Because I'm bored:
These values are taken from air-liquide's vapor pressure tables.
http://encyclopedia.airliquide.com/E...a.asp?GasID=54
http://encyclopedia.airliquide.com/E...a.asp?GasID=53
Because they are vapor pressure tables, we know they are for a saturated mixture, which is more often than not the state found in our magazines during use. A saturated mixture simply means there is both liquid and vapor existing in the container at the same time.
Propylene at 0* C -> 600 KPa
Propane at 0* C -> 450 KPa
25% pressure difference
Propylene at 19* C -> 1100 KPa
Propane at 19* C -> 850 KPa
22.3% pressure difference
So there's nowhere in here we can assume a linear relationship for anything, so there's no point in any further calculations. Not to mention, there is way more at play here than just temperature and pressure. I could write a thesis on it... nope.
Rob's results have a 6.5% velocity difference at 19*C, and since there is a higher relative pressure difference at 0*C, I hypothesize that at lower temperatures we will see a velocity difference higher than 6.5%. A conservative estimate would be 9%, but that's just a completely arbitrary number I came up with.
Fun Facts:
- Propylene has the same pressure at 0*C that Propane does at around 7*C. Do not assume they will act the same at their respective temperatures, but its food for thought.
- Propylene is "Non recommended, significant swelling" for most common o-ring materials. Possible effects on test results could include gas valves not opening completely due to increased friction from swollen o-rings, or leaks cause by excessive swelling of o-rings.
[4th year Mechanical Engineering student for hire....]