Heat Transfer

Question: Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
[A].

0.35

[B].

0.45

[C].

0.55

[D].

0.85

Answer: Option B

Explanation:

No answer description available for this question.

Question: An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is
[A].

4000

[B].

9000

[C].

4600

[D].

3000

Answer: Option A

Explanation:

No answer description available for this question.

Question: A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is
[A].

6000

[B].

24000

[C].

60000

[D].

48000

Answer: Option B

Explanation:

No answer description available for this question.

Question: In natural convection heat transfer, the correlating parameter is the
[A].

Graetz number

[B].

Eckert number

[C].

Grashoff number

[D].

Bond number

Answer: Option C

Explanation:

No answer description available for this question.

Question: For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy
[A].

[B].

[C].

[D].

Answer: Option B

Explanation:

No answer description available for this question.

Question: The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is
[A].

lower tube side pressure drop.

[B].

lower shell side pressure drop.

[C].

higher tube side heat transfer co-efficient.

[D].

higher shell side heat transfer co-efficient.

Answer: Option C

Explanation:

No answer description available for this question.

Question: A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
[A].

5 minutes

[B].

10 minutes

[C].

20 minutes

[D].

40 minutes

Answer: Option A

Explanation:

No answer description available for this question.

Question: A sphere of radius ‘R1’ is enclosed in a sphere of radius ‘R2’. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is
[A].

0

[B].

R2/(R1+R2)

[C].

1

[D].

(R1/R2)2

Answer: Option B

Explanation:

No answer description available for this question.

Question: In pipe flow, heat is transferred from hot wall to the liquid by
[A].

conduction only.

[B].

forced convection only.

[C].

forced convection and conduction.

[D].

free and forced convection.

Answer: Option C

Explanation:

No answer description available for this question.

Question: If Prandtl number is greater than the Schmidt number, then the
[A].

thermal boundary layer lies inside the concentration boundary layer.

[B].

concentration boundary layer lies inside the thermal boundary layer.

[C].

thermal & concentration boundary layers are of equal thickness.

[D].

hydrodynamic(i.e., momentum)boundary layer is thicker than the other two.

Answer: Option A

Explanation:

No answer description available for this question.