Um, I think you might have posted the wrong chart. That chart appears to show constant temperatures.longri wrote:Jim, it doesn't scale that way. The P-T curve is logarithmic. As the temperature drops the pressure differential narrows so you won't get the same fuel flow rate.hikin_jim wrote:Pick whatever PSIG one feels is appropriate at sea level, and one should have that same PSIG at 10,000' in temperatures that are 20 Fahrenheit degrees colder.
edit: Here's a chart to illustrate. You can see that at sea level and 20° a full canister is at about 13 psig whereas at 10,000 feet and 0° it's at about 8 psig. To get the same pressure at 10,000 feet the fuel temperature would have to be about 10°, not zero.
The chart you posted earlier seems clearer to me.
I've been saying that the fuel temperature needs to be about 10 Fahrenheit degrees above the fuel's boiling point to have sufficient canister pressure and that as boiling point varies with elevation, you'll still have sufficient canister pressure if your fuel temperature is 10 Fahrenheit degrees above the boiling point at a given elevation.
I think what you're saying is that simply having the fuel be X degrees above the boiling point is insufficient to predict sufficient canister pressure. What I think you're saying is that it's necessary to know what the psig is for a given temperature and atmospheric pressure of a given fuel mix in order to know whether or not you've got sufficient canister pressure. Am I stating your position correctly?