SOLAR COLLECTOR WITH HEAT PUMP. Latvia University of Agriculture, Faculty of Engineering

Transcription

1 ENGINEERING FOR RURAL DEVELOMENT Jelgv, SOLAR OLLETOR WITH HEAT UM Henr utān, Imnt Zemel, Žn Jeo, Igor Krtut Ltv Unverty of Agrculture, Fculty of Engneerng Abtrct. In order to ncree wter temperture, whch h been heted by the olr collector, het pump uggeted to ue. There theoretcl clculton h been crred out nd the reult how tht by the ue of het pump t poble to me the dometc wter hetng unt, contng of olr collector nd het pump. The objectve of the nvetgton to be the operton of uch unt. In order to be ure bout the wor of the unt there expermentl nvetgton h to be performed. For tht t envged to develop the unt by the ue of flt plte olr collector nd the het pump, whch mde from the refrgertor coolng ggregte worng n oppote drecton. Key word: olr rdton, olr collector, het pump, wter hetng. Introducton Solr collector re wdely ued for hot dometc wter hetng n mny countre of the world. Accordng to over nvetgton durng ummer month t poble to ue olr collector for wter hetng n Ltv too, regrdle of lrge number of cloudy nd rny dy even n ummer tme [1]. On the verge we hve bout 1800 unny hour per yer n compron wth outhern countre whch hve 2200 nd more unny hour per yer, therefore the olr rdton often not enough to rech the necery hot wter temperture by the ue of olr collector only. On cler unny dy the power of globl rdton reche 1000 W m -2, prt of whch drect, nd prt, dffue rdton (Tble 1). My June nd July together gve bout 52 % of totl yerly rdton, but December nd Jnury me only le thn 2 % of yerly rdton n Ltv. Tble 1 Dffue rdton out of globl n Ltv [2] Dffue rdton, % Month I II III IV V VI VII VIII IX X XI XII Yer On the verge n ummer month (Aprl-September) the pecfc olr rdton only bout 500 W m -2 on horzontl urfce. Durng the ret of month the pecfc power of rdton lower nd tht not enough for dometc wter hetng need. Therefore we re loong for wy to ncree the wter temperture by the ue of other techncl men. One of them het pump. The contructon nd prncple of operton of the het pump re well nown nd they re vlble n the mret. We hve mde theoretcl exmnton bout the poblty of multneou wor of olr collector nd het pump one unt, nd now we hve to me n expermentl nvetgton of t operton n rel feld condton. For ll tht the prce of the het pump too hgh for. In order to orgnze the experment we hve to me the unt by ourelve, nd by the ue of cheper nd vlble mterl. The objectve of the nvetgton to cler up the effcency of the common wor of olr collector nd het pump. Mterl nd Method The prncpl cheme of the contructon nd operton of uch unt n Fg. 1 preented, contng of olr collector, hot wter ccumultor nd het pump. For the expermentl nvetgton t envged to me up the unt, n whch het pump the ggregte of refrgertor wll be ued (Fg. 2). To the evportor of the refrgertor ggregte there the het exchnger 10 wth the hot wter tn 8 connected. The rdtor of the refrgertor ggregte wll be ued the condener 14 of the het pump, nd plced nto the hot wter bn

2 ENGINEERING FOR RURAL DEVELOMENT Jelgv, TS TS2 17 Fg. 1. rncpl cheme of the unt of olr collector nd het pump: 1 olr collector; 2 borber of the collector; 3 expnon veel; 4 het crrer nflow vlve; 5 crculton pump; 6 r outlet vlve; 7 hot wter tn; 8 het pump condener; 9 electrc heter; 10 perforted dphrgm; 11 het pump evportor; 12 contr-flow vlve; 13 het exchnger; 14 wter mxng vlve; 15 hot wter conumer; 16 het pump; 17 cold wter nlet; TS temperture enor; control devce 1 13 TS T1 10 T2 14 TS TR T3 TS2 11 Fg. 2. Opertonl cheme of the expermentl unt: 1 olr collector; 2 borber; 3 crculton pump; 4 nlet vlve; 5 flow control vlve; 6 cont-flow vlve; 7 het counter; 8 het exchnger-thermo; 9 expnon veel; 10 het pump evportor; 11 het exchnger of collector crcle; 12 het pump; 13 hot wter torge tn; 14 condener of het pump; TS temperture enor; control unt; TR temperture regultor; T1...3 thermometer The prncple of operton of the ytem followng. When the borber of the collector heted by the un nd the temperture of the het crrer, meured by the enor TS1, become hgher then n the hot wter tn 8 (Fg. 2), meured by the enor TS2, the control devce VB wtche on the pump 3, whch trnform the het from the borber nto the hot wter bn 8. When the temperture n the hot wter tn 8, meured by the enor TS3, reche the vlue tted n the temperture regultor TR, t wtche on the het pump 12. The het pump 12 trnform the het from the hot wter tn 8 to the hot wter tn 13, conumng for th ome mount of electrc energy. 35

