If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

Heat and Mass Transfer
If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

81

3

9

270

81

3

9

270

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Heat and Mass Transfer
Reynolds number is the ratio of

Inertia force to viscous force

Kinematic viscosity to thermal diffusivity

Energy transferred by convection to that by conduction

None of these

Inertia force to viscous force

Kinematic viscosity to thermal diffusivity

Energy transferred by convection to that by conduction

None of these

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Heat and Mass Transfer
Which of the following would lead to a reduction in thermal resistance?

In conduction, reduction in the thickness of the material and an increase in thermal conductivity.

In radiation, increasing the temperature and reducing the emissivity.

In convection, stirring of the fluid and cleaning the heating surface.

All of these

In conduction, reduction in the thickness of the material and an increase in thermal conductivity.

In radiation, increasing the temperature and reducing the emissivity.

In convection, stirring of the fluid and cleaning the heating surface.

All of these

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Heat and Mass Transfer
Sensible heat is the heat required to

Increase the temperature of a liquid of vapour

Change vapour into liquid

Change liquid into vapour

Convert water into steam and superheat it

Increase the temperature of a liquid of vapour

Change vapour into liquid

Change liquid into vapour

Convert water into steam and superheat it

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Heat and Mass Transfer
Thermal conductivity of a material may be defined as the

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 these

Quantity of heat flowing in one second through one cm cube of material when opposite faces are 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 these

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

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Heat and Mass Transfer
Thermal diffusivity is a

Dimensionless parameter

Function of temperature

All of these

Physical property of a substance

Dimensionless parameter

Function of temperature

All of these

Physical property of a substance

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Heat and Mass Transfer

Heat and Mass Transfer If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

Heat and Mass Transfer Reynolds number is the ratio of

Heat and Mass Transfer Which of the following would lead to a reduction in thermal resistance?

Heat and Mass Transfer Sensible heat is the heat required to

Heat and Mass Transfer Thermal conductivity of a material may be defined as the

Heat and Mass Transfer Thermal diffusivity is a

Heat and Mass Transfer
If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

Heat and Mass Transfer
Reynolds number is the ratio of

Heat and Mass Transfer
Which of the following would lead to a reduction in thermal resistance?

Heat and Mass Transfer
Sensible heat is the heat required to

Heat and Mass Transfer
Thermal conductivity of a material may be defined as the

Heat and Mass Transfer
Thermal diffusivity is a