higher water temperature going into the GPU block will result in a lower Δt between the die and the block which means less heat is pulled away.
Ballocks! Ballocks, I say!
What you said is true, but feeding cooler water into the GPU causes less heat to be pumped out the back of the case. Here's why:
Putting the radiator between the hot devices means the water entering the radiator will be much cooler than if it had GPU heat, too. You talk about thermodynamics. Because heat flow rate increases with temperature, feeding cooler water into the radiator causes
the total heat removed from the system to be less.
If you put the radiator after both hot devices, then yes, you pay the price of a warmer GPU. But what you're buying is not just a cooler CPU, but a MUCH cooler CPU. That is more important. You're pulling a lot of heat out of the CPU and putting just a little of it into the water flowing across the GPU.
CPU-wise, it looks good because you have the cooler directly after the CPU (largest Δt).
It's only the largest Δt between the intake and outflow of a hot device. But the user isn't interested in which device has the highest Δt; he cares about the Δt of the radiator. And that is maximized by putting it after the hot devices.
The loop is always in equilibrium because it's a closed system
Wrong again, Albert!
When you first turn the thing on, the CPU is hot and the water is cold. When it reaches equilibrium (which theoretically, it never actually does), the system is pulling much less heat from the CPU than it did at first.
Even if you diddle with the definitions of words to handwave that away, it's still only a closed system in terms of water leaking out. It's not closed thermodynamically because you're feeding bigtime energy into it via the pump. That's what drives the water, and the water is the heat transfer medium. You're also feeding heat into the system via electric power to the two chips and pumping into in the air, which is outside the system.
That's not equilibrium, dude. It's like saying that the water in a firehose doesn't move because the amount going in one end is the same as what sprays out the other one.
The only time your PC is in thermal equilibrium is when the whole thing has been switched off for while.
___________
If past is indeed prologue, instead of saying "Well, I'll be damned, I was wrong!" you'll get mad at me.
-faye kane ♀ joule thief