Counter Flow Heat Exchanger
The counter flow heat exchanger configuration requires that the two fluids flow in opposite directions. The effectiveness-NTU solution is available for counter flow heat exchangers. Solution is from Nellis and Klein.
In addition, counter flow heat exchangers with axial conduction can be simulated using the axialconductionhx subprogram, solution is from Nellis and Klein 2009.
Counter flow heat exchangers with crossflow headers can be considered using the hx_cof_crfhdr function. Solution is from Kays et al 1968.
Example 1:
$UnitSystem SI Mass J K Pa
$VarInfo UA C_dot_1 C_dot_1 C_dot_min Units = 'W/K'
$VarInfo epsilon NTU Units = '-'
UA = 100 [W/K]
C_dot_1 = 50 [W/K]
C_dot_2 = 30 [W/K]
C_dot_min = Min(C_dot_1,C_dot_2)
NTU = UA/C_dot_min
epsilon=hx('counterflow', Ntu, C_dot_1, C_dot_2, 'epsilon')
{Solution:
epsilon = 0.8748}
Example 2:
$UnitSystem SI Mass J K Pa
$VarInfo UA C_dot_1 C_dot_1 C_dot_min Units = 'W/K'
$VarInfo epsilon NTU Units = '-'
C_dot_1 = 50 [W/K]
C_dot_2 = 30 [W/K]
epsilon = 0.74
NTU=hx('counterflow', epsilon, C_dot_1, C_dot_2, 'NTU')
C_dot_min = Min(C_dot_1,C_dot_2)
UA = NTU*C_dot_min
{Solution:
NTU = 1.9
UA = 57.01}