1.Easy
A heat engine takes in 2900 kJ of heat from a hot reservoir and rejects 2320 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 2900 kJQL = 2320 kJ
W = kJ
Heat engines & refrigerators worksheet with answers
2.Easy
A heat engine takes in 4300 kJ of heat from a hot reservoir and rejects 3225 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 4300 kJQL = 3225 kJ
W = kJ
3.Medium
A heat engine works between a hot reservoir at 675 °C and a cold reservoir at 25 °C. It takes in 4800 kJ of heat. Find the most work Wmax it could possibly produce.
TH = 675 °CTL = 25 °CQH = 4800 kJ
Wmax = kJ
4.Medium
A heat engine works between a hot reservoir at 425 °C and a cold reservoir at 15 °C. Find the highest possible thermal efficiency ηmax.
TH = 425 °CTL = 15 °C
ηmax = %
5.Hard
A refrigerator keeps its cold space at 4 °C in a kitchen at 25 °C, removing heat from the cold space at 3 kW. Find the minimum power input Ẇmin.
TH = 25 °CTL = 4 °CQ̇L = 3 kW
Ẇmin = kW
6.Hard
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 15 °C. Both engines have the same thermal efficiency. Find Tm in °C.
TH = 1200 °CTL = 15 °C
Tm = °C
Answer key
- 1. W = 580 kJ
- 2. W = 1075 kJ
- 3. Wmax = 3291 kJ
- 4. ηmax = 58.73 %
- 5. Ẇmin = 0.2273 kW
- 6. Tm = 378.4 °C
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