Recirculating Wort Chiller Question

A couple of months ago I made a recirculating wort chiller that works great.

Currently I use 20lb of ice and water in a 5 gallon bucket for my cold water source but today (being Friday) I had an idea. 20lb of ice costs 6 bucks and for the same price (at the same store) I could get 5lb of dry ice.

If I dumped 5lb of dry ice in my bucket of water do you think I would get better cooling than the 20lb of ice?

Also, could I throw the dry ice directly in the boiling kettle or would that produce some off flavors? (I brew outside, so not worried about the CO2 evaporation).

TIA

 

Have you ever thrown dry ice into boiling water? Pretty cool stuff. I made my kids think I was a magician. I'm not sure if there is any other chemical in dry ice or if it is just truly super cold ice. I know it takes quite some time to sublimate. I probably wouldn't put it directly in the kettle just in case. You could risk a boilover depending on how much head space you have in the kettle.

I'd think you would get better cooling than regular ice.

 

CO2 and H2O at -140C have almost the same heat capacity (Cp). ~1 Joule / Gram * Kelvin. The heat capacity of H2O improves as the temperature increases, solid CO2 gets worse.

If the price per pound was the same, and the ice was really cold, it might make sense. That's just not the reality.

In practice I think you'll have a hard time transferring the heat between the dry ice and the chiller. The CO2 will bubble violently and try to freeze chunks of ice (or worse wort). It will look wicked cool, but I doubt the water in contact with your chiller would be any colder.

If you want that pre-chiller to really rock you could toss a cup or two of rock salt into your ice bucket. Could drop you another 5-10° I'd bet.

 

Good God, do not do this. It seems extremely dangerous.