CTB_DP_KERN

This function estimates pressure drop across a shell-side tube bundle using the Kern equivalent-diameter method. It combines fluid properties, flow rate, geometry, and baffle count to produce a pressure-loss estimate.

The Kern formulation is often used for preliminary shell-and-tube design and quick hydraulic checks.

Excel Usage

=CTB_DP_KERN(m, rho, mu, DShell, LSpacing, pitch, Do, NBaffles, mu_w)

m (float, required): Mass flow rate (kg/s).
rho (float, required): Fluid density (kg/m^3).
mu (float, required): Fluid viscosity (Pa*s).
DShell (float, required): Exchanger shell diameter (m).
LSpacing (float, required): Baffle spacing (m).
pitch (float, required): Tube pitch (m).
Do (float, required): Tube outer diameter (m).
NBaffles (int, required): Number of baffles (-).
mu_w (float, optional, default: null): Viscosity at the wall temperature (Pa*s).

Returns (float): Pressure drop across the bundle, or an error message if invalid.

Example 1: Example Kern pressure drop case

Inputs:

m	rho	mu	mu_w	DShell	LSpacing	pitch	Do	NBaffles
11	995	0.000803	0.000657	0.584	0.1524	0.0254	0.019	22

Excel formula:

=CTB_DP_KERN(11, 995, 0.000803, 0.000657, 0.584, 0.1524, 0.0254, 0.019, 22)

Expected output:

18980.6

Example 2: Without wall viscosity correction

Inputs:

m	rho	mu	DShell	LSpacing	pitch	Do	NBaffles
8	998	0.001	0.6	0.15	0.03	0.02	18

Excel formula:

=CTB_DP_KERN(8, 998, 0.001, 0.6, 0.15, 0.03, 0.02, 18)

Expected output:

3635.97

Example 3: Tighter tube pitch

Inputs:

m	rho	mu	mu_w	DShell	LSpacing	pitch	Do	NBaffles
15	950	0.0009	0.0008	0.5	0.12	0.022	0.018	20

Excel formula:

=CTB_DP_KERN(15, 950, 0.0009, 0.0008, 0.5, 0.12, 0.022, 0.018, 20)

Expected output:

151388

Example 4: Lower flow rate

Inputs:

m	rho	mu	mu_w	DShell	LSpacing	pitch	Do	NBaffles
5	900	0.0012	0.001	0.45	0.1	0.025	0.02	16

Excel formula:

=CTB_DP_KERN(5, 900, 0.0012, 0.001, 0.45, 0.1, 0.025, 0.02, 16)

Expected output:

22100.2

Python Code

Show Code

from ht.conv_tube_bank import dP_Kern as ht_dP_Kern

def ctb_dp_kern(m, rho, mu, DShell, LSpacing, pitch, Do, NBaffles, mu_w=None):
    """
    Compute tube bank pressure drop using the Kern method.

    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:
        m (float): Mass flow rate (kg/s).
        rho (float): Fluid density (kg/m^3).
        mu (float): Fluid viscosity (Pa*s).
        DShell (float): Exchanger shell diameter (m).
        LSpacing (float): Baffle spacing (m).
        pitch (float): Tube pitch (m).
        Do (float): Tube outer diameter (m).
        NBaffles (int): Number of baffles (-).
        mu_w (float, optional): Viscosity at the wall temperature (Pa*s). Default is None.

    Returns:
        float: Pressure drop across the bundle, or an error message if invalid.
    """
    try:
        return ht_dP_Kern(
            m=m,
            rho=rho,
            mu=mu,
            DShell=DShell,
            LSpacing=LSpacing,
            pitch=pitch,
            Do=Do,
            NBaffles=NBaffles,
            mu_w=mu_w,
        )
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

m *

Mass flow rate (kg/s).

rho *

Fluid density (kg/m^3).

mu *

Fluid viscosity (Pa*s).

DShell *

Exchanger shell diameter (m).

LSpacing *

Baffle spacing (m).

pitch *

Tube pitch (m).

Do *

Tube outer diameter (m).

NBaffles *

Number of baffles (-).

mu_w

Viscosity at the wall temperature (Pa*s).