Your comment about putting compressed air through a venturi is almost correct; actually it is a joule thompson nozzle. If you Google on 'joule thompson effect' you will find many references to obtaining low temperatures by expanding a compressed gas. You might want to consider using compressed (actually liquified at around 1800 psi) carbon dioxide and allowing it to expand through a small orifice and then pass through a labyrinth machined in an aluminum plate. You will get temperatures well below 0 Celcius. |