Thermal diffusivity is the most important in heat transfer by (A) Conduction (B) Radiation

Thermal diffusivity is the most important in heat transfer by

(A) Conduction

(B) Radiation

by

1 Answer

Answer :

(A) Conduction

by

Related questions

reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity (C) Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Description : reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by ... Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Last Answer : Option C

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of (A) Mass diffusivity to momentum diffusivity (B) Thermal diffusivity to mass diffusivity (C) Momentum diffusivity to thermal diffusivity (D) None of these

Description : Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of (A) Mass diffusivity to momentum diffusivity (B) Thermal diffusivity to mass diffusivity (C) Momentum diffusivity to thermal diffusivity (D) None of these

Last Answer : (B) Thermal diffusivity to mass diffusivity

Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Description : Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Last Answer : (B) Heat flux

In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Description : In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Last Answer : (C) Thermal conductivity

In fluid flow, and heat and mass transfer, one encounters (i) kinematic velocity (μ), (ii) molecular diffusivity (θ) and thermal diffusivity (α). The units of these quantities are. (A) μ , α and θ all have units of m/s (B) μ , α and θ all have units of m2/s (C) α and θ have units of m2/s, while μ has unit of m/s (D) α and θ have units of m/s, while μ has unit of m2/s

Description : In fluid flow, and heat and mass transfer, one encounters (i) kinematic velocity (μ), (ii) molecular diffusivity (θ) and thermal diffusivity (α). The units of these quantities are. (A) μ , α and θ all have units of m/ ... μ has unit of m/s (D) α and θ have units of m/s, while μ has unit of m2/s

Last Answer : Option C

In which mode of heat transfer, the Biot number is important? (A) Transient heat conduction (B) Natural convection (C) Forced convection (D) Radiation

Description : In which mode of heat transfer, the Biot number is important? (A) Transient heat conduction (B) Natural convection (C) Forced convection (D) Radiation

Last Answer : (A) Transient heat conduction

View factor is important in heat transfer by (A) Steady state conduction (B) Natural convection (C) Forced convection (D) Radiation

Description : View factor is important in heat transfer by (A) Steady state conduction (B) Natural convection (C) Forced convection (D) Radiation

Last Answer : (D) Radiation

Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity (C) In unsteady state heat conduction, heat flows in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

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Last Answer : (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

Fourier's law applies to the heat transfer by (A) Convection (B) Radiation (C) Conduction (D) All (A), (B) & (C)

Description : Fourier's law applies to the heat transfer by (A) Convection (B) Radiation (C) Conduction (D) All (A), (B) & (C)

Last Answer : (C) Conduction

Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called (A) Radiation (B) Natural convection (C) Forced convection (D) Conduction

Description : Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called (A) Radiation (B) Natural convection (C) Forced convection (D) Conduction

Last Answer : (C) Forced convection

When warm and cold liquids are mixed, the heat transfer is mainly by (A) Conduction (B) Convection (C) Radiation (D) Both (A) & (C

Description : When warm and cold liquids are mixed, the heat transfer is mainly by (A) Conduction (B) Convection (C) Radiation (D) Both (A) & (C

Last Answer : (B) Convection

If heat transfer rate varies with the time, it is termed as (A) Forced convection (B) Steady state conduction (C) Monochromatic radiation (D) None of these

Description : If heat transfer rate varies with the time, it is termed as (A) Forced convection (B) Steady state conduction (C) Monochromatic radiation (D) None of these

Last Answer : (D) None of these

Heat transfer by __________ may not necessarily require the presence of a medium. (A) Conduction (B) Natural convection (C) Forced convection (D) Radiation

Description : Heat transfer by __________ may not necessarily require the presence of a medium. (A) Conduction (B) Natural convection (C) Forced convection (D) Radiation

Last Answer : (D) Radiation

In furnaces operating at very high temperature (say) 1250°C, e.g. soaking pit), the maximum heat transfer takes place by (A) Conduction (B) Convection (C) Radiation (D) Cannot be predicted

Description : In furnaces operating at very high temperature (say) 1250°C, e.g. soaking pit), the maximum heat transfer takes place by (A) Conduction (B) Convection (C) Radiation (D) Cannot be predicted

