2 replies to this topic

[ulka_19]

Hello,

 

I work in a petrochemical industry. My question is that there is a Carbon Steel pipe for handling Liquid Propylene. Prior to charging Propylene into this line, we have filled this line with 3 bar N2 gas. Now i want to know how will I calculate the final temperature of Propylene after flashing inside the pipe. I want to know the lowest temperature so that I can check if its matching with the minimum design temperature of the CS pipe.

 

Regards

[latexman]

The lowest temperature occurs at the lowest pressure, so when your valve just cracks open and the first drop of liquid propylene flashes to 3 bar is the lowest pressure and temperature.  Flashing across a valve is isenthalpic, so

 

H(T_upstream, P_upstream) = H(T_unknown, 3 bar)     I assume you know the upstream conditions.

 

After that, the propylene starts filling the pipe and exerts it own vapor pressure, so the downstream pressure increases.

[Bobby Strain]

A proper design would have used low temperature carbon steel that is good for low temperature. And the pipe cost little more.

 

Bobby