra- tur T and gnrating tmpratur T f th ECM Tl.: ; fax: ; g -mail: bjhuang@tpts6.sd.nt.tw 69 is vry imprtant. Th mthd f th dsign f an

2 70 B. J. Huang t al. th ptimal Tg that crrspnds t a maximum COP is dtrmind in th prsnt study. 3. SOLAR COLLECTOR SELECTION FOR EJECTOR COOLING SYSTEM Fr th hat supply f SECS w slctd thr cmmrcially availabl slar cllctrs fr cmparisn. Typ A is a lw-cst spcially dsignd singl-glazd flat-plat slar cllctr with a slctiv surfac. Typ B is a cnvntinal singlglazd slar cllctr with a slctiv surfac. Th diffrnc btwn typ A and typ B cllctr lis in th insulatin layr dsign. Typ A cllctr uss a 10-cm layr f air spac (insulatin) bnath th glass cvr. Typ C is a vacuum-tub slar cllctr with tub-in-sht fin. Th stadystat thrmal prfrmanc curvs f ths slar cllctrs ar (T i T a) h C ]]], A I T Fig. 1. Schmatic diagram f slar jctr cling systm. m CA ]] (Typ A) () WK (T i T a) h C ]]], B I T studid by Huang t al. (1999) and Huang and m Chang (1999). It has bn shwn that th dsign C B ]] (Typ B) WK (3) ECM using R141b as th wrking fluid has bn paramtrs f an jctr ar dpndnt n th prating cnditins (T, P, T, P, T, P ) which (T i T a) c c g g h C C]]], ar rlatd t th spcific nds f th applicatin IT and th quipmnt capability. Th vapratin m tmpratur T C 5.0 ]] is usually in th rang f 5 108C C (Typ C) WK fr air cnditining purpss and abut 5 r (4) 68C fr rfrigratin purpss. Th cndnsing whr IT is th incidnt slar radiatin upn th tmpratur Tc dpnds bth n th hat-rjcting cllctr aprtur (W m ); Ti and Ta ar th quipmnt usd fr th cndnsr and n th typ cllctr inlt and th ambint tmpraturs, f th cling fluid (watr r air). Fr diffrnt rspctivly. Eqs. () and (3) wr btaind frm climatic cnditins it sprads vr a wid rang, tsting rsults f th slar nrgy lab at th usually 8 408C. In th prsnt study, th dsign Natinal Taiwan Univrsity fr th typ A and B calculatin f a R141b ECM fllws th mthd cllctrs. Eq. (4) fr th typ C cllctr was dvlpd by Huang t al. (1999) and Huang and btaind frm th manufacturr. Chang (1999). In th prsnt study, w first dtrmin th Th slctin f gnrating tmpratur Tg is COP f an ECM fr diffrnt climatic cnditins spcially imprtant fr SECS sinc it affcts nt (T c58 408C) in an air cnditining rgim nly th cfficint f prfrmanc f th jctr- (T 588C) and a rfrigratin rgim (T 568C) cling machin (COP ), but als th f- fr a wid rang f gnrating tmpraturs ECM ficincy f th slar cllctr h. An incras in (T C). Th calculatin fllws th g Tg incrass th COPECM but dcrass th h. mthd dvlpd by Huang t al. (1999) and Sinc th vrall fficincy f SECS is th Huang and Chang (1999). Th rsults ar shwn prduct f th particular cfficints in Fig.. As sn frm Fig. COPECM incrass with COP5 COPECM3h, (1) incrasing Tg and T and with dcrasing Tc and

3 Cllctr slctin fr slar jctr cling systm 71 Fig.. Variatin f COP with T fr T 588C and T 568C at diffrnt T. ECM g c anc f a SECS. Cmparisn btwn th diffr- nt typs f slar cllctrs fr hat supply f SECS was first mad. Th slar thrmal nrgy is transprtd t th gnratr by a hating mdium can rach th valu 0.7 at Tg51008C, Tc588C and T588C. Accrding t th prfrmanc f th ECM shwn in Fig., w thn valuat th prfrm- Fig. 3. Variatin f COP with T fr T 588C and T 568C at diffrnt T (cllctr typ A). g c

4 7 B. J. Huang t al. Fig. 4. Variatin f COP with T fr T 588C and T 568C at diffrnt T (cllctr typ B). g c (watr). Th inlt tmpratur f th slar cllc- a givn T g, T c, and T, accrding t Eq. (1). tr was assumd 108C highr than th gnrating Pltting COP fr varius T g, T c, and T,wcan tmpratur f th ECM, i.. Ti5 Tg1108C. Th find th ptimum dsign f a SECS. incidnt slar radiatin is assumd at IT5700 W Figs. 3 5 shw th variatin f COP with Tg m and th ambint tmpratur at Ta5308C. fr T588C and T568C attc58, 3, 36 and Frm this, th thrmal fficincy f a slar 408C. Each curv n Figs. 3 5 has a maximum cllctr h can b calculatd. Th vrall COP valu, which crrspnds t th ptimum gnrat- f th slar cling systm COP is valuatd fr ing tmpratur f th jctr cling machin. Fig. 5. Variatin f COP with T fr T 588C and T 568C at diffrnt T (cllctr typ C). g c

