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.

40 minutes

20 minutes

5 minutes

10 minutes

40 minutes

20 minutes

5 minutes

10 minutes

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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

goes through a maximum.

continues to increase

continues to decrease

goes through a minimum

goes through a maximum.

continues to increase

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Heat Transfer
For hot feed, forward feeding as compared to backward feeding results in __________ economy.

None of these

No effect on

Decreased

Increased

None of these

No effect on

Decreased

Increased

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Heat Transfer
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place

From one part of a body to the another part of the same body

Both B & C

Between two bodies not in physical contact with each other

Between two bodies in physical contact with each other

From one part of a body to the another part of the same body

Both B & C

Between two bodies not in physical contact with each other

Between two bodies in physical contact with each other

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Heat Transfer
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for

Polished bodies only

All bodies

Black painted bodies only

A black body

Polished bodies only

All bodies

Black painted bodies only

A black body

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Heat Transfer
What is the unit of thermal conductivity ?

Kcal/hr.m.°C

Kcal/hr. m² °C

Kcal/hr. °C

Kcal/hr.m

Kcal/hr.m.°C

Kcal/hr. m² °C

Kcal/hr. °C

Kcal/hr.m

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Heat Transfer

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

Heat Transfer For hot feed, forward feeding as compared to backward feeding results in __________ economy.

Heat Transfer Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place

Heat Transfer The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for

Heat Transfer What is the unit of thermal conductivity ?

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

Heat Transfer
For hot feed, forward feeding as compared to backward feeding results in __________ economy.

Heat Transfer
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place

Heat Transfer
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for

Heat Transfer
What is the unit of thermal conductivity ?