Heat engines & refrigerators worksheet with answers

Free printable Heat engines & refrigerators worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

A heat engine takes in 3600 kJ of heat from a hot reservoir and rejects 2160 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 3600 kJQ_L = 2160 kJ

η = %

2.Easy

A heat engine takes in 2400 kJ of heat from a hot reservoir and rejects 1560 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 2400 kJQ_L = 1560 kJ

η = %

3.Medium

A reversible (Carnot) heat engine takes in 2400 kJ of heat from a reservoir at 225 °C and rejects 1461 kJ per cycle. Find the temperature T_L of the cold reservoir in °C.

T_H = 225 °CQ_H = 2400 kJQ_L = 1461 kJ

T_L = °C

4.Medium

A heat engine works between a hot reservoir at 500 °C and a cold reservoir at 20 °C. It takes in 1200 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 500 °CT_L = 20 °CQ_H = 1200 kJ

W_max = kJ

5.Hard

A heat pump delivers 8.5 kW of heat to a heating system at 22 °C, taking heat from a source at 0 °C. Its actual COP is 40% of the Carnot COP between these temperatures. Find the electrical power Ẇ it uses.

T_H = 22 °CT_L = 0 °Cη_II = 40%Q̇_H = 8.5 kW

Ẇ = kW

6.Hard

A heat pump delivers 19.5 kW of heat to a heating system at 21 °C, taking heat from a source at 5 °C. Its actual COP is 55% of the Carnot COP between these temperatures. Find the electrical power Ẇ it uses.

T_H = 21 °CT_L = 5 °Cη_II = 55%Q̇_H = 19.5 kW

Ẇ = kW

Answer key

1. η = 40 %
2. η = 35 %
3. T_L = 30.1 °C
4. W_max = 745 kJ
5. Ẇ = 1.584 kW
6. Ẇ = 1.929 kW

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