上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 44 Chapter 11 Refrigeration Cycles Spring,2017 Prof.,Dr.Yonghua HUANG 强 月M是。 目e http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日G
Engineering Thermodynamics I Lecture 44 Spring, 2017 Prof., Dr. Yonghua HUANG Chapter 11 Refrigeration Cycles http://cc.sjtu.edu.cn/G2S/site/thermo.html
Carnot Refrigeration Cycle Warm region at TH Practical? Uuuut T 3 Condenser TH Turbine Compressor Tc Evaporator m b a Cold region at Tc Oin Coefficient of Performance B area 1-a-b-4-1 Tc(Sa -Sp) inlm area1-2-3-4-1 (TH-Tc)(sa-sp) 阝max= Te 成/m-成/m TH-Tc Represents the maximum theoretical coefficient of performance of any refrigeration cycle operating between regions at Tc and TH 上游充通大 Wednesday,May 03,2017 2 HANGHAI JLAO TONG UNIVERSITY
Wednesday, May 03, 2017 2 Carnot Refrigeration Cycle Practical? Coefficient of Performance β Represents the maximum theoretical coefficient of performance of any refrigeration cycle operating between regions at TC and TH . ?
Departures from the Carnot Cycle Limited△T. 1'→2' Compression liquid-vapor mixture.Wet compression. Most compressors handle vapor only.Dry compression. (Expansion)Turbine Condenser temperature,T Throttling valve Temperature of warm region,TH Temperature of cold region,Tc savings in Te W initial and Evaporator temperature,Tc maintenance costs. b a S 上游充通大 Wednesday,May 03,2017 3 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 3 Departures from the Carnot Cycle • Limited ∆T. • Compression liquid–vapor mixture. Wet compression. Most compressors handle vapor only. Dry compression. savings in initial and maintenance costs. (Expansion) Turbine Throttling valve W 0 1’2’
Vapor-compression refrigeration cycle Evaporator: =h1-h4 m Qin-refrigeration capacity.(kW). Alternative unit:ton of refrigeration,211 k]/min. W Compressor h2 -hy n Condenser ●Condenser /Expansion Avalve Compressor L应 Evaporator M Throttling process Saturated or superheated vapor 20m 上游通大学 Wednesday,May 03,2017 4 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 4 Vapor-compression refrigeration cycle
Working substance:p-h diagram 4000 3000 R134a 2000 cond4055℃ 1000 ressure 900 800 00: 700 ratio 600 500 v阳105C ×2.0-3.0 evap 400 小年年想想年年想中期想期用” 300 200 100 30 Enthalpy [kJ/kg] 40 50 x-0.10 020 0.30 0.40 0.50 0.60 0.70 0.80 0.90 40 20 =020 0.40 0.60 0.80 100 120 140 160 180 200 220 300 150-250W △h≈120~150k/kg 24020280 △h≈25~35k/kg 」in,Ah -evap.r = w im,△h comp.e ≈65% 3.5-6.0kg/hr no.is 50-80W comp,e 上泽文通大学 3.0-5.0 Wednesday,May 03,2017 5 SHANGHAI JIAO TONG UNIVERSITY
Wednesday, May 03, 2017 5 comp,e evap,r COP W Q MSRS 150-250 W Enthalpy [kJ/kg] Pressure ratio 2.0-3.0 h 120~150 kJ/kg Qevap ,r m r h Tevap: 10-25 C Tcond: 40-55 C h 25~35 kJ/kg r comp,e o,is m h W 65% 3.5-6.0 kg/hr 50-80 W 3.0-5.0 R134a Working substance: p-h diagram