What is precluding it from having a small heat exchanger in there? Similar to a mini-split but integrated?

I think it would be pretty hard to power it.

https://www.quora.com/How-many-BTUs-would-you-need-to-cool-j...

>So we have to pump 150 + 22 = 172 watts of heat up a thermal gradient of 10C — more if it's hotter. If I assume a slightly pessimistic factor of 2 for the heat pump, that's an electrical input of about 85 watts to the heat pump, plus some to run fans and coolant pumps in the suit — my guess is that you need a minimum of around 250 watts to power the suit.

>Sounds distinctly unpleasant to wear.

>Edit:: and if the cooling stops, get out of the suit quickly, before you roast.

I dunno, they have interstellar spaceships. Sun on earth is 1kW/m^2 at equator, not sure what it would be on Dune, but doesn't seem that unreasonable that they could have it powered by some advanced solar cells integrated in the suit.