On Sun, 02 Jul 2006 23:50:59 -0500, Richard J Kinch
wrote:

Chris writes:

For water, the heat of fusion is about 80 times specific heat...

So -70 C ice would have almost twice the cooling effect
as the same amount of barely frozen ice, right?

No, because heat load is proportional to temperature differential.

Now if you put that supercooled ice into watery payload that freezes, then
the supercooling heat sink will convert to new ice in the payload, and a
different process is involved that is more "efficient". However, this is
no better than just freezing your food to start with.

Hardly anybody appreciates that temperature and heat are two different
things.

This note looks suspect - especially the "what everybody doesn't know"
bit.

Brian Whatcott Altus OK

Two things I can recommend. The first is the 58 quart Coleman Ultra Xtreme
marine cooler. Both in practical sailor's and my tests it beat the
expensive high end marine coolers by a significant margin.

There is also a product called Technice. It comes as flat sheets that you
hydrate to form little gel packets and then freeze as low as you can get it.
It appears to spread out the hard 32F freezing point so that it absorbs heat
at a fairly even rate. Far better performance than Blue Ice or any of the
other reusable packs.

Last month, May 30 at 8PM to be exact, I packed 12 pounds of steaks, a
Honey Baked ham and 8 pounds of shrimp, all hard frozen in a 58 quart
Coleman Ultra Xtreme marine cooler with 4 sheets of Technice on top and a
beach towel on the bottom. The next morning it was checked on an airline to
St. Thomas where it was lost for 3 days somewhere between Atlanta and Ft.
Lauderdale. The cooler was delivered to West End, Tortola and unpacked on
June 3 about 1 PM and everything was still frozen solid.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"cavelamb" wrote in message
news

Anyone out there use dry ice for refrigeration?

I want to keep the cooler cooler longer.


A couple pounds of dry ice seems like a good idea,
but how to use it?

Mix with wet ice?

Or keep separate?

Richard

On Sat, 1 Jul 2006 22:11:56 -0400, "Glenn Ashmore"
wrote:

The next morning it was checked on an airline to
St. Thomas where it was lost for 3 days somewhere between Atlanta and Ft.
Lauderdale. The cooler was delivered to West End, Tortola and unpacked on
June 3 about 1 PM and everything was still frozen solid.

===========

That 's impressive.

Where do you get the Technice?

I found the best price on ebay. There is a guy on there that sells it.
Apparently pretty reliable because I have suggested him to several people,
all of whom have been very happy with his shipping. The proper term is
"Techni Ice" . In my testing the Techni ice only lasted about 30% longer
than water ice but the temperature averaged about 15F lower. Frozen to 0F
it absorbs about 152 BTU's per pound compared to 176 BTU per pound of water
ice but water ice only absorbs 1 BTU per pound until it gets to 32F and
starts to melt. The gel in Techni Ice starts melting at a lot lower
temperature and is pretty well all melted by the time it reaches 32F.
Apparently it also will absorb more than 1BTU/pound when it is frozen to
very low temperatures although I don't fully understand the physics yet.

The other part of the performance is the Coleman Ultimate Extreme cooler.
It is exactly 1" under the maximum size you can check on an airline and is
about the best insulated mass produced cooler on the market. The "marine"
version cost about $10 more than the regular model but the only real
difference is that it is all white and has an extra set of rope handles
which can handle the rough treatment of baggage handlers. The 50 quart
wheeled model that Wal-Mart carries is nothing like as good.


I keep 5 or 6 sheets in the freezer and just turn the freezer side down to
the lowest setting about 4 days before a trip. All the food goes in Ziploc
bags in the freezer for 3 or 4 days to get it as cold as possible and I pack
the cooler completely full. A towel on the bottom adds a little insulation
to the coldest area and any voids are filled with towels, extra bathing
suits, etc.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Wayne.B" wrote in message
...
On Sat, 1 Jul 2006 22:11:56 -0400, "Glenn Ashmore"
wrote:

The next morning it was checked on an airline to
St. Thomas where it was lost for 3 days somewhere between Atlanta and Ft.
Lauderdale. The cooler was delivered to West End, Tortola and unpacked on
June 3 about 1 PM and everything was still frozen solid.

