In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

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In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

A. Reynold's number

B. Grashoff's number

C. Reynold's number, Grashoff's number

D. Prandtl number, Grashoff's number

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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

A. 1 : 1

B. 2 : 1

C. 1 : 2

D. 4 : 1

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Which of the following statement is correct?

A. A grey body is one which absorbs all radiations incident on it.

B. At thermal equilibrium, the emissivity and absorptivity are same.

C. The energy absorbed by a body to the total energy falling on it, is called emissivity.

D. A perfect body is one which is black in colour.

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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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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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The product of Reynolds number and Prandtl number is known as

A. Stanton number

B. Biot number

C. Peclet number

D. Grashoff number

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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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Unit of thermal conductivity in S.I. units is

A. J/m² sec

B. J/m °K sec

C. W/m °K

D. Option (B) and (C) above

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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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The heat is transferred by conduction, convection and radiation in

A. Melting of ice

B. Boiler furnaces

C. Condensation of steam in condenser

D. None of these

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When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

A. α = 1, ρ = 0 and τ = 0

B. α = 0, ρ = 1 and τ = 0

C. α = 0, ρ = 0 and τ = 1

D. α + ρ = 1 and τ = 0

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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 caused by some mechanical means, is known as

A. Conduction

B. Free convection

C. Forced convection

D. Radiation

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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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In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

A. Parallel flow

B. Counter flow

C. Cross flow

D. All of these

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Total emissivity of polished silver compared to black body is

A. Same

B. Higher

C. More or less same

D. Very much lower

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Joule sec is the unit of

A. Universal gas constant

B. Kinematic viscosity

C. Thermal conductivity

D. Planck's constant

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The radiation emitted by a black body is known as

A. Black radiation

B. Full radiation

C. Total radiation

D. All of these

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Thermal diffusivity of a substance is

A. Directly proportional to thermal conductivity

B. Inversely proportional to density of substance

C. Inversely proportional to specific heat

D. All of the above

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Depending on the radiating properties, a body will be white when

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

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

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

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

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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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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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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 unit of overall coefficient of heat transfer is

A. W/m²K

B. W/m²

C. W/mK

D. W/m

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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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The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

A. Move actually

B. Do not move actually

C. Affect the intervening medium

D. Does not affect the intervening medium

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Absorptivity of a body will be equal to its emissivity

A. At all temperatures

B. At one particular temperature

C. When system is under thermal equilibrium

D. At critical temperature

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According to Prevost theory of heat exchange

A. It is impossible to transfer heat from low temperature source to t high temperature source

B. Heat transfer by radiation requires no medium

C. All bodies above absolute zero emit radiation

D. Heat transfer in most of the cases takes place by combination of conduction, convection and radiation

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Thermal conductivity of a material may be defined as the

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

B. 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

C. Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

D. All of the above

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Cork is a good insulator because it has

A. Free electrons

B. Atoms colliding frequency

C. Low density

D. Porous body

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Thermal conductivity of air with rise in temperature

A. Increases

B. Decreases

C. Remain constant

D. May increase or decrease depending on temperature

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A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

A. A.C_min/U

B. U/A.C_min

C. A.U.C_min

D. A.U/C_min

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Accepted Answer

D. Prandtl number, Grashoff's number

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

Correct Answer :

Show all Heat & Mass Transfer MCQ

Related Questions

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

Which of the following statement is correct?

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

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)

The product of Reynolds number and Prandtl number is known as

In free convection heat transfer, Nusselt number is function of

Unit of thermal conductivity in S.I. units is

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

The heat is transferred by conduction, convection and radiation in

When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

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

In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

Total emissivity of polished silver compared to black body is

Joule sec is the unit of

The radiation emitted by a black body is known as

Thermal diffusivity of a substance is

Depending on the radiating properties, a body will be white when

The emissivity for a black body is

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 grey body is one whose absorptivity

The unit of overall coefficient of heat transfer is

The transfer of heat by molecular collision is smallest in

The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

Absorptivity of a body will be equal to its emissivity

According to Prevost theory of heat exchange

Thermal conductivity of a material may be defined as the

Cork is a good insulator because it has

Thermal conductivity of air with rise in temperature

A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

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In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

Correct Answer :

Show all Heat & Mass Transfer MCQ

Related Questions

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

Which of the following statement is correct?

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

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)

The product of Reynolds number and Prandtl number is known as

In free convection heat transfer, Nusselt number is function of

Unit of thermal conductivity in S.I. units is

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

The heat is transferred by conduction, convection and radiation in

When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

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

In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

Total emissivity of polished silver compared to black body is

Joule sec is the unit of

The radiation emitted by a black body is known as

Thermal diffusivity of a substance is

Depending on the radiating properties, a body will be white when

The emissivity for a black body is

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 grey body is one whose absorptivity

The unit of overall coefficient of heat transfer is

The transfer of heat by molecular collision is smallest in

The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

Absorptivity of a body will be equal to its emissivity

According to Prevost theory of heat exchange

Thermal conductivity of a material may be defined as the

Cork is a good insulator because it has

Thermal conductivity of air with rise in temperature

A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

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)