Air cooler sizing and rating (ht.air_cooler)

ht.air_cooler.Ft_aircooler(Thi, Tho, Tci, Tco, Ntp=1, rows=1)[source]

Calculates log-mean temperature difference correction factor for a crossflow heat exchanger, as in an Air Cooler. Method presented in [R11], fit to other’s nonexplicit work. Error is < 0.1%. Requires number of rows and tube passes as well as stream temperatures.

\[ \begin{align}\begin{aligned}F_T = 1 - \sum_{i=1}^m \sum_{k=1}^n a_{i,k}(1-r_{1,m})^k\sin(2i\arctan R)\\R = \frac{T_{hi} - T_{ho}}{T_{co}-T_{ci}}\\r_{1,m} = \frac{\Delta T_{lm}}{T_{hi} - T_{ci}}\end{aligned}\end{align} \]

Thi : float

Temperature of hot fluid in [K]

Tho : float

Temperature of hot fluid out [K]

Tci : float

Temperature of cold fluid in [K]

Tco : float

Temperature of cold fluid out [K]

Ntp : int

Number of passes the tubeside fluid will flow through [-]

rows : int

Number of rows of tubes [-]


Ft : float

Log-mean temperature difference correction factor []


This equation assumes that the hot fluid is tubeside, as in the case of air coolers. The model is not symmetric, so ensure to switch around the inputs if using this function for other purposes.

This equation appears in [R11]. It has been verified. For some cases, approximations are made to match coefficients with the number of tube passes and rows provided. 16 coefficients are used for each case; 8 cases are considered:

  • 1 row 1 pass
  • 2 rows 1 pass
  • 2 rows 2 passes
  • 3 rows 1 pass
  • 3 rows 3 passes
  • 4 rows 1 pass
  • 4 rows 2 passes
  • 4 rows 4 passes


[R11](1, 2, 3) Roetzel, W., and F. J. L. Nicole. “Mean Temperature Difference for Heat Exchanger Design-A General Approximate Explicit Equation.” Journal of Heat Transfer 97, no. 1 (February 1, 1975): 5-8. doi:10.1115/1.3450288


>>> Ft_aircooler(Thi=125., Tho=45., Tci=25., Tco=95., Ntp=1, rows=4)