I use a plate chiller with a submersible pump hooked up to the water in side of the chiller. I put the pump in a 120 quart ice chest of Ice and just enough water to prime the pump. I have a valve and Temp gauge on the wort out side of the chiller. Also a valve on the water out side of the chiller. When I pump the hot wort through the chiller I make temp changes by metering the water flow and the wort flow until a very steady temp goes into my fermentor. There is enough ice for me to chill a 10 gal batch down to 62. Not a large lose of water. All the left over ice water goes to water my grass and plants at the end of the brew day.

Hard to use the term 'efficient' with all that energy going into freezing the water for the ice............

You can estimate the volume of water needed to cool boiling wort by looking at the energy balance before and after cooling.
This method is a "best case, perfect world" estimate, so it calculates the minimum amount of water necessary, never really attainable, but it bounds the problem.
It doesn't care how the energy was transfered (your specific equipment and process), just how much heat needs to transfer.

It will answer the question: "Can I cool it with this much ice water?", as long as "no" or "maybe" are good enough answers.

Ideal Energy Balance:

The heat energy transfered by cooling 5 gallons of boiling wort to 70°F is equivalent to the energy required to increase the temperature of some minimum volume of ice water to 70°F.

Assuming the specific heat and density of water and wort are about equal (they're not, but close enough for this calc):

5 gal * (212-70)°F = x gal * (70-32)°F

solving for x, x = 18.7 gal of water a 32°F

This ignores all other heat losses or additions during the process and doesn't consider the rate of cooling (and resulting efficiency).

It also ignores the fact that ice needs to change phase into water (absorbing more energy that accounted for here), ambient heating of the ice water that is not perfectly insulated and any heat added by a pump and motor (submersible pumps dissipate heat direcly into the water they are moving.

The other big stored energy source ignored in this calculation is the mass of your kettle/burner at 200+°F! Lots of stored energy in all that stainless steel.

In practice, the flow rate required to maximize the heat exchanger efficiency is painfully slow, and for most cases, not worth the time.

I use 3 gallons if ice added to about 2 gallons of water recirculating thru my immersion chiller to drop the wort from 90°F to about 60°F. This is after I've cooled with tap water.
I divert the inital hot water into my picnic cooler, add some PBW and use it for clean-up. The rest of the water is diverted into a clean plastic trash can for rinsing equipment.

Also, by not keeping it a closed system and diverting the initial hot water, you are getting more cooling out of it since you are raising it from 32 to 180 or so rather than 70..

I take another approach. I do the conventional routine of running tap water through the chiller for the first 15 minutes or so until the wort gets to about 100°, saving the hot water for cleanup. Then I switch to pumping (and recirculating) ice water through the chiller using a small rv water pump and a 10 gallon gott cooler full of ice and water. Even in 90°+ weather, I can get the wort down to around 60°.

+1

Me too (although saving the hot water is a little too green, even for this California liberal )

+1

Right now I dump all the hot water on my lawn and trees. When the brewing moves to the basement, I guess I'll use it for cleanup. Hadn't thought of that. Of course the main thing I want to clean up is the boil kettle. Now you've got me thinking that I could transfer the hot wort to the fermenator and chill in there. Hot waste water goes back into the boil kettle with PBW. I'm liking this idea. This also takes the thermal mass of the BK out of the chilling. The fermenator will be whatever temperature the StarSan solution was.

In my quick scan of the replies I didn't notice anybody mention the biggest problem with this approach... Sanitation. Good luck trying to sanitize the inside of your IC. I have been using a Jamil chiller for about 5 years now and I am very happy with its performance. 5 min to below DMS conversion temp, 5 more minutes to 90. And that is with my hot groundwater in Phoenix. Then I switch to recirculating ice water, like Boog said. I also collect the first 5-6 gallons of hose water in my MT for cleaning. I estimate 15 gallons or so to chill in the summer. In the winter time, I just recirculate 50 degree water from my pool. No waste. I typically brew 80% of all the beer I brew in the cooler months, anyway.


Mylo