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
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

h₁ + h₂ + h₃

1/h₁ + 1/h₂ + 1/h₃

None of these

(h₁.h₂.h₃)1/3

h₁ + h₂ + h₃

1/h₁ + 1/h₂ + 1/h₃

None of these

(h₁.h₂.h₃)1/3

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Heat and Mass Transfer
The concept of overall coefficient of heat transfer is used in case of heat transfer by

Radiation

Convection

Conduction

Conduction and convection

Radiation

Convection

Conduction

Conduction and convection

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Heat and Mass Transfer
According of Kirchhoff's law

Emissive power and absorptivity are constant for all bodies

Emissive power depends on temperature

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

Radiant heat is proportional to fourth power of absolute temperature

Emissive power and absorptivity are constant for all bodies

Emissive power depends on temperature

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

Radiant heat is proportional to fourth power of absolute temperature

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

Conduction

Convection

None of these

Radiation

Conduction

Convection

None of these

Radiation

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Heat and Mass Transfer
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)

tm = (Δt1 - Δt2)/ loge (Δt1/Δt2)

tm = loge (Δt1 - Δt2)/ Δt1/Δt2

tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)

tm = loge (Δt1/Δt2)/ (Δt1 - Δt2)

tm = (Δt1 - Δt2)/ loge (Δt1/Δt2)

tm = loge (Δt1 - Δt2)/ Δt1/Δt2

tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)

tm = loge (Δt1/Δt2)/ (Δt1 - Δt2)

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Heat and Mass Transfer
Upto the critical radius of insulation,

Added insulation will decrease heat loss

Added insulation will increase heat loss

Convective heat loss will be less than conductive heat loss

Heat flux will decrease

Added insulation will decrease heat loss

Added insulation will increase heat loss

Convective heat loss will be less than conductive heat loss

Heat flux will decrease

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Heat and Mass Transfer

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 The concept of overall coefficient of heat transfer is used in case of heat transfer by

Heat and Mass Transfer According of Kirchhoff's law

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

Heat and Mass Transfer 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)

Heat and Mass Transfer Upto the critical radius of insulation,

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
The concept of overall coefficient of heat transfer is used in case of heat transfer by

Heat and Mass Transfer
According of Kirchhoff's law

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

Heat and Mass Transfer
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)

Heat and Mass Transfer
Upto the critical radius of insulation,