===========

That 's impressive.

Where do you get the Technice?

Glenn - Water ice only holds .5 (or less) BTU/lb-degree, so cooling it
down to zero is only adding another 15 BTU per pound for a total of
159 BTU.

Glenn Ashmore wrote:
I found the best price on ebay. There is a guy on there that sells it.
Apparently pretty reliable because I have suggested him to several people,
all of whom have been very happy with his shipping. The proper term is
"Techni Ice" . In my testing the Techni ice only lasted about 30% longer
than water ice but the temperature averaged about 15F lower. Frozen to 0F
it absorbs about 152 BTU's per pound compared to 176 BTU per pound of water
ice but water ice only absorbs 1 BTU per pound until it gets to 32F and
starts to melt. The gel in Techni Ice starts melting at a lot lower
temperature and is pretty well all melted by the time it reaches 32F.
Apparently it also will absorb more than 1BTU/pound when it is frozen to
very low temperatures although I don't fully understand the physics yet.

The other part of the performance is the Coleman Ultimate Extreme cooler.
It is exactly 1" under the maximum size you can check on an airline and is
about the best insulated mass produced cooler on the market. The "marine"
version cost about $10 more than the regular model but the only real
difference is that it is all white and has an extra set of rope handles
which can handle the rough treatment of baggage handlers. The 50 quart
wheeled model that Wal-Mart carries is nothing like as good.


I keep 5 or 6 sheets in the freezer and just turn the freezer side down to
the lowest setting about 4 days before a trip. All the food goes in Ziploc
bags in the freezer for 3 or 4 days to get it as cold as possible and I pack
the cooler completely full. A towel on the bottom adds a little insulation
to the coldest area and any voids are filled with towels, extra bathing
suits, etc.

Lets look at the safety of both suggestions.

1) Nitrogen liquid will boil to gas. The gas is an asphyxiate. Many people
have died from nitrogen. Air contains 21.5% O2 mostly the rest is N2. If
you breath pure N2 the first breath you pass out and the second breath brain
damage and the third death. Think about passing out when reaching for
something in the ice chest. If you fall in your dead; if you fall out you
will probably be ok. The next day you will be ripping out your N2 system.
A closed boat can accumulate N2 which will displace air. Maybe get you in
your sleep or when you go down for a cold one.

2) CO2 is heaver then air and would accumulate in the low parts of the boat.
Same issue as with N2 but it would at least give you some warning signs.

Whats wrong with a little water from melting ice. You are on a boat
right???





"Jeff" wrote in message
. ..
Glenn - Water ice only holds .5 (or less) BTU/lb-degree, so cooling it
down to zero is only adding another 15 BTU per pound for a total of 159
BTU.

Glenn Ashmore wrote:
I found the best price on ebay. There is a guy on there that sells it.
Apparently pretty reliable because I have suggested him to several
people, all of whom have been very happy with his shipping. The proper
term is "Techni Ice" . In my testing the Techni ice only lasted about
30% longer than water ice but the temperature averaged about 15F lower.
Frozen to 0F it absorbs about 152 BTU's per pound compared to 176 BTU per
pound of water ice but water ice only absorbs 1 BTU per pound until it
gets to 32F and starts to melt. The gel in Techni Ice starts melting at
a lot lower temperature and is pretty well all melted by the time it
reaches 32F. Apparently it also will absorb more than 1BTU/pound when it
is frozen to very low temperatures although I don't fully understand the
physics yet.

The other part of the performance is the Coleman Ultimate Extreme cooler.
It is exactly 1" under the maximum size you can check on an airline and
is about the best insulated mass produced cooler on the market. The
"marine" version cost about $10 more than the regular model but the only
real difference is that it is all white and has an extra set of rope
handles which can handle the rough treatment of baggage handlers. The 50
quart wheeled model that Wal-Mart carries is nothing like as good.


