Heat engines & refrigerators worksheet with answers

A heat engine takes in 4300 kJ of heat from a hot reservoir and rejects 3010 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

A refrigerator removes heat from its cold space at a rate of 5.74 kW while its compressor uses 1.4 kW of power. Find the rate Q̇_H at which it rejects heat to the kitchen.

A heat engine works between a hot reservoir at 400 °C and a cold reservoir at 40 °C. Find the highest possible thermal efficiency η_max.

A heat engine works between a hot reservoir at 675 °C and a cold reservoir at 40 °C. It takes in 1800 kJ of heat. Find the most work W_max it could possibly produce.

A Carnot heat engine receives 160 kW of heat from a source at 950 °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 -20 °C and also rejects heat to the surroundings at 20 °C. Find the rate Q̇_L at which heat is removed from the freezer.

Two Carnot engines work in series. Engine A receives heat from a reservoir at 950 °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 20 °C. Both engines have the same thermal efficiency. Find T_m in °C.