Menu ▾ ▴

#107 UO: Heat Exchanger LMTD calc error

3.6
closed
Daniel Medeiros
Major (38)
2016-02-10
2016-01-19
JMB
No

Upon closer examination of the NH3+H2O condensation simulation reported here:

https://sourceforge.net/p/dwsim/discussion/844529/thread/c89168de/?page=1

I found that the LMTD calculation seems to be incorrect by an order of magnitude. Note that I am using the 'CalcBothTemp UA' w/ 'CounterCurrent' method. I had supplied it with the exchanger geometry in an attempt a do a 'Shell&Tube Rating' calculation, therefore the values shown in the HeatExchanger table are remnants of that input data.

Ubuntu 12.04.5 64bit
Mono version 4.2.1 (Stable 4.2.1.102/6dd2d0d Thu Nov 12 09:52:44 UTC 2015)
DWSIM_bin_v36_b5859_beta.zip Build [git-9b6a447] (16/01/2016)

1 Attachments
LMTD_Error.png

Discussion

  • Daniel Medeiros

    Daniel Medeiros - 2016-01-25

    Can you attach the simulation file?

     

  • Daniel Medeiros

    Daniel Medeiros - 2016-02-05
    • status: open --> closed
    • assigned_to: Daniel Medeiros
     

  • Daniel Medeiros

    Daniel Medeiros - 2016-02-05

    This "error" is a consequence of a bug which was corrected in Build 5876.

     

  • Gregor Reichert

    Gregor Reichert - 2016-02-07

    Hi JMB,
    i created a new algorithm which is able to handle even very nasty cases like your example. This sample uses an extremely large heat exchanger surface compared to the small stream flows which created calculation problems.

    Gregor

     

  • JMB

    JMB - 2016-02-10

    Hello Gregor,
    Thank you for finding a fix! I am eager to try it out.

    @Daniel: Am I correct in the assumption that Gregor's fix is not in Build 5876, because it is still not working as expected. If it is not in build 5876, would you kindly publish a new build?

    Thank you!