Temperature

Thickness

Area

Time

D. Time

0.1

0.3

0.7

1.7

Conduction

Convection

Radiation

Conduction and convection

Parallel flow type

Counter flow type

Cross flow type

Regenerator type

Nature of the body

Temperature of the body

Type of surface of the body

All of these

Conduction

Convection

Radiation

Conduction and radiation combined

k/h₀

2k/h₀

h₀/k

h₀/2k

Watt/mK

Watt/m²K²

^{4}

Watt/mK²

The time taken to attain the final temperature to be measured

The time taken to attain 50% of the value of initial temperature difference

The time taken to attain 63.2% of the value of initial temperature difference

Determined by the time taken to reach 100°C from 0°C

Higher

Lower

Same

Depends on the area of heat exchanger

6

9

27

81

Absolute temperature (T)

I²

F

T

25 mm

40 mm

160 mm

800 mm

Its temperature

Nature of the body

Kind and extent of its surface

All of the above

Same

Less

Greater

None of these

A dimensionless parameter

Function of temperature

Used as mathematical model

A physical property of the material

Conduction

Free convection

Forced convection

Radiation

Electric heater

Steam condenser

Boiler

Refrigerator condenser coils

Increases

Decreases

Remain constant

May increase or decrease depending on temperature

Conduction

Convection

Radiation

Conduction and convection

The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature

The wave length corresponding to the maximum energy is proportional to the absolute temperature

The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body

None of the above

Stanton number

Nusselt number

Biot number

Peclet number

Kirchoffs law

Stefan's law

Wien' law

Planck's law

More than those for liquids

Less than those for liquids

More than those for solids

Dependent on the viscosity

Is black in colour

Reflects all heat

Transmits all heat radiations

Absorbs heat radiations of all wave lengths falling on it

Face area

Time

Thickness

Temperature difference

It is impossible to transfer heat from low temperature source to t high temperature source

Heat transfer by radiation requires no medium

All bodies above absolute zero emit radiation

Heat transfer in most of the cases takes place by combination of conduction, convection and radiation

Wien's law

Stefan's law

Kirchhoff's law

Planck's law

Absolute temperature

T²

T⁵

T

Absolute temperature

Square of the absolute temperature

Cube of the absolute temperature

Fourth power of the absolute temperature

h = k/ ρS

h = ρS/k

h = S/ρk

h = kρ/S