Question 11.CSGP.180d: The refrigerant R-22 is used as the working fluid in a conve......
The refrigerant R-22 is used as the working fluid in a conventional heat pump cycle. Saturated vapor enters the compressor of this unit at 10°C; its exit temperature from the compressor is measured and found to be 85°C. If the compressor exit is at 2 MPa what is the compressor isentropic efficiency and the cycle COP?
R-22 heat pump:
Computer Table
State 1: T _{ EVAP }=10^{\circ} C , x =1
h _1=253.42 \,kJ / kg , \quad s _1=0.9129 \,kJ / kg K
State 2: T _2, P _2: \quad h _2=295.17 \,kJ / kg
C.V. Compressor
Energy Eq.: w _{ C \text { ac }}= h _2- h _1=295.17-253.42= 4 1 . 7 5\, k J / k g
State 2s: 2 MPa , s _{2 S }= s _1=0.9129 \,kJ / kg \quad T _{2 S }=69^{\circ} C , h _{2 S }=280.2 \,kJ / kg
Efficiency: \eta=\frac{ w _{ Cs }}{ w _{ C \text { ac }}}=\frac{ h _{2 S }- h _1}{ h _2- h _1}=\frac{280.2-253.42}{295.17-253.42}= 0 . 6 4 1 4
C.V. Condenser
Energy Eq.: q _{ H }= h _2- h _3=295.17-109.6=185.57 \,kJ / kg
COP Heat pump: \beta=\frac{ q _{ H }}{ w _{ C \text { ac }}}=\frac{185.57}{41.75}= 4 . 4 4
