- #1
Redhunter
- 2
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I have a complex mathematical model (about 2000 lines of code) which calculates heat exchanger performance.
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?
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?