1.Easy
A heat engine takes in 3700 kJ of heat from a hot reservoir and rejects 2590 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 3700 kJQL = 2590 kJ
W = kJ
Heat engines & refrigerators worksheet with answers
2.Easy
A heat engine takes in 2400 kJ of heat from a hot reservoir and rejects 1920 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 2400 kJQL = 1920 kJ
W = kJ
3.Medium
A heat engine works between a hot reservoir at 350 °C and a cold reservoir at 30 °C. Find the highest possible thermal efficiency ηmax.
TH = 350 °CTL = 30 °C
ηmax = %
4.Medium
A reversible refrigerator keeps a cold room at 5 °C by removing 8.5 kW of heat, and rejects heat to the surroundings at 30 °C. Find the rate Q̇H at which it rejects heat.
TL = 5 °CTH = 30 °CQ̇L = 8.5 kW
Q̇H = kW
5.Hard
A refrigerator keeps its cold space at -25 °C in a kitchen at 35 °C, removing heat from the cold space at 1.5 kW. Find the minimum power input Ẇmin.
TH = 35 °CTL = -25 °CQ̇L = 1.5 kW
Ẇmin = kW
6.Hard
Two Carnot engines work in series. Engine A receives heat from a reservoir at 1050 °C and rejects heat to an intermediate reservoir at temperature Tm. Engine B takes all that heat and rejects heat to a reservoir at 35 °C. Both engines have the same thermal efficiency. Find Tm in °C.
TH = 1050 °CTL = 35 °C
Tm = °C
Answer key
- 1. W = 1110 kJ
- 2. W = 480 kJ
- 3. ηmax = 51.35 %
- 4. Q̇H = 9.264 kW
- 5. Ẇmin = 0.3627 kW
- 6. Tm = 365.4 °C
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