2 replies to this topic

[mrbabu]

I have a question about the (measured) discharge temperature when modeling a centrifugal compressor for wet gas service (or a turbine with condensate), 

with dry gas, starting from Pin, Tin, Pout, Tout, the polytropic model can estimate good values for shaft horsepower (which i use as safe test),

while, with wet gas, the values calculated for shaft horsepower on the basis of the (measured) discharge temperature can be very different (depending from condensate fraction),

the values are calculated according the polytropic stage with phase equilibria and GERG 2008 models included in Prode Properties,

what do you think ?

[PaoloPemi]

with wet gas (in my opinion) if you know (or can estimate, for example from absorbed power and mechanical efficiency) shaft horsepower better to (estimate) polytropic efficiency from that value,
with wet gas there could be a non-equilibrium condition at discharge, other possible errors (in temperatures) can result from heat transfer, condensate draining etc. etc.
the same for turbines (in turbo compressors),
unfortunately, as far as I know, there are no standards (as ASME PTC10) for wet gas,
the polytropic model with phase equilibria in Prode Properties is accurate (about the same accuracy of reference model in PTC10) but you must use it with care... (the same for other process simulators, of course)
see also similar threads at cheresources...

Edited by PaoloPemi, 15 February 2018 - 12:34 PM.

[mrbabu]

thanks Paolo,

I have found a paper from NTU discussing that solution (i.e. consider shaft horsepower in addition to discharge temperature),

it seems interesting.