Heat Transfer

Question: A __________ evaporator employs an annular downtake.
[A].

basket type

[B].

horizontal

[C].

long tube vertical

[D].

none of these

Answer: Option A

Explanation:

No answer description available for this question.

Question: A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,
[A].

the cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant.

[B].

both the spheres will emit equal amount of radiation per unit time in the beginning.

[C].

both will absorb equal amount of radiation from the surrounding in the beginning.

[D].

both(b) & (c).

Answer: Option D

Explanation:

No answer description available for this question.

Question: A black body does not __________ radiation.
[A].

absorb or emit

[B].

refract

[C].

reflect

[D].

both(b) & (c)

Answer: Option D

Explanation:

No answer description available for this question.

Question: A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.
[A].

10

[B].

>10

[C].

<10

[D].

either (b) or (c), depends on the mass of the body

Answer: Option B

Explanation:

No answer description available for this question.

Question: A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an
[A].

ellipse

[B].

straight line

[C].

parabola

[D].

circular arc

Answer: Option B

Explanation:

No answer description available for this question.

Question: In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
[A].

minimum

[B].

maximum

[C].

zero

[D].

infinity

Answer: Option C

Explanation:

No answer description available for this question.

Question: In case of surface condensers, a straight line is obtained on plotting __________ on an ordinary graph paper.
[A].

1/-0.8

[B].

-0.8

[C].

-2

[D].

1/-2

Answer: Option A

Explanation:

No answer description available for this question.

Question: Harmonic mean temperature difference is given by
[A].

ΔT1. ΔT2

[B].

[C].

[D].

Answer: Option B

Explanation:

No answer description available for this question.

Question: Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by
[A].

keeping the heat transfer surface clean.

[B].

enhancing the fluid pumping rate.

[C].

increasing the tube length.

[D].

none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Question: Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by This is valid for the value of NRe equal to
[A].

< 2100

[B].

2100-4000

[C].

> 4000

[D].

> 10000

Answer: Option D

Explanation:

No answer description available for this question.