3 replies to this topic

[krishnamurthy]

In PRV sizing for fire case for wetted case , if we have fluid with different hydrcarbons, for eg propane, heptane, methane,etc   which hydrocarbon you take for calculating latent heat of vapourization? Pls help 

 

[Bobby Strain]

If you don't have a process simulator, you would have to conduct flash calculations. Or ask for help. Or hire a consultant. Or download and use a free process simulator like DWSim. The usual practice is to conduct multiple flashes to determine the sizing conditions.

 

Bobby

[breizh]

Hi,

You may want to use the methodology explained in the spreadsheet attached ,the most difficult part being the calculation of the mass flowrate released.

If you don't have access to simulator you may want to use the online simulator underneath to calculate a flash .

Properties with Variant Fina Pressure – Quest Consultants

 

EDIT: Aspen Tech document to support.

Good luck,

Breizh 

[PaoloPemi]

krishnamurthy,
you may find many threads discussing this topic : simulators and thermodynamic libraries include specific procedures but if you do not wish to adopt these procedures you can integrate directly with the so called direct integration method discussed in many posts... 

I copy and paste from another thread :

as first step , given a PSV discharge pressure (or a initial value for P), you need to estimate temperature,
for that you can solve a flash operation with specified volume and pressure,
for example, with PRODE PROPERTIES library and Excel, Python, LibreOffice or equivalent tools
t = VPF(stream,p,v)
at that point you can calculate latent heat as difference (Vapor enthalpy - Liquid enthalpy)
dH = (StrSGH(stream)-StrSLH(stream))
to adopt in first step of direct integration,
at each step, you need to estimate heat by fire and the amount of vapor discharged (mass & heat balance),
with PRODE you can solve, for example, a H-P flash operation,
if you include corrections for parameters as heat transfer between vapor and liquid inside vessel etc. the final result should not be too different from predefined procedures (dynamic simulation),

anyway, a point to consider with a PSV is material stress, where possible I prefer rupture disks or depressurization which you can simulate with a equivalent procedure (variable P istead of fixed P).