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[dhyun]

Hi~
I need your helps !!!
During the PSV calculation, I found below formula which is intended for two phase flow rate
calculation by Design Institute for Emergency Relief(DIERS).
I would like to know when to apply(which scenario) this formula.
API 520 do not provide below formula. Thank you for your advice in advance.
Have a nice day.

W2={[(Q/(CpDT)]x[ln((QVfg)/(W2Vol))-1]}+{[Vo/Vfg]x[(W2l)/(CpDT)]}

Q Total heat absorbed (See "External fire case")

Cp Liquid heat capacity at set pressure

DT Temperature rise from set point to accumulated pressure of bubble point liquid

a Initial fraction of the vessel volume occupied by vapour

Vf Liquid specific volume at set pressure

Vg Vapour specific volume at set pressure

Vfg Vf - Vg

Vo 1/{[(1-a)/Vf]+[a/Vg]}

l Latent heat of vapourisation of the liquid at set pressure

W2 Calculated rate of vapour and liquid to be relieved