I have created a very simple shell and tube heat exchanger assembly. When I ran the flow simulation using the assembly, I was able to generate results; however, there seemed to be a leak between the shell and the tubes. I am having trouble creating the design so that there exist two separate flows. I decided to create subassemblies for the shell component and also for the inner tubes and baffles. When I did this, the tube and baffle assembly revealed that the mate was not water tight. The baffle holes are the same size as the OD of the tubes. I have tried to make the holes smaller in order to cause the parts to overlap but the issue was still not resolved. I am unsure of how to go about this issue. Any help would be greatly appreciated. Attached are screenshots which display the water tight error designated by the blue outlines.