Heat Transfer

Question: For a perfectly transparent surface (like gases), the
[A].

absorptivity = 0

[B].

transmissivity = 1

[C].

reflectivity = 0

[D].

all (a), (b) & (c)

Answer: Option B

Explanation:

No answer description available for this question.

Question: A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
[A].

Condensation

[B].

Grashoff

[C].

Stantan

[D].

Brinkman

Answer: Option D

Explanation:

No answer description available for this question.

Question: Boiling point elevation for a strong and concentrated solution is found by Duhring’s rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
[A].

boiling point

[B].

dynamic viscosity

[C].

kinematic viscosity

[D].

density

Answer: Option A

Explanation:

No answer description available for this question.

Question: Dropwise condensation of steam on cooling surface is promoted
[A].

an oily surface.

[B].

when both the steam and the tube are clean.

[C].

only in presence of air.

[D].

none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Question: ‘Duhring’s plot’ is of use in
[A].

extractive distillation

[B].

evaporation

[C].

leaching

[D].

absorption

Answer: Option B

Explanation:

No answer description available for this question.

Question: A __________ surface has the maximum thermal emissivity out of the following.
[A].

black & smooth

[B].

black & rough

[C].

white & smooth

[D].

white & rough

Answer: Option B

Explanation:

No answer description available for this question.

Question: A diathermaneous substance __________ the thermal radiation completely.
[A].

absorbs

[B].

reflects

[C].

transmits

[D].

none of these

Answer: Option C

Explanation:

No answer description available for this question.

Question: Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the
[A].

higher condensing film co-efficient is desired.

[B].

condensate is corrosive in nature.

[C].

lower pressure drop through the exchanger is desired.

[D].

temperature of the incoming vapor is very high.

Answer: Option B

Explanation:

No answer description available for this question.

Question: In a gas-liquid shell and tube heat exchanger, the
[A].

presence of a non-condensible gas decreases the condensing film co-efficient.

[B].

gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature.

[C].

gases to be heated/cooled is normally routed through the shell side, because the corrosion caused by the cooling water or steam condensate remain localised to the tubes.

[D].

all ‘a’, ‘b’ & ‘c’

Answer: Option D

Explanation:

No answer description available for this question.

Question: Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
[A].

laminar

[B].

transition

[C].

both ‘a’ & ‘b’

[D].

highly turbulent

Answer: Option D

Explanation:

No answer description available for this question.