Exercise: Heat Transfer Refrigeration And Air Conditioning

Questions for: Heat Transfer Refrigeration And Air Conditioning

When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
A:
operating the machine at higher speeds
B:
operating the machine at lower speeds
C:
raising the higher temperature
D:
lowering the higher temperature
Answer: D
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Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since
A:
these react with water vapour and cause acid rain
B:
these react with plants and cause green-house effect
C:
these react with oxygen and cause its depletion
D:
these react with ozone layer
Answer: D
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In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.
A:
same
B:
less
C:
greater
D:
Answer: C
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The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h0).
A:
True
B:
False
C:
D:
Answer: A
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The air cooling system mostly used in transport type aircrafts is
A:
simple air cooling system
B:
simple evaporative air cooling system
C:
boot-strap air cooling system
D:
all of these
Answer: C
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