5 Cllctr slctin fr slar jctr cling systm 73 Tabl 1. A slar jctr air-cnditining systm using diffrnt typs f slar cllctrs Cllctr typ A B C Cling capacity, Q (kw) Evaprating tmpratur, T (8C) Cndnsing tmpratur, T (8C) c Optimum gnrating tmpratur, T (8C) g Optimum COP Slar cllctr fficincy, h Optimum COPECM Slar cllctr ara, A (m ) Slar systm cst C, USD 10,30 14,40 4,730 S Pric f slar systm, USD/ m C S/Q, USD/ W cling capacity Tabl. A slar jctr rfrigrating systm using diffrnt typs f slar cllctrs Cllctr typ A B C Cling capacity, Q (kw) Evaprating tmpratur, T (8C) Cndnsing tmpratur, T (8C) c Optimum gnrating tmpratur, T (8C) g Optimum COP Slar cllctr fficincy, h Optimum COPECM Slar cllctr ara, A (m ) Slar systm cst C, USD S Pric f slar systm, USD/ m C S/Q, USD/ W cling Th ptimum COP dcrass with incrasing Tc Th cllctr fficincy valus in Tabls 1 and and dcrasing T. It can b sn that, fr wr calculatd frm Eqs. () (4) using th btaining a highr slar cllctr fficincy, Tg inlt tmpratur Ti5 Tg1 108C. can b chsn at a tmpratur abut 10 t 158C lwr than th crrspnding ptimum valus with nly vry littl ffct n th ptimum COP. 4. DISCUSSION AND CONCLUSION Th ttal installatin cst f th slar cllctr In th prsnt papr, w hav shwn that a systm is stimatd. Tabl 1 shws th SECS fr SECS using cnvntinal singl-glazd slar clair-cnditining applicatin at a fixd cling lctr with slctiv surfacs can b mst cncapacity (10 kw). It is intrsting t nt that, mical by a prpr chic f ptimum gnrating with a prpr slctin f th gnrating tmpra- tmpratur f th ECM. In this cas, fr th tur, an ptimum COPECM can b dtrmind. Fr ptimum gnrating tmpratur in th rang 85 th flat-plat cllctrs (typ A and typ B), h 908C, th slar cllctr fficincy can rach maks littl diffrnc (0.43 against 0.39) but and th vrall COP f a SECS COPECM maks a largr diffrnc (0.44 against rachs abut 0.19 fr air cnditining purpss 0.31). Thugh h and COPECM ar highr (0.54 and 0.10 fr rfrigratin purpss. Th slar and 0.5, rspctivly) fr a SECS using th slar systm cst is arund 1 USD pr watt f cling cllctr typ C, th cst f th vacuum-tub slar capacity in air cnditining applicatins. Th unit cllctr (typ C) is vry high. Th unit cst f a systm cst C S/Q fr rfrigratin applicatins is slar systm C S/Q using typ C cllctr b- abut n tim biggr than that fr th air-cncms th highst. ditining applicatin. It is shwn that th SECS using typ A cllctr is mst cnmical. Th unit slar cling systm cst is arund 1 USD pr watt f NOMENCLATURE cling capacity. Tabl shws th cas f a SECS fr th A ttal slar cllctr ara, m CS slar cllctr cst, USD rfrigratin applicatin. It shws again that th IT slar radiatin intnsity incidnt upn cllctr SECS using typ A cllctr is mst cnmical. aprtur, W m Th unit cst f th slar systm C /Q fr th Q cling capacity, kw S Ta ambint tmpratur t cllctr, 8C rfrigratin applicatin is abut n tim highr Tc critical cndnsing tmpratur f jctr cling than that fr th air-cnditining applicatin. machin, 8C

6 74 B. J. Huang t al. T vaprating tmpratur f jctr cling ma- Huang B. J., Chang J. M., Wang C. P. and Ptrnk V. A. chin, 8C (1999) A 1-D analysis f jctr prfrmanc. Int. J. Rfrig. Tg gnrating tmpratur f jctr cling machin,, C Ti inlt tmpratur t cllctr, 8C jctr dsign. Int. J. Rfrig., Huang B. J. and Chang J. M. (1999) Empirical crrlatin fr COP cfficint f prfrmanc f slar cling systm Huang B. J., Jiang C. B. and Hu F. L. (1985) Ejctr (5cling pwr/ slar nrgy input), dimnsin- prfrmanc charactristics and dsign analysis f jt lss rfrigratin systm. ASME J. Eng. Pwr 107, COP h ECM cfficint f prfrmanc f jctr cling ma- Ptrnk V. A. and Shchtinina N. A. (199) A slar vapr chin (5cling pwr/ hat nrgy input), di- jctr rfrigratr tsting in air cnditining rgim. In mnsinlss Prcdings Wrld Rnwabl Enrgy Cngrss, Sptmbr thrmal fficincy f slar cllctr, dimnsinlss 13 18, Rading, UK, pp Ptrnk V. A., Bulavin I. V. and Samfatv I. Y. (1997) Invstigatin f th mthds incrasing th fficincy f Acknwldgmnts Th prsnt study was supprtd by th slar jctr cling and rfrigratin systms. In Prcd- Natinal Scinc Cuncil f ROC, Taiwan, thrugh grant n. ings ISES 1997 Slar Wrld Cngrss, August 4 30, NSC88-1-E Tajn, Kra, Vl. 4, pp Shchtinina N. A., Zhadan S. Z. and Ptrnk V. A. (1987a) Exprimntal invstigatin f a slar jctr Frn rfrigrating REFERENCES machin. Glitkhnika 3(3), Shchtinina N. A., Zhadan S. Z. and Ptrnk V. A. (1987b) Huang B. J., Chang J. M., Ptrnk V. A. and Zhuk K. B. Cmparisn f th fficincy f varius ways f hating th (1998) A slar jctr cling systm using rfrigrant gnratr f a slar jctr Frn rfrigrating machin. R-141b. Slar Enrgy 64(4 6), 3 6. Glitkhnika 3(4),