Keeping the ice chest cold

[floattuber]

Not a terribly important subject but I thought it would be a fun one.

To keep the ice chest cold on extended camping trips do you want to empty the water from the melting ice or keep it in there?

My thoughts are to keep the cold water in the ice chest because the sun has to heat up the mass of the water and the ice. But the flip side is that water is a better conductor of the heat so it ends up melting the remaining ice faster.

 

[unclesyd]

My hand crank ice cream maker uses brine instead of water and the object of the game is to transfer as much energy as possible in as short of time as possible.

I remember a thermo quiz problem on the cooling of a champagne bottle. You kept the water and ice mixture, slush and the problem was determine the optimum speed to turn the bottle for fastest cooling and a certain end point and how long would it take to achieve the same end point without turning.

With fish you let the cold water run over the fish while minimizing the heat transfer through the walls.

 

[magicme]

unclesyd

as a Hemingway fan, i hate to disagree with a deep sea fisherman, but i have to stand by what i said earlier .... keep the water until it's warmer than you want the beer (or fish) to be ..... as long as the water colder than that temperature, it is keeping the beer (fish) cool.

i'd like to prove that but i usually finish the beer before the ice melts ;>)

magicme

------------------------------------
there's no place like gnome.

 

[jbwick]

Some more food for thought. The specific heat of the components will factor heavily into an analysis of this.

Air 1000 kJK/kg
Liquid H2O 4000 kJK/kg
Solid H2o 2000 kJK/kg

(approximate values)

 

[btrueblood]

I agree with IRstuff & others, if the goal is to keep cold beer cold for as long as possible, conserve the ice by draining the water to reduce the conduction/convection heat transfer from the internal wall to the ice. Another good reason is outlined in the fishy part below, changing "fish juice" to "residue from unwashed hands".

OTOH, if the goal is to rapidly cool warm beer, leave the water in (to keep the convection/conduction to the bottle high)(note also that no drinkable beer comes in a can) until the beer is cold enough to drink, then drain the water out.

Heat capacity: the heat (cold) capacity of water is 1/80 the heat capacity of ice, due to the heat of fusion (80 cal/g ice vs. 1 cal/g water). Until the ice melts, the temp. of the ice/water bath remains at 32 F/0 C, and the water contributes nothing from its heat capacity, since its temperature never changes.

Fish: keeping the fish out of water is best, but the more important reason (besides keeping ice icy longer) is that melting ice yields fresh, pure water. Fishies, even fresh-water fishies, have a saline fluid in their bodies. Soaking a cleaned (dead) fish in fresh water causes its internal, um, juices, to continually leach out of its tissues due to osmotic pressure (note that living fish have cellular mechanisms to resist this effect), the result is the fish's flesh gets soggy and limp, and its eyeballs sink, two signs that most people use to say whether a fish is "fresh" or not. Secondly, the leaching fish fluids make a lovely protein-rich bath for microbes to multiply in, resulting in your fish smelling fishy (the third way people determine fish freshness).

Say this 3 times fast: "leaching fish fluid makes fish smell fishy".

Grant proposal: I believe on the whole, the order of magnitude of drained vs. undrained ice retention time differences would be small, for an average-sized cooler on an average summer day. I further submit that everyone reading this post should pony up $1 US, and I will gladly conduct a side-by-side comparison test, with temperature-instrumented coolers and two cases of bottled microbrew; test protocol would involve removing one bottle from each cooler per 30 minute elapsed time interval, and recording temperatures of the fluids prior to their, ahem, disposal. The test would probably need to be repeated on a second day, swapping coolers, to avoid having a defective cooler skew the results, therefore make it $2 US.

 

[unclesyd]

If I were going fishing I would have to sign up magicme as greenhorn, a provisional half share and btrueblood as first hand (icer), at 1 1/2 share.

 

[MintJulep]

I happen to have access to some nice multi-channel temperature loggers, and would be willing to lease them to the research project at a discount rate.

I would also be willing to assist with the disposal of the waste test fluid.

 

[pmover]

i'll probably get spanked for this posting, but what the heck . . .

why don't you folks just move to alaska where keeping the "refreshments" above freezing is needed in order to enjoy them.

now to my answer, air has a lower coefficient of heat transfer than water does, yes, temp difference between the cooler inside and the atmosphere will be the driving force of heat transfer. a btu is a btu, so to keep cool items cool in a cooler, it is no different than the refrigerator. remove the water. to cool a warm object, cool in water and then place in cooler without water, but with ice.

enjoy!
-pmover

 

[floattuber]

Hah, this thread is turning out pretty good. I still need to thoroughly read through the posts, but there is a well meaning tangent starting to form. While the goal of rapidly cooling down a beverage is a noble one, in this case an extended camping or fishing trip (let's say 3+ days) would dictate the beverages would be cooled in the fridge before the trip in order to preserve the ice as long as possible.

Therefore, to re-iterate, the goal is to conserve the ice as long as possible.

