I'm guessing the designer of this tank mistakenly envisions a beautifully curved sweeping path of air coming down the pipes in the top cap, flowing down the ramps and under the coil then back up the other side to the drip tip.

How they envision two seemingly viscous air flows opposing each other like that I don't know because they lost me at the ramps. Maybe they think the two streams hit underneath the coil then turn up and hug around it before merging at the top?

Anyway, my point is there's far too much intuition in air design and far too little hard science.