Fluid Dynamics Downstream of Valve
Fluid Dynamics Downstream of Valve
(OP)
Hi, I've gotten valuable info here for a number of years, but this is my first post.
I have a situation where a pressurized reservoir of liquid is connected to the inlet of a solenoid valve. The outlet is connected to a length of plastic tubing, which discharges to the atmosphere. With the valve closed, there is liquid in the line downstream (at atmospheric pressure). The valve opens for a short time (min 20msec, max 1sec) and closes, dispensing an amount of liquid out the end of the tubing. I'm interested in modeling the pressure/flow in the tube downstream. I know there are dynamic effects as the pressure builds & decays, but don't know what equations to apply to analyze it.
The steady-state flow in the tubing is laminar, and the liquid is low viscosity (solvent-based, ~0.5cP). The tubing downstream of the valve is .020"ID, 48" lg. The inlet to the valve can be assumed to be at constant pressure.
If I had CFD software available, I would use it, but sadly I don't. :( So I'm looking to do it the old-school way. Let me know if I've left out anything important. Thanks!
I have a situation where a pressurized reservoir of liquid is connected to the inlet of a solenoid valve. The outlet is connected to a length of plastic tubing, which discharges to the atmosphere. With the valve closed, there is liquid in the line downstream (at atmospheric pressure). The valve opens for a short time (min 20msec, max 1sec) and closes, dispensing an amount of liquid out the end of the tubing. I'm interested in modeling the pressure/flow in the tube downstream. I know there are dynamic effects as the pressure builds & decays, but don't know what equations to apply to analyze it.
The steady-state flow in the tubing is laminar, and the liquid is low viscosity (solvent-based, ~0.5cP). The tubing downstream of the valve is .020"ID, 48" lg. The inlet to the valve can be assumed to be at constant pressure.
If I had CFD software available, I would use it, but sadly I don't. :( So I'm looking to do it the old-school way. Let me know if I've left out anything important. Thanks!





RE: Fluid Dynamics Downstream of Valve
If the plastic tubing rises more than 25' above the valve then it is possible that some water will flash before it exits the tubing.
"Whom the gods would destroy, they first make mad "
RE: Fluid Dynamics Downstream of Valve
RE: Fluid Dynamics Downstream of Valve
Best regards, Morten
RE: Fluid Dynamics Downstream of Valve
The old school way was simply to do a series of tests and see if the results were repeatable then create a table or graph of time of opening pulse vs flow or volume. Then if you change one thing at a time such as type of tube you'll know what the effect is.
There are far too many variables and transitory events going on here to even guess at flows and pressure.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way