CTB_WALL_FACTOR

This function computes a wall-property correction factor used to adjust heat-transfer or related correlations for property differences between bulk fluid and wall conditions.

Depending on the selected property option, the factor is based on viscosity, Prandtl number, or temperature ratio, with separate heating and cooling exponents.

Excel Usage

=CTB_WALL_FACTOR(mu, mu_wall, Pr, Pr_wall, T, T_wall, mu_heating_coeff, mu_cooling_coeff, Pr_heating_coeff, Pr_cooling_coeff, T_heating_coeff, T_cooling_coeff, property_option)

• mu (float, optional, default: null): Viscosity of bulk fluid (Pa*s).
• mu_wall (float, optional, default: null): Viscosity at the wall (Pa*s).
• Pr (float, optional, default: null): Prandtl number of bulk fluid (-).
• Pr_wall (float, optional, default: null): Prandtl number at the wall (-).
• T (float, optional, default: null): Bulk fluid temperature (K).
• T_wall (float, optional, default: null): Wall temperature (K).
• mu_heating_coeff (float, optional, default: 0.11): Heating coefficient for viscosity correction (-).
• mu_cooling_coeff (float, optional, default: 0.25): Cooling coefficient for viscosity correction (-).
• Pr_heating_coeff (float, optional, default: 0.11): Heating coefficient for Prandtl correction (-).
• Pr_cooling_coeff (float, optional, default: 0.25): Cooling coefficient for Prandtl correction (-).
• T_heating_coeff (float, optional, default: 0.11): Heating coefficient for temperature correction (-).
• T_cooling_coeff (float, optional, default: 0.25): Cooling coefficient for temperature correction (-).
• property_option (str, optional, default: “Prandtl”): Property used for correction factor (-).

Returns (float): Wall correction factor, or an error message if invalid.

Example 1: Prandtl correction for heating

Inputs:

Pr	Pr_wall	T	T_wall	property_option
1.2	1.1	300	350	Prandtl

Excel formula:

=CTB_WALL_FACTOR(1.2, 1.1, 300, 350, "Prandtl")

Expected output:

1.00962

Example 2: Viscosity correction for cooling

Inputs:

mu	mu_wall	T	T_wall	property_option
0.0008	0.0003	350	300	Viscosity

Excel formula:

=CTB_WALL_FACTOR(0.0008, 0.0003, 350, 300, "Viscosity")

Expected output:

1.11393

Example 3: Temperature ratio correction

Inputs:

T	T_wall	property_option
300	360	Temperature

Excel formula:

=CTB_WALL_FACTOR(300, 360, "Temperature")

Expected output:

0.980144

Example 4: Viscosity correction with defaults

Inputs:

mu	mu_wall	T	T_wall	property_option
0.001	0.0009	320	330	Viscosity

Excel formula:

=CTB_WALL_FACTOR(0.001, 0.0009, 320, 330, "Viscosity")

Expected output:

1.01166

Python Code

Show Code

from ht.conv_tube_bank import wall_factor as ht_wall_factor

def ctb_wall_factor(mu=None, mu_wall=None, Pr=None, Pr_wall=None, T=None, T_wall=None, mu_heating_coeff=0.11, mu_cooling_coeff=0.25, Pr_heating_coeff=0.11, Pr_cooling_coeff=0.25, T_heating_coeff=0.11, T_cooling_coeff=0.25, property_option='Prandtl'):
    """
    Compute wall correction factor for heat transfer properties.

    See: https://ht.readthedocs.io/en/latest/ht.conv_tube_bank.html

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

    Args:
        mu (float, optional): Viscosity of bulk fluid (Pa*s). Default is None.
        mu_wall (float, optional): Viscosity at the wall (Pa*s). Default is None.
        Pr (float, optional): Prandtl number of bulk fluid (-). Default is None.
        Pr_wall (float, optional): Prandtl number at the wall (-). Default is None.
        T (float, optional): Bulk fluid temperature (K). Default is None.
        T_wall (float, optional): Wall temperature (K). Default is None.
        mu_heating_coeff (float, optional): Heating coefficient for viscosity correction (-). Default is 0.11.
        mu_cooling_coeff (float, optional): Cooling coefficient for viscosity correction (-). Default is 0.25.
        Pr_heating_coeff (float, optional): Heating coefficient for Prandtl correction (-). Default is 0.11.
        Pr_cooling_coeff (float, optional): Cooling coefficient for Prandtl correction (-). Default is 0.25.
        T_heating_coeff (float, optional): Heating coefficient for temperature correction (-). Default is 0.11.
        T_cooling_coeff (float, optional): Cooling coefficient for temperature correction (-). Default is 0.25.
        property_option (str, optional): Property used for correction factor (-). Valid options: Viscosity, Prandtl, Temperature. Default is 'Prandtl'.

    Returns:
        float: Wall correction factor, or an error message if invalid.
    """
    try:
        return ht_wall_factor(
            mu=mu,
            mu_wall=mu_wall,
            Pr=Pr,
            Pr_wall=Pr_wall,
            T=T,
            T_wall=T_wall,
            mu_heating_coeff=mu_heating_coeff,
            mu_cooling_coeff=mu_cooling_coeff,
            Pr_heating_coeff=Pr_heating_coeff,
            Pr_cooling_coeff=Pr_cooling_coeff,
            T_heating_coeff=T_heating_coeff,
            T_cooling_coeff=T_cooling_coeff,
            property_option=property_option,
        )
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

mu

Viscosity of bulk fluid (Pa*s).

mu_wall

Viscosity at the wall (Pa*s).

Pr

Prandtl number of bulk fluid (-).

Pr_wall

Prandtl number at the wall (-).

T

Bulk fluid temperature (K).

T_wall

Wall temperature (K).

mu_heating_coeff

Heating coefficient for viscosity correction (-).

mu_cooling_coeff

Cooling coefficient for viscosity correction (-).

Pr_heating_coeff

Heating coefficient for Prandtl correction (-).

Pr_cooling_coeff

Cooling coefficient for Prandtl correction (-).

T_heating_coeff

Heating coefficient for temperature correction (-).

T_cooling_coeff

Cooling coefficient for temperature correction (-).

property_option Optional Viscosity Prandtl Temperature

Property used for correction factor (-).