at initial conditions (32to34F, atm) the sample is in liquid state,
however I think that Prode calculates the liquid phase fraction (at initial conditions) before to simulate the test and (probably) you can enter also the (total) composition of a stream (not sure about this point but it's easy to verify)
(if you don't know that) for liquid phase fraction use the liquid separator operation,
see the manual for details

http://www.prode.com/docs/pppman.pdf

for petroleum fractions you need the additional module, not included in base version.

Hans, I did the test,
the method StrRVP() for calculating Reid Vapor Pressure extracts the liquid fraction (if I include fractions which are vapor at 0C atm) before to simulate the ASTM D323 procedure,
do you have an idea about the possible errors with this procedure ?

Reid vapor pressure is valid for liquids only and not for two phase mixes, so your simulator extracting the liquid fraction to find the RVP is correct.

If you want the RVP for the upstream composition, you'll have to bump up the operating pressure to be above the bubble point pressure of this mix at the current operating temp, so that this composition presents itself as all liquid.

thanks georgeverghese.

in many cases RVP is calculated for petroleum fractions and errors can depend from data regression procedure,
ASTM 6377 includes some RVP data for C5H12 C6H14 and others

I calculated a few values with Prode StrRVP(stream, mode) with mode = 2 meaning liquid saturated with air , the procedure D223

experimental calculated
C5H12 1.12 Bar.a 1.13Bar.a
C6H14 0.74 Bar.a 0.73 Bar.a

according a few tests, for mixtures errors (measured vs. calculated) are in the range 2-5% (on the average for different simulators)