# Problem with Condensator-Evaporator (TL-2P) block in simscape fluids

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Lorenzo Oliveri on 21 Nov 2023
Answered: Yifeng Tang on 3 Jan 2024
I have a question to ask about the Simscape Fluids Condensator-Evaporator (TL-2P) block. Once the window that allows you to modify the parameters of this block is open, you must first choose the flow arrangement: as specified in the help, the "cross flow" configuration defines the flow of the two fluids in a perpendicular direction to each other, while "parallel flow ” and “counter flow” define a parallel flow direction of the two flows, but the first one in the same direction while the second one in the opposite direction. If you choose the crossflow configuration, it is possible to define that one of the two fluids flows inside a bank of tubes while the other will hit the tubes outside, perpendicular to the direction of flow of the previous one. The “flow perpendicular to a bank of circular tubes” option remains valid even if the selected flow arrangement is “counter flow”. I therefore must ask how Simulink interprets during the simulation the configuration in which there is a "counter flow" (where in theory the fluid should flow in the same direction but in the opposite direction to the first) together with the "Flow perpendicular to bank of circular tubes”.

Yifeng Tang on 3 Jan 2024
Hi Lorenzo,
I too agree that having counter flow and flow perpendicular to bank of tubes at the same time doesn't quite make sense. That said, mathematically these two settings are responsible for the heat transfer effectiveness and convective heat transfer coefficient correlation calculations, respectively. So it's possible to blend them in equations, but you are right, I can't imagine how they would be built physically.
This part of the documentation explains how flow geometry affects the heat transfer coefficient correlation:
The heat transfer coefficient is then used to calculate the total thermal resistence, then e-NTU, then effectiveness. The equation for effectiveness depends on flow configuration (parallel/counter/cross), as explained in this part of the documentation:
Hope this helps.
Yifeng

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