Radiators in automobile

Condensers and boilers in steam plants

Condensers and evaporators in refrigeration and air conditioning units

All of the above

D. All of the above

P = 0, x = 0 and a = 1

P=1, x = 0, and a = 0

P = 0, T= 1, and a = 0

X = 0, a + p = 1

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

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

In radiation, increasing the temperature and reducing the emissivity.

All of the above

Fourier equation

Stefan-Boltzmann equation

Newton Reichmann equation

Joseph-Stefan equation

More than those for liquids

Less than those for liquids

More than those for solids

Dependent on the viscosity

6

9

27

81

Emissivity

Transmissivity

Reflectivity

Intensity of radiation

_{1} r_{2} (T_{1} - T_{2})/ (r_{2} - r_{1})

_{1} r_{2} (T_{1} - T_{2})/ (r_{2} - r_{1})

_{1} r_{2} (T_{1} - T_{2})/ (r_{2} - r_{1})

_{1} r_{2} (T_{1} - T_{2})/ (r_{2} - r_{1})

Conduction

Convection

Radiation

Scattering

Energy transferred by convection to that by conduction

Kinematic viscosity to thermal diffusivity

Inertia force to viscous force

None of the above

Varies with temperature

Varies with wavelength of the incident ray

Is equal to its emissivity

Does not vary with temperature and. wavelength of the incident ray

Glass

Water

Plastic

Air

Different heat contents

Different specific heat

Different atomic structure

Different temperatures

Equal to one

Greater than one

Less than one

Equal to Nusselt number

0.45

0.55

0.40

0.75

Solids

Liquids

Gases

None of these

Conduction

Convection

Radiation

Conduction and radiation combined

Irregular surfaces

Nonuniform temperature surfaces

One dimensional cases only

Two dimensional cases only

Directly proportional to the surface area of the body

Directly proportional to the temperature difference on the two faces of the body

Dependent upon the material of the body

All of the above

Is black in colour

Reflects all heat

Transmits all heat radiations

Absorbs heat radiations of all wave lengths falling on it

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.

_{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}

Black body

Grey body

Opaque body

White body

Reynold's number

Grashoff's number

Reynold's number, Grashoff's number

Prandtl number, Grashoff's number

Its temperature

Nature of the body

Kind and extent of its surface

All of the above

Thermal resistance

Thermal coefficient

Temperature gradient

Thermal conductivity

Conduction

Convection

Radiation

None of these

Wien's law

Planck's law

Stefan's law

Fourier's law

Higher

Lower

Same

Depends on the area of heat exchanger

Less than those for gases

Less than those for liquids

More than those for liquids and gases

More or less same as for liquids and gases

Domestic refrigerators

Water coolers

Room air conditioners

All of these