I've certainly seen people in costumes with 80mm PC case fans blowing out the back, to provide some air circulation. So circulating and venting ambient air isn'

I've certainly seen people in costumes with 80mm PC case fans blowing out the back, to provide some air circulation. So circulating and venting ambient air isn't unusual. And there are vests that circulate chilled water [1] for military and astronaut use - although the military one linked puts the chiller in a vehicle and each passenger plugs themselves into it. For portable use I suppose the question is whether a battery-powered cooler provides more cooling than the same weight in ice packs. [1] https://www.med-eng.com/product/cooling-vest/ https://www.med-eng.com/product/cooling-vest/