Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning

11. 

For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is __________ that for counter flow.

A. equal to
B. less than
C. greater than

Answer: Option A

Explanation:

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12. 

A vapour absorption refrigerator uses __________ as a refrigerant.

A. water
B. ammonia
C. freon
D. aqua-ammonia

Answer: Option D

Explanation:

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13. 

Thermal conductivity of air increases with rise in temperature.

A. Correct
B. Incorrect

Answer: Option A

Explanation:

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14. 

The material of pipe lines for a system using ammonia as a refrigerant should be copper.

A. Yes
B. No

Answer: Option B

Explanation:

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15. 

The wave length corresponding to the maximum energy is inversely proportional to the absolute temperature. This statement is called Planck's law.

A. Yes
B. No

Answer: Option B

Explanation:

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