FT_AIRCOOLER

This function calculates the log-mean temperature-difference correction factor F_T for air-cooler style crossflow exchangers. It uses a fitted explicit relation based on stream temperatures, tube-pass count, and row count.

The correction factor adjusts ideal LMTD to account for non-ideal exchanger flow arrangement:

\Delta T_{\text{effective}} = F_T\,\Delta T_{\text{LMTD,ideal}}

This is useful for thermal design and rating when exchanger geometry departs from true countercurrent flow.

Excel Usage

=FT_AIRCOOLER(Thi, Tho, Tci, Tco, Ntp, rows)

Thi (float, required): Hot fluid inlet temperature (K).
Tho (float, required): Hot fluid outlet temperature (K).
Tci (float, required): Cold fluid inlet temperature (K).
Tco (float, required): Cold fluid outlet temperature (K).
Ntp (int, optional, default: 1): Number of tube passes (-).
rows (int, optional, default: 1): Number of tube rows (-).

Returns (float): Log-mean temperature difference correction factor, or an error message if invalid.

Example 1: Four rows with one pass

Inputs:

Thi	Tho	Tci	Tco	Ntp	rows
125	45	25	95	1	4

Excel formula:

=FT_AIRCOOLER(125, 45, 25, 95, 1, 4)

Expected output:

0.550509

Example 2: Two rows with two passes

Inputs:

Thi	Tho	Tci	Tco	Ntp	rows
180	90	30	120	2	2

Excel formula:

=FT_AIRCOOLER(180, 90, 30, 120, 2, 2)

Expected output:

0.901058

Example 3: Three rows with one pass

Inputs:

Thi	Tho	Tci	Tco	Ntp	rows
150	70	40	110	1	3

Excel formula:

=FT_AIRCOOLER(150, 70, 40, 110, 1, 3)

Expected output:

0.664608

Example 4: Single row with one pass

Inputs:

Thi	Tho	Tci	Tco	Ntp	rows
110	60	20	80	1	1

Excel formula:

=FT_AIRCOOLER(110, 60, 20, 80, 1, 1)

Expected output:

0.532634

Python Code

Show Code

from ht.air_cooler import Ft_aircooler as ht_Ft_aircooler

def Ft_aircooler(Thi, Tho, Tci, Tco, Ntp=1, rows=1):
    """
    Compute the LMTD correction factor for an air cooler crossflow exchanger.

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

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

    Args:
        Thi (float): Hot fluid inlet temperature (K).
        Tho (float): Hot fluid outlet temperature (K).
        Tci (float): Cold fluid inlet temperature (K).
        Tco (float): Cold fluid outlet temperature (K).
        Ntp (int, optional): Number of tube passes (-). Default is 1.
        rows (int, optional): Number of tube rows (-). Default is 1.

    Returns:
        float: Log-mean temperature difference correction factor, or an error message if invalid.
    """
    try:
        return ht_Ft_aircooler(Thi=Thi, Tho=Tho, Tci=Tci, Tco=Tco, Ntp=Ntp, rows=rows)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Thi *

Hot fluid inlet temperature (K).

Tho *

Hot fluid outlet temperature (K).

Tci *

Cold fluid inlet temperature (K).

Tco *

Cold fluid outlet temperature (K).

Ntp

Number of tube passes (-).

rows

Number of tube rows (-).