Chapter 9, Problem 9.104P

SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS Example 2:- Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 MPa and -10°C at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50°C. The refrigerant is cooled in the condenser to 26°C and 0.72 MPa and is throttled to 0.15 MPa. Disregarding any heat trans fer and pressure drops in the connecting lines between the components; determine (a) the rate of heat removal from the refrigerated space and the power input to the compressor, and (b) the coefficient of performance of the refrigerator. Solution: - P 0.14 MPa T=-10 C dut 246.36 kJ/kg OF P 0.8 MPa h2 = 286.69 kJ/kg P 0.72 MPa T= 26 C h3 = 87.83 kJ/kg h3 = h = 87.83 KJ/kg h4 = h3 (throttling) h4 87.83 kJ/kg 0.8 MPa 0.72 MPa/ 26 C 0.15 MPa 0.14 MPa -10°C SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS SAMARRA RING

SUBJECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS Example 2:- Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 MPa and -10°C at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50°C. The refrigerant is cooled in the condenser to 26°C and 0.72 MPa and is throttled to 0.15 MPa. Disregarding any heat trans fer and pressure drops in the connecting lines between the components; determine (a) the rate of heat removal from the refrigerated space and the power input to the compressor, and (b) the coefficient of performance of the refrigerator. Solution: - P 0.14 MPa T=-10 C 212 h 246.36 kJ/kg da OF SAMARRA P 0.8 MPa VER h2 = 286.69 kJ/kg O P 0.72 MPa T= 26 C hg = 87.83 kJ/kg h3 =h = 87.83 KJ/kg h4 = h3 (throttling) h4 87.83 kJ/kg 0.8 MPa 50°C 0.72 MPa/ 26 C 0.15 MPa 0.14 MPa -10°C SUBIECT: THERMODYNAMIC COURSE: II ASSI.LACTURE: NATIQ ABBAS RING

A refrigeration system operated on an ideal vapor-compression using R-12 with a vaporizing temperature of -10 degrees Celsius and a condensing temperature of 30 degrees Celsius, it requires 15 hp to drive the motor of the compressor. Find the ff: Enthalpies at each point of the cycle in kJ/kg Refrigerating Capacity in TOR • Mass of the Refrigerant in kg/s Percent Quality in the mixture Heat Rejected in kW Coefficient of Performance • Schematic and P-h Diagram