A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.

Heat Transfer
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.

5 minutes

40 minutes

20 minutes

10 minutes

5 minutes

40 minutes

20 minutes

10 minutes

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Heat Transfer
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?

Thickness of the wall

Temperature difference between the two surfaces of the wall

Area of the wall perpendicular to heat flow

Material of the wall

Thickness of the wall

Temperature difference between the two surfaces of the wall

Area of the wall perpendicular to heat flow

Material of the wall

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Heat Transfer
In case of evaporators, liquid entrainment results primarily due to

high heat transfer rate

high vacuum in the evaporator

foaming of the solution

high heat transfer rate

high vacuum in the evaporator

foaming of the solution

high heat transfer rate

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Heat Transfer
The critical radius 'r' of insulation on a pipe is given by

r = 2k/h

r = k/h

r = k/2h

r = h/k

r = 2k/h

r = k/h

r = k/2h

r = h/k

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Heat Transfer
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.

film

pool

none of the listed here

transition

film

pool

none of the listed here

transition

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Heat Transfer
Thermal diffusivity of a material

All of these

Has the unit m² /sec

Is defined as K/ρ . Cp

Is the ratio of thermal conductivity to thermal capacity

All of these

Has the unit m² /sec

Is defined as K/ρ . Cp

Is the ratio of thermal conductivity to thermal capacity

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Heat Transfer

Heat Transfer Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?

Heat Transfer In case of evaporators, liquid entrainment results primarily due to

Heat Transfer The critical radius 'r' of insulation on a pipe is given by

Heat Transfer When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.

Heat Transfer Thermal diffusivity of a material

Heat Transfer
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?

Heat Transfer
In case of evaporators, liquid entrainment results primarily due to

Heat Transfer
The critical radius 'r' of insulation on a pipe is given by

Heat Transfer
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.

Heat Transfer
Thermal diffusivity of a material