When Tony fires blasts or flies at very high speeds, why does his armour not heat up? When he lifts someone and flies with them, like in the picture below, why does it not cause any damage to Tony, as well as the other person?
In the 1970s, it was mentioned that the armor had some sort of a thermocouple device, that could convert extremes of heat and cold into electricity (which is a real thing - but is almost certainly horribly misapplied, in this context). It always read to me like a concept the writer had heard about, and simply plugged in without necessarily understanding how it would work in reality - but, hey, that still requires less hand-waving than some aspects of the armor....
In particular, I found a reference to this in IRON MAN (vol 1) #92, cover dated November 1976. Iron Man is fighting the Melter - and, conveniently enough, the thermocouple is broken at that point, making the fight much more of a challenge. The armor is actually ruined.
Note that this does nothing to explain how unshielded people he's carrying are protected from wind/friction damage. Nor does it explain other effects of high-speed flight and maneuvering, like managing G-force, or preventing Tony's body from being bounced around in the armor (which, one would think, is a lot like how concussions happen, with the brain getting bounced around in the skull).