Heat Transfer MCQs

Question 1

Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the

Accepted Answer

Constant temperature equal to that of the base

Answer

Surrounding temperature

Answer

Average temperature of the fin

Answer

Temperature of the fin end

Question 2

Double pipe heat exchangers are preferably useful, when

Accepted Answer

Requirement of heat transfer area is low

Answer

High viscosity liquid is to be cooled

Answer

Overall heat transfer co-efficient is very high

Answer

A corrosive liquid is to be heated

Question 3

The thermal boundary layer at NPr > 1

Accepted Answer

Is thinner than hydrodynamic boundary layer

Answer

Is thicker than hydrodynamic boundary layer

Answer

And the hydrodynamic boundary layer are identical

Answer

Disappears

Question 4

Maximum heat transfer rate is achieved in __________ flow.

Accepted Answer

Turbulent

Answer

Co-current

Answer

Counter-current

Answer

Laminar

Question 5

(NRe.NPr)(D/L) is called the __________ number

Accepted Answer

Graetz

Answer

Peclet

Answer

Stanton

Answer

None of these

Question 6

In a boiling curve, the peak heat flux is called the __________ point.

Accepted Answer

Burnout

Answer

Nusselt

Answer

Leidenfrost

Answer

Boiling

Question 7

Sensible heat of hot industrial flue gases can not be recovered by a/an

Accepted Answer

None of these

Answer

Economiser

Answer

Regenerator

Answer

Ceramic recuperator

Question 8

LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is

Accepted Answer

<1

Answer

0

Answer

1

Answer

>1

Question 9

Maximum heat transfer rate is obtained in __________ flow.

Accepted Answer

Turbulent

Answer

Laminar

Answer

Creeping

Answer

Transition region