

  • 4
  • @BigGeneral Give us anything you got ;) Though the problem with an experiment is for it to be conclusive, you would need many replicates... and this bounty only has a 6 days left. – Lost Feb 9 '12 at 1:04

18 Answers 18






Coleman agrees:







  • 8
  • 2
  • 2
  • 1
    @theUg, that experiment was about the quickest way to cool a 6-pack of beer. – Tom Collins Oct 26 '14 at 14:35





Results. Temperature data is shown in the figure below.

Cooler Results Figure



  • @KentFisher how bout them pictures? – nhinkle Oct 27 '14 at 16:26
  • 2
    Why is there a visible difference within the first hour from the experiment start? – Roflo May 6 '15 at 20:24
  • I had to sign-up just to upvote this. @Roflo --- I think that this is due to unavoidable errors like the different temperature of the store-bought ice, so I think that the results could be even more on the side of not removing the ice --- you could probably almost shift the red line up so that it coincides with the black one in the first hours. – Rmano Jun 20 '15 at 10:41














  • 1
  • 2
  • It's not easy (for me) to agree that "the amount of heat entering the cooler is basically the same whether you drain or don't drain". Water has much higher thermal conductivity compared to air, so I expect more heat (per unit of surface area) to enter the water touching the sides of the cooler than to enter air touching the sides of the cooler. The starting conditions are also unusual: you are comparing a cooler with 1 lb ice and no water to one with 1 lb ice and 1 gallon (~8 lbs) of water starting out at zero. So 9 times as much cooling "stuff" in the second cooler! – BeeOnRope Apr 27 '18 at 1:06
  • The real comparison should start out with the same amount of ice in both coolers, and no water, and then describe how the system evolves from there (i.e., the water all should originate from the ice). – BeeOnRope Apr 27 '18 at 1:07
  • To address the “water transfers heat faster than air” comments, consider all the heat comes in from the outside. The same amount of heat enters the closed box regardless of the contents inside. With the water inside, it absorbs more of that heat than air. This means less of that heat gets absorbed by the beer or food than if all of that heat warmed the contents. – bmike Aug 9 '18 at 22:48






More here

  • Actually I asked "as cold as possible for as long as possible"... I want it all ;) – Lost Feb 8 '12 at 4:13
  • 1
    +1 for "replacing the water with warm air" -- never really considered that either. – Lost Feb 8 '12 at 4:17
  • 2




  • Don't you put your sandwiches in ziploc baggies? For extra water resistance, keep the bagged sandwiches on top of the ice. – wallyk Jul 25 '17 at 16:58







This is a great topic deserving of some controlled experimentation. In general the system is non-linear, but can be analyzed in a piece-wise linear fashion the same way many other difficult problems are approached. Some thoughts on the matter;

  1. conduction not convection, is the main transport mechanism,

  2. cold does not exist, only the absence of heat,

  3. heat transfer is a function of temperature difference between the inside and outside of the cooler, cooler thickness, thermal conductivity (w/m-k) of the cooler material, and surface area of the cooler.

You can use Fourier's law of heat transfer to calculate how much heat in watts enters the cooler through its walls. As ice melts, it takes 3.3x10^5 joules/kg to do so. Remembering that a watt is a joule/second you can then calculate how long a given mass of ice will last. Heat, like electricity, takes the path of least resistance.

Water, at 24X the thermal conductivity of air, provides a low thermal impedance path for heat to reach the ice, so if a block of ice is sitting in a water bath it should melt at a faster rate. I would like to propose and experiment where the ice and melt water in one cooler are kept segregated, and one where the ice and melt water are not.

At the time that the ice is completely melted, the two systems are the same in mass and phase (all liquid) but perhaps not temperature or even at the same time. Then its a different process, but with different initial conditions (temperature). There are some variables which have to be controlled in order to see the effects of draining vs not draining the water, namely ambient temperature has to be monitored and kept the same for both, admitting outside are into the system has to be eliminated, the coolers must be identical, the mass of the ice has to be measured.

