Date: Tue, 9 Mar 2010 08:11:14 -0600
Reply-To: Mike South <msouth@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike South <msouth@GMAIL.COM>
Subject: Re: subject Re: Ice Cream Camping
In-Reply-To: <C7BB1565.987A%mwmiller@cwnet.com>
Content-Type: text/plain; charset=ISO-8859-1
On Mon, Mar 8, 2010 at 10:58 PM, Mike Miller <mwmiller@cwnet.com> wrote:
> Just a comment: Ice is not necessary 32 degrees F. It can be colder,
> actually much colder, much much colder. Just not hotter.
>
But getting the ice colder does not necessarily add that much cooling
capacity. If you have 1 gram of water at 33 degrees you need to take about
a half calorie of heat away from it in order to turn it into a gram of water
at 32 degrees. In order to take that gram of water at 32 degrees to a gram
of ice at 32 degrees, you need to take 80 calories out of it. The phase
change from solid to liquid requires the removal of a lot of energy, which
is what gives ice its cooling capacity. In order for your milk to melt the
ice it has to take 80 calories out of every gram.
To take a gram of ice from 32 degrees to 31 degrees requires the removal of
only a quarter calorie if I remember right (ice has about half the heat
capacity of water). So if you take the gram of ice down to 0 F you've only
removed 8 more calories of heat.
(All the calculations herein are somewhat rough because I was assuming for
simplicity that a degree Fahrenheit is about half a degree celsius, which is
not quite accurate.)
n.b.--when people talk about "calories" in food they are really referring to
kilocalories. Wanted to bring that up just in case this discussion is
giving anyone the idea that they can lose a significant amount of weight by
melting ice cubes in their mouth. I just measured one from my fridge, it
was 23 grams. So melting it in my mouth will take 1840 calories, or 1.84
"food calories". Of course my body will also be taking the runoff up to 98
F, but at only a half cal per degree, so with 23 grams that only gives me
about 3/4ths of a food calorie. Also there's the cooling capacity lost
through my breath while the ice cube sits in my mouth. Isn't science fun?
let's see...vanagon content, vanagon content.... well, the contents of my
vanagon includes a Dometic fridge. Anyone know how many calories of propane
heat it takes to remove 80 calories of heat from water in the Dometic?
Speaking of Dometics I just lit mine for the first time (WOOHOO!) this last
week after going through some of the very extensive instructions from Roger
Sisler's awesome
"Dometic RM182 Getting it to work again in 151 pictures" flickr collection
http://www.flickr.com/photos/werksforwagens/sets/72157594499353583/ (or
http://tinyurl.com/dometic )
One thing that set of photos helped me do is understand that the thing I
thought was the jet was actually the themocouple probe. Which probably
means I shouldn't be working on propane stuff I guess.
Something to keep in mind if you're doing a recondition on the 182b is to
make sure you get the end of the burner (
http://www.flickr.com/photos/werksforwagens/368328598/in/set-72157594499353583/)
(the end with the slits, away from the jet) into the little slot that
holds it in place. When I was putting mine back together I didn't realize
the slot was there and I had it on top of the slot instead of inside it.
This put it up against the thing that is supposed to spark, grounding it.
D'oh!
Anyway, it lit! Thanks Roger (and others who have taken the time to write
up reconditioning instructions).
Next thing I'm going to do is check the temperature of the internal fins to
see if I need to refresh the themal mastic. Unless people advise that I
just go ahead and do that step? I was very pleased with the condition of
the rubber gasket material around the burn box, which made me think that
perhaps other parts might be in better shape than one might expect after 25
years.
mike
> David B. can comment on this I bet.
>
> Mike in Marin
>
> On 3/8/10 7:53 PM, "Richard Koerner" <rjkinpb@SBCGLOBAL.NET> wrote:
>
> > Dry ice would be too expensive; going to a nearby Ice Cream joint defeats
> my
> > purpose; I want to have ice cream out in the middle of nowhere!! One tip
> from
> > the list was to realize that ice cream at 32 F (as in packed in ice) is
> not
> > the same as ice cream at 0 F (like in the refrigerator at home, which I
> assume
> > is something like 0 F).
> >
>
