Heat Transfer
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m².K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m².K. The overall heat transfer co-efficient at this time is

894W/m².K
287 W/m².K
1200W/m².K
333W/m².K

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

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