I have a complex mathematical model (about 2000 lines of code) which calculates heat exchanger performance.(adsbygoogle = window.adsbygoogle || []).push({});

Using Q=UxAxLMTD I want to iterate the entering temperature until I find that the installed surface satisfies a target duty.

At present I

1 guess an entering temperature and from the duty calculate the leaving and mean temperature.

2 Calculate various fluid properties, Reynolds No, Prandtl No etc and so a U-value

3 Using the target duty, I calculate the required surface

4 I compare the required surface with the actual surface and make a correction factor

ie k x ((Required-Actual)/Actual)

where k is say 0.25

5 New entering temperature = previous entering temp x (1- correction)

after playing about with k I generally get convergence at between 5 and 40 iterations but sometimes I get oscillation about the solution.

The books I have seem to use first and second order derivatives but my process is too complex for that. Any simple solutions?

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# Convergence algorithm needed

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