[Ali_qasim]

Hi everyone,
I am modeling a cross-flow energy exchanger for heat transfer from humid air to a cold fluid separated by the membrane. I have performed the simulation and for validation purposes, compared the results with experimental results and analytical calculations. I used the effectiveness-NTU method for the analytical calculations of sensible effectiveness.
Surprisingly, there is a huge difference between the analytical and numerical simulation values.
I have used symmetry boundary conditions in numerical analysis (half domain is modeled with a half flow rate).
In the case of analytical calculations, do I need to use “half domain with half flow rate” or “full domain with full flow rate”??? In both cases, the results are different.
Regards,

[CFDfan]

Originally Posted by Ali_qasim

Hi everyone,
I am modeling a cross-flow energy exchanger for heat transfer from humid air to a cold fluid separated by the membrane. I have performed the simulation and for validation purposes, compared the results with experimental results and analytical calculations. I used the effectiveness-NTU method for the analytical calculations of sensible effectiveness.
Surprisingly, there is a huge difference between the analytical and numerical simulation values.
I have used symmetry boundary conditions in numerical analysis (half domain is modeled with a half flow rate).
In the case of analytical calculations, do I need to use “half domain with half flow rate” or “full domain with full flow rate”??? In both cases, the results are different.
Regards,

1. Are the full domain/full flow rate results closer to reality?

[Ali_qasim]

Originally Posted by CFDfan

1. Are the full domain/full flow rate results closer to reality?

Dear CFDfan,
Thank you for your response.
In the case of numerical simulation results, I am getting a sensible effectiveness of 94% according to specified mass flow rates of air and liquid solution. In this case, the half domain is modeled with the use of symmetry boundary conditions.
I am a little bit confused with the selection of the domain to be used for the analytical calculations. So I have done analytical calculations with the following two cases:
1. Half Domain: In this case, I am getting very high values of effectiveness with most of the cases (changing flow rate), almost 98-99% of the sensible effectiveness.
2. Full Domain: In this case, sensible effectiveness is at ~80%. the difference in this case is high w.r.t numerical simulation.