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This is my first question on the Physics site. I stink at thermodynamics so please forgive errors in my question.

Here's the background: my coffeemaker makes coffee over 200°F. I want to rapidly cool it down. Target temp doesn't really matter but let's say to 130°F. For whatever reason* I thought I would cool down my coffee by freezing a thick rod of stainless steel and stirring it around in the coffee for a few seconds. Then it occurred to me that there are ice cream scoops with a non-toxic oil in the handle that is supposed to keep your hand from getting cold and also heat up the ice cream for easy scooping. (Coffee Joulies™ have paraffin wax in them.)

https://www.amazon.com/dp/B0002U34EW/?tag=stackoverfl08-20

I like the idea of using this because now I don't have to buy a solid bar of stainless steel plus, I can scoop ice cream (albeit slowly since I am freezing the scoop.)

My question is: how does the oil in the handle of the scoop increase the scoop's ability to cool down my coffee?

The scoop is made of aluminum. I don't know how much oil is in the handle, or even what exactly the oil is. But this stack said it was oil:
https://cooking.stackexchange.com/questions/46157/why-cant-this-ice-cream-scoop-go-in-the-dishwasher I'm not sure how the scoop is supposed to work, but I suspect that the oil stores (room temperature) heat and warms up the ice cream to make it easier to scoop. I'm hoping the opposite is true: that the oil will store (freezer temperature) lack-of-heat and absorb heat from the coffee. Is that sound?

Also, if anyone thinks the scoop is going to explode, please mention that too.

Thanks!

*I don't want to use ice because it will water down the coffee. I don't want to use coffee ice cubes because I'm lazy and also I don't have room in my freezer for an extra tray. I don't want to use metal ice cubes or Coffee Joulies™ or stuff that I have to fish out of my glass because, well just because. I don't want to buy a cold plate like for beer kegs. Let's just go with the premise.

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  • $\begingroup$ I think it should work at least as any other metal spoon. The trick of the special spoon is not symmetric (see answer). But why not experiment? The material is not water so, assuming it freezes, it shouldn't expand. $\endgroup$
    – Alchimista
    Commented Oct 18, 2017 at 20:10
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    $\begingroup$ Get a thick coffee cup and chill it $\endgroup$
    – paparazzo
    Commented Oct 18, 2017 at 21:01

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TLDR; Get a heavy mug and chill it.

The paraffin in the scoop is functioning as a heat capacitor more than a heat conductor. A solid aluminum scoop of the same dimensions would conduct heat almost as well for large temperature gradients, and better for small temperature gradients (the difference here is whether the temperature gradient can drive significant convective flow). When you first put the scoop in the coffee, the convection will be going like crazy, but my estimation below makes me suspect that the temperature gradient will have become very small before the coffee reaches the desired temperature. It sounds to me like you are looking for a method to reach your desired temperature very quickly, so I will ignore heat exchange with the surroundings, which occurs more slowly.

To simplify the math, lets say you are cooling the coffee from 100 degrees C and the scoop is initially chilled to 0 degrees C. Lets also assume that there is 200 g of coffee, 100 g of aluminum, and 50 g of paraffin (I have the scoop you linked and weighed it). The heat capacity of the paraffin is about 2.5 J/gK, that of the aluminum is about 0.9 J/gK while that of the coffee is about 4.1 J/gK. So without exchanging heat with the surroundings, the system will reach a temperature of about 79 degrees C. That's progress, but it's still pretty hot!

That was ignoring the coffee mug, however. The thick mugs in my cabinet range from 400 g to 600 g, and the heat capacity of the ceramic is around 0.8 J/gK. So with the right chilled mug you can get almost twice the conductive cooling that the scoop gives you! That would bring you to a drinkable temperature very quickly, even without the scoop. So Paparazzi hit the nail on the head with his comment.

As a final comment, the ice cream scoop manufacturer warns on their website to keep the scoop below 140 degrees F.

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  • $\begingroup$ [Duncan Harris drops the mic] $\endgroup$
    – Xplodotron
    Commented Feb 22, 2018 at 20:29
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Those things work by convection. If the substance in the scoop is solid, it can't convect and you'd be better off using a heat pipe or a silver/copper rod.

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