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.

New worksheet Practise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________ Date: ____________

1.Easy

A heat engine takes in 4900 kJ of heat from a hot reservoir and rejects 3185 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 4900 kJQ_L = 3185 kJ

η = %

2.Easy

A heat engine takes in 1500 kJ of heat from a hot reservoir and rejects 1050 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.

Q_H = 1500 kJQ_L = 1050 kJ

η = %

3.Medium

A heat engine works between a hot reservoir at 650 °C and a cold reservoir at 5 °C. It takes in 3700 kJ of heat. Find the most work W_max it could possibly produce.

T_H = 650 °CT_L = 5 °CQ_H = 3700 kJ

W_max = kJ

4.Medium

A reversible (Carnot) heat engine takes in 1800 kJ of heat from a reservoir at 300 °C and rejects 921 kJ per cycle. Find the temperature T_L of the cold reservoir in °C.

T_H = 300 °CQ_H = 1800 kJQ_L = 921 kJ

T_L = °C

5.Hard

A refrigerator keeps its cold space at -10 °C in a kitchen at 32 °C, removing heat from the cold space at 0.5 kW. Find the highest possible coefficient of performance COP_max.

T_H = 32 °CT_L = -10 °CQ̇_L = 0.5 kW

COP_max =

6.Hard

A heat pump keeps a house at 20 °C while it is 0 °C outside, delivering 8 kW of heat to the house. Find the minimum power input Ẇ_min.

T_H = 20 °CT_L = 0 °CQ̇_H = 8 kW

Ẇ_min = kW

Answer key

1. η = 35 %
2. η = 30 %
3. W_max = 2585 kJ
4. T_L = 20.11 °C
5. COP_max = 6.265
6. Ẇ_min = 0.5458 kW

Full step-by-step solutions: practise this topic on examproblems.com.