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JT effect

JT effect

JT effect

(OP)

I am not an engineer, so forgive my ignorance.  I need to know if there is a formula for determining the delta T when taking a pressure drop across a valve.  Specifically, what information do I need other than the inlet/outlet pressures, specific gravity (this is natural gas) and inlet temperature?  Thanks for your help.  

RE: JT effect

Usually, I use a Mollier chart (or similar thermodynamic chart) for methane for something like this (the GPSA data book has a copy if there is one around, so will Perry's as will many other books).  For less than 10% of C2s and heavier, the Mollier chart still gives you a reasonable dT compared to something like Pro/II.

You find the starting pressure and temperature and then drop straight down (assuming the x axis is enthalphy, otherwise you follow a constant enthalphy line) to your outlet pressure and read off the resulting temperature.

I don't remember seeing a simple equation like you are hoping to find and nothing is popping out of some of my engineering textbooks.

RE: JT effect

(OP)

TD2K, thanks for your help.  I was hoping to find a formula to put in a spreadsheet.  BTW, what section of Perry's are these charts.  I couldn't find it.  Thanks.

RE: JT effect

They are in section 2 of the 6th Edition.

RE: JT effect

A very rough rule of thumb is half a degree cel. pr bar of pressure drop. But its surpricingly accurate anyway for most appl. up to 100 bar and no condensation.

Best Regards

Morten

RE: JT effect

dear sir:
i want to know what is the effect of heat transfer by conduction , by convection and by raiation . and thank you

RE: JT effect

You will propably never read this beeing a visitor and all but a few pieces of advice:

1) Dont ad a question to a random tread - create a new tread
2) Your question is mush to general.Best advice to expect will be a number of references to good text books.

Best Regards

Morten

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