Heat Transfer MCQs

Question 1

Which of the following situations can be approximated to a steady state heat transfer system?

Accepted Answer

10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless-steel pipe exposed to atmospheric air at 35°C

Answer

A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C

Answer

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C

Answer

A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Question 2

While the total emissivity of a perfect black body is unity, the same for a real body is

Accepted Answer

Between 0 and 1

Answer

0

Answer

1

Answer

> 1

Question 3

Pick out the wrong statement:

Accepted Answer

Heat sensitive materials should be concentrated in high pressure evaporators

Answer

The capacity of an evaporator is reduced by the boiling point elevation

Answer

Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger

Answer

Steam jet ejector is used for vapor compression in a thermal recompression evaporator

Question 4

The Graetz number is concerned with the

Accepted Answer

Heat transfer in laminar flow

Answer

Mass transfer between a gas and a liquid

Answer

Absorption with chemical reaction

Answer

Heat transfer in turbulent flow

Question 5

Unit of thermal conductivity in S.I. units is

Accepted Answer

(B) and (C) above

Answer

J/m2 sec

Answer

J/m °K sec

Answer

W/m °K

Question 6

Thermal conductivity of solid metals with rise in temperature normally

Accepted Answer

Decreases

Answer

Increases

Answer

Remains constant

Answer

May increase or decrease depending on temperature

Question 7

In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by

Accepted Answer

CM (thickness)

Answer

HR (time)

Answer

SQM (area)

Answer

°C (temperature)

Question 8

Heat transfer takes place as per

Accepted Answer

Second law of the thermodynamics

Answer

Zeroth law of thermodynamics

Answer

First law of thermodynamics

Answer

Kirchoff's law

Question 9

Depending on the radiating properties, a black body will be black when

Accepted Answer

ρ = 0, τ = 0 and α = 1

Answer

ρ = 1, τ = 0 and α = 0

Answer

ρ = 0, τ = 1 and α = 0

Answer

τ = 0, α+ρ = 1