Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning

21. 

The emissive power of a body depends upon its

A. temperature
B. physical nature
C. wave length
D. all of these

Answer: Option D

Explanation:

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22. 

An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be

A. 25 mm
B. 40 mm
C. 160 mm
D. 800 mm

Answer: Option A

Explanation:

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23. 

A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is

A. h1 + h2 + h3
B. (h1h2h3)1/3
C.
D. none of these

Answer: Option D

Explanation:

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24. 

The dehumidification process, on the psychrometric chart, is shown by

A. horizontal Sine
B. vertical line
C. inclined line
D. curved line

Answer: Option B

Explanation:

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25. 

The vertical and uniformly spaced lines on a psychrometric chart indicates

A. dry bulb temperature
B. wet bulb temperature
C. dew point temperature
D. specific humidity

Answer: Option A

Explanation:

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