3 ENGINEERING FOR RURAL DEVELOMENT Jelgv, Reult nd Dcuon In order to hve ttonery-worng regme t dfferent rdton power on the collector, nted of olr rdton there electrc lmp wth controlled power wll be ued. For the power meurng und obtned energy regtrton n the collector crcle there the het counter 7 wll be ued. For the regtrton of the mount of het ccumulted n the hot wter tn 13, t envged to ue the meurement of the thermometer T1 Tn nd formul (1) where: Q Q het energy, produced by collector, W h -1 ; G mount of het crrer, g; p 3 = G T, (1) pecfc het of het crrer, J -1 g -1 (for wter b p = J -1 g -1 ); T b dfference between the het crrer nlet nto borber T nd outlet To temperture. T = T T,. (2) b In order to nlyze the operton of the developed ytem the followng umed: the ytem wll operte t the rnge of mbent r temperture T = 0 30 ; temperture n the het exchnger tn 8 T = 25 ; temperture n the hot wter tn 13 T = 70 ; mxmum het crrer temperture t the outlet of borber T 30 ; w ex o o mx = dfference between het crrer nlet nd mbent r temperture T T = 0 30 or on the verget T = 15. A the dfference between the temperturet w T ex = = 45, then from Tble 2 the het trnfer coeffcent of the het pumpε = 4. 0 [3]. Tble 2 Het pump trnfer coeffcent dependng on condener nd evportor temperture dfference T w T ex = T T, ε For the experment t envged to ue the refrgertor frot ggregte XKB8-ЛМУ wth power = 160 W. Then the power produced by the unt = ε = = 640 [W]. (3) u For the operton of the unt the necery power of the olr collector [3] In our ce u = u. (4) ε 640 = 640 = 480 [W]. (5) 4 On the other hnd the power of the olr collector cn be determned = A η K ( T T )], (6) [ S 0 where: power of olr collector, W; A borber re, m 2 ; 36

4 ENGINEERING FOR RURAL DEVELOMENT Jelgv, power of rdton on the collector urfce, W m -2 ; η optcl effcency of the collector; ο K totl het loe coeffcent of collector, W m -2-1 ; T het crrer verge temperture n the borber, ; ev T het crrer nlet temperture nto borber, ; T mbent temperture,. The optcl coeffcent η ο of the olr collector doe not depend on the ntenty of olr rdton on the collector urfce, nd temperture dfference T T. It clculted by expreon ηo = α τ, (7) where τ coeffcent of penetrblty of olr ry through the gl pne ( ); α borpton coeffcent of olr rdton by the borber ( ). The effcency of olr collector [4]: where T T η = ηo K = ηo K y, (8) y T T =. (10) If the het lo of the collector chrcterzed by two coeffcent [5], then 2 1 ( T T ) 2 ( T T ) η = ηo +, (11) where 1, 2 het lo coeffcent of the collector. The ntntneou effcency of the collector gven where where F ' effcency of the borber [6]. ( α K y) η = F' τ, (12) K K0 F'=, (13) K o het trnfer retnce from het crrer to the mbent r, W m The vlue of the het lo coeffcent for flt plne olr collector depend on the type of the collector well t degn, nd re collected n Tble 3. Tble 3 Numercl vlue of optcl nd het lo coeffcent for dfferent type of collector [4] Type of collector Optcl effcency η o Het lo coeffcent K, W m -2-1 Wthout electve coutng nd gl The me wth one gl The me wth two gle Selectve coutng wth one gl Wth vcuum tube

5 ENGINEERING FOR RURAL DEVELOMENT Jelgv, houng the type of the olr collector t purpoeful to ue the monogrm gven n Fg. 3. For exmple, n our ce due to mll dfference between the temperture T T = 15 from Fg. 3 t een tht ung the collector wthout gl cover t effcency t the rdton ntenty = 400 W m -2 wll be bout If the temperture dfference T T wll chnge from 0 to 30, the vlue of effcency wll chnge from 0.95 to 0. Better reult wll be obtned ung the ordnry collector wth one gl cover. It wll operte t mller rdton ntenty, for exmple, t = 300 W m -2 nd the temperture dfference of Effcency 1, 0 T T from 0 to 30 nd t effcency wll be wth n the lmt 0, 8 Hot wter Hetng 0, 6 0, 4 Swmng pool 0, 2 ollector wthout gl Wth vcuum tube Selectve wth one gl Wth two gle Wth one gl ,05 0,10 (Tv To)/ 0,15 = 200 W/m (Tv To); o Fg. 3. The collector effcency dependng on the power of the olr rdton nd degn of the collector, well the verge dfference between the het crrer temperture n the borber nd urroundng r temperture ( T T ) Ung the ordnry collector wth two gl cover t effcency wll be lover t mll temperture dfference, but hgher t hgher temperture dfference, tht From the monogrm t een tht hgher effcency nd n wde temperture rnge wll be of collector wth electve cotng. Ung th type of collector t poble to heghten the temperture vlue gven for the het exchnger tn, for exmple, from 25 to 40. In tht ce the het pump wll operte t the temperture dfference T T = 20 nd the vlue of t het trnfer coeffcent wll be bout 8. The collector wll be more expenve, but the conumpton of electrcty, lover. To cler out the reltonhp between thee fctor one of more mportnt objectve of th experment. 38

6 ENGINEERING FOR RURAL DEVELOMENT Jelgv, oncluon 1. For more precely nvetgton of the ue of het pump n common unt wth olr collector, expermentl nvetgton hve to be crred out. 2. At hgher effcency olr collector re opertng when ther borber plte hve electve cotng. Reference 1. L.Kncevc, I.Zemel, M.Krtpon. oblte of Wter Hetng by Solr Energy n Ltv. roceedng of the 5th Reerch nd Development onference of entrl nd Etern Europen Inttute of Agrculturl Engneerng. rt 2. Urne, Kev, 2007, pp Швер Ц.А., x Борисовский Ц.А. Климат Риги. Рига: Авотс, стр. 3. Хайнрих Г., Найорк Х., Нестлерю В. Теплонасосные установки для отопления и горячего водоснабжения. Москва: Энергоиздат, стр. 4. Харченко Н.В. Индивидуальные солнечные установки. Москва: Энергоиздат, стр. 5. euer F.A., Remmer K.H., Schnu M. Solr Therml Sytem. Berln: Solrprx, p Yog Gowm D., Kreth F., Kreder J.F. rncple of Solr Engneerng. New Yor: Tylor & Frnc Group, p