When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

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When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

A. Conduction

B. Convection

C. Radiation

D. Conduction and convection

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An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

A. 25 mm

B. 40 mm

C. 160 mm

D. 800 mm

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

A. Same

B. More

C. Less

D. Depends on other factors

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A grey body is one whose absorptivity

A. Varies with temperature

B. Varies with wavelength of the incident ray

C. Is equal to its emissivity

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

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The unit of Stefan Boltzmann constant is

A. Watt/cm² °K

B. Watt/cm4 °K

C. Watt²/cm °K⁴

D. Watt/cm² °K⁴

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The heat of sun reaches to us according to

A. Conduction

B. Convection

C. Radiation

D. None of these

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The logarithmic mean temperature difference (t_m) is given by (where Δt₁ and Δt₂ are temperature differences between the hot and cold fluids at entrance and exit)

A. t_m = (Δt₁ - Δt₂)/ log_e (Δt₁/Δt₂)

B. t_m = log_e (Δt₁/Δt₂)/ (Δt₁ - Δt₂)

C. t_m = t_m = (Δt₁ - Δt₂) log_e (Δt₁/Δt₂)

D. t_m = log_e (Δt₁ - Δt₂)/ Δt₁/Δt₂

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Heat is closely related with

A. Liquids

B. Energy

C. Temperature

D. Entropy

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The thermal diffusivities for gases are generally

A. More than those for liquids

B. Less than those for liquids

C. More than those for solids

D. Dependent on the viscosity

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According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to

A. Absolute temperature

B. Square of temperature

C. Fourth power of absolute temperature

D. Fourth power of temperature

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The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to

A. -1/3

B. -2/3

C. 1

D. -1

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The amount of radiation mainly depends upon the

A. Nature of the body

B. Temperature of the body

C. Type of surface of the body

D. All of these

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In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

A. Convection

B. Radiation

C. Conduction

D. Both convection and conduction

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The value of Prandtl number for air is about

A. 0.1

B. 0.3

C. 0.7

D. 1.7

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In free convection heat transfer, Nusselt number is function of

A. Grashoff number and Reynold number

B. Grashoff number and Prandtl number

C. Prandtl number and Reynold number

D. Grashoff number, Prandtl number and Reynold number

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According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

A. Pb = pa - pv

B. Pb = pa + pv

C. Pb = pa × pv

D. Pb = pa/pv

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

A. I.C. engine

B. Air preheaters

C. Heating of building in winter

D. None of the above

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The emissivity for a black body is

A. 0

B. 0.5

C. 0.75

D. 1

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Metals are good conductors of heat because

A. Their atoms collide frequently

B. Their atoms are relatively far apart

C. They contain free electrons

D. They have high density

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The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as

A. Thermal coefficient

B. Thermal resistance

C. Thermal conductivity

D. None of these

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All radiations in a black body are

A. Reflected

B. Refracted

C. Transmitted

D. Absorbed

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

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

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

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

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

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When heat is transferred by molecular collision, it is referred to as heat transfer by

A. Conduction

B. Convection

C. Radiation

D. Scattering

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Total heat is the heat required to

A. Change vapour into liquid

B. Change liquid into vapour

C. Increase the temperature of a liquid or vapour

D. Convert water into steam and superheat it

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The amount of heat flow through a body by conduction is

A. Directly proportional to the surface area of the body

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

C. Dependent upon the material of the body

D. All of the above

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A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,

A. The better insulation must be put inside

B. The better insulation must be put outside

C. One could place either insulation on either side

D. One should take into account the steam temperature before deciding as to which insulation is put where

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The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called

A. Conduction

B. Convection

C. Radiation

D. None of these

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Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in

A. Electric heater

B. Steam condenser

C. Boiler

D. Refrigerator condenser coils

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The natural convection air cooled condensers are used in

A. Domestic refrigerators

B. Water coolers

C. Room air conditioners

D. All of these

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The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

A. Equal to one

B. Greater than one

C. Less than one

D. Equal to Nusselt number

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40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

A. 0.45

B. 0.55

C. 0.40

D. 0.75

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Accepted Answer

C. Radiation

When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

Correct Answer :

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Related Questions

An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

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

A grey body is one whose absorptivity

The unit of Stefan Boltzmann constant is

The heat of sun reaches to us according to

The logarithmic mean temperature difference (t_m) is given by (where Δt₁ and Δt₂ are temperature differences between the hot and cold fluids at entrance and exit)

Heat is closely related with

The thermal diffusivities for gases are generally

According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to

The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to

The amount of radiation mainly depends upon the

In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

The value of Prandtl number for air is about

In free convection heat transfer, Nusselt number is function of

According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

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

The emissivity for a black body is

Metals are good conductors of heat because

The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as

All radiations in a black body are

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

When heat is transferred by molecular collision, it is referred to as heat transfer by

Total heat is the heat required to

The amount of heat flow through a body by conduction is

A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,

The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called

Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in

The natural convection air cooled condensers are used in

The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

Also checkout

When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

Correct Answer :

Show all Heat & Mass Transfer MCQ

Related Questions

An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

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

A grey body is one whose absorptivity

The unit of Stefan Boltzmann constant is

The heat of sun reaches to us according to

The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit)

Heat is closely related with

The thermal diffusivities for gases are generally

According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to

The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to

The amount of radiation mainly depends upon the

In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

The value of Prandtl number for air is about

In free convection heat transfer, Nusselt number is function of

According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

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

The emissivity for a black body is

Metals are good conductors of heat because

The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as

All radiations in a black body are

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

When heat is transferred by molecular collision, it is referred to as heat transfer by

Total heat is the heat required to

The amount of heat flow through a body by conduction is

A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,

The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called

Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in

The natural convection air cooled condensers are used in

The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

Also checkout

The logarithmic mean temperature difference (t_m) is given by (where Δt₁ and Δt₂ are temperature differences between the hot and cold fluids at entrance and exit)