Pressure drop vs. Valve opening in Critical flow
Pressure drop vs. Valve opening in Critical flow
(OP)
Hi, I am struggling in modeling of multiphase flow valve in oil and gas production pipeline.
I am using Hydro long model, and trying to find C_T value (Throttling coefficient) to be matched with the measured pressure drop.
One interesting thing I found is for critical flow pressure drop decreases as decreasing valve opening (C_T value), while the pressure drop increases as decreasing valve opening for subcritical flow case.
I am looking for some theoretical background why pressure drop decreases as decreasing valve opening in critical flow. Is there anyone who knows why? Or my result is completely wrong?
Thanks.
Best regards,
Keunsoo
I am using Hydro long model, and trying to find C_T value (Throttling coefficient) to be matched with the measured pressure drop.
One interesting thing I found is for critical flow pressure drop decreases as decreasing valve opening (C_T value), while the pressure drop increases as decreasing valve opening for subcritical flow case.
I am looking for some theoretical background why pressure drop decreases as decreasing valve opening in critical flow. Is there anyone who knows why? Or my result is completely wrong?
Thanks.
Best regards,
Keunsoo





RE: Pressure drop vs. Valve opening in Critical flow
It may or may not be valid, but critical flow in a multiphase line is absolutely the most chaotic condition that we see in fluid mechanics--gas flow is choked, but liquid flow is not, at what point does the liquid see very low pressure, what is the JT component, and a thousand other unknowables. Any assumption will be wrong at least as often as it is right.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Pressure drop vs. Valve opening in Critical flow
Either subcritical or critical flow, my model includes phase change - mass fraction is from the pressure and temperature measurement in three positions of valve: 1) valve inlet, 2) valve outlet, 3) downstream of valve when flow reattach the wall.
Then can we find more clear answer why pressure drop decreases as closing valve more..?