I like iced coffee when the weather is hot, and I like to drink it black (or nearly black) and undiluted. What is a good setup for cooling freshly brewed coffee quickly, without a lot of hassle? I'm talking about normal brewed coffee, not cold brew.
At Starbucks, they seem to put ice in your cup and then pour coffee directly over the ice. This works, but it uses a lot of ice, and by the time you're done drinking it, the melting ice has started to dilute the coffee. You also just can't fit very much coffee in a cup this way, because so much space is taken up by the ice.
I've tried putting a whole bunch of water in a big pan, then sticking a thin-walled metal cup in the water and pouring the coffee into the cup to cool. This cools the coffee rapidly at first, but then the cooling process gets extremely slow. I think part of the problem is that the conduction and convection processes are slow, and also that the water's heat capacity isn't super huge, compared to the heat of melting of ice.
I homebrew beer, and to cool my wort, I have a coil of copper tubing that I insert into the pot and run water through from a garden hose. This is pretty efficient, but works for a quantity orders of magnitude greater than a cup of coffee. It uses a huge amount of water.
Below is a method that I'm currently messing around with. The pan of water is to take the initial heat off of the coffee and make sure the coffee is cool enough so that I don't melt a hole through the plastic parts or release bad chemicals into the coffee from the plastic. I then put some ice in the ziplock bag and stick it in. After a few minutes I can take the cup out of the pan. The ice melts, and then I replace it with fresh ice. This setup seems not too bad, but still kind of slow and wasteful. It uses up a lot of ice. I can wash and reuse the bag.
Is there a better way to do this? I'm fantasizing about weird gadgets such as an aquarium pump sending pre-chilled vodka or ice water through a closed loop of tubing. Or maybe putting pieces of brass or copper in the freezer.