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Temperature of Steam After it goes through a PRV

Temperature of Steam After it goes through a PRV

Temperature of Steam After it goes through a PRV

(OP)
I am trying to determine the temperature of the steam after it goes through a pressure reducing valve (prv).

The upstream pressure is 600 psig @ saturation temperature. The down stream pressure is 400 psig.

From my understanding going through a prv the enthalpy of the system should stay the same.

Therefore, I usually look up the enthalpy at the higher pressure then look up the properties of the steam with the lower pressure and same enthalpy. Thus I get the down stream temperature. For the case above the enthaply at saturation temperature are listed below.

Enthalpy of saturated 600 psig steam is 1203.50 btu/lb

Enthalpy of saturated 400 psig steam is 1205.16 btu/lb

Therefor my method does not work to get the temperature or any properties of the lower pressure steam. Is there a more accurate way to calculate the down pressure steam?

RE: Temperature of Steam After it goes through a PRV

The enthalpy of the system (in theory) stays the same. Some of the steam will condense.

RE: Temperature of Steam After it goes through a PRV

(OP)
Goober Dave,

Thanks for the link, but that is what I use to get my properties. The problem is if I put in 400 psig with 1203.5 BTU i get an error.

RE: Temperature of Steam After it goes through a PRV

(OP)
MisterDonut,

Thanks, so if i understand correctly the 400 psig steam will just be at saturation temperature?

OJ

RE: Temperature of Steam After it goes through a PRV

The steam will be at 400 psig but it will be "wet," meaning a mixture of saturated steam and saturated liquid.

RE: Temperature of Steam After it goes through a PRV

If the 600# steam is at saturation is is about 488*f. When you reduce the pressure you are not reducing the temperature so the 400# steam should be slightly superheated still around 488*f. Unless you desuperheat it it will remain hotter than saturation. Another point to ponder if enthalpy is btu/lb than the more the lbs or psi the more the btu's??

RE: Temperature of Steam After it goes through a PRV

dabigoj - correct. There is an inflection point at about 460 psia.

Good luck,
Latexman

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Temperature of Steam After it goes through a PRV

If you reduced the pressure while keeping enthalpy constant, you will get superheated steam. So you have to look up the temperture on the superheated steam tables.

http://www.spiraxsarco.com/resources/steam-enginee...

Scroll down to "The effects of reducing steam pressure"

RE: Temperature of Steam After it goes through a PRV

Forget what I just said. Damn I wish I could delete my post. Should have thought it through before posting. Right out of uni. My bad.

RE: Temperature of Steam After it goes through a PRV

Thermo, red flag your post (or posts) and tell the system administrators why you want to delete or edit them.

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