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 3000 kJ of heat from a hot reservoir and rejects 2100 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 3000 kJQ_L = 2100 kJ

η = %

2.Easy

A heat engine takes in 3100 kJ of heat from a hot reservoir and rejects 1705 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 3100 kJQ_L = 1705 kJ

W = kJ

3.Medium

A heat engine works between a hot reservoir at 325 °C and a cold reservoir at 35 °C. Find the highest possible thermal efficiency η_max.

T_H = 325 °CT_L = 35 °C

η_max = %

4.Medium

A heat engine works between a hot reservoir at 350 °C and a cold reservoir at 30 °C. It takes in 1800 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 350 °CT_L = 30 °CQ_H = 1800 kJ

W_max = kJ

5.Hard

A heat pump delivers 9 kW of heat to a heating system at 22 °C, taking heat from a source at 2 °C. Its actual COP is 45% of the Carnot COP between these temperatures. Find the electrical power Ẇ it uses.

T_H = 22 °CT_L = 2 °Cη_II = 45%Q̇_H = 9 kW

Ẇ = kW

6.Hard

A heat engine takes in 1700 kJ of heat from a reservoir at 900 °C, produces 748 kJ of work and rejects the rest to a reservoir at 40 °C, per cycle. Find the total entropy generated S_gen per cycle.

T_H = 900 °CT_L = 40 °CQ_H = 1700 kJW = 748 kJ

S_gen = kJ/K

Answer key

1. η = 30 %
2. W = 1395 kJ
3. η_max = 48.48 %
4. W_max = 924.3 kJ
5. Ẇ = 1.355 kW
6. S_gen = 1.591 kJ/K

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