I keep 5 or 6 sheets in the freezer and just turn the freezer side down
to the lowest setting about 4 days before a trip. All the food goes in
Ziploc bags in the freezer for 3 or 4 days to get it as cold as possible
and I pack the cooler completely full. A towel on the bottom adds a
little insulation to the coldest area and any voids are filled with
towels, extra bathing suits, etc.

On Sat, 01 Jul 2006 04:29:08 GMT, cavelamb
wrote:


Anyone out there use dry ice for refrigeration?

I want to keep the cooler cooler longer.


A couple pounds of dry ice seems like a good idea,
but how to use it?

Mix with wet ice?

Or keep separate?

Richard

The CO2 evolved from dry ice is too cold for chilling food and drinks
directly, but it can keep the water ice from melting so quickly.
This suggests a cooler within a cooler - the inner cooler giving
off CO2 gas which bubbles through a water ice mixture, which chills
the food container.

Dry ice provides a tidy explosion if its vapor has nowhere to go, and
it is not a good breathing gas - but at least it gives plenty of
warning - we are designed to pant if the CO2 proportion rises
(unlike low O2 which induces unconsciousness with no warning at all.)

You might take a look at the electric cooler boxes. Either way,
expanded polystyrene is an excellent insulation.

Brian Whatcott Altus OK

I have routinely taken a half gallon of ice cream on our Kayak
excursions. It is inside a smaller lunchbox size cooler with about 5
lbs of dryice on top, and that cooler placed inside another cooler.
Works great. The only problem has been that the ice cream was sometimes
still frozen (after 3 days) too rock hard to dispense. It hat to sit
out for thirty minutes to get a scoop in it.

I doubt it's advantageous to use dry ice for a longer cooler duration.
Three days seems to be the maximum. But if you want to keep things
frozen, it's perfect. It's available around here in any local grocery
store, from a special "Dry Ice" freezer by the entrance.

Brian Whatcott wrote:

On Sat, 01 Jul 2006 04:29:08 GMT, cavelamb
wrote:


Anyone out there use dry ice for refrigeration?

I want to keep the cooler cooler longer.


A couple pounds of dry ice seems like a good idea,
but how to use it?

Mix with wet ice?

Or keep separate?

Richard


The CO2 evolved from dry ice is too cold for chilling food and drinks
directly, but it can keep the water ice from melting so quickly.
This suggests a cooler within a cooler - the inner cooler giving
off CO2 gas which bubbles through a water ice mixture, which chills
the food container.

Dry ice provides a tidy explosion if its vapor has nowhere to go, and
it is not a good breathing gas - but at least it gives plenty of
warning - we are designed to pant if the CO2 proportion rises
(unlike low O2 which induces unconsciousness with no warning at all.)

You might take a look at the electric cooler boxes. Either way,
expanded polystyrene is an excellent insulation.

Brian Whatcott Altus OK

Well, I asked, didn't I.

Thanks to all for the information.

As it worked out a couple or three pounds of dry ice in one corner of the
ice chest kept the rest of the wet ice well frozen for three days. (!)

I think the wet ice is acting as insulation to protect the food stuff from
the dry ice - depending on how close stuff is to the dry stuff.

My boat is an 18 foot Capri (Catalina) so we don't have a lot of room to
play with. But with the companionway open at all there doesn't seem to be
much danger from CO2. There is just not enough dry ice in the box to make
much CO2 very rapidly (as was pointed out several times).

BUT! It really does keep the cooler cooler longer...

Thanks folks,

Richard

On Thu, 06 Jul 2006 16:41:41 GMT, cavelamb
wrote:

I think the wet ice is acting as insulation to protect the food stuff from
the dry ice - depending on how close stuff is to the dry stuff.

That is exactly the right way to use dry ice in a cooler box.
Otherwise there are problems with things that come in direct contact
such as beverage cans which will quick freeze and rupture.

The one exception is carboard juice boxes which don't seem to mind
being frozen, and actually make an excellent ice substitute if frozen
in advance.