Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for

Heat Transfer
Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for

Cylinder

Cube

Sphere

Equal for all the three

Cylinder

Cube

Sphere

Equal for all the three

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Heat Transfer
In a heat exchanger, one transfer unit means

Both A and B

The size of the exchanger in which heat transfer rate is 1 kcal/hr

None of these

A section of the exchanger in which change in temperature of one stream equals the average driving force in the section

Both A and B

The size of the exchanger in which heat transfer rate is 1 kcal/hr

None of these

A section of the exchanger in which change in temperature of one stream equals the average driving force in the section

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Heat Transfer
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?

Fouling characteristic

None of these

Corrosiveness

Viscosity

Fouling characteristic

None of these

Corrosiveness

Viscosity

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Heat Transfer
For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

NPr-1/3

NPr-1

NPr

NPr1/3

NPr-1/3

NPr-1

NPr

NPr1/3

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Heat Transfer
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer

Increases exponentially

Increases

Remains unaffected

Decreases

Increases exponentially

Increases

Remains unaffected

Decreases

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Heat Transfer
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient

continues to decrease

goes through a minimum

continues to increase

goes through a maximum.

continues to decrease

goes through a minimum

continues to increase

goes through a maximum.

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Heat Transfer

Heat Transfer In a heat exchanger, one transfer unit means

Heat Transfer Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?

Heat Transfer For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

Heat Transfer With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer

Heat Transfer As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient

Heat Transfer
In a heat exchanger, one transfer unit means

Heat Transfer
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?

Heat Transfer
For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

Heat Transfer
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer

Heat Transfer
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient