IS_CHOKED_LIQ

Evaluates whether a liquid valve operating point is choked (critical) using IEC 60534 criteria.

Depending on available factors, choking is determined by:

\Delta P > F_L^2(P_1 - F_FP_{sat})

\Delta P \ge \left(\frac{F_{LP}}{F_P}\right)^2(P_1 - F_FP_{sat})

The function returns True when the supplied condition indicates choked flow.

Excel Usage

=IS_CHOKED_LIQ(dP, P_up, Psat, FF, FL, FLP, FP)

dP (float, required): Pressure drop across the valve [Pa]
P_up (float, required): Upstream absolute pressure [Pa]
Psat (float, required): Liquid vapor pressure at inlet temperature [Pa]
FF (float, required): Liquid critical pressure ratio factor [-]
FL (float, optional, default: null): Liquid pressure recovery factor of a valve without attached fittings [-]
FLP (float, optional, default: null): Combined liquid pressure recovery factor with attached fittings [-]
FP (float, optional, default: null): Piping geometry factor [-]

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

Example 1: Choked flow scenario

Inputs:

dP	P_up	Psat	FF	FL
1000000	2000000	100000	0.9	0.5

Excel formula:

=IS_CHOKED_LIQ(1000000, 2000000, 100000, 0.9, 0.5)

Expected output:

true

Example 2: Non-choked flow scenario

Inputs:

dP	P_up	Psat	FF	FL
10000	2000000	100000	0.9	0.9

Excel formula:

=IS_CHOKED_LIQ(10000, 2000000, 100000, 0.9, 0.9)

Expected output:

false

Example 3: Choked with fittings (FLP/FP)

Inputs:

dP	P_up	Psat	FF	FLP	FP
800000	1000000	50000	0.8	0.4	0.9

Excel formula:

=IS_CHOKED_LIQ(800000, 1000000, 50000, 0.8, 0.4, 0.9)

Expected output:

true

Example 4: Non-choked with fittings

Inputs:

dP	P_up	Psat	FF	FLP	FP
50000	1000000	50000	0.8	0.8	0.9

Excel formula:

=IS_CHOKED_LIQ(50000, 1000000, 50000, 0.8, 0.8, 0.9)

Expected output:

false

Python Code

Show Code

from fluids.control_valve import is_choked_turbulent_l as fluids_is_choked

def is_choked_liq(dP, P_up, Psat, FF, FL=None, FLP=None, FP=None):
    """
    Determines if a liquid 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_l

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

    Args:
        dP (float): Pressure drop across the valve [Pa]
        P_up (float): Upstream absolute pressure [Pa]
        Psat (float): Liquid vapor pressure at inlet temperature [Pa]
        FF (float): Liquid critical pressure ratio factor [-]
        FL (float, optional): Liquid pressure recovery factor of a valve without attached fittings [-] Default is None.
        FLP (float, optional): Combined liquid pressure recovery factor with attached fittings [-] Default is None.
        FP (float, optional): Piping geometry factor [-] Default is None.

    Returns:
        bool: True if flow is choked (critical), False otherwise.
    """
    try:
      dP = float(dP)
      P_up = float(P_up)
      Psat = float(Psat)
      FF = float(FF)

      if FL is not None:
        FL = float(FL)
      if FLP is not None:
        FLP = float(FLP)
      if FP is not None:
        FP = float(FP)

      if dP < 0:
        return "Error: Pressure drop must be non-negative."
      if P_up <= 0:
        return "Error: Upstream pressure must be positive."
      if Psat < 0:
        return "Error: Saturation pressure must be non-negative."
      if FF <= 0:
        return "Error: FF must be positive."
      if FL is not None and FL <= 0:
        return "Error: FL must be positive."
      if FLP is not None and FLP <= 0:
        return "Error: FLP must be positive."
      if FP is not None and FP <= 0:
        return "Error: FP must be positive."

      if FL is None and (FLP is None or FP is None):
        return "Error: Provide FL or both FLP and FP."

      return fluids_is_choked(dP=dP, P1=P_up, Psat=Psat, FF=FF, FL=FL, FLP=FLP, FP=FP)
    except Exception as e:
      return f"Error: {str(e)}"

Online Calculator

dP *

Pressure drop across the valve [Pa]

P_up *

Upstream absolute pressure [Pa]

Psat *

Liquid vapor pressure at inlet temperature [Pa]

FF *

Liquid critical pressure ratio factor [-]

Liquid pressure recovery factor of a valve without attached fittings [-]

FLP

Combined liquid pressure recovery factor with attached fittings [-]

Piping geometry factor [-]