Last Answer : (C) Radiation

Maximum heat transfer in high temperature furnaces is by (A) Conduction (B) Convection (C) Radiation (D) Either (A), (B) or (C); depends on the type of furnace

Description : Maximum heat transfer in high temperature furnaces is by (A) Conduction (B) Convection (C) Radiation (D) Either (A), (B) or (C); depends on the type of furnace

Last Answer : (C) Radiation

Gibbs phase rule finds application, when heat transfer occurs by (A) Conduction (B) Convection (C) Radiation (D) Condensation

Description : Gibbs phase rule finds application, when heat transfer occurs by (A) Conduction (B) Convection (C) Radiation (D) Condensation

Last Answer : (D) Condensation

In a furnace with heating element temperature at 1700°C, the dominant mechanism of heat transfer will be (A) Conduction (B) Radiation (C) Natural convection (D) Forced convection

Description : In a furnace with heating element temperature at 1700°C, the dominant mechanism of heat transfer will be (A) Conduction (B) Radiation (C) Natural convection (D) Forced convection

Last Answer : (B) Radiation

Heat transfer by __________ is almost absent in case of fluidised bed drying operation. (A) Radiation (B) Conduction (C) Convection (D) Both (B) & (C)

Description : Heat transfer by __________ is almost absent in case of fluidised bed drying operation. (A) Radiation (B) Conduction (C) Convection (D) Both (B) & (C)

Last Answer : A) Radiation

Heat transfer to the water wall in a high pressure water wall type boiler furnace is mainly by (A) Conduction (B) Convection (C) Radiation (D) Both 'a' & 'b'

Description : Heat transfer to the water wall in a high pressure water wall type boiler furnace is mainly by (A) Conduction (B) Convection (C) Radiation (D) Both 'a' & 'b'

Last Answer : Option C

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is: (A) Free convection (B) Entry length problem in laminar forced conduction (developing thermal boundary layer) (C) Mixed convection (both free and forced) (D) Forced convection

Description : When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is: (A) Free convection (B) Entry length problem in laminar forced ... (developing thermal boundary layer) (C) Mixed convection (both free and forced) (D) Forced convection

Last Answer : (C) Mixed convection (both free and forced)

. (NSh /NRe .NSc ) is termed in mass transfer operation as the (A) Stanton number (B) Peclet number (C) Thermal diffusivity (D) Momentum diffusivity

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Last Answer : (A) Stanton number

Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the (A) Mass transfer co-efficient (B) Thermal diffusivity (C) Kinematic viscosity (D) Volumetric diffusivity

Description : Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the (A) Mass transfer co-efficient (B) Thermal diffusivity (C) Kinematic viscosity (D) Volumetric diffusivity

Last Answer : (A) Mass transfer co-efficient

Transfer of heat energy from a heater coil to the cooking vessel takes place through the process of- (1) Convection only (2) Conduction and convection only (3) Radiation and convection only (4) Convection, conduction and radiation

Description : Transfer of heat energy from a heater coil to the cooking vessel takes place through the process of- (1) Convection only (2) Conduction and convection only (3) Radiation and convection only (4) Convection, conduction and radiation

Last Answer : (3) Radiation and convection only Explanation: Conduction is the transfer of heat energy by direct contact, convection is the movement of heat by actual motion of matter; radiation is the transfer of energy with the help of electromagnetic waves.

____ is the transfer of heat from one particle to another by contact. a. Conduction c. Radiation b. Convection d. Combustion

Description : ____ is the transfer of heat from one particle to another by contact. a. Conduction c. Radiation b. Convection d. Combustion

Last Answer : a. Conduction

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because (A) Convection becomes important (B) Conduction becomes important (C) Radiation becomes important (D) Sub-cooled boiling occurs

Description : Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because (A) Convection becomes important (B) Conduction becomes important (C) Radiation becomes important (D) Sub-cooled boiling occurs

Last Answer : (C) Radiation becomes important

What refers to the transfer of energy between a solid surface and the adjacent fluid that is in motion?  A. Conduction  B. Convection  C. Radiation  D. Electrification

Description : What refers to the transfer of energy between a solid surface and the adjacent fluid that is in motion?  A. Conduction  B. Convection  C. Radiation  D. Electrification

