What is the correct answer?

4

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

Conduction

Free convection

Forced convection

B. Free convection

Related Questions

What is the correct answer?

4

The ratio of the energy absorbed by the body to total energy falling on it is called

Absorptive power

Emissive power

Absorptivity

Emissivity

What is the correct answer?

4

The concept of overall coefficient of heat transfer is used in heat transfer problems of

Conduction

Convection

Conduction and convection

What is the correct answer?

4

The most commonly used method for the design of duct size is the

Velocity reduction method

Equal friction method

Static regains method

Dual or double method

What is the correct answer?

4

The automobile radiator is a heat exchanger of

Parallel flow type

Counter flow type

Cross flow type

Regenerator type

What is the correct answer?

4

If the temperature of a solid surface changes from 27°C to 627°C, then its emissive power changes in the ratio of

6

9

27

81

What is the correct answer?

4

The rate of energy transferred by convection to that by conduction is called

Stanton number

Nusselt number

Biot number

Peclet number

What is the correct answer?

4

The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to

Stanton number

Biot number

Peclet number

Grashoff number

What is the correct answer?

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

According of Kirchhoff's law

Radiant heat is proportional to fourth power of absolute temperature

Emissive power depends on temperature

Emissive power and absorptivity are constant for all bodies

Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body.

What is the correct answer?

4

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

k. A. (dT/dx)

k. A. (dx/dT)

k. (dT/dx)

k. (dx/dT)

What is the correct answer?

4

A perfect black body is one which

Is black in colour

Reflects all heat

Transmits all heat radiations

Absorbs heat radiations of all wave lengths falling on it

What is the correct answer?

4

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

First law of thermodynamics

Newton's law of cooling

Newton's law of heating

Stefan's law

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

What is the correct answer?

4

The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as

Kirchoffs law

Stefan's law

Wien' law

Planck's law

What is the correct answer?

4

The unit of Stefan Boltzmann constant is

Watt/cm² °K

Watt/cm4 °K

Watt²/cm °K⁴

Watt/cm² °K⁴

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

Fouling factor is used

In heat exchanger design as a safety factor

In case of Newtonian fluids

When a liquid exchanges heat with a gas

None of the above

What is the correct answer?

4

The value of Prandtl number for air is about

0.1

0.3

0.7

1.7

What is the correct answer?

4

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

Wien's law

Planck's law

Stefan's law

Fourier's law

What is the correct answer?

4

LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is

Higher

Lower

Same

Depends on the area of heat exchanger

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

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

Thermal coefficient

Thermal resistance

Thermal conductivity

None of these

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

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

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

The amount of radiation mainly depends upon the

Nature of the body

Temperature of the body

Type of surface of the body

All of these

What is the correct answer?

4

Which of the following has maximum value of thermal conductivity?

Aluminium

Steel

Brass

Copper

What is the correct answer?

4

The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)

Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)

Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]

Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)

Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)

What is the correct answer?

4

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

α = 1, ρ = 0 and τ = 0

α = 0, ρ = 1 and τ = 0

α = 0, ρ = 0 and τ = 1

α + ρ = 1 and τ = 0

What is the correct answer?

4

According to Prevost theory of heat exchange

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

Heat transfer by radiation requires no medium

All bodies above absolute zero emit radiation

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