158) 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).

Right

Wrong

Answer is:

Right

Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

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Related Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

159) In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.

same

less

greater

none of these

Answer is:

greater

160) Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since

these react with water vapour and cause acid rain

these react with plants and cause green-house effect

these react with oxygen and cause its depletion

these react with ozone layer

Answer is:

these react with ozone layer

161) When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

operating the machine at higher speeds

operating the machine at lower speeds

raising the higher temperature

lowering the higher temperature

Answer is:

lowering the higher temperature

162) The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.

low

high

normal

none of these

Answer is:

high

Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

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158) 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).

Right

Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

Related Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

159) In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.

greater

160) Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since

these react with ozone layer

161) When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

lowering the higher temperature

162) The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.

high

Heat Transfer Refrigeration and Air Conditioning MCQ with Answers

158) 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).