Cold drinks, hot days
September 4, 2020 9:03 PM   Subscribe

It's supposed to be hot outside this weekend, and I would like to have an iced beverage in the park with a friend. I have two insulated bottles (1 small, 1 large). Does it make a difference whether I pack the ice and liquid separately (ice in the small bottle, liquid in the large), or mix them together before filling both bottles?
posted by btfreek to Science & Nature (10 answers total)
 
If you don't want to dilute your drinks, you might want to put the ice in the small one so you can drain off the cold water before mixing with your drink.

On the other hand I think if the drink is well chilled and then combined with the ice, the cold drink + ice will be slower to warm than ice starting out surrounded by room temperature air. So my guess is that mixed will retain the cold better than separate.
posted by metahawk at 9:07 PM on September 4, 2020 [2 favorites]


Is this a drink where dilution would make a serious difference? If you pack the ice separately, you can drain off any melt before combining.

But unless you can get your uniced beverage icy cold before you put it in the container, you're going to get dilution when it hits the ice.

If you could, though, I would suggest segregating just so you can get both as cold as possible. If some component of the beverage could be frozen in advanced, even better to freeze it and put it in one container, then mix onsite.
posted by Lyn Never at 9:08 PM on September 4, 2020 [1 favorite]


Well, ice can be colder than the freezing point of water. You could pack the colder ice and the beverage chilled almost to freezing, keep them separate in the vacuum bottles, and squeeze a bit more of the cold out of the ice. Might not make much of a difference. Most of the cold of ice comes from going from solid to liquid.
posted by zengargoyle at 10:25 PM on September 4, 2020


I say put all the ice in the big one and fill the rest of the space with liquid, and then put the remaining liquid in the smal one. Then when you get to the park, drink from the big one until there's enough room for what's in the small one, and at that point pour the liquid from the small one into the big one and let it cool down before drinking it.

My rationale is that you'll get the best result by minimizing the total heat that flows into the two containers. For a given temperature difference between inside and outside, the big one will absorb less heat per volume of liquid because the ratio of surface area to volume is less for the big one and heat flow is proportional to surface area. Ice has the effect of keeping any water in contact with it at 0 °C, because as heat flows in it will melt the ice instead of heating the liquid, so you want the liquid that will stay at the lowest temperature to be in the most efficient container, and the liquid that heats up to be in the less efficient container, because as the liquid heats up in that container the rate of heat flow will go down.
posted by jamjam at 10:57 PM on September 4, 2020


heat flow is proportional to surface area

To be precise, it's proportional to boundary area multiplied by the difference in temperatures either side of the boundary, and inversely proportional to the thermal resistance of the boundary (higher for well-insulated boundaries).

If the initial temperature difference is fixed, then the way to minimize heat flow is to use as little boundary area as possible for any given mass of substance. If the thermal resistance of the available containers is similar - for example, if they're all vacuum-in-mirrored-glass thermos types - that means using as few containers as possible, and choosing short squat containers rather than long thin ones.

In fact there are enough unknown variables here that if I were in your situation and seriously interested in the difference you're asking about, what I'd do instead of relying on opinions solicited online is set up both the scenarios you're considering and measure them.

I wouldn't bother with thermometers because in a mixture of ice and meltwater they're going to be reading 0°C most of the time anyway; I'd just be comparing how easy it was to make sure that my drinking cup included a bit of unmelted ice, how much of that ice stuck around until the end of the drink, and how watered-down the drinks ended up tasting.

What I would expect to find after doing this experiment is that in almost all cases it doesn't make enough of a consistent difference to be worth worrying about. But it's an interesting question and I'd be curious to find out whether that expectation is correct.
posted by flabdablet at 11:22 PM on September 4, 2020 [5 favorites]


It also depends on the drink. If you can get your hands on a small cooler, you can bring plenty of ice, no matter the drink, to enjoy it all cold. More ice is always good.
posted by vrakatar at 11:24 PM on September 4, 2020 [1 favorite]


Freeze the drink into ice cubes. No dilution problem.
posted by Crystalinne at 3:04 AM on September 5, 2020 [3 favorites]


There are certainly two questions happening here. One is "will a different strategy give me a cold beverage for longer?" and the other is the well answered "will a different strategy prevent dilution?"

For question one, if you have a nice modern two wall insulated vessel, put in a cold drink with ice and stop thinking about it. The performance of modern insulated cups and thermoses is amazing and if you pack it full of ice, you'll hardly have any drink to drink because you'll have a cup of ice instead.

I have little to add to the dilution question.
posted by advicepig at 5:54 AM on September 5, 2020


Thanks all - as you may have surmised from the lack of detail in the question and its categorization under "Science and Nature", this was more of an idle curiosity I had rather than a matter of serious picnic logistics. In any case, I went with the separate ice and liquid for The Aesthetic (tm) of pouring a drink over ice and everything worked fine. (Also, I used my Zojirushi food jar to store the ice and pre-cooled it in the freezer and there was seriously no discernible melting in the jar AT ALL despite going through a 2 hour bike/transit ride in 35C weather, amazing.)
posted by btfreek at 6:04 PM on September 5, 2020 [1 favorite]


In any case, I went with the separate ice and liquid for The Aesthetic (tm) of pouring a drink over ice and everything worked fine.

What's really good about that is the way you avoided getting hung up on the wrong problem in order to solve the right one. Well done you.
posted by flabdablet at 8:21 PM on September 5, 2020


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