Pressure across an orifice/choke plate

In summary, the conversation discusses the process of designing an orifice plate to control the mass flow of compressed air in a pipe. The total pressure and static pressure drop while the velocity increases, and this is due to momentum losses. The concept of choked flow is also mentioned. The individual is seeking further clarification on why the total pressure must drop.
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Hi,
I've been trying to calculate the diameter for an orifice plate so that when inserted in a pipe it restricts the mass flow to the value I want (1.5 kg/s of compressed air, total pressure= 400 psia, T=300K). So essentially I am trying to design a choke plate. When a flow goes across an orifice plate, does the total pressure drop ? I can understand that the static pressure drops and velocity increases. But I simply can't get why the total pressure has to drop. Does it have something to do with momentum losses ?
Answering this would really help me sort out my confusion.

Thanks
N
 
Engineering news on Phys.org

1. What is an orifice/choke plate and how does it affect pressure?

An orifice/choke plate is a restriction in a fluid flow system, typically in the form of a plate with a small hole or narrow opening. It affects pressure by causing a decrease in pressure as the fluid passes through the restricted area.

2. How is pressure measured across an orifice/choke plate?

Pressure across an orifice/choke plate can be measured using a pressure gauge or manometer. The gauge is placed before and after the orifice/choke plate, and the difference in pressure readings is the pressure drop across the restriction.

3. What factors affect pressure across an orifice/choke plate?

The pressure drop across an orifice/choke plate is affected by the size and shape of the restriction, the density and viscosity of the fluid, and the velocity of the fluid before and after the restriction.

4. How does the pressure across an orifice/choke plate change with flow rate?

The pressure drop across an orifice/choke plate increases with increasing flow rate. This is because as the fluid flows faster through the restriction, there is less time for the pressure to equalize, resulting in a larger pressure drop.

5. What is the purpose of using an orifice/choke plate in a fluid flow system?

An orifice/choke plate is often used to control and regulate the flow rate of a fluid. By creating a restriction, the flow rate can be reduced and pressure can be controlled. It can also be used to measure the flow rate of a fluid by relating the pressure drop to the flow rate using a calibrated equation.

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