Is the symbol for
heat transfer coefficent h, or a U? You use both and I can't find the difference
between them.
h is the heat transfer coefficient between a bulk fluid at temperature
Tbulk and a wall at Tsurface. It's used as a boundary
condition in solving for temperature profiles.
U is the OVERALL heat transfer coefficient, and it represents
the heat transfer between the bulk fluid on the inside of a unit, and the
bulk fluid on the outside of the unit. So for a heat exchanger U describes
the heat transfer between the bulk fluid on the shell-side and the bulk
fluid on the tube-side.
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