Dear all,
In small scale applications (HVAC or ORC), plate heat exchangers are often divided in multiple zones including subcooled, two-phase and superheated regions.
For modelling single-phase zone, state-of-the-art correlations (e.g. correlations from Thonon, Martin, Wanniarachchi, etc.) or self-calibrated equations are often used to simulate either subcooled liquid and superheated vapour flows. But if you look at the original data set used for their calibration, they all have been calibrated with liquid-only conditions.
I am concerned about the extrapolability of these correlations to vapour flows. For instance, can you reliably use a correlation i.e.
Nu = C*Re^m * Pr^0.333
for vapour conditions while the C and m parameters are identified with liquid conditions? If you do so, you will get a higher heat transfer coefficient for the vapour zone than for the liquid one, which is a bit surprising to me.
Would anybody could confirm me this or provide further info? also, if you know any paper studying vapour phase heat transfer in BPHEXs, I'll be happy if you could share it (I haven't found any ..).
Thanks :)
Rémi
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