Date:         Thu, 25 Sep 1997 07:49:44 8
Reply-To:     Wes Neuenschwander <wesn@ESKIMO.COM>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
Comments:     Authenticated sender is <wesn@mail.eskimo.com>
From:         Wes Neuenschwander <wesn@ESKIMO.COM>
Subject:      Re: D'OH (metic) fridge
Comments: To: "James H. McCarthy" <jimhmc@MIT.EDU>, vanagon@lenti.med.umn.edu

> Would it make sense to start the cool down by placing containers of ice
> in the fridge, then replacing them with the cold food at departure time?
> Jim McCarthy, '87 Westy, Somerville, MA At 11:24 PM 9/22/97 UT, Dennis
> Haynes wrote:
> >It will take much longer than 2 hours for the fridge to cycle and start
> >cooling.  You need to fill the fridge to hold the cold.  An empty fridge will
> >immediatey dump all the cold air upon opening the door.
> >
> >Dennis
>

That doesn't really address the central problem - which is the lag time
between starting the fridge and getting the refrigeration system to start
generating cooling power.  The Vanagon fridges all use a process called
"absorption cooling", which is fundamentally different from the more
familiar mechanical refrigeration systems used in home and commercial
refrigerators.  The main advantage of adsorption refrigeration - in this
application - is that it can be readily powered with propane fuel.  The
downside is that the "absorption cycle" has a relatively slow response
time.  In the Dometic units it may take an hour to reach full cooling
capacity.  Pre-cooling the fridge doesn't get around this problem;
you'll still have a lag between starting the fridge and getting good
cooling.

My strategy is to simply start the fridge well in advance of when I'll
need it.  If I'm planning on leaving on a trip in the morning, I'll plug
it into 115 V the night before (or start it on propane).  I also try to
pre-cool all the food I plan on loading, since the Dometic units have
pretty limited cooling capacity (in addition to be slow on the get-go).
If I don't have the time to pre-cool the fridge, I just load and go and
take my chances.

In any case, use of a small fan - in the fridge compartment - will really
speed things up, and give you more cooling.

-Wes

Wes Neuenschwander
Seattle, WA
wesn@eskimo.com