Question 11.CSGP.179d: In an actual refrigeration cycle using R-12 as the working f......
In an actual refrigeration cycle using R-12 as the working fluid, the refrigerant flow rate is 0.05 kg/s. Vapor enters the compressor at 150 kPa, −10°C, and leaves at 1.2 MPa, 75°C. The power input to the compressor is measured and found be 2.4 kW. The refrigerant enters the expansion valve at 1.15 MPa, 40°C, and leaves the evaporator at 175 kPa, −15°C. Determine the entropy generation in the compression process, the refrigeration capacity and the coefficient of performance for this cycle.
Actual refrigeration cycle
1: compressor inlet T _1=-10^{\circ} C , P _1=150 \,kPa
2: compressor exit T _2=75^{\circ} C , P _2=1.2 \,MPa
3: Expansion valve inlet T _3=40^{\circ} C
P _3=1.15 \,MPa
5: evaporator exit T _5=-15^{\circ} C , P _5=175 \,kPa
Table B.3 h _1=184.8, \quad s _1=0.7324, h _2=226.7, \quad s _2=0.741
CV Compressor: h _1+ q _{\text {COMP }}+ w _{\text {COMP }}= h _2 ; \quad s _1+\int dq / T + s _{ gen }= s _2
C.V. Evaporator
COP: \beta=q_L / w_{C O M P}=106.9 / 48.0= 2 . 2 3
