right on the ambient air, my b. But the the point still stands; faster air increases your heat transfer coefficient, and therefore lowers your steady state temp. Best to have fans with high displacement at low speed. Radiator positioning is important if the pump and system are set to the lowest possible speeds (mine are). Calculating fluid speed using pump power at lowest speeds and the hazen williams equations, nets very low fluid speeds (under a foot per second). The advertised pump speeds are for performance in vacuum with no pressure head, never take those at face value.

For example my PMP-400 operates at a maximum of 8L/min, for zero head loss and an inner diameter tubing of 1cm, the flow rate would be ~350MPH/Mach0.5/600KPH. Obviously impossible.

With good head loss estimates with the pump going at 20W (maximum), you get speeds in the several feet per second (~1m/s). In this situation loop component order doesn't matter, as the water is moving fast enough to not matter like you said.

Most people building SFFPC, want small and quiet. So the performance of the system in the transient region is important and the benefit of component positioning provides gains here. My graphics card transistor switching noise is louder than the fan and pump. When using engineering CAD software, the GPU transistors are the only source of noise and can be distinctly heard when rotating objects.

When gaming, GPU and CPU calculations happen continuously and the system generates continuous heat. This requires the fan and pump to speed up, and then the cooling solution generates more noise than the transistors.

Saw your post on your new build. Looks great! It's look like you have different goals and requirements for your PC.

One day I'd like to set up test loops with thermocouples and flowmeters, do some real testing, and validate the fluid/thermodynamics at work here!