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 worksheetPractise 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
hot reservoircold reservoirEQH​ = 3800 kJQL​ = 2660 kJW = ?

A heat engine takes in 3800 kJ of heat from a hot reservoir and rejects 2660 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

QH = 3800 kJQL = 2660 kJ
W = kJ
2.Easy
kitchencold spaceRQ̇H​ = ?Q̇L​ = 2.8 kWẆ = 0.8 kW

A refrigerator removes heat from its cold space at a rate of 2.8 kW while its compressor uses 0.8 kW of power. Find the rate Q̇H at which it rejects heat to the kitchen.

Q̇L = 2.8 kWẆ = 0.8 kW
Q̇H = kW
3.Medium
TH​ = 450 °CTL​ = 10 °CEQH​QL​W

A heat engine works between a hot reservoir at 450 °C and a cold reservoir at 10 °C. Find the highest possible thermal efficiency ηmax.

TH = 450 °CTL = 10 °C
ηmax = %
4.Medium
TH​ = 650 °CTL​ = 40 °CEQH​ = 2500 kJQL​W = ?

A heat engine works between a hot reservoir at 650 °C and a cold reservoir at 40 °C. It takes in 2500 kJ of heat. Find the most work Wmax it could possibly produce.

TH = 650 °CTL = 40 °CQH = 2500 kJ
Wmax = kJ
5.Hard
TH​ = 30 °CTL​ = 5 °CRQ̇H​Q̇L​ = 1.5 kWẆ

A refrigerator keeps its cold space at 5 °C in a kitchen at 30 °C, removing heat from the cold space at 1.5 kW. Find the highest possible coefficient of performance COPmax.

TH = 30 °CTL = 5 °CQ̇L = 1.5 kW
COPmax =
6.Hard
1200 °CTm​ = ?40 °CABWA​WB​

Two Carnot engines work in series. Engine A receives heat from a reservoir at 1200 °C and rejects heat to an intermediate reservoir at temperature Tm. Engine B takes all that heat and rejects heat to a reservoir at 40 °C. Both engines produce the same work. Find Tm in °C.

TH = 1200 °CTL = 40 °C
Tm = °C

Answer key

  1. 1. W = 1140 kJ
  2. 2. Q̇H = 3.6 kW
  3. 3. ηmax = 60.84 %
  4. 4. Wmax = 1652 kJ
  5. 5. COPmax = 11.13
  6. 6. Tm = 620 °C

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