Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

Heat and Mass Transfer
Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

0.084027777777778

0.16736111111111

0.042361111111111

0.043055555555556

0.084027777777778

0.16736111111111

0.042361111111111

0.043055555555556

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Heat and Mass Transfer
Film coefficient is defined as the ratio of

Thickness of film of fluid to the temperature drop through the films of fluids

Temperature drop through the films of fluids to the thickness of film of fluids

Thickness of film of fluid to the thermal conductivity

Thermal conductivity to the equivalent thickness of the film of fluid

Thickness of film of fluid to the temperature drop through the films of fluids

Temperature drop through the films of fluids to the thickness of film of fluids

Thickness of film of fluid to the thermal conductivity

Thermal conductivity to the equivalent thickness of the film of fluid

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Heat and Mass Transfer
Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

0.002

0.02

0.1

0.01

0.002

0.02

0.1

0.01

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Heat and Mass Transfer
The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

Radiation

Forced convection

Free convection

Conduction

Radiation

Forced convection

Free convection

Conduction

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Heat and Mass Transfer
The heat transfer by conduction through a thick sphere is given by

Q = 4πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 8πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 6πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 2πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 4πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 8πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 6πkr1 r2 (T1 - T2)/ (r2 - r1)

Q = 2πkr1 r2 (T1 - T2)/ (r2 - r1)

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Heat and Mass Transfer
Absorptivity of a body will be equal to its emissivity

At all temperatures

At one particular temperature

At critical temperature

When system is under thermal equilibrium

At all temperatures

At one particular temperature

At critical temperature

When system is under thermal equilibrium

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Heat and Mass Transfer

Heat and Mass Transfer Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

Heat and Mass Transfer Film coefficient is defined as the ratio of

Heat and Mass Transfer Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

Heat and Mass Transfer The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

Heat and Mass Transfer The heat transfer by conduction through a thick sphere is given by

Heat and Mass Transfer Absorptivity of a body will be equal to its emissivity

Heat and Mass Transfer
Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

Heat and Mass Transfer
Film coefficient is defined as the ratio of

Heat and Mass Transfer
Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

Heat and Mass Transfer
The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

Heat and Mass Transfer
The heat transfer by conduction through a thick sphere is given by

Heat and Mass Transfer
Absorptivity of a body will be equal to its emissivity