HEAT TRANSFER QUIZ

With increase in temperature, the thermal conductivity of a gas

May increase or decrease depending on the type of gas

Increases

Remains same

Decreases

TRUE ANSWER : ?
YOUR ANSWER : ?

Double pipe heat exchangers are preferably useful, when

A corrosive liquid is to be heated

Requirement of heat transfer area is low

Overall heat transfer co-efficient is very high

High viscosity liquid is to be cooled

TRUE ANSWER : ?
YOUR ANSWER : ?

With increase in temperature, the thermal conductivity of most liquids

Decreases

Remains same

First increases upto a certain temperature and then becomes constant

Increases

TRUE ANSWER : ?
YOUR ANSWER : ?

Fouling factor

Does not provide a safety factor for design

Accounts for additional resistances to heat flow

Is a dimensionless quantity

None of these

TRUE ANSWER : ?
YOUR ANSWER : ?

Log mean temperature difference (LMTD) cannot be used, if

heat transfer co-efficient over the entire heat exchanger is not constant

the heat capacity is not constant and there is a phase change.

there exists an unsteady state

none of the listed here

TRUE ANSWER : ?
YOUR ANSWER : ?

The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m².K. At steady state, the temperature of the right face in °C is

63.8

77.2

48.7

71.2

TRUE ANSWER : ?
YOUR ANSWER : ?

Heat flux, as defined in heat flow is analogous to __________ in electricity flow.

Voltage

Resistance

Current

None of these

TRUE ANSWER : ?
YOUR ANSWER : ?

1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is

200

520

500

400

TRUE ANSWER : ?
YOUR ANSWER : ?

In case of a vertical tube evaporator, with increase in the liquor level, the

True temperature drop increases

Both B and C

Capacity of the evaporator is decreased

Capacity of the evaporator is increased

TRUE ANSWER : ?
YOUR ANSWER : ?

In Biot number, the characteristic length used is the ratio of the __________ of the solid.

Perimeter to surface area

Surface area to volume

Surface area to perimeter

Volume to surface area

TRUE ANSWER : ?
YOUR ANSWER : ?