[AR] Re: Thoughts on low pressure fuels...
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 25 May 2015 04:59:04 -0400
On Mon, May 25, 2015 at 09:20:11AM +1200, Lloyd Droppers wrote:
As far as vaporization is concerned it does matter what temperature the
fuel vaporizes at. While your comment is valid in that 2000-(-20) and 2000-
100 are only 5% off vaporization temperature ofset from ambient also
matters. For a thought experiment if you are injecting a liquid at 10C and
one vaporizes at 20C and the other vaporizes at 100C the propellant that
vaporizes at 100C take 10 times longer to start to "boil" with the same
heat input all other factors being equal.
Yes, but to get it to finish boiling, you also need to put in the
latent heat of evaporation, which is commonly as much energy as it
takes to raise the temperature 100 deg C or more. (Let's see --
engineeringtoolbox.com gives the heat of vaporization of propane as
428 kJ/kg and the specific heat as 2.4 kJ/(kg*K), so as much energy to
evaporate as to raise the temperature by 178 C, versus kerosene at 251
and 2.01 (same units), so 125 C.) Adding that in makes the difference
much less prominent.
--
Norman Yarvin
http://yarchive.net/blog
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