There are times I may want to go diving after going somewhere, without driving home to get my gear (i.e. after work). Is it safe to leave an aluminum tank in a hot car for hours at time? For example sunny 90 degree weather.
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That may be the first time I've seen someone make that calculation not in Kelvin. However, given that the tank is going to heat from the inside out, I've always wondered if you have to take the coefficient of thermal expansion (CTE) of the aluminum into account as well. The pressure might actually drop at first!As @JahJahwarrior said the governing equation is PV=nRT. Volume, number ofmoles, and the gas constant do not change so we are left with P1/T1=P2/T2. Where temperature is absolute.
Solving for P2 we get P2=(P1*T2)/T1
Let's say we go from 70°F(529.67°R) to 120°F(579.67°R). Putting the absolute temps in we get that P2=1.094*P1 or a 9.4% increase in pressure. A 3600 psi fill would become 3939.8psi.
Going from 70°F to 140°F gives us P2=1.132*P1 or a 13.2% increase. We go from 3600psi to 4075.8psi.
I used a starting pressure of 3600psi but you could apply the ratio from the temperatures to any starting pressure regardless of units.
That may be the first time I've seen someone make that calculation not in Kelvin.
Oh, I know what the unit is. It's that the Venn diagram of people who make gas law calculations and those who use Fahrenheit for them is almost disjoint.Kelvin is absolute tempature for Celsius, Rankine is absolute tempature when using Fahrenheit which is not used so much anymore. Rankine is a US customary unit and was used, and still is to a lesser degree, before Kelvin became the standard for scientific calculations.
Oh, I know what the unit is. It's that the Venn diagram of people who make gas law calculations and those who use Fahrenheit for them is almost disjoint.
Also, I realize that another effect that might be taken into account is that at 200 bar the ideal gas law starts to break down somewhat. I would guess that as it gets heated there might be increasingly nonlinear effects. So southside's calculation may be a lower bound.