NU_HORIZ_CYL

This function computes natural-convection Nusselt number for a horizontal cylinder using a selectable ht correlation. If no method is specified, the underlying library default selection logic is used.

The calculation uses Prandtl and Grashof numbers through Rayleigh number behavior:

Ra = Gr\,Pr

and returns a dimensionless Nusselt number based on cylinder diameter.

Excel Usage

=NU_HORIZ_CYL(Pr, Gr, Nu_horiz_cyl_method)

Pr (float, required): Prandtl number at film temperature (dimensionless).
Gr (float, required): Grashof number based on cylinder diameter (dimensionless).
Nu_horiz_cyl_method (str, optional, default: null): Correlation name (string).

Returns (float): Nusselt number based on cylinder diameter (dimensionless).

Example 1: Horizontal cylinder default method

Inputs:

Pr	Gr
0.72	10000000

Excel formula:

=NU_HORIZ_CYL(0.72, 10000000)

Expected output:

24.8642

Example 2: Horizontal cylinder Morgan method

Inputs:

Pr	Gr	Nu_horiz_cyl_method
0.69	2630000000	Morgan

Excel formula:

=NU_HORIZ_CYL(0.69, 2630000000, "Morgan")

Expected output:

151.388

Example 3: Horizontal cylinder Churchill-Chu method

Inputs:

Pr	Gr	Nu_horiz_cyl_method
0.69	2630000000	Churchill-Chu

Excel formula:

=NU_HORIZ_CYL(0.69, 2630000000, "Churchill-Chu")

Expected output:

139.135

Example 4: Horizontal cylinder Kuehn-Goldstein method

Inputs:

Pr	Gr	Nu_horiz_cyl_method
0.69	2630000000	Kuehn & Goldstein

Excel formula:

=NU_HORIZ_CYL(0.69, 2630000000, "Kuehn & Goldstein")

Expected output:

122.993

Python Code

Show Code

from ht.conv_free_immersed import Nu_horizontal_cylinder as ht_Nu_horizontal_cylinder

def Nu_horiz_cyl(Pr, Gr, Nu_horiz_cyl_method=None):
    """
    Select and calculate a Nusselt number correlation for a horizontal cylinder.

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

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

    Args:
        Pr (float): Prandtl number at film temperature (dimensionless).
        Gr (float): Grashof number based on cylinder diameter (dimensionless).
        Nu_horiz_cyl_method (str, optional): Correlation name (string). Valid options: Morgan, Churchill-Chu, Kuehn & Goldstein. Default is None.

    Returns:
        float: Nusselt number based on cylinder diameter (dimensionless).
    """
    try:
        result = ht_Nu_horizontal_cylinder(Pr, Gr, Method=Nu_horiz_cyl_method)
        if result is None:
            return "Error: Result is None"
        return float(result)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Pr *

Prandtl number at film temperature (dimensionless).

Gr *

Grashof number based on cylinder diameter (dimensionless).

Nu_horiz_cyl_method

Correlation name (string).