Leave the system undisturbed, measure the inside water and air temperature at as many places as possible using thin thermocouples and a digital thermometer. Allow the experiment to run well past the expected lifespan of the ice. Some sort of viewing port capability would be helpful to examine the state of the ice without perturbing the system.


The thermal conductivity of air is 0.000057

The thermal conductivity of water is 0.0014




See this fine article about cooler packing and draining.

  • 6
  • 2
  • 4
  • 6
  • 3


  • Sure, draining the cold water is "bummer" - but that's not the only effect. You have to also consider the effect of the water the other 99.9% when the cooler is closed: it conducts heat better so probably increases the amount of heat entering the cooler. – BeeOnRope Apr 27 '18 at 1:13

As Dangeranger stated,

water is 24.5 times more conductive than air














  • 1
  • 5
  • 1
    At meltB, if (as you are saying) there is less heat energy in cooler B, the ice will NOT be all melted unless it was already fully melted in cooler A. It takes the exact same amount of energy to melt the exact same amount of ice, regardless of conditions. – Kevin Feb 12 '12 at 18:50

Removing water from the cooler always means the ice lasts longer - solid (ice) transfers heat slowest, then gas (air inside cooler), then liquid (melted ice). This is explained by the Zeroteh Law of thermodynamics. All three work to achieve equilibrium by becoming the same temperature. Remove the fastest heat-transferring part and your ice lasts longer. The classic experiment is placing an ice cube in a mesh bag and suspending it with string and lever over a clear glass containing cold water. Notice the ice melts faster where it is submerged than in the air. The air insulates the thin layer of melted ice above, but the liquid quickly exchanges heat with the ice to melt it, until all are in equilibrium. Using the drain to remove the melted water means more insulating air and solid ice in the cooler to maintain cold contents, and longer lasting ice.








It depends.

A simple fact: You conduct HEAT. You do not conduct COLD. Wrap your head around that.

2nd Simple Fact: Water conducts HEAT more efficiently than air.

Now, if you're trying to chill warm items, then use water to conduct the heat out of them and transfer it to the frozen water (ice). That will chill them quicker than just air.

However, if you're trying to keep chilled items cold, you want to prevent the transfer of heat from the environment (via the outside skin of the cooler, across the insulation or air gap, through the interior skin) to the items. In this case, air is the best choice; drain the water.

So, you catch a fish. Quench it quickly in one ice chest with ice and water to get it chilled, then put it into an ice chest with the ice kept separate from the contents and with the water drained.

  • The problem with this logic is that it takes less heat energy to re-warm a fish than the fish and several gallons of water. So if the heat is flowing in at the same rate with and without the water, keeping the water keeps the whole system cool longer. – Kevin Mar 1 '16 at 18:00
  • The heat flows (out of the fish) faster with the water. And flows (back in) to the fish slower with air. – Tank Mar 1 '16 at 20:57
  • Heat only flows back into the fish if there is a temperature difference. With a fish in water at the same temperature, there is no heat flow back in from the water directly. The heat flows into the cooler (fish or fish+water) at a rate dependent on the temperature difference (inside vs. outside). The temperature change due to heat flow is dependent on how much there is to heat. Thus, the heat flowing into a cooler takes much longer to heat both the fish and water than just the fish. – Kevin Mar 1 '16 at 21:12
  • The conductivity of water is roughly 24 times that of a similar volume of air. The water AIDS the conduct of heat...it does not impede the conduct of heat when compared to air...engineeringtoolbox.com/thermal-conductivity-d_429.html – Tank Mar 3 '16 at 19:46
  • 2
    Yes, but that's irrelevant to what I'm saying. The rate of heat flowing into the cooler is determined solely by the temperature difference between the inside and the outside; water's higher thermal conductivity just means the temperature inside equalizes more quickly. Because water has a higher specific heat, it will take more heat energy to warm the water's temperature. Since the rate of heat flowing in is the same, the water's temperature, and therefore the fish's, will rise more slowly. – Kevin Mar 3 '16 at 20:06

