The last 20 degrees takes the longest IMO..
He is right, not only is it his opinion, but it is scientific fact....
I have used bags of ice lots of times and it works like a charm. Quick, easy and never had an infection. Don't forget ice is cold so bacteria is inhibited, wort is hot so bacteria is inhibited, hops in wort inhibit bacteria. Pitch health yeast and given those odds they will win every time.
Truth, the rate of heat transfer is a linear function of the temperature differential. Boom, science!
Okay fine.
2 gallons of ice at -5F is 6962 grams. 3 gallons of water at 180F is 11020g.
Combined weight of 17982g
Specific heat of water is 4.186 J/g*C.
Joules released when melting 6962 grams of ice is 2328402 J.
Mixture of 2 gallons of 32F water, and 3 gallons of 180F water is 5 gallons at 122.7F.
Accounting for heat of fusion, Tf= (-2328402/(4.186*17982)) + 122.7 =91.7 C.
Oh look my previous post off the top of my head was actually 1.7C lower...
If however you can use a cold water bath to lower the wort to about 150-160, the resulting water/ice mixture should end up around pitching temps ~upper 60s to mid 70s.
I'm glad to hear that it's always worked for you.
Odds, however, are against this working every time. Partly because the wort is still too warm to pitch the yeast. Warm wort in the "danger zone" is more likely to harbor and encourage contaminates. If the wort is cooled to under 90 degrees, and then cold water or ice is added and the wort reaches a temperature in the 60s and yeast is added, then it's likely to be ok.
In my practical experience, 3 gallons of boiling wort + 2 gallons of ice = 100 degree wort. I thought it was a brilliant idea, until I actually tried it. Then I had 5 gallons of 100 degree wort that took hours to cool in an ice bath. It's far easier (and faster) to cool 3 gallons in an ice bath to under 100 degrees, and then add cold water and/or ice to get to 60 degrees or thereabouts and add the yeast.
ice is colder than 32F.......
most freezers are set to around -5F. so -5F is probably a good place to start for ice temperature.
you also benefit from the specific heat of fusion. changing phases takes energy. 144 BTU/lb. give or take. provides much more cooling load than the above posters have modeled.
Anything wrong with pouring 3 gallons of hot wort onto 2 gallons of ice to make a 5 gallon batch?
Your kidding right?
Your kidding right?
Your kidding right?
Okay fine.
2 gallons of ice at -5F is 6962 grams. 3 gallons of water at 180F is 11020g.
Combined weight of 17982g
Specific heat of water is 4.186 J/g*C.
Joules released when melting 6962 grams of ice is 2328402 J................more random numbers....
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