using (boiled) ice to cool the wort?
Won't the ice melt when you boil it? (j/k
)
If you add 2.5 gal of 212F wort to 2.5 gal 40F water,
you will have 5 gal of ~126F wort.
Then there's nothing else that can be done.
It would be better to cool the wort to 100-110F first.
Then when you mix with cold water it will be ~70F.
You can put your kettle in the sink with cold tap water and/or ice
and watch the thermometer until it's right.
If you want add ice directly to the wort, you have to do some math to figure out the amount needed:
The specific heat of water is 1 calorie per gram per degree C
and the latent heat of fusion is 80 calories per gram.
To raise the temp of 1 gram ice from -20C to 20C requires 120 cal.
So to cool 9 liters (~ 9 kg) of wort from 100C to 20C takes 720 kcal,
about 6 kg (13.2 pounds) of ice.
Roughly 14 ice cube trays.
So you would have to use a lot of time and energy to boil then freeze that much water.
And if you do it all at once you may spoil any food that's in there.
Hope this helps.