The turbo for your freezer
Wind-chill factor is the lowering of body temperature due to the passing flow of lower temperature air. The InnoChiller works by utilizing the effect from wind-chill.
A surface can exchange energy through these 4 different ways:
Conduction (energy exchange through solids such as glass or aluminium)
Convection (energy exchange through air or liquids)
Radiation (this is how we get the energy from the sun and why it feels hot standing close to a fire)
Evaporation (this is how we cool down our bodies, the sweat evaporates from our skin which cools us down)
The InnoChiller uses forced convection to create the chill effect, you can say that the InnoChiller is speeding up the energy exchange by increasing the airflow around the beverage and thereby improving the convection.
All objects are surrounded by a layer of stagnant air which acts like an insulator. Fast moving air disrupts this layer of stagnant air and allows colder air to get in contact with the surface of the object.
Disrupting this boundary layer is the sole purpose of the InnoChiller, this is why it speeds up the cooling and this is why it works.
The energy exchange step by step
Have you ever thought about what actually happens when the temperature changes while you cool down a beer in a fridge or freezer?
Let's use a warm beer as an example and discuss how the cold air from the freezer is converted into refreshing cold beer instead.
The temperature conversion takes place in 3 steps:
Convection from the cold freezer air through the boundary layer of stagnant air on the can
Conduction through the solid aluminum can that contains the beer
Convection from the aluminum through the stagnat beer on the inside of the aluminum can
So basically, convection --> conduction --> convection, three states where the energy is exchanged.
This is what happens when you cool down your beer in the freezer or fridge, and you should expect to wait +/- 50 min. or more before your beer has been cooled down from 23 C to 8C (73F to 46F) .
Why does it take so much time?
The reason why it takes approx. 50 min. to cool down the beer in a freezer is almost only related to the first convection step where the cold air from the freezer is passing the boundary layer of stagnant air around the beer can.
Air is insulating super effective, especially stagnant air which is how most houses are insulated.
The time it takes for the energy to convert through conduction of the aluminum, and the other convection through the stagnant beer, is not what causes much resistance in the process, both aluminum and liquid are pretty good heat conductors.
So we need to do something about the first convection step and the stagnant air to get cold beers faster, and this is where the InnoChiller comes to rescue.
Cool down in 9 min. with the InnoChiller
The InnoChiller makes it possible to cool down the can of beer in only 9 min. when used in a freezer.
Basically the only thing the InnoChiller does, is to "shave" the first convection layer of stagnant air thinner which thereby speeds up the cooling process.
The InnoChiller simply creates a high velocity air speed inside the compartment from a powerful fan installed in the back end of the unit.
Of course the InnoChiller still depends on an ambient temperature which is lower than the temperature you wish to achieve on your beverages, but it will always speed up the cooling time according to the temperature difference you expose the InnoChiller to.
So we have discussed convection and conduction, what about evaporation?
The way we humans can cool down in the hot summer heat, or when we exercise, is by sweating.
Water, or sweat, has a very high specific heat density and that's why it's extremely efficient in removing heat from the body.
When the body heats up we start to sweat and the sweat evaporates due to the heat the body creates. This effect works best on days with low humidity and that's also why heat can feel unbearable in areas with high humidity.
Chilling a can outside in the summer
You can actually utilize the effect from evaporation if you want to cool down a bottle of wine when you're out of ice cubes on the beach.
By wrapping a wet paper towel around the bottle you introduce a layer of water that can evaporate from the bottle and thereby create the chilling effect from evaporating the water.
This technique works best if the bottle is placed in the shadow and with some ventilation on a day with low humidity. This method is not particularly fast but it gets the job done if you're out of other options.
I have heard wrapping a bottle of wine with wet towel and put it in the freezer will cool it down in 5 min.
It has really shocked us to see how many people actually believe in this myth. However, it is easy to understand why some people misunderstands this concept, because if it works outside in the summer heat it must work even better inside a freezer, right?
Not exactly, let's talk about what happens when you put a wrapped wet towel around a bottle of wine and expose it to the conditions inside of a freezer.
Firstly the cold air inside the freezer cannot contain very much water and will soon be saturated with maximum amount of water vapor. This prevents the wet towel from evaporating and thereby defeats the whole purpose wrapping a wet towel around your bottle.
Secondly, by adding a wet towel to your bottle you actually insulate the bottle with one more layer of resistance, if the water can't evaporate. Besides, this introduces water into your freezer and makes frost to build up.
