Saturation steam flow through pipeline
Saturation steam flow through pipeline
(OP)
Dear All,
Do I have to suppose that when the saturated steam flows through a pipeline it expands (due to friction losses, in my case about 2 bars) according to the isenthalpic-adiabatic model similar to the saturated steam expansion through a pressure control valve or an orifice?
Is the saturated steam becomes superheated along the line?
Thanks in advance, Mike
Do I have to suppose that when the saturated steam flows through a pipeline it expands (due to friction losses, in my case about 2 bars) according to the isenthalpic-adiabatic model similar to the saturated steam expansion through a pressure control valve or an orifice?
Is the saturated steam becomes superheated along the line?
Thanks in advance, Mike





RE: Saturation steam flow through pipeline
RE: Saturation steam flow through pipeline
Can you please explain why no ?
RE: Saturation steam flow through pipeline
As for superheat, since I never thought of this and came across first time, I would give it some thought before responding. So far, I assumed saturated conditions.
RE: Saturation steam flow through pipeline
It is conceivable that if the line was very well insulated but had a high pressure drop then the pressure could drop faster along the line than the corresponding saturation pressure due to heat loss. In this case you could get superheat developing but I would say that this is very much a non-typical situation.
To get to the specific behavior in your application you would have to work out how much heat is transferred through the pipe wall and insulation, and then knowing the heat content of the steam at the downstream end (from this calculation) and the pressure (from the friction pressure drop) you can work out whether you have had some condensation or else generated some superheat.
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Saturation steam flow through pipeline
RE: Saturation steam flow through pipeline
It is very interesting issue.
I did an estimation of the pressure drop of the saturation steam through the about 1 km pipeline using the WinSim simulator.
Based on the WinSim that used adiabatic model,steam at the pipe outlet is superheated. Is this make sence?
If J-T effect is applicable for this case?
In which case the isenthalpic-adiabatic model can be used?
RE: Saturation steam flow through pipeline
In general, it is not a bad estimate to assume the flow of steam in a header or pipeline is incompressible. If you are working with high pressure steam and relatively low pressure drops then the steam density is virtually constant over the length of the pipeline. You can treat it as an adiabatic or even isothermal compressible flow if you want to be a bit more accurate in your calculation of the pressure drop. But you cannot then use that assumption to determine the exact condition of the steam at the exit. These assumptions are OK for determining the density changes because they are so small, but not OK if you want to determine the exact condition of the exit steam.
As the steam flows down the pipeline it will cool because of heat losses. This increases the density. But the pressure decreases because of friction. This decreases the density. Overall you will find only a small change in density unless you have a very non-typical installation.
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Saturation steam flow through pipeline
Thanks for your explanation.
I would like to ask you a last question.
Why a steam expansion through the orifice is differ from the saturated steam expansion through the pipeline from the thermodinamic point of view.
Why the 1st process is isenthalpic and 2nd not.
RE: Saturation steam flow through pipeline
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"