Heat Transfer MCQs

Question 1

The advantage of backward feed multiple effect evaporators over forward feed units is that

Accepted Answer

Most concentrated liquid is at highest temperature

Answer

Heat sensitive material can be handled

Answer

There is no additional cost of pumping

Answer

Equal heat transfer co-efficients exist in various effects

Question 2

The ratio of momentum diffusivity to thermal diffusivity is the __________ number.

Accepted Answer

Prandtl

Answer

Nusselt

Answer

Stanton

Answer

Grashoff

Question 3

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is

Accepted Answer

4.36

Answer

2.36

Answer

120.36

Answer

Dependent on NRe only

Question 4

Water always boils when its

Accepted Answer

Saturated vapour pressure equals the external pressure on its surface

Answer

Temperature reaches 100° C

Answer

Vapour pressure equals 76 cm of Hg

Answer

Saturated vapour pressure is less than the atmospheric pressure

Question 5

Which one gives the monochromatic emissive power for black body radiation?

Accepted Answer

Planck's law

Answer

Kirchhoffs law

Answer

Wien's law

Answer

Stefan-Boltzman law

Question 6

If heat transfer rate varies with the time, it is termed as

Accepted Answer

None of these

Answer

Forced convection

Answer

Steady state conduction

Answer

Monochromatic radiation

Question 7

Vibrations in the tubes of a shell and tube heat exchanger is induced due to the

Accepted Answer

All of the above

Answer

Flow of fluid on the tube and shell sides

Answer

Oscillations in the flow of shell/tube sides fluid

Answer

Vibrations transmitted through piping and/or supports due to external reasons

Question 8

Radiation heat losses from satisfactorily insulated high pressure boilar may be about __________ percent.

Accepted Answer

7

Answer

1

Answer

18

Answer

26

Question 9

Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?

Accepted Answer

Sieder-Tate equation

Answer

Dittus-Boeltier equation

Answer

Nusselt equation

Answer

None of these