A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

Heat Transfer
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

55.5

0.15

555

0.55

55.5

0.15

555

0.55

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Heat Transfer
With increase in temperature, the thermal conductivity of a gas

Increases

Remains same

May increase or decrease depending on the type of gas

Decreases

Increases

Remains same

May increase or decrease depending on the type of gas

Decreases

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Heat Transfer
Agitated film evaporator is suitable for concentrating __________ liquids.

Very thin

Corrosive

Viscous

Foaming

Very thin

Corrosive

Viscous

Foaming

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Heat Transfer
During crystallisation, formation of crystal can occur in __________ solution only.

All of these

Undersaturated

Saturated

Supersaturated

All of these

Undersaturated

Saturated

Supersaturated

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Heat Transfer
Vacuum is generally maintained in the vapour space of an evaporator mainly to

Achieve very high concentration of the final product

Get economical temperature difference by using moderate pressure steam

Concentrate heat sensitive materials

Facilitate forward feeding in multiple effect evaporation

Achieve very high concentration of the final product

Get economical temperature difference by using moderate pressure steam

Concentrate heat sensitive materials

Facilitate forward feeding in multiple effect evaporation

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Heat Transfer
Economy of an evaporator is influenced by the

Steam pressure

Both B & C

Number of effect

Feed temperature

Steam pressure

Both B & C

Number of effect

Feed temperature

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Heat Transfer

Heat Transfer With increase in temperature, the thermal conductivity of a gas

Heat Transfer Agitated film evaporator is suitable for concentrating __________ liquids.

Heat Transfer During crystallisation, formation of crystal can occur in __________ solution only.

Heat Transfer Vacuum is generally maintained in the vapour space of an evaporator mainly to

Heat Transfer Economy of an evaporator is influenced by the

Heat Transfer
With increase in temperature, the thermal conductivity of a gas

Heat Transfer
Agitated film evaporator is suitable for concentrating __________ liquids.

Heat Transfer
During crystallisation, formation of crystal can occur in __________ solution only.

Heat Transfer
Vacuum is generally maintained in the vapour space of an evaporator mainly to

Heat Transfer
Economy of an evaporator is influenced by the