I would say it depends from application,
for process design in many cases a 1-3 % error is acceptable,
in other cases (for example fiscal metering etc.) one wish to obtain best accuracy.
suparida,
there are several threads discussing this topic at eng-tips,
see for example
http://www.eng-tips.com/viewthread.cfm?qid=329093
which includes a Excel page to simulate the PSV as isentropic nozzle,
the method (based on rigorous API HEM procedure) is not too different from that...
there are several posts at cheresources and here discussing these topics,
Prode Properties (even the free version !) includes both CPA (Cubic Plus Association) and several EOSs + activity such as NRTL (with complex mixing rules), these models should be able to predict water-methanol equilibria...
providing you know composition (for example in realtime from DCS, local GC etc.)
you may code an accurate model of compressor in your PLC,
if that is not possible,
there are soft sensors which can model a screw compressor (or a different type) as polytropic stage, see...
if it's for a single valve and have some pressure allowance you may accept sonic flow (mach number 1) in some section of discharge piping, providing that resulting pressure drop (note that higher pressure in some section = higher density = lower velocity = higher mass flow acceptable for sonic...
I am evaluating the results from different packages (GERG, CPA and Peng Robinson with complex mixing rules) to calculate phase equilibria and thermodynamic properties of natural gas with CO2, glycol and water,
as software I utilize PRODE PROPERTIES,
I notice that setting the BIPs from internal...
for a PSV flashing you may consider two different models, HEM and HNE,
you will find a detailed discussion of HEM model in API,
these models will predict the amount of vapor and liquid at PSV outlet,
the main difference is that HNE do not condider a homogeneous equilibrium (as HEM) but only a...
as said by PaoloPemi depending from the amount of condensate you may need a procedure to calculate phase equilibria along a polytropic path,
for a recent project we have utilized Prode Properties,
results have been found in agreement with manufacturer's simulation,
(the problem there is the...
Thanks a lot both of you,
zdas04
yes, it is the GPSA graph, actually I have not the ASTM standard but I think the GPSA graph is reasonably reliable (altough not much accurate, see my comment below)
PaoloPemi
I have tested ISO18453 and it seems to give accurate values, I think I'll adopt the...
for a stream containing hydrocarbons (C1-C9) and water (< 1000 ppm) I am calculating water dew point and hydrocarbon dew point, my reference tools GPSA manual and process simulator (Aspen) give very different results, I think process simulator is wrong, I selected Peng Robinson model as...
