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 2500 kJ of heat from a hot reservoir and rejects 1500 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 2500 kJQ_L = 1500 kJ

W = kJ

2.Easy

A heat engine takes in 2800 kJ of heat from a hot reservoir and rejects 1540 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 2800 kJQ_L = 1540 kJ

η = %

3.Medium

A heat engine works between a hot reservoir at 625 °C and a cold reservoir at 10 °C. It takes in 3500 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 625 °CT_L = 10 °CQ_H = 3500 kJ

W_max = kJ

4.Medium

A heat engine works between a hot reservoir at 375 °C and a cold reservoir at 35 °C. Find the highest possible thermal efficiency η_max.

T_H = 375 °CT_L = 35 °C

η_max = %

5.Hard

A heat pump delivers 16.5 kW of heat to a heating system at 55 °C, taking heat from a source at 0 °C. Its actual COP is 45% of the Carnot COP between these temperatures. Find the electrical power Ẇ it uses.

T_H = 55 °CT_L = 0 °Cη_II = 45%Q̇_H = 16.5 kW

Ẇ = kW

6.Hard

A heat engine takes in 600 kJ of heat from a reservoir at 650 °C, produces 198 kJ of work and rejects the rest to a reservoir at 35 °C, per cycle. Find the total entropy generated S_gen per cycle.

T_H = 650 °CT_L = 35 °CQ_H = 600 kJW = 198 kJ

S_gen = kJ/K

Answer key

1. W = 1000 kJ
2. η = 45 %
3. W_max = 2397 kJ
4. η_max = 52.46 %
5. Ẇ = 6.146 kW
6. S_gen = 0.6546 kJ/K

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