Fire-Liquid Relief PSV Sizing-Latent heat of vaporization

[DMCChem]

Hello All,

I am sizing PSVs for an Offshore Platform facility. One of the cases is PSV-123 on a Heat Exchanger Tubeside (Well-fluid),Shellside is a Heat Medium. I need some guidance on estimating Latent Heat of Vaporization using Hysys. I did the following..
1. Take copy of Hysys-PFD stream i.e. Tubeside inlet stream-100.
2. Raise the stream pressure to PSV set P+21% overP, not changing Temp &/or vapor fraction
3. Add a Heater. Set Del.P across heater = 0 psi, Set outlet stream vapor fraction= (inlet stream vapor fraction +0.01).
4.The Heater calculates the heat-duty added for vaporization of 1% of inlet stream.
5. Latent Heat of Vap = [Heat Duty of Heater]/[(Outlet stream vapor-phase mass flowrate)-(inlet stream vapor-phase mass flowrate]

using above-5steps, I get a very huge no.as Latnt heat, something like 4200 btu/lb. Thats where I am puzzled if I am using a wrong approach?? Please correct/guide.
I appreciate any input in this area which I take as a learning opportunity. Thanks.

 

[MortenA]

check what the phase of the vaour phase consists of.

What is you abs. pressure? You may be into the dense phase and there is no latent heat (but that i assume would make it impossible to find where the water fration was not either 1 or 0

Oh, and do the calculation for the liquid phase only (that is separate liquid and vapours and add the heater downstream the sep.
Best regards, Morten