It is so not true that water mixed ice keeps food cold. Try your own experiment and see that it is true. This is exactly how you make ice cream, but just with some salt. Here is how you do it: 1) Buy your cooler according to size. Dont buy a cooler that it too big. 2) Fill the cooler with pre-chilled items. Try and reduce the air space as much as possible. This will dramatically extend the 'cold' 3) Top off with ice. 4) The Ice Melts. 5) Melted Ice turns to water and carries off heat. 6) Drain the warmer melted water. Heat goes right out the drain tube. Ice remains colder for MUCH longer. Half a day over my 3 day weekends. NOTE...This is a mostly closed system. Neither 'Dried' (Not Dry Ice...but not wet ice) nor water/ice slurry works well when kids are always leaving the lid open and warm air blows in.


The consensus around the people i travel with is varied and the best answer to this is "it depends".

Keep the water in - Keeping the water in does add thermal capacity but it's not as good as ice. Water absorbs about 1 BTU/lb/F. When all the ice has melted the cooler will start warming immediately, the water will absorb heat at that rate. I would call "Cold" somewhere below 45F, so 1lb of water will absorb about 13 BTU's while it's warms up from 32F. When ice melts, it absorbs about 144BTU/lb(enthlapy of formation) at a constant 32F temperature so keeping the water in the cooler gives another 9% thermal capacity before the cooler reaches 45F. There are a couple of factors that may lessen this 9% such as the ice will melt a little faster since it's sitting in a bath of water(the heat transfer from the remaining ice to the inside cooler wall will be higher when bathed in water) but it depends.

Also you will have cooler soup when you leave the water in. If this is your food cooler, i don't think it's worth keeping the water in. If it's your beer/drinks cooler than i don't think it's a bad idea to leave the water in.

Drain the Water - Well for one, you avoid making cooler soup. Also the ice will last a longer time for a couple of reasons.

Heat transfer from the ice to the cooler wall will decrease.(Warm air will displace the water however the effect minuscule, even really hot 90F, humid 90%RH, air will add about 0.04 BTU/lb of water displaced. Considering ice absorbs around 144BTU/lb it's about a 0.03% impact so i'm going to ignore that effect). Water has a huge thermal capacity and conductivity compared or air. Heat transfer from the ice soaking in water to the cooler wall is relatively perfect convection and conduction from the ice to inside of the cooler wall. Especially if the water is moving at all, like sloshing around on a boat or in a car. Air on the other hand, is a very poor conductor and has pretty terrible thermal capacity compared to water on a volume basis(a pound of air takes up about hundred gallons while a pound of water is only a pint).

How much longer the ice will last depends on the cooler, conditions and some really complicated heat transfer theory. Making an educated guess that draining the water would increase the insulating ability from the ice to the outside by a 0.5 r-value.(if anyone is interested and able to come up with a full scale transfer model of the inside of a cooler please do, i would love to refine this estimate) A typical 1 inch foam cooler(think $25-30 cooler) with an r-value of 5, the ice will last about 10% longer draining the water. However if you have a 2-3inch rotomolded cooler(think $300+ cooler) than you looking at only a 3-5% increase in ice lifetime. That's less than the 9% increase you get from warming up the cooler soup!!

Don't worry too much about exactly how much longer you can keep things cold since it really don't make a huge difference. I subscribe to the drain the water theory since it assures my cooler is always getting lighter and i don't have a cooler full of soupy water. Lugging around a warmish brew of old food and beer water effin sucks.

PS. I'm relatively confident in my numbers but if anything i have here is orders of magnitude wrong than please post and update.



  • 3

One test I've done was to fill two cups with partly ice and emptied one cup every 5 minutes. The ice in the cup that was emptied of its water lasted longer than the ice that sat in the melted water. Showed easily the best way to make ice last longer. Seems it could be a different story if your aim is to keep the cooler temperature colder for longer. But if I'm keeping food cool I like to keep it relatively dry.

protected by Reinstate Monica Aug 8 '18 at 20:42


Would you like to answer one of these unanswered questions instead?