Last Answer : Convection

____ is the transfer of energy in the form of electromagnetic waves. a. Compulsion c. Convection b. Radiation d. Conduction

Description : ____ is the transfer of energy in the form of electromagnetic waves. a. Compulsion c. Convection b. Radiation d. Conduction

Last Answer : b. Radiation

Loss of heat from untagged steam pipe to the ambient air is by (A) Conduction (B) Convection (C) Radiation (D) All (A), (B) & (C)

Description : Loss of heat from untagged steam pipe to the ambient air is by (A) Conduction (B) Convection (C) Radiation (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

In reverberatory furnace, charge is heated mainly by (A) Conduction (B) Natural convection (C) Radiation of heat from the roof of the combustion chamber (D) None of these

Description : In reverberatory furnace, charge is heated mainly by (A) Conduction (B) Natural convection (C) Radiation of heat from the roof of the combustion chamber (D) None of these

Last Answer : (C) Radiation of heat from the roof of the combustion chamber

In salt bath furnace, heat is transferred to the charge mainly by (A) Conduction (B) Convection (C) Radiation (D) None of these

Description : In salt bath furnace, heat is transferred to the charge mainly by (A) Conduction (B) Convection (C) Radiation (D) None of these

Last Answer : (A) Conduction

The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________ (A) 1 (B) 0.5 (C) 10 (D) 0

Description : The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________ (A) 1 (B) 0.5 (C) 10 (D) 0

Last Answer : (A) 1

If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is (A) 0 (B) 1 (C) < 1 (D) > 1

Description : If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is (A) 0 (B) 1 (C) < 1 (D) > 1

Last Answer : (B) 1

In physical terms, Schmidt number means (A) Thermal diffusivity/mass diffusivity(B) Thermal diffusivity/momentum diffusivity(C) Momentum diffusivity/mass diffusivity(D) Mass diffusivity/thermal diffusivity

Description : In physical terms, Schmidt number means (A) Thermal diffusivity/mass diffusivity (B) Thermal diffusivity/momentum diffusivity (C) Momentum diffusivity/mass diffusivity (D) Mass diffusivity/thermal diffusivity

Last Answer : (C) Momentum diffusivity/mass diffusivity

The Schmidt number which is defined as, μ/ρ D, is the ratio of the (A) Momentum diffusivity to the mass diffusivity (B) Thermal diffusivity to the mass diffusivity (C) Momentum diffusivity to the thermal diffusivity (D) None of these

Description : The Schmidt number which is defined as, μ/ρ D, is the ratio of the (A) Momentum diffusivity to the mass diffusivity (B) Thermal diffusivity to the mass diffusivity (C) Momentum diffusivity to the thermal diffusivity (D) None of these

Last Answer : (A) Momentum diffusivity to the mass diffusivity

Which of the following has the same dimension as mass diffusivity? (A) Momentum flux (B) Kinematic viscosity (C) Thermal diffusivity (D) Both (B) and (C)

Description : Which of the following has the same dimension as mass diffusivity? (A) Momentum flux (B) Kinematic viscosity (C) Thermal diffusivity (D) Both (B) and (C)

Last Answer : (D) Both (B) and (C)

Pick out the wrong statement. (A) The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr= 1 (B) 1 Nm3 of dry air is lighter than 1Nm3 of humid air (C) The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity

Description : Pick out the wrong statement. (A) The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr= 1 (B) 1 Nm3 of dry air is lighter ... ) The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity

Last Answer : (B) 1 Nm3 of dry air is lighter than 1Nm3 of humid air

With increase in temperature, the rate of leaching increases, because the (A) Diffusivity of solute increases (B) Viscosity of solvent decreases (C) Thermal conductivity of solute increases (D) None of these

Description : With increase in temperature, the rate of leaching increases, because the (A) Diffusivity of solute increases (B) Viscosity of solvent decreases (C) Thermal conductivity of solute increases (D) None of these

Last Answer : (A) Diffusivity of solute increases

Prandtl number is the ratio of (A) Mass diffusivity to thermal diffusivity (B) Momentum diffusivity to thermal diffusivity (C) Thermal diffusivity to mass diffusivity (D) Thermal diffusivity to momentum diffusivity

