C2H4 / C3H6 Enthalpy function h(T,P)

[AndreChE]

Dear all

Does any know, for ethylene and propylene, the h(T,P) function without chart/table interpolations?

I'm doing an energy balance to put in the DCS to the operators regarding centrifugal ethylene and propylene compressors.

Since the first stages discharges are internally mixed with the incoming suctions, there is not possibility to calculate it as a polytropic process.

My idea is more simple, since it is a "pure" component:

Three stages (3 suctions, 1 common discharge):

m1*h1 + m2*h2 + m3*h3 - m4*h4 = Wtotal + Qloss (1/2% ??)

Range of pressure/temperature: 0 to 20 barg; -50 to 120ºC

Thank you all
AndreChE

 

[25362]

Andre, isn't the information given by the NIST Chemistry WebBook good enough ?

 

[AndreChE]

I cannot find any function with Temperature and pressure as independent variables...

 

[dcasto]

The GPSA data book has curves with H for C2= and C3= that could be givena polynomial function. You could take values from the curves and enter into excel, plot them then have excel do a linear regresion.

Other than that, use a packeaged program or NIST to plot points in an area around where each condition exists.

Finally, WinSim has a proceedure that allows you to use its equations of state and enthapy routines via an excel addin.

 

[pmover]

AndreChe,

a suggestion . . . is it possible to have the input parameters (i.e. P & T) transmitted to another computer to compute the values, then transmit the computed values back to DCS for analysis? A little more work, but at least the DCS processor is not busy with calcs (already busy with control, etc.) such as this. I/Other engrs have accomplished this as compressor performance (energy balance) result data is sometimes not needed as often as DCS scans/updates.

Good luck!
-pmover