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​ = 3300 kJQL​ = 2475 kJW = ?

A heat engine takes in 3300 kJ of heat from a hot reservoir and rejects 2475 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

QH = 3300 kJQL = 2475 kJ
W = kJ
2.Easy
hot reservoircold reservoirEQH​ = 2200 kJQL​ = 1760 kJW = ?

A heat engine takes in 2200 kJ of heat from a hot reservoir and rejects 1760 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.

QH = 2200 kJQL = 1760 kJ
W = kJ
3.Medium
TH​ = 700 °CTL​ = 10 °CEQH​QL​η = 35%

A heat engine receives heat from a source at 700 °C and rejects heat to the surroundings at 10 °C. Its actual thermal efficiency is 35%. Find its second-law efficiency ηII, the ratio of the actual efficiency to the Carnot efficiency.

TH = 700 °CTL = 10 °Cη = 35%
ηII = %
4.Medium
TH​ = 800 °CTL​ = ?EQH​ = 3600 kJQL​ = 916 kJW

A reversible (Carnot) heat engine takes in 3600 kJ of heat from a reservoir at 800 °C and rejects 916 kJ per cycle. Find the temperature TL of the cold reservoir in °C.

TH = 800 °CQH = 3600 kJQL = 916 kJ
TL = °C
5.Hard
TH​ = 650 °CTL​ = 20 °CEQH​ = 1500 kJQL​ = 990 kJW = 510 kJ

A heat engine takes in 1500 kJ of heat from a reservoir at 650 °C, produces 510 kJ of work and rejects the rest to a reservoir at 20 °C, per cycle. Find the total entropy generated Sgen per cycle.

TH = 650 °CTL = 20 °CQH = 1500 kJW = 510 kJ
Sgen = kJ/K
6.Hard
TH​ = 450 °CTL​ = 25 °CEQH​ = 1600 kJQL​ = 1040 kJW = 560 kJ

A heat engine takes in 1600 kJ of heat from a reservoir at 450 °C, produces 560 kJ of work and rejects the rest to a reservoir at 25 °C, per cycle. Find the total entropy generated Sgen per cycle.

TH = 450 °CTL = 25 °CQH = 1600 kJW = 560 kJ
Sgen = kJ/K

Answer key

  1. 1. W = 825 kJ
  2. 2. W = 440 kJ
  3. 3. ηII = 49.36 %
  4. 4. TL = −0.09294 °C
  5. 5. Sgen = 1.752 kJ/K
  6. 6. Sgen = 1.276 kJ/K

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