1.Easy
A refrigerator removes heat from its cold space at a rate of 5.06 kW while its compressor uses 2.3 kW of power. Find the rate Q̇H at which it rejects heat to the kitchen.
Q̇L = 5.06 kWẆ = 2.3 kW
Q̇H = kW
Heat engines & refrigerators worksheet with answers
2.Easy
A refrigerator removes heat from its cold space at a rate of 6.21 kW while its compressor uses 2.3 kW of power. Find the rate Q̇H at which it rejects heat to the kitchen.
Q̇L = 6.21 kWẆ = 2.3 kW
Q̇H = kW
3.Medium
A reversible refrigerator keeps a cold room at -18 °C by removing 5.5 kW of heat, and rejects heat to the surroundings at 30 °C. Find the rate Q̇H at which it rejects heat.
TL = -18 °CTH = 30 °CQ̇L = 5.5 kW
Q̇H = kW
4.Medium
A reversible refrigerator keeps a cold room at 5 °C by removing 2.5 kW of heat, and rejects heat to the surroundings at 28 °C. Find the rate Q̇H at which it rejects heat.
TL = 5 °CTH = 28 °CQ̇L = 2.5 kW
Q̇H = kW
5.Hard
A Carnot heat engine receives 60 kW of heat from a source at 600 °C and rejects heat to the surroundings at 25 °C. All of its work drives a Carnot refrigerator that removes heat from a freezer at -10 °C and also rejects heat to the surroundings at 25 °C. Find the rate Q̇L at which heat is removed from the freezer.
TH = 600 °CT0 = 25 °CTL = -10 °CQ̇H = 60 kW
Q̇L = kW
6.Hard
A heat pump keeps a house at 21 °C while it is -5 °C outside, delivering 12 kW of heat to the house. Find the highest possible coefficient of performance COPmax.
TH = 21 °CTL = -5 °CQ̇H = 12 kW
COPmax =
Answer key
- 1. Q̇H = 7.36 kW
- 2. Q̇H = 8.51 kW
- 3. Q̇H = 6.535 kW
- 4. Q̇H = 2.707 kW
- 5. Q̇L = 297.1 kW
- 6. COPmax = 11.31
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