Re: Winter Fuels
Lawson Dickson (wld@ZEPPO.GEOSURV.GOV.NF.CA)
Fri, 3 Nov 1995 09:47:37 NST
In answer to this question, here is my 2 cents-worth (in Canadian money).
> What I would like to know is how cold is too cold for propane. I have seen a
> youth member of our unit use a propane stove at temps in the minus teens.
> That's a little chilly.
The boiling point of propane at normal pressure is minus 42.1 degrees C which
is about minus 45 degrees F. Below 42.1 degrees C, propane will remain liquid
i.e., it will not produce a gas (that's the stuff we used for cooking etc.).
Remember that the propane in your tank is turned into a liquid by pressuring
the propane and removing heat. This is how most gases are liquified.
The liquid propane in the tank can reach this low temperature all by itself
simply because of the process of gas formation (boiling), as heat will be taken
from the liquid propane and its temperature will drop. When you open the
valve, the liquid propane (which is at whatever temperature it has been stored
at) will want to boil as the pressure has been reduced. This process, however,
still requires heat. This is termed latent heat. (This is why wet hands get cold
when they start to dry).
I am sure we have seen frost on the outside of propane tanks even during the
summer. The more gas that is being used - the more latent heat that is
required to allow gas to form.
Below minus 20 degrees C, propane gas formation can be slow and cooking and
heating can be very inefficient, as the temperature of the liquid propane in
the tank is lowered towards minus 42.1 degrees C (the boiling point of propane).
Below minus 42.1 degrees C, you can forget propane gas as a source of fuel.
If confused, check your old high school physics book.
Rocky, 1st Cowan Heights Venturers, B Company,
St. John's, Newfoundland, Canada
Department of Natural Resources
St. John's, Newfoundland, Canada A1B 4J6
E-mail : firstname.lastname@example.org
Terry Howerton Sakima Group, Inc. SCOUTER Magazine Kansas City