Heat engines & refrigerators worksheet with answers

A heat engine takes in 1300 kJ of heat from a hot reservoir and rejects 1040 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

A heat pump with a coefficient of performance of 3.6 delivers 18.5 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 0 °C by removing 1.5 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 2800 kJ of heat from a reservoir at 625 °C and rejects 1023 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 700 °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 10 °C. Both engines have the same thermal efficiency. Find T_m in °C.

A Carnot heat engine receives 130 kW of heat from a source at 450 °C and rejects heat to the surroundings at 20 °C. All of its work drives a Carnot refrigerator that removes heat from a freezer at -5 °C and also rejects heat to the surroundings at 20 °C. Find the rate Q̇_L at which heat is removed from the freezer.