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 1280 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 1600 kJQ_L = 1280 kJ

W = kJ

2.Easy

A heat engine takes in 4000 kJ of heat from a hot reservoir and rejects 2400 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

Q_H = 4000 kJQ_L = 2400 kJ

W = kJ

3.Medium

A reversible (Carnot) heat engine takes in 500 kJ of heat from a reservoir at 300 °C and rejects 243 kJ per cycle. Find the temperature T_L of the cold reservoir in °C.

T_H = 300 °CQ_H = 500 kJQ_L = 243 kJ

T_L = °C

4.Medium

A heat engine works between a hot reservoir at 500 °C and a cold reservoir at 15 °C. It takes in 1700 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 500 °CT_L = 15 °CQ_H = 1700 kJ

W_max = kJ

5.Hard

Two Carnot engines work in series. Engine A receives heat from a reservoir at 800 °C and rejects heat to an intermediate reservoir at temperature T_m. Engine B takes all that heat and rejects heat to a reservoir at 40 °C. Both engines have the same thermal efficiency. Find T_m in °C.

T_H = 800 °CT_L = 40 °C

T_m = °C

6.Hard

A heat pump keeps a house at 21 °C while it is 0 °C outside, delivering 10 kW of heat to the house. Find the minimum power input Ẇ_min.

T_H = 21 °CT_L = 0 °CQ̇_H = 10 kW

Ẇ_min = kW

Answer key

1. W = 320 kJ
2. W = 1600 kJ
3. T_L = 5.401 °C
4. W_max = 1066 kJ
5. T_m = 306.6 °C
6. Ẇ_min = 0.7139 kW

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