What is the correct answer?

4

# Heat conducted through per unit area and unit thick face per unit time when temperature difference between opposite faces is unity, is called

Thermal resistance

Thermal coefficient

Thermal conductivity

### Correct Answer :

D. Thermal conductivity

### Related Questions

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4

# Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)

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

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

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

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

What is the correct answer?

4

# The transfer of heat by molecular collision is smallest in

Solids

Liquids

Gases

None of these

What is the correct answer?

4

# Depending on the radiating properties, a body will be black when

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 = 0 Where a = absorptivity, p = reflectivity, X = transmissivity.

What is the correct answer?

4

# Which of the following statement is wrong?

The heat transfer in liquid and gases takes place according to convection.

The amount of heat flow through a body is dependent upon the material of the body.

The thermal conductivity of solid metals increases with rise in temperature

Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference.

What is the correct answer?

4

# According to Stefan's law, the total radiation from a black body per second per unit area is proportional to

Absolute temperature

T⁵

T

What is the correct answer?

4

# Log mean temperature difference in case of counter flow compared to parallel flow will be

Same

More

Less

Depends on other factors

What is the correct answer?

4

# An ordinary passenger aircraft requires a cooling system of capacity.

2 TR

4 TR

8 TR

10 TR

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4

# According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the

Absolute temperature

Square of the absolute temperature

Cube of the absolute temperature

Fourth power of the absolute temperature

What is the correct answer?

4

# Depending on the radiating properties, body will be transparent when

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

What is the correct answer?

4

# Which of the following statement is correct?

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.

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4

# Upto the critical radius of insulation,

Added insulation will increase heat loss

Added insulation will decrease heat loss

Convective heat loss will be less than conductive heat loss

Heat flux will decrease

What is the correct answer?

4

# Depending on the radiating properties, a body will be opaque when

P = 0, x = 0 and a = 1

P=1, x = 0 and a = 0

P = 0, x = 1 and a = 0

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

What is the correct answer?

4

# The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.

Equal to

Directly proportional to

Inversely proportional to

None of these

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4

# According to Newton's law of cooling, the heat transfer from a hot body to a cold body is

Directly proportional to the surface area

Directly proportional to the difference of temperatures between the two bodies

Either (A) or (B)

Both (A) and (B)

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4

# Which of the following is the case of heat transfer by radiation?

Blast furnace

Heating of building

Cooling of parts in furnace

Heat received by a person from fireplace

What is the correct answer?

4

# The ratio of surface convection resistance to the internal conduction resistance is known as

Grashoff number

Biot number

Stanton number

Prandtl number

What is the correct answer?

4

# The heat of sun reaches to us according to

Conduction

Convection

None of these

What is the correct answer?

4

# Which of the following is a case of steady state heat transfer?

I.C. engine

Air preheaters

Heating of building in winter

None of the above

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4

# The expression Q = ρ AT4 is called

Fourier equation

Stefan-Boltzmann equation

Newton Reichmann equation

Joseph-Stefan equation

What is the correct answer?

4

# In a shell and tube heat exchanger, baffles are provided on the shell side to

Improve heat transfer

Provide support for tubes

Prevent stagnation of shell side fluid

All of these

What is the correct answer?

4

# Heat transfer by radiation mainly depends upon

Its temperature

Nature of the body

Kind and extent of its surface

All of the above

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4

# Reynolds number is the ratio of

Energy transferred by convection to that by conduction

Kinematic viscosity to thermal diffusivity

Inertia force to viscous force

None of the above

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4

# A grey body is one whose absorptivity

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

What is the correct answer?

4

# The unit of overall coefficient of heat transfer is

kcal/m²

kcal/hr °C

kcal/m² hr °C

kcal/m hr °C

What is the correct answer?

4

# Emissivity of a white polished body in comparison to a black body is

Higher

Lower

Same

Depends upon the shape of body

What is the correct answer?

4

# The use of heat exchangers is made in

Condensers and boilers in steam plants

Condensers and evaporators in refrigeration and air conditioning units

All of the above

What is the correct answer?

4

# 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

1 : 1

2 : 1

1 : 2

4 : 1

What is the correct answer?

4

# Stefan Boltzmann law is applicable for heat transfer by

Conduction

Convection

Conduction and radiation combined

What is the correct answer?

4

# A non-dimensional number generally associated with natural convection heat transfer is

Grashoff number

Nusselt number

Weber number

Prandtl number

What is the correct answer?

4

Temperature

Wave length

Physical nature

All of the above