FYI, someone who has worked in wind tunnel testing provided me with this information:
Quote:
The stream is not actually smoke, which comes from combustion, but condensed oil vapour that forms a cloud, like steam, but more persistent. One material used is polypropylene glycol (this is not antifreeze, which is polyethylene glycol). I think that fog juice, used in the theatre industry, is primarily polypropylene glycol. It is passed through a small diameter stainless steel hypodermic tube (1/16" od) and heated by passing a current through the tube, which should be insulated and held inside an outer, non-conducting tube, like a large hollow fishing rod. The overall length is between 2 ft. and 6 ft., depending on requirement. A variac or variable current DC current supply can do the job. The voltage need not exceed about 25v.
Aerolab sells such a product. Look at www.aerolab.com select the tab 'speciality' then 'smoke generators'.
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EDIT: link to smoke generator brochure PDF from that company -
http://www.aerolab.com/downloadable-...enbrochure.pdf