# Pressure Regulators

1. Oct 10, 2016

### K41

I'm struggling to understand how pressure regulators work (and total pressure in general). I currently have an open system. So the pressurized air goes through the regulator and afterwards (after going through some further pipe), enters the atmosphere. I will assume the hydrostatic variations in pressure are negligible. The gas is incompressible and at room temperature.

I placed a manometer gauge before the pressure regulator. It measures the static pressure. It reads 10 Bar. This is where I start to get confused:

1) Does the reading of 10 Bar on the manometer before the regulator mean that the flow is barely moving? Or better worded, would I need a pitot tube the determine the total pressure, subtract the two to find the dynamic pressure and find the velocity..

2) Can anyone explain how the regulator works specifically in terms of static and dynamic pressure? I've seen plenty of explanations but they just refer to "pressure" and I need something in terms of static and dynamic to make things clearer for me. I'm thinking when the regulator is "fully open", does that mean the dynamic pressure is lowest (large area opening therefore lower velocity) and so the static pressure is highest?

3) If I placed the same manometer AFTER the pressure regulator, would it read zero bar?

4) If the manometer after the regulator had some small value of pressure, would that mean there is something downstream of the regulator (i.e. between the regulator and the atmosphere) that was causing some "resistance". Is this "resistance" restricting the dynamic pressure and therefore increasing the static pressure or is it dissipating the energy into heat and therefore reducing the total pressure? In the latter, why would the pressure gauge still read an increase in static pressure?

5) If I had a valve, placed after the regulator, which was closed, what would the reading on the manometer be? I originally thought it would read 10 Bar if the regulator was fully open. But if the regulator was half open, what would it read?

6) Just a general thing. When people refer to "pressure drop", do they mean that the total pressure has reduced? How does this effect the pressure gradient in the Navier-Stokes eqns?

Last edited: Oct 10, 2016
2. Oct 15, 2016