The Iceni
Medical Moderator
Originally posted by Ber Rabbit
Unfortunately my assigned lecture is Charles' Law. The way I was taught its only use in diving is when you are dealing with hot fills or leaving your scuba tank in the sun. The basic relationship I was taught was that as temperature increases, pressure increases (the molecules move faster).
Thanks,
Ber
Hi Ber and Jamie,
Add in Van der Waals', Graham's and Poisseuille's Laws and Avogadro's number and you can really confuse!
This is Van der Waals' version of the gas equation;
(P + n^2 *a/V^2)(V-nb) = RT
(Wher R the universal gas constant, and about 22.4 litres per mol and "a" and "b" are constant for each gas)
On a more serious note though, Ber, perhaps your instructor is after an explanation for "short fills".
By the way, did you know that it matters not a jot what the tempertaure of the cylinder is when it is put to use? A cold cylinder (under the artctic ice) may show a drop in pressure due to the cold, or it may show an increase in pressure due to heat from the sun (in the tropics) but provided it has been filled to working pressure at the rated temperature (usually 15 degrees C) it will contain exactly the same amount of gas.
It will therefore last just as long.
This is because every molecule of each breath that you take is heated to body temperature (and water vapour is added) by the time it reaches - and fills - the lungs. So for all practical purposes you will be breathing your air or gas mix at 37 degrees C.
Does this make any sense? :mean: