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)

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

A. Higher

B. Lower

C. Same

D. Depends upon the shape of body

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Thermal conductivity of solid metals with rise in temperature normally

A. Increases

B. Decreases

C. Remain constant

D. May increase or decrease depending on temperature

Discuss this answer

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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Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

A. Cold body to hot body

B. Hot body to cold body

C. Smaller body to larger body

D. Larger body to smaller body

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Which of the following statement is wrong?

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

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

C. The thermal conductivity of solid metals increases with rise in temperature

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

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The use of heat exchangers is made in

A. Radiators in automobile

B. Condensers and boilers in steam plants

C. Condensers and evaporators in refrigeration and air conditioning units

D. All of the above

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A grey body is one whose absorptivity

A. Varies with temperature

B. Varies with the wave length of incident ray

C. Varies with both

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

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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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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 transfer takes place as per

A. Zeroth law of thermodynamics

B. First law of thermodynamic

C. Second law of the thermodynamics

D. Kirchoff's law

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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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Pick up the wrong case. Heat flowing from one side to other depends directly on

A. Face area

B. Time

C. Thickness

D. Temperature difference

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An ordinary passenger aircraft requires a cooling system of capacity.

A. 2 TR

B. 4 TR

C. 8 TR

D. 10 TR

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When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

A. Black body

B. Grey body

C. Opaque body

D. White body

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The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as

A. Emissivity

B. Transmissivity

C. Reflectivity

D. Intensity of radiation

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The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

A. First law of thermodynamics

B. Newton's law of cooling

C. Newton's law of heating

D. Stefan's law

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The automobile radiator is a heat exchanger of

A. Parallel flow type

B. Counter flow type

C. Cross flow type

D. Regenerator type

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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

A. Conduction

B. Free convection

C. Forced convection

D. Radiation

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The unit of overall coefficient of heat transfer is

A. kcal/m²

B. kcal/hr °C

C. kcal/m² hr °C

D. kcal/m hr °C

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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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Which of the following property of air does not increase with rise in temperature?

A. Thermal conductivity

B. Thermal diffusivity

C. Density

D. Dynamic viscosity

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According to Wien's law, the wavelength corresponding to maximum energy is proportion to

A. Absolute temperature (T)

B. I²

C. F

D. T

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Fourier's law of heat conduction gives the heat flow for

A. Irregular surfaces

B. Nonuniform temperature surfaces

C. One dimensional cases only

D. Two dimensional cases only

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The value of the wavelength for maximum emissive power is given by

A. Wien's law

B. Planck's law

C. Stefan's law

D. Fourier's law

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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

Discuss this answer

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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The highest thermal diffusivity is of

A. Iron

B. Lead

C. Concrete

D. Wood

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Fouling factor is used

A. In heat exchanger design as a safety factor

B. In case of Newtonian fluids

C. When a liquid exchanges heat with a gas

D. None of the above

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The transfer of heat by molecular collision is smallest in

A. Solids

B. Liquids

C. Gases

D. None 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

Discuss this answer

Accepted Answer

A. t_m = (Δt₁ - Δt₂)/ log_e (Δt₁/Δt₂)

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)

Correct Answer :

Show all Heat & Mass Transfer MCQ

Related Questions

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

Thermal conductivity of solid metals with rise in temperature normally

The amount of heat flow through a body by conduction is

Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

Which of the following statement is wrong?

The use of heat exchangers is made in

A grey body is one whose absorptivity

The amount of radiation mainly depends upon the

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

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Metals are good conductors of heat because

Pick up the wrong case. Heat flowing from one side to other depends directly on

An ordinary passenger aircraft requires a cooling system of capacity.

When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as

The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

The automobile radiator is a heat exchanger of

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

The unit of overall coefficient of heat transfer is

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

Which of the following property of air does not increase with rise in temperature?

According to Wien's law, the wavelength corresponding to maximum energy is proportion to

Fourier's law of heat conduction gives the heat flow for

The value of the wavelength for maximum emissive power is given by

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

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

The highest thermal diffusivity is of

Fouling factor is used

The transfer of heat by molecular collision is smallest in

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

Also checkout

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)

Correct Answer :

Show all Heat & Mass Transfer MCQ

Related Questions

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

Thermal conductivity of solid metals with rise in temperature normally

The amount of heat flow through a body by conduction is

Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

Which of the following statement is wrong?

The use of heat exchangers is made in

A grey body is one whose absorptivity

The amount of radiation mainly depends upon the

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

Heat transfer takes place as per

Metals are good conductors of heat because

Pick up the wrong case. Heat flowing from one side to other depends directly on

An ordinary passenger aircraft requires a cooling system of capacity.

When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a

The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as

The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

The automobile radiator is a heat exchanger of

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

The unit of overall coefficient of heat transfer is

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

Which of the following property of air does not increase with rise in temperature?

According to Wien's law, the wavelength corresponding to maximum energy is proportion to

Fourier's law of heat conduction gives the heat flow for

The value of the wavelength for maximum emissive power is given by

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

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

The highest thermal diffusivity is of

Fouling factor is used

The transfer of heat by molecular collision is smallest in

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

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)