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 1600 kJ of heat from a hot reservoir and rejects 1120 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 1600 kJQ_L = 1120 kJ

W = kJ

2.Easy

A heat engine takes in 1400 kJ of heat from a hot reservoir and rejects 840 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 1400 kJQ_L = 840 kJ

W = kJ

3.Medium

A heat engine works between a hot reservoir at 200 °C and a cold reservoir at 30 °C. It takes in 1400 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 200 °CT_L = 30 °CQ_H = 1400 kJ

W_max = kJ

4.Medium

A heat engine works between a hot reservoir at 500 °C and a cold reservoir at 5 °C. It takes in 4200 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 500 °CT_L = 5 °CQ_H = 4200 kJ

W_max = kJ

5.Hard

A refrigerator keeps its cold space at 2 °C in a kitchen at 25 °C, removing heat from the cold space at 2 kW. Find the minimum power input Ẇ_min.

T_H = 25 °CT_L = 2 °CQ̇_L = 2 kW

Ẇ_min = kW

6.Hard

A heat pump keeps a house at 22 °C while it is -5 °C outside, delivering 11 kW of heat to the house. Find the minimum power input Ẇ_min.

T_H = 22 °CT_L = -5 °CQ̇_H = 11 kW

Ẇ_min = kW

Answer key

1. W = 480 kJ
2. W = 560 kJ
3. W_max = 503 kJ
4. W_max = 2689 kJ
5. Ẇ_min = 0.1672 kW
6. Ẇ_min = 1.006 kW

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