Question { IOCL, 16075 }

how FOULING effectd the heat transfer rate

Answer

Fouling increases the thickness of the heat transfer
surface. It add an extra heat resistances a result
it decrease the heat transfer rate.
Since rate of heat transfer is inversely proportional to the
thickness of the heat transfer surface and fouling increases
the thickness, therefore fouling decreases the heat
transfer rate.

Question { NFTDC, 23161 }

What is difference between Overall heat transfer coeficient
& individual heat transfer coefficient

Answer

There are two type of heat transfer co-efficient.
Internal heat transfer co-efficient and external heat
transfer co-efficient. they are separately called individual
heat transfer coefficient. and the combined effect of them
to heat transfer is called Overall heat transfer coeficient.