This means the heat transfer now need to go through 5 steps instead of only 3:
Convection from the cold freezer air through the boundary layer of stagnant air on the wet towel
Conduction through the wet paper towel
Convection through the stagnant water between the towel and the bottle
Conduction through the solid glass bottle that contains the wine
Convection from the bottle through the stagnat wine on the inside of the bottle
In some cases you might actually be lucky get some evaporation going inside your freezer which will speed up the process, but the difference is easy to overlook and some times the result is even worse when using the wrapped towel in the freezer, like John who actually managed to slow down the cooling time by using the towel hack, see more here:
Let's test it!
Because this myth is so widely misunderstood we think it's a good idea to make some tests to really show what is going on and to have some data to back our statement above.
We will make a total of 3 tests on both beer cans and wine bottles inside a freezer:
With wet paper towel
Without paper towel
With wet paper towel
Without paper towel
We want to make as good condition for the wet paper towel hack as possible, so we decided to use one single layer of towel so the insulating effect is as little as possible and the evaporating effect is as good as possible.
For the wine test we used the following setup:
Normal household chest freezer half full frozen goods
Omega temperature logger RDXL4SD
Start temp. in each test approx. 23C/73F
All measured temperatures have been done in the liquid - not on the outside of the can/bottle
Wine in InnoChiller
Wine in wet towel
Wine without wet towel
Results for wine bottle:
It is safe to say that the difference is significant in InnoChillers favor
Cans in InnoChiller
Results for cans:
Results for cans:
Can with wet towel
Can without wet towel
Even with a wet towel wrapped around the beer it takes more than 40 min. to cool down
Hopefully the information and tests provided on this page will help bust the wet towel myth and give a clear picture of which cooling method is fastest.
So what's next?
Ice and water - the mother of all cool downs... or?
So what is faster than the InnoChiller if you want to cool down as fast as possible. Ice and water of course! (some people think salt will help for some reason, so we included this as well).
We thought this would be a piece of cake to demonstrate. After all, who doesn't know that ice and water mixture will cool down your wine or beer in no time?
Luckily we had a bunch of ice cube laying in the freezer, about 1 kg or so.
So we just took the first bucket we could find and poured in some water, added a bunch of salt and topped it up with ice cubes.
The set up looked like this:
Adding salt to the water
Adding the ice cubes to the water
Adding the wine bottle
After inserting the bottle of wine into the water - salt - ice mix we definitely thought that even with this basic setup we would achieve cool down times far better than what the InnoChiller was capable of delivering. Let's face it, this would exactly be the kind of setup a normal person would bring out in case of a distressed situation with no cold rosé.
We had to stop this test after 20 min. after only reaching a cool down from 23C to 17C.
Of course the graph for this test was never going to be accepted by the hardcore critics of the InnoChiller, they would argue that there wasn't enough ice cubes, that the bottle wasn't fully covered etc. and actually this result surprised ourselves as well...
And after cleaning the table from salt, melted water, and used plastic bags from the ice cube we started to think about what went wrong.
So what to do?
Don't be fooled, we weren't happy with the result either, our background as engineers told us to expect a different result, so we got in complete Mythbuster mode and went to the closest convenience store and bought up 8 kg of pre made ice cubes in total, including a higher bucket so that the bottle could be fully submerged in the ice water.
We would like to stress that 8 kg of ice is far more than normal households have in stock, it is a lot of ice cubes!
Supplied with a brand new bucket and a mountain of ice cubes we commenced the second test, we wanted to show that ice cubes are the absolute fastest way of cooling down a bottle of wine!
The next setup looked something like this:
Overview of the new purchases
2 kg of ice, and of course, salt...
Fully submerged bottle in ice water
So this got us really excited! Being a physics nerd you got to love things like this...
The graph from this test was a bit weird, we had to shake the bottle a numerous of times to know what the average temp. was of the liquid, this might even have helped the cool down time due to the stirred water when shaking the bottle, but the start and end temp. is correct. However, the graph wasn't what we had hoped for:
Still the cool down time was longer than what the InnoChiller achieved.
So what to do now?
We had to come up with some kind of explanation for what was going on here. Clearly these results was very surprising to us and we started discussing what caused this.
As a possible explanation we looked into the temp. difference between the surface of the water and bottom of the water in both the shallow and the high bucket. If you look closely in both setups you will find an additional blue temp. probe which was used to measure the water temp. throughout the tests.
