DP_ESDU_LOW_FIN

This function evaluates air-side pressure drop for low-fin tube banks using the ESDU correlation. The calculation includes both acceleration and friction contributions, with friction affected by Reynolds number, fin-to-bare-length ratio, and pitch geometry.

\Delta P = (K_{\text{acc}} + n_{\text{rows}}K_f)\,\frac{1}{2}\rho v_{\max}^2

It is suited to low-fin crossflow geometries and uses flow properties referenced to the bundle minimum flow area.

Excel Usage

=DP_ESDU_LOW_FIN(m, A_min, A_increase, flow_area_contraction_ratio, tube_diameter, fin_height, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, mu)
  • m (float, required): Mass flow rate across the tube bank (kg/s).
  • A_min (float, required): Minimum flow area (m^2).
  • A_increase (float, required): Surface area ratio relative to bare tube (-).
  • flow_area_contraction_ratio (float, required): Ratio of minimum to face area (-).
  • tube_diameter (float, required): Bare tube diameter (m).
  • fin_height (float, required): Fin height above the bare tube (m).
  • bare_length (float, required): Bare tube length between fins (m).
  • pitch_parallel (float, required): Tube pitch parallel to flow (m).
  • pitch_normal (float, required): Tube pitch normal to flow (m).
  • tube_rows (int, required): Number of tube rows (-).
  • rho (float, required): Air density (kg/m^3).
  • mu (float, required): Air viscosity (Pa*s).

Returns (float): Pressure drop across the finned tube bank (Pa), or an error message if invalid.

Example 1: Baseline low-fin tube bank

Inputs:

m A_min A_increase flow_area_contraction_ratio tube_diameter fin_height bare_length pitch_parallel pitch_normal tube_rows rho mu
1.1 3.8 11.5 0.42 0.02 0.004 0.0025 0.05 0.06 4 1.2 0.000018

Excel formula:

=DP_ESDU_LOW_FIN(1.1, 3.8, 11.5, 0.42, 0.02, 0.004, 0.0025, 0.05, 0.06, 4, 1.2, 0.000018)

Expected output:

0.187157

Example 2: Higher flow rate and larger tubes

Inputs:

m A_min A_increase flow_area_contraction_ratio tube_diameter fin_height bare_length pitch_parallel pitch_normal tube_rows rho mu
1.9 4.8 9.8 0.5 0.025 0.005 0.003 0.06 0.07 6 1.1 0.000019

Excel formula:

=DP_ESDU_LOW_FIN(1.9, 4.8, 9.8, 0.5, 0.025, 0.005, 0.003, 0.06, 0.07, 6, 1.1, 0.000019)

Expected output:

0.494035

Example 3: Compact bundle geometry

Inputs:

m A_min A_increase flow_area_contraction_ratio tube_diameter fin_height bare_length pitch_parallel pitch_normal tube_rows rho mu
0.9 3.4 13.5 0.36 0.016 0.0035 0.002 0.045 0.055 3 1.25 0.000017

Excel formula:

=DP_ESDU_LOW_FIN(0.9, 3.4, 13.5, 0.36, 0.016, 0.0035, 0.002, 0.045, 0.055, 3, 1.25, 0.000017)

Expected output:

0.124318

Example 4: Many rows with moderate flow

Inputs:

m A_min A_increase flow_area_contraction_ratio tube_diameter fin_height bare_length pitch_parallel pitch_normal tube_rows rho mu
1.4 4.2 10.8 0.45 0.018 0.0042 0.0028 0.052 0.062 8 1.18 0.0000185

Excel formula:

=DP_ESDU_LOW_FIN(1.4, 4.2, 10.8, 0.45, 0.018, 0.0042, 0.0028, 0.052, 0.062, 8, 1.18, 0.0000185)

Expected output:

0.404805

Python Code

Show Code 
from ht.air_cooler import dP_ESDU_low_fin as ht_dP_ESDU_low_fin

def dP_ESDU_low_fin(m, A_min, A_increase, flow_area_contraction_ratio, tube_diameter, fin_height, bare_length, pitch_parallel, pitch_normal, tube_rows, rho, mu):
    """
    Compute air-side pressure drop for low-fin tube banks.

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

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

    Args:
        m (float): Mass flow rate across the tube bank (kg/s).
        A_min (float): Minimum flow area (m^2).
        A_increase (float): Surface area ratio relative to bare tube (-).
        flow_area_contraction_ratio (float): Ratio of minimum to face area (-).
        tube_diameter (float): Bare tube diameter (m).
        fin_height (float): Fin height above the bare tube (m).
        bare_length (float): Bare tube length between fins (m).
        pitch_parallel (float): Tube pitch parallel to flow (m).
        pitch_normal (float): Tube pitch normal to flow (m).
        tube_rows (int): Number of tube rows (-).
        rho (float): Air density (kg/m^3).
        mu (float): Air viscosity (Pa*s).

    Returns:
        float: Pressure drop across the finned tube bank (Pa), or an error message if invalid.
    """
    try:
        return ht_dP_ESDU_low_fin(
            m=m,
            A_min=A_min,
            A_increase=A_increase,
            flow_area_contraction_ratio=flow_area_contraction_ratio,
            tube_diameter=tube_diameter,
            fin_height=fin_height,
            bare_length=bare_length,
            pitch_parallel=pitch_parallel,
            pitch_normal=pitch_normal,
            tube_rows=tube_rows,
            rho=rho,
            mu=mu,
        )
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Mass flow rate across the tube bank (kg/s).
Minimum flow area (m^2).
Surface area ratio relative to bare tube (-).
Ratio of minimum to face area (-).
Bare tube diameter (m).
Fin height above the bare tube (m).
Bare tube length between fins (m).
Tube pitch parallel to flow (m).
Tube pitch normal to flow (m).
Number of tube rows (-).
Air density (kg/m^3).
Air viscosity (Pa*s).