The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are

Heat Transfer
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are

(COP)R = (COP)HP = 0.6

(COP)R = (COP)HP = 2.5

(COP)R = 2.5; (COP)HP = 1.5

(COP)R = 1.5; (COP)HP = 2.5

(COP)R = (COP)HP = 0.6

(COP)R = (COP)HP = 2.5

(COP)R = 2.5; (COP)HP = 1.5

(COP)R = 1.5; (COP)HP = 2.5

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Heat Transfer
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be

0.55

0.35

0.85

0.45

0.55

0.35

0.85

0.45

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Heat Transfer
The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.

None of these

Reynolds

Prandtl

Colburn

None of these

Reynolds

Prandtl

Colburn

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Heat Transfer
The ratio of momentum diffusivity to thermal diffusivity is the __________ number.

Prandtl

Stanton

Nusselt

Grashoff

Prandtl

Stanton

Nusselt

Grashoff

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Heat Transfer
In which mode of heat transfer, the Biot number is important?

Natural convection

Transient heat conduction

Forced convection

Radiation

Natural convection

Transient heat conduction

Forced convection

Radiation

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Heat Transfer
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

Buoyancy of the bubbles produced at active nucleation site

Existence of thermal boundary layer

None of these

Temperature gradient produced due to density difference

Buoyancy of the bubbles produced at active nucleation site

Existence of thermal boundary layer

None of these

Temperature gradient produced due to density difference

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Heat Transfer

Heat Transfer Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be

Heat Transfer The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.

Heat Transfer The ratio of momentum diffusivity to thermal diffusivity is the __________ number.

Heat Transfer In which mode of heat transfer, the Biot number is important?

Heat Transfer Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

Heat Transfer
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be

Heat Transfer
The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.

Heat Transfer
The ratio of momentum diffusivity to thermal diffusivity is the __________ number.

Heat Transfer
In which mode of heat transfer, the Biot number is important?

Heat Transfer
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the