Is the temperature up or down for liquid after the throttling valve?
Is the temperature up or down for liquid after the throttling valve?
(OP)
Hi, everyone! while doing hysys simulation, I found that following the J-T valve,the hydrocarbon gas T decreased, but for crude oil(liquid), it increased. why? is the liquid different from the gas on T passing through J-T valve? thanks in advance





RE: Is the temperature up or down for liquid after the throttling valve?
RE: Is the temperature up or down for liquid after the throttling valve?
RE: Is the temperature up or down for liquid after the throttling valve?
RE: Is the temperature up or down for liquid after the throttling valve?
RE: Is the temperature up or down for liquid after the throttling valve?
I would like to make a small technical correction. There are two types of work, PV work and shaft work (such as an expander). In the case of a gas there is real PV work (change in volume) so we get some temperature reduction for a real gas when pressure on the upstream is exchanged for volume on the downstream, but not nearly what we get when shaft work is extracted via an expander- which is why a turbo expander can generate some real cold temperatures.
With a liquid stream there is no PV work if a constant volume assumption is used- this is the technical correction of your statement. All the pressure energy upstream must become heat which shows up as temperature on the downstream side.
Another interesting fact is that for an ideal gas, there is no tmperature change on throttling because enthalpy is only a function of temperature- you can test this in the simulation by choosing an ideal gas model for the properties. The enthalpy of a real gas is usually modeled as the ideal gas enthalpy + an enthalpy departure term which incorporates pressure into the enthalpy calculation. This is how a real gas model calculates the temperature change.
This is my mental model which is very conventional. Others may arrive at the same conclusion via other thought processes.
best wishes,
SShep
RE: Is the temperature up or down for liquid after the throttling valve?
MortenA
you are right, i assign the name of J-T valve,describing the function, there is no j-t valve.thank you so much.
Hi,25362
thank you for the thread provided.it includes many useful informations
RE: Is the temperature up or down for liquid after the throttling valve?
RE: Is the temperature up or down for liquid after the throttling valve?