Heat engines & refrigerators worksheet with answers

A refrigerator removes heat from its cold space at a rate of 4.16 kW while its compressor uses 1.3 kW of power. Find its coefficient of performance COP_R.

A heat engine takes in 2600 kJ of heat from a hot reservoir and rejects 1820 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

A heat engine works between a hot reservoir at 800 °C and a cold reservoir at 30 °C. Find the highest possible thermal efficiency η_max.

A reversible refrigerator keeps a cold room at 2 °C by removing 6 kW of heat, and rejects heat to the surroundings at 20 °C. Find the rate Q̇_H at which it rejects heat.

A Carnot heat engine receives 40 kW of heat from a source at 600 °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 -15 °C and also rejects heat to the surroundings at 20 °C. Find the rate Q̇_L at which heat is removed from the freezer.

A refrigerator keeps its cold space at 2 °C in a kitchen at 35 °C, removing heat from the cold space at 0.5 kW. Find the highest possible coefficient of performance COP_max.