1.Easy
A heat engine takes in 2800 kJ of heat from a hot reservoir and rejects 1540 kJ to a cold reservoir in each cycle. Find the net work W it produces per cycle.
QH = 2800 kJQL = 1540 kJ
W = kJ
Heat engines & refrigerators worksheet with answers
2.Easy
A heat engine takes in 3300 kJ of heat from a hot reservoir and rejects 2145 kJ to a cold reservoir in each cycle. Find its thermal efficiency η.
QH = 3300 kJQL = 2145 kJ
η = %
3.Medium
A reversible (Carnot) heat engine takes in 2600 kJ of heat from a reservoir at 200 °C and rejects 1638 kJ per cycle. Find the temperature TL of the cold reservoir in °C.
TH = 200 °CQH = 2600 kJQL = 1638 kJ
TL = °C
4.Medium
A reversible (Carnot) heat engine takes in 1400 kJ of heat from a reservoir at 400 °C and rejects 630 kJ per cycle. Find the temperature TL of the cold reservoir in °C.
TH = 400 °CQH = 1400 kJQL = 630 kJ
TL = °C
5.Hard
Two Carnot engines work in series. Engine A receives heat from a reservoir at 850 °C and rejects heat to an intermediate reservoir at temperature Tm. Engine B takes all that heat and rejects heat to a reservoir at 20 °C. Both engines produce the same work. Find Tm in °C.
TH = 850 °CTL = 20 °C
Tm = °C
6.Hard
A Carnot heat engine receives 100 kW of heat from a source at 1000 °C and rejects heat to the surroundings at 20 °C. All of its work drives a Carnot refrigerator that removes heat from a freezer at -5 °C and also rejects heat to the surroundings at 20 °C. Find the rate Q̇L at which heat is removed from the freezer.
TH = 1000 °CT0 = 20 °CTL = -5 °CQ̇H = 100 kW
Q̇L = kW
Answer key
- 1. W = 1260 kJ
- 2. η = 35 %
- 3. TL = 24.93 °C
- 4. TL = 29.77 °C
- 5. Tm = 435 °C
- 6. Q̇L = 825.6 kW
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