D_FOR_NTUBES_VDI

This function estimates tube bundle diameter from tube count with the VDI correlation, including tube pass count and layout angle effects. It is a practical approximate sizing model for exchanger bundle geometry.

The model can be expressed as D_{bundle} = f(N, N_{tp}, D_o, p, \theta) using VDI coefficients.

Excel Usage

=D_FOR_NTUBES_VDI(N, Ntp, Do, pitch, angle)

N (int, required): Number of tubes (-).
Ntp (int, required): Number of tube passes (-).
Do (float, required): Tube outer diameter (m).
pitch (float, required): Tube pitch (m).
angle (int, optional, default: 30): Tube layout angle (degrees).

Returns (float): Outer diameter of tube bundle (m).

Example 1: VDI bundle diameter example

Inputs:

N	Ntp	Do	pitch	angle
970	2	0.00735	0.015	30

Excel formula:

=D_FOR_NTUBES_VDI(970, 2, 0.00735, 0.015, 30)

Expected output:

0.50036

Example 2: VDI estimate with four passes

Inputs:

N	Ntp	Do	pitch	angle
450	4	0.01905	0.025	30

Excel formula:

=D_FOR_NTUBES_VDI(450, 4, 0.01905, 0.025, 30)

Expected output:

0.588657

Example 3: VDI estimate for square layout

Inputs:

N	Ntp	Do	pitch	angle
800	4	0.025	0.03125	90

Excel formula:

=D_FOR_NTUBES_VDI(800, 4, 0.025, 0.03125, 90)

Expected output:

1.03804

Example 4: VDI estimate for small bundle

Inputs:

N	Ntp	Do	pitch	angle
120	1	0.0127	0.016	45

Excel formula:

=D_FOR_NTUBES_VDI(120, 1, 0.0127, 0.016, 45)

Expected output:

0.199872

Python Code

Show Code

from ht.hx import D_for_Ntubes_VDI as hx_D_for_Ntubes_VDI

def D_for_Ntubes_VDI(N, Ntp, Do, pitch, angle=30):
    """
    Estimate tube bundle diameter from tube count using the VDI method.

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

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

    Args:
        N (int): Number of tubes (-).
        Ntp (int): Number of tube passes (-).
        Do (float): Tube outer diameter (m).
        pitch (float): Tube pitch (m).
        angle (int, optional): Tube layout angle (degrees). Default is 30.

    Returns:
        float: Outer diameter of tube bundle (m).
    """
    try:
        result = hx_D_for_Ntubes_VDI(N=N, Ntp=Ntp, Do=Do, pitch=pitch, angle=angle)
        return result
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

N *

Number of tubes (-).

Ntp *

Number of tube passes (-).

Do *

Tube outer diameter (m).

pitch *

Tube pitch (m).

angle

Tube layout angle (degrees).