Hi Fellow Engineers,
I want to verify the thermal relief valve capacity in LNG transfer line (thousands of feet, 24"). The line is cold insulated
The bubble point is -157F at relieving pressure 297 psig
(1) When T<-157F, I use the thermal relief equation in API 521
In this case, the required relief area is only a small fraction of a 3/4" valve
(2) When T>-157F, LNG will vaporize. I calculated the vapor relief rate base on heat transfer rate divided by latent heat of LNG
For this case, the required is much larger.
My question: is the method I used in (2) when T>-157F correct?
Thank you.
Leo