A friendly piece of advice regarding that fan you're using to keep a cool head. It's just because I just finished modding my helmet with a fan-based cooling system.
It looks like an old VGA-cooler (TNT2/Geforce or something) with the heatspreader still attached). A couple of things come to mind if that's the case.
1) you've mounted the fan to force air away from your head (airflow goes IN the fan, and goes out through the coolerbody). That thermal design is made to cool the thing UNDERNEATH that coolerbody, not what's in front of it.
Do with this info as you will. You might not need it, but I did learn a thing or two about "keeping a helmet livable" these last couple of days.
I've mounted mine the other way round : the fans suck in cool air (they sit behind the rebreather tubes of the MK VI helmet) and gently blow this on my face. I experimented with several different fan setups and speeds and my testpilot (my daughter) instantly agreed this was the best solution.
When trying to "suck the heat away" like your fan is mounted, she commented "it didn't help a bloody bit".
While I do understand the iron man helmet does not have an exhaust/intake there, the pure fact your suit is metal turns it into one giant heatsink (unless you're planning to stick in out in the glaring sun at noon that is .... don't think that's good idea
) but that being said, it wouldn't surprise me if force-circulating the air at your face while circulating it from within the walls of your metal helmet will be a better solution even with the lack of air intake ports.
2) if that's indeed an old, salvaged GPU cooler than at that design and age, I'd suspect it is or it will be on the way out soon. Also, and this speculation from my side : the noise level of these kinds of GPU coolers ... let's just say silence was not the main priority, certainly not when running at 12V like spec'ed. Some of these coolers allow undervolting to approx 7V making them much more bearable in terms of noise production, but this of course puts a major handicap on the produced airflow.
3) based upon my personal experience, you might be better of with two fans running at a lower speed than one at higher speed. While the overall airflow won't be that different, the noise level sure will be. It's important to have as-silent-as-possible fans inside a helmet I think to keep in comfortable.
Any noise coming from the fans (slight inbalance, minor trembling by sleeve bearing on the way out ...) will be amplified a hunderd times inside the helmet even if you can't hear that when testing the fan outside the helmet.
I use 2 small 35x35mm fans (dirt cheap from Ebay - 5 of them for 6€ - I can dig up the link if needed) which make NO noise when you let them run freely on you table or whatever, yet when I mounted them in my helmet there's stil a clear buzz to be heared. And that using fans that are dead-silent, rated for 5V operation and undervoltaged to 4.5 for good measure.
My first trial was also with a salvaged AMD K7-cpu cooler : it felt like I was sitting in some kind of Tsunami-stricken disaster area.
But yes, having a fan inside makes a helmet far more comfortable and not just in terms of fogging. When done in the correct manner, it allows the wearer to keep the helmet on for a very long time without the usual problems.
I also experimented with a low cost air pump running at 12V, think it was meant for a fish tank, and that worked really well, but the hose that started under the chest armor and ran up to the top/inside of the helmet was a major pain in the neck.
