Boiling Point at altitude?

Hi Flighttest,

Here is a chart of BP vs Vapor Pressure for Water:

This is based on the Antoine equation.

The Antoine equation solved for Vapor Pressure is:

where:

VP = vapor pressure in mmHg

A = 4.65430

B = 1435.264

C = -64.848

T = BP in ºC

If you can relate an altitude to atmospheric pressure (in this case the vapor pressure), you can then relate the BP to an altitude.

Hope this helps,

Mike

Great Info Mikerho.

Thanks for the help. I did finally work thru the info and posted a surprising result. When I plot altitude vs. boiling point of water, the relationship is basically linear.

Appreciate your input!

jim

"The Properties of Steam" by Keenan & Keyes provide the data you seek up to a point.

Try Google and Dogpile for "boiling point of water vs. altitude" and similar terms. You should find several sources.

ou need data that relates pressure and temperature to fluid state. Such data sets are called phase diagrammes.

Get a friend that knows a bit about physics to explain to you what a phase diagramme is and how the boiling point of water relates to water vapour pressure when water changes its nature from a liquid to a gas.

Check out "The Thermodynamic Properties of Steam", by Mayhew & Rogers. Inside it is a table giving the International Standard Atmosphere, giving pressure versus altitude. Earlier in the publication is a table giving boiling temperature versus pressure. This lot should be all that is needed.

I was able to use the equation that Mikerho provided. Using the Antoine equation lead, I was able to find another equation that seems to work very well. The interesting thing is that the boiling point becomes a linear relationship when plotted against altitude instead of pressure. I was not expecting this but it was a pleasant surprise. Somehow, these are more directly related. This was educational!

Again, I appreciate the help.