On Sat, 01 Jul 2006 10:09:07 +0100, Chris Newport
wrote:

Hmmmm - Carbon dioxide in a boat.
Darwin removes any idiots who try this from the gene pool, hopefully
before they breed and produce more idiots.

Boats on distance races have been using dry ice on frozen foods for a
long time and I have never heard of any problems. The quantities are
small and the evaporation rate low. We used two different approaches:
one was to put it in the bottom of the ice box under the blocks of
water ice to extend their life, and the second was to pack a prefrozen
meal in a styrofoam cooler packed with a block of dry ice.

Chris wrote:
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?

Wrong. You should look up the Heat Capacity of cold ice. Its only
0.5 BTU/lb-degree at freezing, but it goes down so that by -50 F its
only 0.4.

Since the Heat of Fusion is 144 BTU/lb, sub-cooling even 100 degrees
only adds a small amount of cooling capacity.

Hardly 'hadly effective'.

No, its hardly effective.


And yes, twice as much ice also works, but we knew that.
That's why I recommended to carry an extra cooler w/ ice,
not a lab freezer. But I am sure a liquid nitgrogen cooler
would be practical fo use on a boat, too.


Richard J Kinch wrote:
Chris writes:

IF you want to go high tech and do have access to lab freezers (where
else would you get dry ice..., you can also 'supercool' your normal
ice before the trip. Ice at -70 C will last a lot longer than at -3 C,
with no extra weight.
For water, the heat of fusion is about 80 times specific heat, so
supercooling ice is hardly effective. You're much better off just using a
little more ice.

Dry ice is no good for refrigeration because it is too cold and difficult
to regulate to a higher temperature. By the time you build a contraption
to regulate the chill, you've lost any weight advantage over ice, assuming
you don't need sub-freezing temperatures.

I remember as a child seeing another child severely injured at my dad's
company picnic. Someone brought popsicles in dry ice, the kid got into
them, and took a lick.

Liquid nitrogen is a more practical wasting refrigerant since the liquid is
easy to throttle. That's what some reefer trucks use.

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.

OK, let's look at the fallacies of both your scenarios:

Rick wrote:
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.

GROSS exaggeration. This assumes you purge *all* the lung volume with
each breath (when it's typically only about 30% or less) and that there
are no O2 reserves in circulating hemoglobin or stored myoglobin.
Neither is the case. It also assumes (at 12-15 breaths per minute) that
brain damage occurs in 10-15 seconds. Right.

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.

N2 evaporation does not *displace* air, it dilutes the O2 concentration.
For a sleeping individual, oxygen concentration does not become
dangerous until it reaches about 10%. That means you'd need to
evaporate sufficient N2 to equal the volume inside the boat, and you'd
have to do it without ventilation. Not very likely. My boat doesn't
hold 30 PSIA, does yours?

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.

It gives exactly the same warning signs as N2. No more, no less. You'd
require the same volume of subliming CO2 as evaporating N2 to cause O2
deprivation issues.

Bottom line, you must have ventilation in any sleeping environment. You
exhale CO2, you'll recall, so you'll die in a sealed box or without
subliming CO2 or evaporating N2. That's just common sense.

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

I don't use CO2 in my boat, but I've been using it for years in my
Vanagons' Dometic NH3 "refrigerator", and it's posed no problems. I put
in about 2 lbs which lasts about 3 days. 2 lbs sublimes to about 510
liters, in a van with an interior volume of approx. 6800L. When you do
the math, that results in a total O2 dilution of 7.5%, or a final O2
concentration of 19.9% which is well above OSHA's TEEL limit of 19.5%
for a confined space entry. This again assumes that no ventilation
occurred over the 3 days.

When you do the math, it just isn't a problem when using any reasonable
amounts, and with only normal ventilation (which should *always* be
ensured under *any* use conditions).

Keith Hughes

Hey it sounds like we got a volunteer.

I personally know of 2 deaths due to folks breathing N2. Thats pure N2.

