IS_CHOKED_GAS

Overview

The IS_CHOKED_GAS function determines if the gas flow through a control valve is choked (critical). Choked flow occurs when the velocity of the gas reaches the speed of sound at the vena contracta, preventing further flow increase with decreasing downstream pressure.

The condition is checked using the differential pressure ratio x, the specific heat ratio factor Fgamma, and the critical pressure ratio factor xT (or xTP if fittings are present).

This implementation uses the fluids library.

This example function is provided as-is without any representation of accuracy.

Excel Usage

=IS_CHOKED_GAS(x, Fgamma, xT, xTP)

• x (float, required): Differential pressure ratio (dP/P1) [-]
• Fgamma (float, required): Specific heat ratio factor [-]
• xT (float, optional, default: null): Pressure difference ratio factor of a valve without fittings [-]
• xTP (float, optional, default: null): Pressure difference ratio factor of a valve with fittings [-]

Returns (bool): True if flow is choked (critical), False otherwise.

Examples

Example 1: Non-choked flow example

Inputs:

x	Fgamma	xT
0.544	0.929	0.6

Excel formula:

=IS_CHOKED_GAS(0.544, 0.929, 0.6)

Expected output:

false

Example 2: Choked flow example

Inputs:

x	Fgamma	xT
0.6	0.929	0.6

Excel formula:

=IS_CHOKED_GAS(0.6, 0.929, 0.6)

Expected output:

true

Example 3: Non-choked with fittings

Inputs:

x	Fgamma	xTP
0.544	0.929	0.625

Excel formula:

=IS_CHOKED_GAS(0.544, 0.929, 0.625)

Expected output:

false

Example 4: Choked with fittings

Inputs:

x	Fgamma	xTP
0.8	0.929	0.625

Excel formula:

=IS_CHOKED_GAS(0.8, 0.929, 0.625)

Expected output:

true

Python Code

from fluids.control_valve import is_choked_turbulent_g as fluids_is_choked

def is_choked_gas(x, Fgamma, xT=None, xTP=None):
    """
    Determines if a gas flow in a control valve is choked (critical) or not according to IEC 60534.

    See: https://fluids.readthedocs.io/fluids.control_valve.html#fluids.control_valve.is_choked_turbulent_g

    This example function is provided as-is without any representation of accuracy.

    Args:
        x (float): Differential pressure ratio (dP/P1) [-]
        Fgamma (float): Specific heat ratio factor [-]
        xT (float, optional): Pressure difference ratio factor of a valve without fittings [-] Default is None.
        xTP (float, optional): Pressure difference ratio factor of a valve with fittings [-] Default is None.

    Returns:
        bool: True if flow is choked (critical), False otherwise.
    """
    try:
      x = float(x)
      Fgamma = float(Fgamma)

      if xT is not None:
        xT = float(xT)
      if xTP is not None:
        xTP = float(xTP)

      if x < 0:
        return "Error: Differential pressure ratio must be non-negative."
      if Fgamma <= 0:
        return "Error: Fgamma must be positive."

      if xT is None and xTP is None:
        return "Error: Either xT or xTP must be provided."

      return fluids_is_choked(x=x, Fgamma=Fgamma, xT=xT, xTP=xTP)
    except Exception as e:
      return f"Error: {str(e)}"

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