Heat Transfer
Low thermal conductivity of heat insulating materials is due to its

Dense structure
High proportion of air space
High specific heat
None of these

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Heat Transfer
In a shell and tube heat exchanger,

The relationship is not generalised
The temperature drops in the two fluids and the wall are proportional to individual resistances
The temperature drop is inversely proportional to the resistance across which the drop occurs
There is no relationship between temperature drop and resistance

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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

44 min
22 min
51 min
15 min

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