Description : Prandtl number is the ratio of (A) Mass diffusivity to thermal diffusivity (B) Momentum diffusivity to thermal diffusivity (C) Thermal diffusivity to mass diffusivity (D) Thermal diffusivity to momentum diffusivity

Last Answer : (B) Momentum diffusivity to thermal diffusivity

The ratio of momentum diffusivity to thermal diffusivity is the __________ number. (A) Prandtl (B) Nusselt (C) Stanton (D) Grashoff

Description : The ratio of momentum diffusivity to thermal diffusivity is the __________ number. (A) Prandtl (B) Nusselt (C) Stanton (D) Grashoff

Last Answer : (A) Prandtl

The ratio of kinematic viscosity to thermal diffusivity is called the __________ number. (A) Peclet (B) Prandtl (C) Stanton (D) Nusselt

Description : The ratio of kinematic viscosity to thermal diffusivity is called the __________ number. (A) Peclet (B) Prandtl (C) Stanton (D) Nusselt

Last Answer : (B) Prandtl

Prandtl number is the ratio of (A) Momentum diffusivity to mass diffusivity (B) Momentum diffusivity to thermal diffusivity (C) Thermal diffusivity to mass diffusivity (D) Thermal diffusivity to momentum diffusivity

Description : Prandtl number is the ratio of (A) Momentum diffusivity to mass diffusivity (B) Momentum diffusivity to thermal diffusivity (C) Thermal diffusivity to mass diffusivity (D) Thermal diffusivity to momentum diffusivity

Last Answer : (B) Momentum diffusivity to thermal diffusivity

Thermal diffusivity of a material (A) Has the unit m2 /sec (B) Is defined as K/ρ . Cp (C) Is the ratio of thermal conductivity to thermal capacity (D) All (A), (B) and (C)

Description : Thermal diffusivity of a material (A) Has the unit m2 /sec (B) Is defined as K/ρ . Cp (C) Is the ratio of thermal conductivity to thermal capacity (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Prandtl number is the reciprocal of (A) Thermal diffusivity/Momentum diffusivity (B) Thermal diffusivity × Momentum (C) Thermal diffusivity × Mass diffusivity (D) Mass diffusivity × Momentum diffusivity

Description : Prandtl number is the reciprocal of (A) Thermal diffusivity/Momentum diffusivity (B) Thermal diffusivity × Momentum (C) Thermal diffusivity × Mass diffusivity (D) Mass diffusivity × Momentum diffusivity

Last Answer : (A) Thermal diffusivity/Momentum diffusivity

Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) (A) 1/k (B) k (C) k2 (D) 1/k2

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Last Answer : (B) k

1. __________ of air does not increase with increase in temperature. (A) Density (B) Thermal diffusivity (C) Viscosity (D) Thermal conductivi

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Last Answer : Option A

The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns. (A) 0.38-0.78 (B) 0.5-50 (C) 100-1000 (D) 5-50

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Last Answer : (B) 0.5-50

By which of the following methods could a cup of hot coffee lose heat if placed on a metal table in a room? (a) Conduction and radiation (b) Conduction and convection (c) Convection and radiation (d) Conduction, convection, radiation and evaporation

Description : By which of the following methods could a cup of hot coffee lose heat if placed on a metal table in a room? (a) Conduction and radiation (b) Conduction and convection (c) Convection and radiation (d) Conduction, convection, radiation and evaporation

Last Answer : Ans:(d)

By what process is heat transmitted from the filament of an evacuated electric bulb to the glass? (a) Conduction (b) Convection (c) Radiation (d) Heat cannot be transmitted through vacuum

Description : By what process is heat transmitted from the filament of an evacuated electric bulb to the glass? (a) Conduction (b) Convection (c) Radiation (d) Heat cannot be transmitted through vacuum

Last Answer : Ans:(c)

Even after sunset, the air near the Earth's surface continue to receive heat due to – (1) Insolation (2) Terrestrial Radiation (3) Conduction (4) Convection

Description : Even after sunset, the air near the Earth's surface continue to receive heat due to – (1) Insolation (2) Terrestrial Radiation (3) Conduction (4) Convection

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Heat is transmitted from higher temperature to lower temperature through the actual motion of the molecules in – (1) Conduction (2) Convection (3) Radiation (4) Both conduction and convection

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