Heat Transfer
Prandtl number is the ratio of

Thermal diffusivity to mass diffusivity
Momentum diffusivity to mass diffusivity
Momentum diffusivity to thermal diffusivity
Thermal diffusivity to momentum diffusivity

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Heat Transfer
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

Both the spheres will emit equal amount of radiation per unit time in the beginning
Both will absorb equal amount of radiation from the surrounding in the beginning
Both B & C
The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant

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Heat Transfer
Steam trap is used to

Remove water resulting from partial condensation of steam
Stop the supply of steam
Condense the steam flowing in the pipeline
None of these

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Heat Transfer
1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m² and the overall heat transfer co-efficient to the liquid is 1500 W/m².°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be

22 min
15 min
51 min
44 min

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