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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Name: ____________________ Date: ____________

1.Easy

A heat pump with a coefficient of performance of 4.4 delivers 17 kW of heat to a house. Find the electrical power Ẇ it uses.

COP_HP = 4.4Q̇_H = 17 kW

Ẇ = kW

2.Easy

A heat engine takes in 4300 kJ of heat from a hot reservoir and rejects 3010 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 4300 kJQ_L = 3010 kJ

η = %

3.Medium

A heat engine works between a hot reservoir at 700 °C and a cold reservoir at 25 °C. Find the highest possible thermal efficiency η_max.

T_H = 700 °CT_L = 25 °C

η_max = %

4.Medium

A heat engine works between a hot reservoir at 600 °C and a cold reservoir at 30 °C. It takes in 3800 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 600 °CT_L = 30 °CQ_H = 3800 kJ

W_max = kJ

5.Hard

A heat pump keeps a house at 20 °C while it is 2 °C outside, delivering 12 kW of heat to the house. Find the highest possible coefficient of performance COP_max.

T_H = 20 °CT_L = 2 °CQ̇_H = 12 kW

COP_max =

6.Hard

A refrigerator keeps its cold space at 2 °C in a kitchen at 28 °C, removing heat from the cold space at 2 kW. Find the minimum power input Ẇ_min.

T_H = 28 °CT_L = 2 °CQ̇_L = 2 kW

Ẇ_min = kW

Answer key

1. Ẇ = 3.864 kW
2. η = 30 %
3. η_max = 69.36 %
4. W_max = 2481 kJ
5. COP_max = 16.29
6. Ẇ_min = 0.189 kW

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