THE OVERALL HEAT TRANSFER COEFFICIENT

1)

2) In the analysis of heat exchangers, it is convenient to combine all the thermal resistances in the path of heat flow from the hot fluid to the cold one into a single resistance R

b) NOTE but  unless  Hence overall heat transfer coefficient U of a heat exchanger is meaningless unless the area on which it is based is specified.

c) When the wall thickness is tube is small and thermal conductivity is high then  and