In an indirect heater the heat is supposed to be transferred from the fire tube to bath liquid and bath liquid to process fluid. I intend to calculate the heat transfer coefficient from stagnant bath liquid to the process fluid which is flowing. I need help to select appropriate heat transfer coefficient model in this regard. Please advise.
note: the sample of indirect heater is attached
Heat Transfer in Fire Tube heaters is discussed in Chapter 8 of GPSA, 12th Edition, see Example 8-2 to 8-4 and Fig. 8-34. The controlling thermal resistance is usually in the natural convention of the external liquid bath.
It means the heat transfer coefficient for bath liquid to process fluid is not much important here. The heat-flux will be same all through as fire tube heat-flux through the bath fluid. Am I right?
I think no single heat transfer coefficient suitable for your problem.
You need to get the overall heat transfer coeff, which is considering the convection got from the stagnan bath liquid to the outer surface of process fluid pipe, the conduction through its pipe, and the convection from the inner pipe to the process fluid.
You can read any heat exchanger books or any chapter in a heat transfer book discussing about heat exchanger.
Hopefully it is useful for you....
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