NU_EXT_CYL

This function evaluates the Nusselt number for forced crossflow over a single cylinder by selecting a specific correlation or automatically choosing a default method. Optional wall Prandtl number and viscosity terms are passed through for methods that support property-ratio corrections.

The computation follows a method-dispatch pattern:

Nu = f_{\text{method}}(Re, Pr, Pr_w, \mu, \mu_w)

Excel Usage

=NU_EXT_CYL(Re, Pr, Prw, mu, muw, cylinder_method)
  • Re (float, required): Reynolds number with respect to cylinder diameter (-).
  • Pr (float, required): Prandtl number at either free stream or wall temperature (-).
  • Prw (float, optional, default: null): Prandtl number at wall temperature (-).
  • mu (float, optional, default: null): Viscosity at free stream temperature (Pa*s).
  • muw (float, optional, default: null): Viscosity at wall temperature (Pa*s).
  • cylinder_method (str, optional, default: null): Correlation method name (-).

Returns (float): Nusselt number with respect to cylinder diameter (-).

Example 1: External cylinder default method

Inputs:

Re Pr
6071 0.7

Excel formula:

=NU_EXT_CYL(6071, 0.7)

Expected output:

40.3833

Example 2: External cylinder with wall Prandtl

Inputs:

Re Pr Prw
7992 0.707 0.69

Excel formula:

=NU_EXT_CYL(7992, 0.707, 0.69)

Expected output:

49.25

Example 3: External cylinder with viscosity correction inputs

Inputs:

Re Pr mu muw
15000 2.5 0.0011 0.0008

Excel formula:

=NU_EXT_CYL(15000, 2.5, 0.0011, 0.0008)

Expected output:

127.606

Example 4: External cylinder with explicit method

Inputs:

Re Pr cylinder_method
12000 0.7 Sanitjai-Goldstein

Excel formula:

=NU_EXT_CYL(12000, 0.7, "Sanitjai-Goldstein")

Expected output:

67.5877

Python Code

Show Code 
from ht.conv_external import Nu_external_cylinder as ht_Nu_external_cylinder

def Nu_ext_cyl(Re, Pr, Prw=None, mu=None, muw=None, cylinder_method=None):
    """
    Calculate the Nusselt number for crossflow across a single cylinder using a selected correlation.

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

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

    Args:
        Re (float): Reynolds number with respect to cylinder diameter (-).
        Pr (float): Prandtl number at either free stream or wall temperature (-).
        Prw (float, optional): Prandtl number at wall temperature (-). Default is None.
        mu (float, optional): Viscosity at free stream temperature (Pa*s). Default is None.
        muw (float, optional): Viscosity at wall temperature (Pa*s). Default is None.
        cylinder_method (str, optional): Correlation method name (-). Valid options: Sanitjai-Goldstein, Churchill-Bernstein, Fand, McAdams, Zukauskas, Whitaker, Perkins-Leppert 1964, Perkins-Leppert 1962. Default is None.

    Returns:
        float: Nusselt number with respect to cylinder diameter (-).
    """
    try:
        return ht_Nu_external_cylinder(Re=Re, Pr=Pr, Prw=Prw, mu=mu, muw=muw, Method=cylinder_method)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Reynolds number with respect to cylinder diameter (-).
Prandtl number at either free stream or wall temperature (-).
Prandtl number at wall temperature (-).
Viscosity at free stream temperature (Pa*s).
Viscosity at wall temperature (Pa*s).
Correlation method name (-).