Heat engines & refrigerators worksheet with answers

A refrigerator removes heat from its cold space at a rate of 3.23 kW while its compressor uses 1.7 kW of power. Find the rate Q̇_H at which it rejects heat to the kitchen.

A heat pump with a coefficient of performance of 3.3 delivers 6 kW of heat to a house. Find the rate Q̇_L at which it takes heat from the outside air.

A reversible refrigerator keeps a cold room at 2 °C by removing 4 kW of heat, and rejects heat to the surroundings at 40 °C. Find the rate Q̇_H at which it rejects heat.

A reversible (Carnot) heat engine takes in 4900 kJ of heat from a reservoir at 350 °C and rejects 2148 kJ per cycle. Find the temperature T_L of the cold reservoir in °C.

Two Carnot engines work in series. Engine A receives heat from a reservoir at 1050 °C and rejects heat to an intermediate reservoir at temperature T_m. Engine B takes all that heat and rejects heat to a reservoir at 30 °C. Both engines have the same thermal efficiency. Find T_m in °C.

A heat engine takes in 2200 kJ of heat from a reservoir at 350 °C, produces 550 kJ of work and rejects the rest to a reservoir at 40 °C, per cycle. Find the total entropy generated S_gen per cycle.