Interesting. I'll have to read up on this some more. I suppose the same
principle won't work well in the freezer box

Doug
s/v Callista

"Glenn Ashmore" wrote in message
news:JVvTc.28578$Jo1.27533@lakeread01...


Doug Dotson wrote:

I guess that depends upon the lid configuration and how often it
is opened. I have a Coleman Extreme and find the ice lasts alot
longer if you drain off the excess water. Perhaps leaving a little in
bottom
is a good idea. I tend to rely on the laws of physics rather than
ad hype from vendors.

Doug
s/v Callista

Coleman isn't the only source of that information. Hormel provides a
camping tips booklet that says the same thing as did an article last
year in Trailer Sailor. There is definitely some good physics behind
the principle.

As long as the water is close to the target temperature of the box,
there are several advantages over a dry box, especially when the box is
refrigerated.

Basically the heat enters the box by adding warm drinks, allowing warm
air in when the box is opened or through the outer surfaces. There is
not much you can do about adding warm drinks except cut back on the beer
consumption but by reducing the amount of warm air that can get in heat
gained due to opening can be minimized.

The speed heat comes through the sides is directly related to the
difference between the inside surface of the box and the outside. It
does not matter if the box is full of water or air. As long as the
difference in temperature is the same. The evaporator coils are close
to the inside surface and will operate at a temperature about 10-15º
below the target temperature of the box. Water transfers the heat from
warm drinks to the coils faster than air so the temperature is more even
all over the box. If there is no water move the heat quickly the inside
surfaces next to the coils will get much colder which increases the rate
that the heat will come through the sides.

The compressor WILL run longer with the box full of water to cool the
box the same amount but it will run less often once it reaches the
target temperature. Net result is an overall energy savings.

Here is a pretty good explination using ice only but the effects
described are magnified with a refrigerated box:
http://www.madsci.org/posts/archives...3228.Ph.r.html

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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