Reynold's number

Grashoff's number

Reynold's number, Grashoff's number

Prandtl number, Grashoff's number

D. Prandtl number, Grashoff's number

1 : 1

2 : 1

1 : 2

4 : 1

A grey body is one which absorbs all radiations incident on it.

At thermal equilibrium, the emissivity and absorptivity are same.

The energy absorbed by a body to the total energy falling on it, is called emissivity.

A perfect body is one which is black in colour.

Cold body to hot body

Hot body to cold body

Smaller body to larger body

Larger body to smaller body

_{m} = (Δt_{1} - Δt_{2})/ log_{e} (Δt_{1}/Δt_{2})

_{m} = log_{e} (Δt_{1}/Δt_{2})/ (Δt_{1} - Δt_{2})

_{m} = t_{m} = (Δt_{1} - Δt_{2}) log_{e} (Δt_{1}/Δt_{2})

_{m} = log_{e} (Δt_{1} - Δt_{2})/ Δt_{1}/Δt_{2}

Stanton number

Biot number

Peclet number

Grashoff number

Grashoff number and Reynold number

Grashoff number and Prandtl number

Prandtl number and Reynold number

Grashoff number, Prandtl number and Reynold number

J/m² sec

J/m °K sec

W/m °K

Option (B) and (C) above

S.H/(S.H + L.H)

(S.H + L.H) /S.H

(L.H - S.H)/S.H

S.H/(L.H - S.H)

Melting of ice

Boiler furnaces

Condensation of steam in condenser

None of these

α = 1, ρ = 0 and τ = 0

α = 0, ρ = 1 and τ = 0

α = 0, ρ = 0 and τ = 1

α + ρ = 1 and τ = 0

Conduction

Free convection

Forced convection

Radiation

Electric heater

Steam condenser

Boiler

Refrigerator condenser coils

Parallel flow

Counter flow

Cross flow

All of these

Same

Higher

More or less same

Very much lower

Universal gas constant

Kinematic viscosity

Thermal conductivity

Planck's constant

Black radiation

Full radiation

Total radiation

All of these

Directly proportional to thermal conductivity

Inversely proportional to density of substance

Inversely proportional to specific heat

All of the above

P = 0, x = 0 and a = 1

P=1, T = 0 and a = 0

P = 0, x = 1 and a = 0

X = 0, a + p = 1 Where a = absorptivity, p = reflectivity, x = transmissivity

0

0.5

0.75

1

Conduction

Free convection

Forced convection

Radiation

Varies with temperature

Varies with the wave length of incident ray

Varies with both

Does not vary with temperature and wave length of the incident ray

W/m²K

W/m²

W/mK

W/m

Solids

Liquids

Gases

None of these

Move actually

Do not move actually

Affect the intervening medium

Does not affect the intervening medium

At all temperatures

At one particular temperature

When system is under thermal equilibrium

At critical temperature

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

Quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C

Quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C

Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

All of the above

Free electrons

Atoms colliding frequency

Low density

Porous body

Increases

Decreases

Remain constant

May increase or decrease depending on temperature

_{min}/U

_{min}

_{min}

_{min}