Question

1. In a real single stage refrigeration cycle using R 134-a as the working fluid the refrigeration flow rate is 0.1 kg/s. Vapor enters the compressor at 140 kPa and - 10 C and leaves it at 1.2 MPa and 80 C. The power input to the non-adiabatic compressor is measured and found to be 7.05 kW. The refrigerant enters the expansion valve at 1.2 MPa and 40 C. Find: a. (5%) The refrigeration capacity in ton. b. (5%) The COP of the cycle. c. (10%) The rate of the compressor heat transfer (show whether the heat is transferred to or from the compressor). d. (5%) The isentropic efficiency of the compressor.

Answer 1

Expansion value Evapnet Compren 119 Refrigerant R-134-a m = Dikg/sec P, = 140 kPa 10°C Ti = 10°c P₂ = 1.2 MPa T, so'c (Power): 7056 compresor Pa = 1.2 MPa To = 40°C To'= 70°C a HI: 260 kJ/kg H₂ = 310 kJ/kg H3 = 105kJ/kg H4 : jork/ry a) Refrigeration Capcity = m (H1-HA) = 01/260-105) Isentropic efficiency of = 15.5 kJ/sec Ae I compreuer = 15 kW T2 -T, 70-10 COP of cycle Refrigeration Capacity Work done by compreiar Im = 0.817 = 85.7.VA = 2.127 52-5,20 - Heat transfer by compreeser I 52 1.07 kJ/kg = (H₂-H1) = 50kJ/ka si=1.02 kJ 1kgt - mxro conxro o o Heat is thamfered - 5 /sec to the - Tz-T, - 2010 S 7.01