EFFICIENT USING OF LOW-GRADE HEAT OWING TO HEAT PUMPS BEHAVIOUR ENHANCEMENT

Transcription

1 IV Mink International Seinar Heat Pipe, Heat Pup, Rrigerator Mink, Belaru, Septeber -7, 000 EFFICIENT USING OF LOW-GRADE HEAT OWING TO HEAT PUMPS BEHAVIOUR ENHANCEMENT Y. A Kuza-Kichta., A. S Sedlov, D. V. Buyakov Mocow Power Engineering Intitute (Technical univerity), Departent of Power Station and Theral Phyic, Mocow, Ruia Abtract By ean of heat tranfer enhanceent in the evaporator and condener it i poible to perfect HPI feature and obtain a reducing their cot. Method of heat tranfer enhanceent in the heat pup evaporator are analyed. In Mocow Power Engineering Intitute are conducted a heat tranfer enhanceent tudie in two-phae abience by intered porou coating. The equation for the teperature difference, at which the boiling begin, i obtained fro the teperature ditribution analyi in a coating. The expreion for heat tranfer coficient at boiling on urface with porou coating i obtained. The data on boiling heat tranfer of water for urface without and with porou coating are preented. Efficiency of heat tranfer enhanceent uing in frot achine evaporator i deterined by teting drink cooler of copreor type OH-0-. On internal urface of piral tube there i evaporator with porou coating. Diaeter of copper particle ~ 0 Mk. Thickne of coating ~ 0.. Poroity ~ 60%. It i dicovered that porou coating in the evaporator bring to the liquid cooling peedup. A drink cooling tie decreae about 0 % when the porou coating in the evaporator i ued. KEYWORDS Heat pup, heat tranfer enhanceent, evaporator, condener, intered porou coating, cooler of drink, drink cooling tie. INTRODUCTION Heat pup find a broad uing in row of leading countrie. However in Ruia they have liited preading []. Main reaon i their coparatively high cot. In odern condition exit poibilitie of ficient uing the heat pup intallation (HPI) alo in our country. By ean of heat tranfer enhanceent in the evaporator and condener it i poible to perfect HPI feature and obtain a reducing their cot. Thi will allow utiliing enorou low-grade heat quantity, which are at preent thrown in the urround abience. For condenation heat tranfer enhanceent are ued the urface with the artificial roughne: groove, knurl and direct or pecial rib. Heat tranfer coficient on pipe at condenation i poible vatly to enlarge by ean of finning and coplex for thorn. Increaing heat tranfer coficient for the pipe with thorn, unconnected in iediate conjunction with the urface developent, can be ufficiently big (up to tie)[]. Method of heat tranfer enhanceent in the heat pup evaporator are analyed. It i hown that ficient heat tranfer enhanceent ethod at boiling i urface with porou coating uing []. Such coating tiulate a foring the bubble nucleu and harply raie boiling heat tranfer. The heat tranfer enhanceent poibilitie by ean of porou coating are analyed. In Mocow Power Engineering Intitute are conducted tudie a heat tranfer enhanceent in twophae abience by intered porou coating. Porou coating have different thickne and particle diaeter and are ade fro different etal powder. The experiental data are obtained, proce odel and accounting trategie and recoendation on practical ue of heat tranfer intenifier 7

2 deigned. The optial heat tranfer intenifier feature have been deterined that allowing to raie device production or to reduce etal conuption and to increae reliability of HPI. INVESTIGATION RESULTS The tet ection i vertical or horizontal tube diaeter 8, length up to 000. The intered porou coating with thickne 0, 0, conit of copper and teel. The invetigation occurred at water a velocitie of kg/, preure of 0, 6,0 MPa and tea qualitie up to,. The vertical tet ection ha a thin 0, wall and coparatively all pace between the therocouple. The zone with different echani of heat tranfer are dined through the change of wall teperature fluctuation intenity. The inaccuracy of heat tranfer coficient deterination i le then 0 %. Porou coating with optial characteritic have a poitive influence on the heat tranfer at the nucleate boiling. The equation for the teperature difference at which the boiling begin, i obtained fro the analyi of teperature ditribution in a coating [] : ΔT = σt q& ( + Re 0 ) ρ rλ., () with 0 Re. 0. λ = λ CM γ + ε λcm ε λ ε λ ( γ) + +, γ = ε. Fro equation () follow that the value fective theral conductivity λ. ΔT i reduced with decreaing flow rate and increaing The nucleation ite denity agnification at boiling on a urface with a porou coating can be characterized by the following quantity N D D rρ Δ T ax ax D = cr T, () σ where value i dined by angle lope of a boiling curve, D ax -axial pore diaeter. = aδ / λ b, b =, a = -6,*0 (W/ K) () + We aue that thi value i equal to the particle diaeter. The expreion for heat tranfer coficient at boiling on urface with porou coating i obtained in []: + ( ) D r + + λ ρ ax " + α = K q υ rρ" δ σt, () 7

