- #1
nhaskins
- 2
- 0
When you compress air it heats, and when you decompress it it cools, but how much?
Working from http://en.wikipedia.org/wiki/Gay-Lussac's_law I find the equation
pressure/temperature=constant
so I derived for example
if the air is 10°C (283.16°K) and the pressure is 14PSI so...
14/283.16 = 0.04944
increase the pressure by 90 PSI
104/2103.5 = 0.04944
maintian pressure, but decrease temperature to almost ambient (16.84°C)
104/290 = 0.3586
decrease pressure to ambient
14/39.04 = 0.3586
i.e. I compress a tank of air to 90psi above ambient air pressure of 14psi at 10 degrees celcius, I let it cool to almost ambient (just for easier math) and when I shoot the air out it decompresses and cools to 39 Kelvin. It doesn't sound right.
Then I realized that equation required mass and volume to remain constant.
http://en.wikipedia.org/wiki/Combined_gas_law gives me a more complete equation
(pressure x volume)/temperature = constant
but that would mean when I increassed the pressure by compacting the air I would, for example, decrease the volume by ten times thus increasing the pressure ten times and the temperature would remain constant.
Please, what am I missing?
Working from http://en.wikipedia.org/wiki/Gay-Lussac's_law I find the equation
pressure/temperature=constant
so I derived for example
if the air is 10°C (283.16°K) and the pressure is 14PSI so...
14/283.16 = 0.04944
increase the pressure by 90 PSI
104/2103.5 = 0.04944
maintian pressure, but decrease temperature to almost ambient (16.84°C)
104/290 = 0.3586
decrease pressure to ambient
14/39.04 = 0.3586
i.e. I compress a tank of air to 90psi above ambient air pressure of 14psi at 10 degrees celcius, I let it cool to almost ambient (just for easier math) and when I shoot the air out it decompresses and cools to 39 Kelvin. It doesn't sound right.
Then I realized that equation required mass and volume to remain constant.
http://en.wikipedia.org/wiki/Combined_gas_law gives me a more complete equation
(pressure x volume)/temperature = constant
but that would mean when I increassed the pressure by compacting the air I would, for example, decrease the volume by ten times thus increasing the pressure ten times and the temperature would remain constant.
Please, what am I missing?