Consider a Carnot cycle executed in a closed system with air as the working fluid. The maximum pressure in the cycle is 1300kPa while the maximum temperature is 950K. If the entropy increase during the isothermal heat rejection process is 0.25kJ/kgK and the net work output is 100kJ/kg, determine: (a) the minimum pressure in the cycle (191kPa ) (b) the heat rejection from the cycle (137.5kJ) (c) the thermal efficiency of the cycle. (42\%) (d) If an actual heat engine cycle operates between the same temperature limits and produces 5200kW of power for an air flow rate of 95kg/s, determine the second law efficiency of this cycle. (54\%) T4T1=(P4P1)k1/ks=cplnT3T4RlnP3P4 Q- A heat engine operates between two reservoirs, one at 400C and the other at 50C. The engine produces 7.5kW of power and rejects heat into the cold reservoir at a rate of 9kW. a- Find the efficiency of the heat engine. (0.455) b - Is the engine reversible? (0.52) A household refrigerator that has a power input of 450W and a COP of 2.5 is to cool 5 large watermelons, 10kg each, to 8C. If the watermelons are initially at 20 C, determine how long it will take for the refrigerator to cool them. The watermelons can be treated as water whose specific heat is 4.2kJ/kgC. Is your answer realistic or optimistic? (37min) Refrigerant-134a enters the condenser of a residential heat pump at 800kPa and 35 C at a rate of 0.018kg/s and leaves at 800kPa as a saturated liquid. If the compressor consumes 1.2kW of power, determine (a) the COP of the heat pump and (b) the rate of heat absorption from the outside air. (2.64,1.96kW) A commercial refrigerator with R134a as the working fluid is considered. At the evaporator inlet R-134a enters at 120kPa with quality of 0.2 and leaves as saturated vapour at 120kPa and 20C. Determine the mass flow rate of the refrigerant and the rate of heat rejected considering overall COP 1.2 and compressor input power 450W. (0.0031kg/s,0.99kW)