Ice Water Bath vs Glycol Bath

[dwinfiel]

I am relatively new to home brewing and have just been using an Ice/Water bath to bring my wort to pitching temps. I have only been doing extract brews, boiling 2-3 gal and topping with cold water.

I have seen discussions of using a glycol chiller with a pump to circulating glycol through a freezer. My question is could I just stick the boiling pot directly into a tub of 0F glycol instead of an Ice/Water mixture. I don't a lot about thermodynamics, is the cooling capacity from the change of state from Ice to water that much greater than just cold liquid glycol?

What I was envisioning was putting 5 gal of 0F glycol in a Igloo 60-Quart Ice Cube cooler and sticking the brew pot in the cold glycol. After the cooling is done, the glycol could be drained from the cooler and put back in the freezer.

What about a water/propylene glycol slush (around 35% glycol), would this still have the cooling capacity as the phase change from Ice/water. Only 1-2 gal of glycol would be needed to make the solution.

Thanks,
David

 

[ncbrewer]

I'm rusty on these calculations, but per Wikipedia https://en.wikipedia.org/wiki/Ethylene_glycol#Coolant_and_heat_transfer_agent "Pure ethylene glycol has a specific heat capacity about one half that of water. So, while providing freeze protection and an increased boiling point, ethylene glycol lowers the specific heat capacity of water mixtures relative to pure water. A 50/50 mix by mass has a specific heat capacity of about 3140 J/kg C (0.75 BTU/lb F) three quarters that of pure water, thus requiring increased flow rates in same system comparisons with water." So the more glycol in the solution, the less cooling it will do per pound. I figure if you had 5 gallons of pure glycol at 0F cooling 5 gallons of near boiling wort ( similar to plain water), they would reach 142F at equilibrium. Even pure water, taking the extreme, would reach 106F at equilibrium. It doesn't look practical to me.

 

[freisste]

The positive aspect of glycol is that it can be colder than water and still be pumped (i.e., it freezes at a lower temperature). If you aren't using that fact, you aren't using glycol correctly. Much better than your suggestion would be to use a cold water bath to cool the boiling wort and then use flowing glycol to cool to pitching temp.