# Accurately calculating the pressure drop through an orifice

• Mo Samatar

#### Mo Samatar

I have a scenario where a specific nozzle is defined to have a flow of 900cc/min.
The flow co-efficient for this nozle is defined @9.8 MPa -> flow co-efficient= 0.85.

If I then run fluid through this nozzle at say 200 MPa and I would like to calculate the pressure drop.
My understanding is taht I would not get an accurate answer using the flow co-efficient of 0.85 as this is valid at 9.8 MPa.

Therefore how can I calculate the pressure drop?

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## Answers and Replies

The easiest way to calculate the pressure drop across a nozzle is to use the Bernoulli equation. The Bernoulli equation states that the sum of the potential energy and kinetic energy of the fluid is constant. This means that if you know the inlet pressure, outlet pressure, and velocity of the fluid at both the inlet and outlet, you can calculate the pressure drop across the nozzle.Assuming you have all of the necessary information, the pressure drop across the nozzle can be calculated with the following equation:Pressure Drop = (Inlet Pressure) - (Outlet Pressure) + (1/2)*(Inlet Velocity^2 - Outlet Velocity^2)In this case, since you know the flow rate, you can use the equation for flow rate to calculate the velocities at both the inlet and outlet. Once you have those values, you can substitute them into the Bernoulli equation to calculate the pressure drop.