3 with K = 0,0 +,8 p / p CR. Thi coficient take the preure fect into account. In Fig. the data on boiling heat tranfer of water for urface without and with porou coating are preented: for copper with a thickne of 0,, for tainle teel with a thickne of 0, and for tainle teel by thickne of 0,. With a reduction of porou coating theral reitance the heat tranfer coficient increae. In Fig. the calculation reult of heat tranfer coficient on the equation () are copared with experiental data. q, W/ Δ T, K 0 Fig.. Boiling heat tranfer of water (P = 0. MPa) - copper coating, thickne 0, - tainle teel coating, thickne 0, - tainle teel coating, thickne 0, - urface without coating - propoed equation Efficiency of heat tranfer enhanceent uing in frot achine evaporator i deterined by teting drink cooler of copreor type OH-0-. Device chee i hown on Fig.. The apparatu include copreor, evaporator, and condener. Evaporator preent itelf copper piral pipe by the diaeter 0 and length. Diaeter of piral tube arrangeent i 0. Spiral tube i preed to internal urface of tainle teel barrel, ituated in average part of cooled liquid tank. A a working liquid the F - wa ued in drink cooler. Volue of the device ОН-0- cooled liquid for 60 litre ( tank on 0 litre). The tet are carried out with two cooler of drink. One of the ha evaporator with porou coating on internal urface of piral tube. The coating i ade by intering. Diaeter of copper particle ~ 0 Mk. Thickne of coating ~ 0.. Poroity ~ 60%. The coating characteritic are optiized by ean of []. Reult of tet are hown on Fig. a dependencie of cooled liquid teperature fro tie for two cooler. It i dicovered that porou coating in the evaporator bring to the liquid cooling peedup. Beide, i reached ore even cooling of liquid in liquid cooler. A drink cooling tie decreae about 0 % when the porou coating in the evaporator i ued. Conequently, the neceary urface of drink cooler evaporator can be reduced about 0%. The experiental data are reproduced during 6 onth and ore high reliability in functioning of cooler, having evaporator with porou coating, i obtained. It i neceary to note that drink cooler deign, in which evaporator - a piral pipe i preed to the 7

4 barrel, being urface of cooling, i not optiu. In thi cae fect of heat tranfer enhanceent in the evaporator i ued only partly. 6 Fig.. Principle che e of drink cooler. - co preor; - condener; - drying filter; - capillary tube;,6 - evaporator. o C Т L in τ Fig.. D rink cooling teperature dependence o n tie - evaporator without porou coating - evaporator with porou coating Noenclature Sybol SI unit Decription P Pa Preure Q W/² heat flux R kj/kg vaporization heat T K Teperature Δ T K wall and liquid aturation teperature difference Re Reynold nuber α W/(² K) heat tranfer coficient δ Thickne ε Poroity λ W/ K theral conductivity ν / dynaic coficient of vicoity ρ kg/³ Denity σ N/ coficient of interfacial tenion 7

5 Indexe CM coating aterial Cr Critical Effective ax Maxial nucleate boiling porou coating Saturation Fluid Vapour Rerence. Goelaury V.I., Vezirihvily O.Sh., The ficiency of heat pup applying. Rrigerating technique, 986, No. 6.. Bergle A.E., Augentation of heat tranfer, two-phae, International Encyclopedia of heat and a tranfer, pp.7, Kuza-Kichta Y.A., Method of heat tranfer enhanceent, M.: MPEI., pp.7, 99.. Kuza-Kichta Yu. A, Bartch G. et al., Influence of porou coating on heat tranfer under different boiling regie in vertical channel.,. Heat Tranfer Conference Ruian, Koendantov A.S., Kuza-Kichta Yu.A. at al., Method of porou coating production in tube. Authorcertificate N 70, Kuza-Kichta Yu.A., Koendantov A.S, Burdunin M.N. et al., Heat tranfer enhanceent invetigation in vaporgenerating channel with porou coating, Theral Engineering, N, pp