Yeah air motors and turbines do not need cooling. They need heating. Adiabatic cooling effects mean the air flow cools down quite a bit, and the colder air loses pressure thus loses the potential to do work. Unfortunately, warming up a moving air mass is more problematic than it seems. The conductivity of air with an aluminum wall is fairly poor for the flow speeds usually encountered. That is, a piston expands and the air cools itself with the change in volume. This may happen within say 100uS. The thermal conductivity of 65F cylinder walls will not significantly rewarm the air within that 100uS. This issue affects air motors of any size or density, but of course high power density air motors have even worse problems as it struggles to have a large warm sink with the air and avoid freezing water or even frozen CO2 in the path. Yeah it does make some sense to push the exhaust into a heat exchanger, let it warm up and regain pressure, and push it through another expansion chamber (cylinder or turbine). That still has flow rate issues and a whole new set of complications though. Danny Sean Breheny wrote: > I think that they do have the option of ejecting water but I think > that is to cool the bit and the tooth, not the handpiece. > > Sean > > > On Mon, Nov 3, 2008 at 6:10 AM, Alan B. Pearce wrote: > >>> The dental handpieces won't eject oil, I'm fairly sure of that. >>> >> I suspect they eject water - that ends up in the patients mouth after >> cooling the tool ... >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist