×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Keeping the ice chest cold

Keeping the ice chest cold

Keeping the ice chest cold

(OP)
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.  

RE: Keeping the ice chest cold

Buy two identical ice chests, try it, and report back.  Or suggest it to the Mythbusters.

RE: Keeping the ice chest cold

I'd say drain it.  Convective coefficient between water and inside wall is much higher than between air and inside wall.

Same reason a bottle of beer will cool much faster in a bucket of ice water than in the freezer.

RE: Keeping the ice chest cold

I've always kept the water because you are dumping cooling.  The ice chest is suppose to stop the heat transfer.

RE: Keeping the ice chest cold

I'd dump the water.  The increased thermal conductivity from the water simply makes it tougher for the ice chest itself to keep in the cold.  It would probably also help, a bit, to put the chest on a couple of rails, to limit the external thermal conduction.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Keeping the ice chest cold

Keep your ice in the plastic bag from the convenience store.  When it melts, the water does not make contact with the ice chest walls, so the convection with the inside wall does not change.

RE: Keeping the ice chest cold

keep the water up to a point because it takes longer to heat up that mass of water, then dump the water as soon as it's warmer than you want the beer to be.

keep a wet towel covering the cooler.... keep it wet.

magicme

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

RE: Keeping the ice chest cold

I suppose it would depend on the cooler design, and the relative contributions to total "R" of outside film coefficient, foam insulation, and inside film coefficient. Then there is the matter of separate areas for heat transfer: wetted and unwetted inside foam surfaces. The contact of water with the foam at the bottom of the cooler will provide a better coefficient (less R) for that part of the total area, but that part of the total R for that area may be insignificant. As long as there is ice and water, and the heat transfer is relatively slow, then the water and ice temperatures will stay at 0 C. Once the ice has just about melted, then having the mass of the water will be an advantage.

Better designs? Thicker foam at the bottom and partly up the sides to compensate for the water contact. An internal ice container, made of aluminum, to keep meltwater from contacting the foam. Of course, "better" depends on whether the purpose of the cooler is to cool things placed into the cooler or to keep cool things already prechilled before placement into the cooler. But the OP did specify "camping trip."

RE: Keeping the ice chest cold

Solution:

Drink all beer before ice melts...use a funnel if needed. have fun.

RE: Keeping the ice chest cold

iirc heat conduction through a wall (the cooler) is dependent only on the delta T. Then the heat transfer would be constant regardless of the contents. That being the case you would be better off with the water.

It would seem that the conductivity of the water would only be an issue if there were significant mixing of the ice-water-beer.

There are many variables to consider imo this would be an interesting science fair project for a young student.

RE: Keeping the ice chest cold

I vote dump the water. Air inside the cooler is a better insulator than water. There is more than convection on the outside of the cooler, condensation on the outside of the cooler seems to stay below the water line.

RE: Keeping the ice chest cold

Quote:

heat conduction through a wall (the cooler) is dependent only on the delta T

Only true if delta T is constant.  Air and water result in different delta T, since air, being less conductive, sucks up more of the delta T, leaving less delta T across the insulation.  This is the reason that double pane windows are more efficient at insulating.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Keeping the ice chest cold

  

Quote:

heat conduction through a wall (the cooler) is dependent only on the delta T

True if your boundary is the interior surface of the wall.

If we are considering the heat transfer out of the beer to the ambient air, then you have to consider the convective film coefficient.  Water's will be much higher than air.

RE: Keeping the ice chest cold

IRstuff are you suggesting that the cooler wall is permated by air or water depending on the contents of the cooler?

MintJulep I assumed at the intial state the contents of the cooler were at a uniform temperature and the ambient air is the higher temperature. Hence heat would travel from the outside and eventually to the beer.

All of the energy reaching the contents must pass through the wall. Granted the contents will eventually warm and the delta T will shrink but it will be slow (if the cooler is any good). So which can absorb more energy and increase in temperature the least?

RE: Keeping the ice chest cold

This is actually a non-trivial problem isn't it?  Transient, multiple heat transfer modes in parallel, as well as mass transfer.

