CP_SAT_ANC

This function calls CoolProp’s saturation ancillary equations for a chosen fluid, output property, and quality branch. It is useful for quickly generating saturation-curve values without a full state solve.

The ancillary evaluation is:

y = g(\text{name}, \text{output}, Q, \text{input}, x)

where Q selects the liquid or vapor branch and x is the specified input value.

Excel Usage

=CP_SAT_ANC(name, output, Q, input, value)

• name (str, required): CoolProp fluid name.
• output (str, required): Requested ancillary output property code.
• Q (int, required): Quality branch selector (typically 0 for liquid, 1 for vapor).
• input (str, required): Input variable code used by the ancillary equation.
• value (float, required): Input value for the ancillary equation in SI units.

Returns (float): Saturation ancillary property value for the requested fluid and branch.

Example 1: Water vapor pressure ancillary from temperature

Inputs:

name	output	Q	input	value
Water	p	1	T	373.15

Excel formula:

=CP_SAT_ANC("Water", "p", 1, "T", 373.15)

Expected output:

101414

Example 2: Water saturation temperature ancillary from pressure

Inputs:

name	output	Q	input	value
Water	T	0	P	101325

Excel formula:

=CP_SAT_ANC("Water", "T", 0, "P", 101325)

Expected output:

373.125

Example 3: R134a saturation temperature ancillary from pressure

Inputs:

name	output	Q	input	value
R134a	T	0	P	702801

Excel formula:

=CP_SAT_ANC("R134a", "T", 0, "P", 702801)

Expected output:

300

Python Code

Show Code

import CoolProp.CoolProp as CP

def cp_sat_anc(name, output, Q, input, value):
    """
    Evaluate a CoolProp saturation ancillary property for a fluid and branch quality.

    See: https://coolprop.org/apidoc/CoolProp.CoolProp.html#CoolProp.CoolProp.saturation_ancillary

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

    Args:
        name (str): CoolProp fluid name.
        output (str): Requested ancillary output property code.
        Q (int): Quality branch selector (typically 0 for liquid, 1 for vapor).
        input (str): Input variable code used by the ancillary equation.
        value (float): Input value for the ancillary equation in SI units.

    Returns:
        float: Saturation ancillary property value for the requested fluid and branch.
    """
    try:
        def normalize_code(code: str) -> str:
            # CoolProp parameter codes are case-sensitive. Map common lower-case aliases to the correct codes.
            if not isinstance(code, str):
                return code
            code_str = code.strip()
            lcode = code_str.lower()
            if lcode in ("p", "pressure"):
                return "P"
            if lcode in ("rho", "density", "d", "dmass", "dmolar"):
                return "D"
            if lcode in ("t", "temperature"):
                return "T"
            if lcode in ("h", "enthalpy"):
                return "Hmass"
            if lcode in ("s", "entropy"):
                return "Smass"
            if lcode in ("u", "internal_energy"):
                return "Umass"
            if lcode in ("cp", "cpmass"):
                return "Cpmass"
            if lcode in ("cv", "cvmass"):
                return "Cvmass"
            return code_str

        output_norm = normalize_code(output)
        input_norm = normalize_code(input)

        # CoolProp's saturation_ancillary does not support calculating density directly from temperature.
        # For density outputs (D/Dmass) with temperature input, compute the saturation pressure first,
        # then evaluate density at that pressure.
        if output_norm == "D" and input_norm == "T":
            p_sat = CP.saturation_ancillary(name, "P", Q, "T", value)
            return CP.saturation_ancillary(name, output_norm, Q, "P", p_sat)

        return CP.saturation_ancillary(name, output_norm, Q, input_norm, value)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

name *

CoolProp fluid name.

output *

Requested ancillary output property code.

Q *

Quality branch selector (typically 0 for liquid, 1 for vapor).

input *

Input variable code used by the ancillary equation.

value *

Input value for the ancillary equation in SI units.