I came around to that way of thinking, Julian.
My new (air) setup with 120mm OEM panaflos makes less noise than my pump did... I had no fans when I was on water (save an 80mm Panaflo L1A in my PSU @ 4v...it only started half the time).
But the evolution of passive:
At first I had a bucket. It was copper (pure!), but it leaked, and stained my carpet. I grew angry. It also had good temps when you first booted up, but they just kept climbing and climbing and climbing:
Then I moved to a more innovative solution. This is just about the WORST design in the world, but it was an exercise in soldering and it was the only thing that fit behind my rafters. Plus, due to the cold (I used Windshield Wiper Fluid), I saw temps well below chilly:
I used this in Dec, Jan, and Feb in Pennsylvania.
This came to an end when this happened:
It froze.
Next I tried some 3/8"OD Copper coil from Home Depot:
This was not a good solution. Nice temps, but it leaked constantly.
So, onto this 1/2" coil I got off ebay for $12 shipped:
This worked very well, and I was happy. But if it's working just fine, then, as the saying goes, try really really hard to break it.
So finally the best design yet. It's not mine, it's a man by the name of Gerwin who resides over at Procooling, or at least used to. He used compression fittings, I soldered.
When I added the coil, I lost about 5c:
The design of the Gerwin radiator is to minimize resistance, and still have a lot of water pass through a lot of tubing. Water will take the path of least resistance, or the shortest one. There is no shortest route in Gerwin's design, and it works well. However I recall asking him some time later about it, and he said he'd doubled the size of his, making it about 6ft by 4ft, and mentioned that it did absolutely nothing for his temps but was splendidly fun.
Later I tried using commercial radiators passively, but always ended up either selling them or returning them because I'm a cheap ******* and they were expensive. My Gerwin radiator cost me about $9 in tubing and $4 in Ts and 90 degree elbows at the Home Depot. I used to idle around 30, but if anyone saw my thread regarding my TC-4 and a very small problem with corrosion, right before I dismantled it I had a load of around 41 without the coil.
There are much better solutions out there; I've seen them (and have pictures of them). But the Gerwin radiator is by far the best for the money I ever tried.
Cheers,
lex