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

Achieve very high concentration of the final product
Facilitate forward feeding in multiple effect evaporation
Get economical temperature difference by using moderate pressure steam
Concentrate heat sensitive materials

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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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