"Keith Hughes" wrote in message
...
OK, let's look at the fallacies of both your scenarios:

Rick wrote:
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.

GROSS exaggeration. This assumes you purge *all* the lung volume with
each breath (when it's typically only about 30% or less) and that there
are no O2 reserves in circulating hemoglobin or stored myoglobin. Neither
is the case. It also assumes (at 12-15 breaths per minute) that brain
damage occurs in 10-15 seconds. Right.

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.

N2 evaporation does not *displace* air, it dilutes the O2 concentration.
For a sleeping individual, oxygen concentration does not become dangerous
until it reaches about 10%. That means you'd need to evaporate sufficient
N2 to equal the volume inside the boat, and you'd have to do it without
ventilation. Not very likely. My boat doesn't hold 30 PSIA, does yours?

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.

It gives exactly the same warning signs as N2. No more, no less. You'd
require the same volume of subliming CO2 as evaporating N2 to cause O2
deprivation issues.

Bottom line, you must have ventilation in any sleeping environment. You
exhale CO2, you'll recall, so you'll die in a sealed box or without
subliming CO2 or evaporating N2. That's just common sense.

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

I don't use CO2 in my boat, but I've been using it for years in my
Vanagons' Dometic NH3 "refrigerator", and it's posed no problems. I put
in about 2 lbs which lasts about 3 days. 2 lbs sublimes to about 510
liters, in a van with an interior volume of approx. 6800L. When you do
the math, that results in a total O2 dilution of 7.5%, or a final O2
concentration of 19.9% which is well above OSHA's TEEL limit of 19.5% for
a confined space entry. This again assumes that no ventilation occurred
over the 3 days.

When you do the math, it just isn't a problem when using any reasonable
amounts, and with only normal ventilation (which should *always* be
ensured under *any* use conditions).

Keith Hughes

Would you mind doing the math for
10 lbs of -70 C ice,
10 lbs of 0 C Ice, and
10 lbs of 0 C water?
I don't have the temp dependent specific heat curves.

Thanks,

Chris

Jeff wrote:
Chris wrote:
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?

Wrong. You should look up the Heat Capacity of cold ice. Its only
0.5 BTU/lb-degree at freezing, but it goes down so that by -50 F its
only 0.4.

Since the Heat of Fusion is 144 BTU/lb, sub-cooling even 100 degrees
only adds a small amount of cooling capacity.

Hardly 'hadly effective'.

No, its hardly effective.


And yes, twice as much ice also works, but we knew that.
That's why I recommended to carry an extra cooler w/ ice,
not a lab freezer. But I am sure a liquid nitgrogen cooler
would be practical fo use on a boat, too.


Richard J Kinch wrote:
Chris writes:

IF you want to go high tech and do have access to lab freezers (where
else would you get dry ice..., you can also 'supercool' your normal
ice before the trip. Ice at -70 C will last a lot longer than at -3 C,
with no extra weight.
For water, the heat of fusion is about 80 times specific heat, so
supercooling ice is hardly effective. You're much better off just using a
little more ice.

Dry ice is no good for refrigeration because it is too cold and difficult
to regulate to a higher temperature. By the time you build a contraption
to regulate the chill, you've lost any weight advantage over ice, assuming
you don't need sub-freezing temperatures.

I remember as a child seeing another child severely injured at my dad's
company picnic. Someone brought popsicles in dry ice, the kid got into
them, and took a lick.

Liquid nitrogen is a more practical wasting refrigerant since the liquid is
easy to throttle. That's what some reefer trucks use.

So where did these folks find that pure N2? Sure not
in the bilge of a boat, because it mixes into the air
readily. It does not 'displace air'.
And yes, any gas mix without oxygen will kill you
if breathed from a bottle for a few minutes. That
doesn't have to do anything with fridges.


Rick wrote:
Hey it sounds like we got a volunteer.

I personally know of 2 deaths due to folks breathing N2. Thats pure N2.

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