Question

An ideal vapor-compression refrigerant cycle operates at steady state with Refrigerant 134a as the working fluid. Saturated vapor enters the compressor at -10°C, and saturated liquid leaves the condenser at 28°C. The mass flow rate of refrigerant is 5 kg/min. Determine (a) The compressor power, in kW (b) The refrigerating capacity, in tons. (c) The coefficient of performance. Sketch the system on a T-s diagram with full label. A vapor-compression heat pump with a heating capacity of 500 kJ/min is driven by a power cycle with a thermal efficiency of 25%. For the heat pump, Refrigerant 134a is compressed from saturated vapor at -10°C to the condenser pressure of 10 bar. The isentropic compressor efficiency is 80%. Liquid enters the expansion valve at 9.6 bar, 34°C. For the power cycle, 80% of the heat rejected is transferred to the heated space. (a) Determine the power input to the heat pump compressor, in kW. (b) Evaluate the ratio of the total rate that heat is delivered to the heated space to the rate of heat input to the power cycle. Discuss. Sketch the system on a T-s diagram with full label.

Answer 1

TA 3/ 221.21 1. iliven Ti = -10°C { h = hge 244:51 kJlig 21=1 Us=sg=0.93166 kJ/kg-K P2 = Psat@a8c Pa = 727.31 KPA?h2=271 KJ/kg SIE52 Pg=727.31 KPA <h3 = 90.69 kJ/kg Az =0 J 43=h4=90.69 kJ/kg a) The compressor power, - Wan= m(ha-hi) 4 200.TAKPA وتر The = 5 kq (271-244:51) Nin=2.21 kW weefrigeration capacity, &=mlhi-ha) (24451-90.69) L = 12.82 KW Xbore L = 3:66 ton c) COP=8 = 12-822 COP-5.8)