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Date:         Mon, 16 May 2005 10:56:15 -0700
Reply-To:     Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Subject:      Re: measuring propane level in a tank
Comments: To: Richard A Jones <jones@COLORADO.EDU>
In-Reply-To:  <4288B85F.7070801@colorado.edu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 5/16/2005 8:12 AM Richard A Jones wrote:

> Determining the level of propane in a tank is harder than > you might think. Propane boils at -44 degrees F; only the > pressure in the tank keeps it liquid, the same as your > sealed radiator system keeps the water liquid at temps > above 212 degrees F. > > The amount of liquid propane in the tank has no connection > to the vapor pressure of the gas in the space above it-- > only temperature does. At -45, the vapor pressure is zero. > At -20 it is 11 PSIG, rising to 257 at 130 degrees. This > is why you cannot measure the remaining liquid propane by > any kind of pressure gauge. The pressure remains constant > (at a fixed temp) until the last molecule of liquid propane > boils. > > What you can do is attempt to find the level on the tank > where the liquid/gaseous line is. When you are using > propane, some of the liquid is turning to gas. The > molecules becoming gas take the heat, leaving the liquid > colder. Ergo, just find that temperature gradient point. > Again, compare to water. A pan of boiling water stays at > 212 degrees (at sea level--the pressure factor again) until > all gone. All the heat you apply to the pan goes out in > those hot water vapor molecules. You can't get the liquid > water hotter than its boiling point. > > Campingworld (for example) has two "gauges" that do that: > http://www.campingworld.com/browse/products/index.cfm?prodID=4800&src=SRQB > > or http://tinyurl.com/dv8qq > http://www.campingworld.com/browse/skus/index.cfm?skunum=4317&tab=desc > or http://tinyurl.com/drkeu > How well these would work on our skinny horizontal tanks, I don't > know. How well they really work on larger DOT tanks, I don't > know either. ;-) > > Next time I'm near CW, I'll get them and experiment. Of course > it may mean that I also have to get the one-piece RVer jumpsuit, > some 12V patio lights with American flag motif, the giant outdoor > carpet and the gizmos to dispense paper plates one-at-a-time....

We want to see pictures.

--

Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 83.5 Westfalia: Mellow Yellow ("The Electrical Banana") KG6RCR


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