Stream Properties in Promax

[Berenger]

Good day everyone,

I do require some assistance on some datasheets that I am working on. The data sheets are for valves and a couple of the properties required are specific gravity and viscosity. As we all know Promax does not give these values for the overall streams but, instead, gives the values for the individual phases of the stream (gas, light liquid, heavy liquid). If it is just a liquid stream, Promax will give the overall AND individual values for the liquid steams. However, if it is a combination of gas and liquid, Promax does not give these values for the overall stream. So, how can I calculate this overall values given the phase values?

How can I get the overall stream properties? I thought I could get a weighted average of the properties, for example if the ratio of the phases are 0.4907 and 0.5093 (light liquid, heavy liquid) and the specific gravities are 0.7420 and 0.9964 respectively. I took the weighted average for an overall value of 0.8716, i.e (0.4907*0.7420)+(0.5093*0.9664). Promax gave a very different value of 0.7633.

Same thing for viscosity. Viscosities were given as 1.0245 (LL) and 0.839 (LL). The weighted average is 0.93. promax gives a value of 1.009.

 

[Berenger]

Or, is it that I use the vapor properties if its a vapor stream with little liquid and use the liquid property if its a liquid stream with little vapor?

Thanks for all your anticipated assistance.

 

[PaoloPemi]

I do not know Promax but for valves data sheets, standards as ISA require separate properties for vapor and liquid phases,
you can have only one vapor phase so when present your simulator should give transport properties for that,
for liquids (and solids) you can have more than one phase,
the solution which I adopt with my software (PRODE) is to force a simple VLE flash (not multiphase) so that there can be only one liquid phase and, when present, the program gives the properties.
There could be cases with two-phases (gas+liquid) at valve inlet,
I do not know standards for these calc's so I ask manufacturers or apply a version of HEM / HNE model included in PRODE.