Cross Flow Both Unmixed
The cross flow heat exchanger configuration requires that the two fluids flow perpendicular to each other. The unmixed configuration indicates that the fluid cannot mix with itself across the width of the heat exchanger as it flows; practically, this means that the fluid can support a temperature gradient in the direction perpendicular to the flow direction. The effectiveness-NTU and Log Mean Temperature Difference solutions are both available for cross flow heat exchangers where both fluids are unmixed. Solution is from Nellis and Klein.
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 = 75 [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('crossflow_both_unmixed', Ntu, C_dot_1, C_dot_2, 'epsilon')
{Solution:
epsilon = 0.7632}
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 = 0.61
NTU=hx('crossflow_both_unmixed', 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 = 1.341
UA = 40.23}