Heat enters the cooler's exterior skin via combined convection, radiation and conduction if in contact with some solid such as the ground or a picnic table.

Passes through the exterior skin via conduction.

Passes to the insulation.  If we assume bonded closed cell insulation we can simplify to conduction.

Passes to inner skin, same simplified assumption.

From the inner skin:

Convection to the air.

Lets start with 100% ice, 0% water.  Conduction where the ice is touching the inner skin.

Conduction to any beer containers that may be in contact with the skin.

Radiation to ice and beer containers.

Ice begins to melt.

Add convection from skin to water, water to ice and water to beer containers.

Add radiation between water and inner skin, water and any ice that remains "high and dry", and between water and beer containers.

As the ice melts, the volume occupied by H2O decreases, leading to infiltration of warm outside air.

Obviously the initial conditions will affect all of this as well.

On thing is clear however, in summer conditions, by the time the system reaches a steady-state condition the beer will be too warm to drink (unless you are British).



RE: Keeping the ice chest cold

MintJulep has nailed the problem statement .... and it is far from a trivial problem (but a fun problem that would be a great lab project for a heat transfer course .... hmmmm)

magicme

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

RE: Keeping the ice chest cold

I'm assuming that the wall has either water or air on one side and air on the hot side.  When you do the 1-D heat flow path, you'll find that the interior air consumes more of the total delta T from the ice to the external air, therefore, there's less delta T across the insulation in that particular case, and therefore, there's less heat transfer.  

Using some typical, yet arbitrarily chosen, numbers, water results in 28 W/m^2 transferred through the insulation, while air results in 17 W/m^2 transferred through the insulation.  A difference in 10ÂșC in the delta T across the insulation between water and air on the inside.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Keeping the ice chest cold

IRstuff

it seems you are disregarding the masses (water versus air). it takes a lot longer time to change the temperature of a cooler filled with cold water than a cooler filled with cold air ... i did not run any numbers but i think that would offset the differences in conduction (water vs air).

i think mass is a big factor in this problem.

magicme

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

RE: Keeping the ice chest cold

I have solved the problem through Edisonian Research and astute observations. I don't go fishing on boats that don't drain the water off their coolers.

I do considerable deep sea fishing in the Gulf of Mexico with numerous extended trips of 2 to 4 days where the ice has to last. I drain the water off all coolers both large and small and use a wooden grid in the bottom of all coolers to insure they drain.

On the larger boat we go to great lengths to insure the coolers drain and that they are air tight and are only opened when it is required. On one of the boats we have a box that holds about 1500 pounds of ice and we can stay 4 days and still arrive with fresh fish. On the larger boat  we can carry about 60,000 pounds of ice and can stay about 20 days.

Anecdotal:
Several years ago I had an acquaintance that believed in keeping water in his cooler. While in a fishing tournament he caught a 22+ pound red snapper. He put the fish in his cooler and started for home. He broke down and had to be towed to the dock. While checking the fish at the scales the weigh master deemed that the fish had soured therefore it must have been caught before the start. All his ice had melted and and the warm fish soured in the 5 hrs it took to get to the dock. A 11 pound Red Snapper won the tournament and the $1,000 prize.

RE: Keeping the ice chest cold

let me rephase the question slightly, do you drtain the water off your homemade ice cream maker?  

The reason to drain the water off the ice in a boat iw weight and room (for the fish).

You drain water you are loosing energy unless the water is warmer than outside the box.

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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)

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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.  

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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

RE: Keeping the ice chest cold

(OP)
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).

RE: Keeping the ice chest cold

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

RE: Keeping the ice chest cold

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

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

(OP)
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.  

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

(OP)
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.

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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

RE: Keeping the ice chest cold

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.

RE: Keeping the ice chest cold

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

RE: Keeping the ice chest cold

OOPS missed a NOT in the 2 line should have said (im NOT even sure...)

Morten

RE: Keeping the ice chest cold

Why don't drink all the beer upfront? Like that you don't need the ice chest anymore...Like I say when I come across a bad wine:"The diffcult part is the first bottle"...

RE: Keeping the ice chest cold

(OP)
But then what do you drink for the rest of the week?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources