Wednesday, April 22, 2015

Formula for Power Needed to Heat a Volume of Air



We've had this formula kicking around since college days. Not sure if we're using it out of its useful range so might be good to check this with a valid source.





By this formula, where
  • Exit temperature is 500F (it's cooler than that by the time it soaks through the herbs)
  • Room temp is 75F
  • Normal inhale is .25 CFM (roughly 2 liters in a 15 sec inhale by our testing)
  • The thing being "cooled" is the vapor box's heating element and surrounding glass

P(W) = 169 * (.25) * ( 533K / 297K - 1) = 33.6W



We need about 34W to heat the air in a normal inhale... theoretically. (our normal is pretty big actually.. this could be cut in half) This puts the hits we like out of the range of a handheld battery.

After heatup our vaporizer runs at 34W, although this is kind of a coincidence because the user only inhales at this .25CFM rate for 7-10 sec and the heating ceramic and surrounding glass stores heat that it can give up during a longer vapor draw. If someone were to inhale constantly at .25CFM our vaporizer will consume something closer to 100W.




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