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Fire-Liquid Relief PSV Sizing-Latent heat of vaporization

Fire-Liquid Relief PSV Sizing-Latent heat of vaporization

Fire-Liquid Relief PSV Sizing-Latent heat of vaporization

(OP)
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.

RE: Fire-Liquid Relief PSV Sizing-Latent heat of vaporization

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

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