Latent Heat of Vaporization

[FoxRox]

I'm trying to size a safety relief valve for a 2-phase separator.

Per the Crosby Pressure Relief Valve Engineering Handbook:

W = Q/Hvap

Where:
W = Mass flow, lbs/hr
Q = Total heat absorption to the wetted surface, BTU/hr
Hvap = Latent heat of vaporization, BTU/lb

My problem is Hvap. It's easy to look up Hvap for a given pure fluid at atmospheric pressure, but how does one go about calculating/estimating Hvap for an oil-water-gas mixture at 250 psi.

Is this something that has to be measured using a sample of the emulsion? Or is there a "trick" or "industry standard" that I can use to get around this hangup.

Thanks,

Luke

 

[gocougs1]

Usually PSV sizing is given to chemical engineers, but for a mixture of fluids the standard approach is to consider each distinct fluid phase separately. So you would need to calculate the latent heat (Hvap) of water, then the oil mixture. For the oil mixture we typically consider the latent heat of the 5-10% fraction for PSV sizing.

 

[MortenA]

I agree with gocougst, but if you dont have access to process simulator (required for this approach)API 520 has a nomograph for estimating latent heat for "pure single component parafin".. his can be used but will usually give a low value=> large PSV