Heat Transfer

Question: For specified tube outside diameter, higher BWG means higher
[A].

tube thickness

[B].

cross-sectional area

[C].

weight per unit length

[D].

none of these

Answer: Option B

Explanation:

No answer description available for this question.

Question: A body is called grey if the monochromatic emissivity of the body is
[A].

zero

[B].

unity

[C].

same for all wavelengths

[D].

different for all wavelengths

Answer: Option C

Explanation:

No answer description available for this question.

Question: With increase in temperature, the thermal conductivity of a gas
[A].

increases.

[B].

decreases.

[C].

remains same.

[D].

may increase or decrease depending on the type of gas.

Answer: Option A

Explanation:

No answer description available for this question.

Question: “The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is __________ law.
[A].

Kirchoffs

[B].

Planck’s

[C].

Wien’s displacement

[D].

Stefan-Boltzman

Answer: Option A

Explanation:

No answer description available for this question.

Question: Absorptivity and refletivity of a perfect black body are respectively
[A].

1 and 0

[B].

0 and 1

[C].

1 and ∞

[D].

0 and 0.5

Answer: Option A

Explanation:

No answer description available for this question.

Question: In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always
[A].

< 1

[B].

> 1

[C].

1

[D].

∞

Answer: Option A

Explanation:

No answer description available for this question.

Question: Corrosiveness of steam condensate is due to the presence of
[A].

CO2

[B].

dissolved O2

[C].

both (a) & (b)

[D].

neither (a) nor (b)

Answer: Option C

Explanation:

No answer description available for this question.

Question: In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is
[A].

infinity.

[B].

zero.

[C].

same as average heat transfer co-efficient for tube side.

[D].

none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Question: The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film )
[A].

(ΔT)2

[B].

ΔT

[C].

(ΔT)1/4

[D].

(ΔT)3/2

Answer: Option C

Explanation:

No answer description available for this question.

Question: At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical ?
[A].

0.5

[B].

1

[C].

1.5

[D].

80

Answer: Option B

Explanation:

No answer description available for this question.