This measurement showed a slightly higher temperature at the bottom of the bucket, 4-6 C compared to 0 C in the area where the ice was.
As ice is lighter than water and thereby tends to float in water most of the ice was in the top of the bucket, making the water near the ice colder than the water at the bottom of the bucket.
The solution was simple, put as much ice in the bucket as possible and thereby ensure a uniform temperature throughout the whole bucket.
This third setup looked exactly like the second, only with more ice:
4.5 kg of ice, and yes, salt...
2nd probe showing 0 C all over the bucket
This was the third attempt to show how "superior" ice was in cooling down beverages in the fastest way possible, and the result was:
Similar results as the previous test
Of course we showed that ice and water is better than the wet towel trick but we thought this would be a clear example of how good ice and water was in cooling down your wine or beers compared to the InnoChiller, but this attempt failed badly. The purpose of this test wasn't to promote the InnoChiller, it was to show that we knew which cooling method was best, but we were wrong.
Is this the end of the ice and water trick?
Well, not exactly. Lets see what happens when we use a can of coke/beer instead a bottle of wine.
The can was placed in the water from the last wine bottle test like this:
This time we finally got the result we had "hoped" for! The can was cooled down faster than what the InnoChiller was able to do.
This test gave us some confidence back although the ice in water trick is still on "thin ice", and not convincing at all. Here is the result of one single can in 4.5 kg og ice plus water mixture:
Here it is proven that ice and water is a faster way of cooling down a can than using the InnoChiller
The last test here showing the cool down of a can is actually very nicely, the delay in cooling is very low due to the high heat transfer in the aluminum can. It is extremely exciting to see how the efficiency of the water/ice mixture is getting lower and lower as the temp. is decreasing. At some point the curve for the InnoChiller and the water/ice mixture will intercept and the InnoChiller will, once again, win the battle.
So what is the explanation for this?
Temperature of water/ice vs temperature of the air inside a freezer
A mixture of ice and water will always be exactly 0 degrees Celsius, whereas the air inside the freezer will remain much lower.
Some people argue that by adding salt to the ice/water mixture will lower the freezing point of the water and thereby lower the temperature of the water when the ice cubes have been added to the mixture.
There is a few challenges with this idea:
1. The energy that needs to be removed to cool down ice is not much, the specific heat value of ice is only 2 kJ/kg/C., so to cool down one kg of ice from 0C to -20C you only have to remove 20x2=40 kJ. Most likely there will be a temp. drop in the water below 0C but it wont take long for the temp. to stabilize on exactly 0C once the ice cubes starts to melt.
2. The energy required to be removed to make ice cubes is approx. 333 kJ for one kg. This is the hole point of using ice cubes the extra 40 kJ you gain by adding the salt wont make a difference and you even have to cool down the salt itself.
This is why adding the salt wont help a lot, under ideal condition there might be a small amount of time to save, but this is quickly lost just by finding all the things you need to set it this up.
We used salt in all tests above.
UPDATE - more salt!
Based on the above tests we have been approached by people who think we didn't use enough salt and claiming that it was the reason why the test wasn't better than the InnoChiller.
We are pretty sure that adding more salt wont change the cool down time a lot, but for the sake of science (and because we think it's fun) we decided to give it another go to completely bust the salt myth.
So off to the store again and buy even more ice and a bunch of salt, this was how the test was set up:
0.6 kg of salt was used
Adding the salt to the ice, then adding water
Approx. 4.5 kg of ice
Yes! The temp. went to -1 C in the water
Even before we started to prepare for this test we knew that setting all this up just to cool down a bottle of wine completely defeats the purpose of "quick" chill. It took time to find all the things and like we said before, 4 kg of ice is a lot, it's one full bucket and most people wont have access to this much ice - use the ice to make Mojitos instead.
Anyway, let's take a look on the result:
The result is almost the same as seen on the previous test
To be fair the initial temp. of the bottle was 23.7 C this time compared to approx. 23 C in all the previous tests, but this doesn't change that the extra added salt only had a minor effect, almost impossible to see from the graph.
All in all we are very surprised that water and ice is not faster than the InnoChiller, we have not made tests with water and ice before because we were sure that the result would be much, much better than the InnoChiller, and the whole purpose of the InnoChiller was to make a product for fast chilling without being depended on having ice cubes ready.
But of course we are glad to see these results!