Enter the pressure drop, upstream pressure, and flow coefficient into the calculator to determine the choked flow rate. This calculator helps in evaluating the maximum flow rate of a compressible fluid through a valve or orifice at which the velocity of the fluid reaches the speed of sound.

## Choked Flow Formula

The following formula is used to calculate the choked flow rate:

Q = Cv * sqrt(ΔP * (2 * P1 - ΔP))

Variables:

• Q is the choked flow rate (gallons per minute)
• Cv is the flow coefficient
• ΔP is the pressure drop across the valve or orifice (psi)
• P1 is the upstream pressure (psi)

To calculate the choked flow rate, multiply the flow coefficient by the square root of the pressure drop times the difference between twice the upstream pressure and the pressure drop.

## What is Choked Flow?

Choked flow is a phenomenon that occurs when the flow rate of a compressible fluid through a valve or orifice is limited by the sonic velocity of the fluid. It happens when the pressure drop across the valve or orifice is equal to or greater than half of the upstream pressure. At this point, the flow rate does not increase with a further decrease in downstream pressure, and the velocity of the fluid at the smallest cross-section of the valve or orifice reaches the speed of sound.

## How to Calculate Choked Flow?

The following steps outline how to calculate the Choked Flow.

1. First, determine the flow coefficient (Cv).
2. Next, determine the pressure drop across the valve or orifice (ΔP) in psi.
3. Next, determine the upstream pressure (P1) in psi.
4. Next, gather the formula from above = Q = Cv * sqrt(ΔP * (2 * P1 – ΔP)).
5. Finally, calculate the Choked Flow (Q) in gallons per minute.
6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Flow coefficient (Cv) = 50

Pressure drop (ΔP) = 100 psi

Upstream pressure (P1) = 300 psi