Heat Transfer

Question: Choose the correct equation.
[A].

Nu = (Re) (Pr) (Gz)

[B].

Nu = (Re) (Pr) (St)

[C].

Nu = (Re)(Pr)

[D].

Nu = (Pr)(St)

Answer: Option B

Explanation:

No answer description available for this question.

Question: Dietus-Boelter equation used for the determination of heat transfer co-efficient is valid
[A].

for fluids in laminar flow.

[B].

for fluids in tubulent flow.

[C].

when Grashhoff number is very important.

[D].

for liquid metals.

Answer: Option B

Explanation:

No answer description available for this question.

Question: For what value of Prandtl number, St = f/2?
[A].

1.5

[B].

1

[C].

> 1

[D].

< 1

Answer: Option B

Explanation:

No answer description available for this question.

Question: In forced convection, the heat transfer depends on
[A].

Re, Pr

[B].

Re, Gr

[C].

mainly Gr

[D].

Re only

Answer: Option A

Explanation:

No answer description available for this question.

Question: Natural convection is characterised by
[A].

Grashhoff number

[B].

Peclet number

[C].

Reynolds number

[D].

Prandtl number

Answer: Option A

Explanation:

No answer description available for this question.

Question: Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is
[A].

0.1

[B].

>1

[C].

< 1

[D].

l

Answer: Option A

Explanation:

No answer description available for this question.

Question: At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the
[A].

buffer zone

[B].

turbulent core

[C].

both (a) and (b)

[D].

viscous sub-layer

Answer: Option D

Explanation:

No answer description available for this question.

Question: Heat transfer co-efficient (h1) for liquids increases with
[A].

increasing temperature.

[B].

decreasing temperature.

[C].

decreasing Reynolds number.

[D].

none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Question: Fouling factor
[A].

is a dimensionless quantity.

[B].

does not provide a safety factor for design.

[C].

accounts for additional resistances to heat flow.

[D].

none of these.

Answer: Option C

Explanation:

No answer description available for this question.

Question: Nusselt number is the ratio of the
[A].

temperature gradient of the wall to that across the entire pipe.

[B].

temperature difference to the temperature gradient at the wall.

[C].

heat flux at the wall to that across the entire pipe.

[D].

none of these

Answer: Option C

Explanation:

No answer description available for this question.