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

Heat and Mass Transfer
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

0.084027777777778

0.042361111111111

0.16736111111111

0.043055555555556

0.084027777777778

0.042361111111111

0.16736111111111

0.043055555555556

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Heat and Mass Transfer
Which of the following is expected to have highest thermal conductivity?

Solid ice

Melting ice

Water

Steam

Solid ice

Melting ice

Water

Steam

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Heat and Mass Transfer
Thermal diffusivity of a substance is

Directly proportional to the thermal conductivity

Inversely proportional to density of substance

All of these

Inversely proportional to specific heat

Directly proportional to the thermal conductivity

Inversely proportional to density of substance

All of these

Inversely proportional to specific heat

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Heat and Mass Transfer
Heat transfer takes place as per

Second law of the thermodynamics

First law of thermodynamic

Kirchoff's law

Zeroth law of thermodynamics

Second law of the thermodynamics

First law of thermodynamic

Kirchoff's law

Zeroth law of thermodynamics

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Heat and Mass Transfer
Fouling factor is used

In heat exchanger design as a safety factor

In case of Newtonian fluids

None of these

When a liquid exchanges heat with a gas

In heat exchanger design as a safety factor

In case of Newtonian fluids

None of these

When a liquid exchanges heat with a gas

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Heat and Mass Transfer
A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is

1/h₁ + 1/h₂ + 1/h₃

(h₁.h₂.h₃)1/3

None of these

h₁ + h₂ + h₃

1/h₁ + 1/h₂ + 1/h₃

(h₁.h₂.h₃)1/3

None of these

h₁ + h₂ + h₃

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Heat and Mass Transfer

Heat and Mass Transfer 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

Heat and Mass Transfer Which of the following is expected to have highest thermal conductivity?

Heat and Mass Transfer Thermal diffusivity of a substance is

Heat and Mass Transfer Heat transfer takes place as per

Heat and Mass Transfer Fouling factor is used

Heat and Mass Transfer A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is

Heat and Mass Transfer
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

Heat and Mass Transfer
Which of the following is expected to have highest thermal conductivity?

Heat and Mass Transfer
Thermal diffusivity of a substance is

Heat and Mass Transfer
Heat transfer takes place as per

Heat and Mass Transfer
Fouling factor is used

Heat and Mass Transfer
A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is