I had access to a multi channel data logger at my previous job but not here. I think I'll run a test with two identical cups, some ice and a manual data logger (aka me).

 

[unclesyd]

I have a friend that managed an ice plant that supplies at lot the corner markets and spirit stores, lot of both, in this area. He has mentioned to me sevral time that he took a hit on bag ice sales we the stores started selling cool case beverages. A lot of the stores now have self service walk in coolers which really hit the ice sales. His worst enemy was the chain grocery stores their own brand of ice and the large display of cool cases.

KEEP YOUR ICE DRY

 

[jte]

As unclesyd mentioned, "keep your ice dry." So, to add another tangent, my local grocery store has two freezers. One for ice at ordinary cost, and another for dry ice at something like 3x more cost. So... is it worth it to get the dry ice?

jt

 

[IRstuff]

Of course, it's dry.


And it doesn't get wet like regular ice.

TTFN

FAQ731-376

 

[Clyde38]

Why not use both? As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice.

 

[floattuber]

jte, the advantage of using dry ice is that you can keep things frozen, like ice cream. You can't do that with normal water ice.

If you combine dry ice and water ice I assume you'd have to keep them seperated? Otherwise the water will melt the dry ice really fast and you'd just have a fog machine on your hands.

 

[unclesyd]

floattuber,

We use wet ice to keep stuff frozen on the larger fishing boats. We have pens where we stack frozen boxes of bait. We essentially use the wet ice for insulation of the frozen bait.
We do the same for food stuff but take the liberty to drop the temperature of the food to -40F prior to packing in ice.
This will keep stuff frozen for about 20 days if the pens are not opened but once a day.

After twenty days the bait gets salted and the crew eats can goods.

Before the advent of those little blue thingies we would ship fresh seafood with dry ice. There have been shipments to Japan using dry ice.

 

[floattuber]

Yeah, but that doesn't work with a normal size ice chest and all the practical things like non-frozen food that must also be included in the same ice chest. Ice cream will melt in about a day.

 

[BruceTS]

This is an easy one, from actual testing without a doubt draining the water will make the ice last the longest. I once thought that keeping the water was the way to go, but from experience, draining the water made the ice last longer on my offroad trips.

Now why is this possible? one thing that nobody has mentioned is the effect of ice and water sloshing around in the chest. What does this do? it causes the water to become colder than ice sitting still in water. Similar to adding salt to make the water colder than the ice.

When I used to leave the water in the chest, I would have to add an additional bag of ice daily to keep things cool. By draining the water, I was able to go 3 to 4 days before adding an additional bag. Without water, there is no movement, so there is a siginificant reduction in heat transfer.

 

[unclesyd]

I'm running a test tonight. About an hour ago a buddy brought me a 48 quart cooler filled with 15-16 count shrimp, "White", caught in Pensacola Bay today. It is so hot here that taking I didn't want to take any chances keeping the shrimp overnight until I can head them.
Some are in my cooler that has tabs on the feet to prevent wear and also as stated above keep the box off the deck.
It also has a wood grate in the bottom.
The other is a standard 48 quart cooler with no adornments.

Both will drain to dismay of the neighbor's cats. So I'll have a check in the morning a which is the best.

 

[Getrdun]

The solution ...
don't use ice, frozen beer works great(efficient as well)
Take one ice chest for each day
Put frozen beer and food into chest and duct tape all seams
As long as no one takes a peep inside, and the cooler stays in the shade you can enjoy a cold beer and sitting in your lawn chair on the border a full week after departure

... Have fun

 

[FiltrationEngineer]

Here's my take:

You use ice to take advantage of the latent heat of melting. The temperature in the inside of the cooler should be zero C until all ice has melted.

Assumption: the R value of the insulation is >>> than the difference in convective heat transfer between the inside wall of the cooler & water and inside cooler & air or the convective heat tranfer between the ice and the water.

If my assumption is true, the heat transfer from the cooler is mostly insulated by the cooler insulation, not by the difference in convective heat transfer between water & cooler or air & cooler. If you leave the water in the cooler, once all the ice melts, you are left with zero C degree water that must be heated. Water has a very high heat capacity compared to almost any other substance (such as air). So I say you leave the water in.

 

[MortenA]

BruceTS has observed what i think is the explanation:

It depends on wether you want ICE for as long as possible or if you want it cold as long as possible (im even sure the last case will ever win out to favour keeping the water) - here is why:

As long as the ice is COLDER than freezing (0 deg C sorry SI) then the "cold" comes from HEATING the ice. Once the ice starts to melt the cold comes from MELTING the ice. Now as many has said - the water increases the heat transfer - and propably A LOT! So in order to keep ice for as long as possible you should drain the chest continiously (a drain hole would propably be justifiably even though heat loss here is higher.

On the other hand - once all the ice is melted you still have the heat capacity from 0 deg C to say 10 deg C - that also count for someting but i think in most cases draining would be the way to go - unless you have VERY good insulation on the box.


Best regards

Morten