Cross Flow Both Mixed
The cross flow heat exchanger configuration requires that the two fluids flow perpendicular to each other. The mixed configuration indicates that the fluid can mix with itself across the width of the heat exchanger as it flows; practically, this means that the fluid cannot support a temperature gradient in the direction perpendicular to the flow direction. The effectiveness-NTU solution is available for cross flow heat exchangers where both fluids are mixed. 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_mixed', Ntu, C_dot_1, C_dot_2, 'epsilon')
{Solution:
epsilon = 0.6841}
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_mixed', 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 = 1.478
UA = 44.33}