1.Easy
A heat engine takes in 1700 kJ of heat from a hot reservoir and rejects 1105 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 1700 kJQL = 1105 kJ
W = kJ
Heat engines & refrigerators worksheet with answers
2.Easy
A heat engine takes in 2500 kJ of heat from a hot reservoir and rejects 1625 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 2500 kJQL = 1625 kJ
W = kJ
3.Medium
A reversible refrigerator keeps a cold room at -20 °C by removing 7 kW of heat, and rejects heat to the surroundings at 40 °C. Find the rate Q̇H at which it rejects heat.
TL = -20 °CTH = 40 °CQ̇L = 7 kW
Q̇H = kW
4.Medium
A reversible refrigerator keeps a cold room at 2 °C by removing 6 kW of heat, and rejects heat to the surroundings at 40 °C. Find the rate Q̇H at which it rejects heat.
TL = 2 °CTH = 40 °CQ̇L = 6 kW
Q̇H = kW
5.Hard
A refrigerator keeps its cold space at 2 °C in a kitchen at 28 °C, removing heat from the cold space at 3.5 kW. Find the minimum power input Ẇmin.
TH = 28 °CTL = 2 °CQ̇L = 3.5 kW
Ẇmin = kW
6.Hard
A heat pump delivers 8.5 kW of heat to a heating system at 35 °C, taking heat from a source at -10 °C. Its actual COP is 35% of the Carnot COP between these temperatures. Find the electrical power Ẇ it uses.
TH = 35 °CTL = -10 °CηII = 35%Q̇H = 8.5 kW
Ẇ = kW
Answer key
- 1. W = 595 kJ
- 2. W = 875 kJ
- 3. Q̇H = 8.659 kW
- 4. Q̇H = 6.829 kW
- 5. Ẇmin = 0.3307 kW
- 6. Ẇ = 3.547 kW
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