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Date:         Tue, 8 Sep 2009 11:38:55 -0700
Reply-To:     Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject:      Re: Pulled out my stock fridge - now my faucet doesn't work...??
Comments: To: Steve Williams <sbw@SBW.ORG>
In-Reply-To:  <200909081751.n88Hpma23281@sbw.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 9/8/2009 10:51 AM Steve Williams wrote:

> At 09:56 AM 9/8/2009, Rocket J Squirrel wrote: >> It takes a pretty long exposure to warm air to raise the temp of a >> can of beer even a couple degrees. > > Oh, right, well, I understand that the stuff in the fridge doesn't warm > up much when I open the door. That's not what I was concerned about. > I understand I'm making my fridge more efficient by storing many more > BTUs of cold per cc in my 3.5-litre water jug than if I just left air > in there. > > What I'm concerned about is the loss of the cold AIR that inevitably > fills the space between the bananas and the bottle of salad dressing. > > When you open the door of a stock fridge to cool off your toes, how > many grams of propane or millwatts of electricity does it take to cool > the warm air that replaced the cold air that flowed out? (As opposed > to just leaving that cold air inside, as the top-opening fridge mostly > does.)

I dunno. It's gonna depend on how many calories the reefer's heat-moving engine (compressor and coils, ammonia cycle system, etc.) can remove from the interior per unit energy. I guess the only way to determine that is to put a couple gallons of warm water into the reefer and see how much power or cc's of propane it uses to cool the water by, say, 10 degrees. Then simple back of envelope math will tell how much energy is needed to cool the considerably smaller amount of heat found in the water vapor in the interior air.

But my guess is that inefficiencies such as the system turning on right after "seeing" the new warm air instead of waiting for a little bit to allow the foodstuffs to cool that bit of air will use a lot more power over the long haul far more than the bitty amount of energy used to cool that bit of warm air. If the reefer's thermostat is located high in the cabinet then a bitty fan that can keep the internal circulating will give it a more accurate picture of the actual thermal conditions that if the cooler air is allowed to pool beneath it where it can't see it.

-- Mike "Rocket J Squirrel" Elliott 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano Bend, OR KG6RCR


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