Hmmmm, Joule-thomson effect is an interesting concept. Although I was more looking for something as an alternate form of cooling, instead of having the need for electricity to power a compressor.
Ammonium Nitrate is a point, didn't think of that. Thank you for that suggestion.
A flame is an exothermic reaction as it is created by a chemical reaction which releases energy to it's environment, causing the heat and plasma. So it wouldn't really be what I was meaning.
Thank you all for your suggestions.