WALL_FACTOR_NU

This function computes a wall-property correction factor for convective heat-transfer correlations. It adjusts constant-property Nusselt-number predictions using a viscosity (or Prandtl) ratio evaluated at bulk and wall conditions.

The correction uses a power-law form:

\frac{Nu}{Nu_{cp}} = \left(\frac{\mu}{\mu_{wall}}\right)^n

The exponent n depends on whether the flow is laminar or turbulent and whether liquid or gas coefficients are selected.

Excel Usage

=WALL_FACTOR_NU(mu, mu_wall, turbulent, liquid)
  • mu (float, required): Viscosity of fluid away from the wall (Pa*s).
  • mu_wall (float, required): Viscosity of the fluid at the wall (Pa*s).
  • turbulent (bool, optional, default: true): Whether turbulent coefficients are used.
  • liquid (bool, optional, default: false): Whether liquid-phase coefficients are used.

Returns (float): Wall correction factor for heat transfer (-).

Example 1: Turbulent liquid example

Inputs:

mu mu_wall turbulent liquid
0.0008 0.0003 true true

Excel formula:

=WALL_FACTOR_NU(0.0008, 0.0003, TRUE, TRUE)

Expected output:

1.11393

Example 2: Laminar liquid example

Inputs:

mu mu_wall turbulent liquid
0.0008 0.0003 false true

Excel formula:

=WALL_FACTOR_NU(0.0008, 0.0003, FALSE, TRUE)

Expected output:

1.14719

Example 3: Turbulent gas example

Inputs:

mu mu_wall turbulent liquid
0.000015 0.000013 true false

Excel formula:

=WALL_FACTOR_NU(0.000015, 0.000013, TRUE, FALSE)

Expected output:

1.07417

Example 4: Laminar gas example

Inputs:

mu mu_wall turbulent liquid
0.000015 0.000013 false false

Excel formula:

=WALL_FACTOR_NU(0.000015, 0.000013, FALSE, FALSE)

Expected output:

1

Python Code

Show Code 
from ht.core import wall_factor_Nu as ht_wall_factor_Nu

def wall_factor_Nu(mu, mu_wall, turbulent=True, liquid=False):
    """
    Compute a wall correction factor for Nusselt number calculations.

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

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

    Args:
        mu (float): Viscosity of fluid away from the wall (Pa*s).
        mu_wall (float): Viscosity of the fluid at the wall (Pa*s).
        turbulent (bool, optional): Whether turbulent coefficients are used. Default is True.
        liquid (bool, optional): Whether liquid-phase coefficients are used. Default is False.

    Returns:
        float: Wall correction factor for heat transfer (-).
    """
    try:
        return ht_wall_factor_Nu(mu, mu_wall, turbulent=turbulent, liquid=liquid)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Viscosity of fluid away from the wall (Pa*s).
Viscosity of the fluid at the wall (Pa*s).
Whether turbulent coefficients are used.
Whether liquid-phase coefficients are used.