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I have a question about convective heat transfer coefficients. I am trying to figure out how much steam I can condense in this specific heat exchanger.

Steam at 9 MPa is condensed in a 1 shell pass, two tube pass type heat exchanger which contains a total of 280 U shaped tubes inside the shell.

The steam is condensed in the shell. I know the geometry of the tubes. The saturation temp at this pressure is 307 C.

The resistance in the system is the sum of steam convection, wall conduction and water convection.

I am not sure how to compute $h_o$, the convective heat transfer coefficient on the steam side since I am trying to calculate how much flow I can use, and $h_o$ depends on the steam flow rate (or velocity).

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  • $\begingroup$ When you do find correlations for this, make sure that you're looking at ones for condensation. This generally much stronger than ordinary convection(in terms of heat flux). The physical process is very different due to the formation of liquid on the fold surface. $\endgroup$ – user3823992 Oct 21 '14 at 15:50
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Convective heat transfer is an engineering topic and is subject to much uncertainty. Heat transfer coefficients are normally obtained from correlations based on experimental data and backed up with theoretical analysis. If you have no other source of information, I suggest you start by taking a look at Thermopedia : http://www.thermopedia.com/content/652/

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There are a few things to consider here:

1) The heat transfer coefficient of the steam is normally substantially higher than that for water, so this coefficient will not be your limiting factor. If a similar heat exchanger exists, take measurements and calculate the overall heat transfer coefficient, which I expect will be in the range of 200-400 BTU/hr-ft^2-degF.

2) When I worked in industry, I don't recall ever seeing a heat exchanger operating with absolutely full pressure on the shell. There is normally a control valve upstream of the heat exchanger, and a controller that manipulates the valve to control the condensing pressure/temperature of the steam. If you are intending to operate at full shell pressure, your process will no longer be controlled, which could present problems if you have associated process variables that need to be kept on specification. If you do need to maintain controllability, assume that your control valve will be run at a maximum of 90% open, and account for pressure drop at that operating point.

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