recirculating counterflow chilling water?

[IslandLizard]

Since this question was never answered I went ahead and did some tests. [...]

It would be more efficient to first use regular tap water to bring the wort temps down 60-80°F to 140-120°F.*
Then switch to ice water.**

* You can recapture that hot water in a couple buckets for clean-up, or doing dishes.

** Doing a single pass until the wort temp has dropped to 20-40°F above pitching temps is (probably) a more efficient process. Then recirculate. You can recapture the water from the single pass too.

 

[Horseflesh Inferno]

It would be more efficient to first use regular tap water to bring the wort temps down 60-80°F to 140-120°F.*
Then switch to ice water.**

* You can recapture that hot water in a couple buckets for clean-up, or doing dishes.

** Doing a single pass until the wort temp has dropped to 20-40°F above pitching temps is (probably) a more efficient process. Then recirculate. You can recapture the water from the single pass too.

Well true, but I don't recirculate the wort. It just goes from kettle to fermenter in one pass so it has to come out at pitching temps. I don't have a pump for that so I have to rely on gravity to get it through the counterflow.

 

[FloppyKnockers]

My $0.02

I put a bucket full of water in my lager fridge set at ~33° a few days before brew day. On brew day, I use ground water to get the wort below 100°. During the summer, that can be a taller task than you think, but once I hit that temp, I disconnect the hose from the faucet and connect a pond pump to my counterflow chiller and let'r rip. I put the discharge end in my cold bucket and recirculate.

For an extra boost, I keep Gatorade bottles of ice in my freezer. I'll aim the discharge hose into the bottle and dump into the bucket. This keeps the almost freezing water from warming up too fast. I can go from 100° to 70° in about 10 minutes on a 5-gallon batch. This method keeps me brewing through the Texas summers.

 

[Deadalus]

I had an idea for what I am calling a "perpetual spring chilling" that I have built and was testing. I hadn't read this thread, it was something I arrived at independently, but since this thread came up I decided I should write up the build as it is similar and there were similar options suggested in here too. Could even be other posts considering it too, somebody always beats me to it!

 

[Horseflesh Inferno]

My $0.02

I put a bucket full of water in my lager fridge set at ~33° a few days before brew day. On brew day, I use ground water to get the wort below 100°. During the summer, that can be a taller task than you think, but once I hit that temp, I disconnect the hose from the faucet and connect a pond pump to my counterflow chiller and let'r rip. I put the discharge end in my cold bucket and recirculate.

For an extra boost, I keep Gatorade bottles of ice in my freezer. I'll aim the discharge hose into the bottle and dump into the bucket. This keeps the almost freezing water from warming up too fast. I can go from 100° to 70° in about 10 minutes on a 5-gallon batch. This method keeps me brewing through the Texas summers.

I like that idea about putting the discharge hose into a bottle. I'll have to try that out.

Do you recirculate the wort back into the kettle, or use an immersion chiller for the initial cool down?

Last week when I brewed it was 105 here in the high desert of southern California.

 

[FloppyKnockers]

I like that idea about putting the discharge hose into a bottle. I'll have to try that out.

Do you recirculate the wort back into the kettle, or use an immersion chiller for the initial cool down?

Last week when I brewed it was 105 here in the high desert of southern California.

No immersion chiller. All my chilling is done with a counterflow and the wort gets pumped back into the kettle.

 

[Deadalus]

dyqik:
I should have corrected beermanpete on his post where he incorrectly states I'm assuming a mixing of water. I'm not. I clearly state I'm assuming a 100% efficient heat exchanger and I back that up with simple arithmetic that always uses 10G for all three steps of my example. If I were mixing water, step 2 would necessarily use 20G, and so on.

You are making the same mistake beermanpete makes. It doesn't matter how you go about it, it is the total amount of heat that has to be extracted from the wort, and under ideal conditions as in my example, it will take a lot of cold water to accomplish that. It makes no difference if it's a CFC, a plate chiller, an immersion chiller, etc. All they do is provide the vehicle for the heat extraction. The AMOUNT of heat to be extracted remains the same regardless of method.

The physics of the process is what I was trying to describe by a purposely optimistic example. Real life conditions would invariably be worse. I don't care what you use, the amount of heat to be extracted says a certain amount of offsetting cold needs to be provided.

Old argument and poster has not been here in several years. But the way it is presented in post #6 (below) assumes mixing that's what the formula assumes. The simple logic part is however a mistake in logic used to get you there. Using the three steps, RoatanBill has used the mixing formula at each step but at the next step, reintroduced the 38F water. If the answer of a final temp of 60 is correct, using 38F as the cold water temperature, we could solve the equation for Qc. So,
10*(212-60)=Qc*(60-38)
10*152=22QC
QC~69.1 gallons.

It could also be solved for Tf
10*(212-Tf)=30*(Tf-38)
2120-10Tf=30Tf-1140
3260=40Tf
Tf=81.5F

But neither leads to the answer as presented.
The 3 individual calculations are correct using the formula given but the problem was not specified in this manner, i.e. three separate recirculation (mixing) steps (RoatanBill assumes 100% heat exchange technically). It does suggest something interesting and that is that if you break the mixing up into smaller volumes, less water is necessary. Which is so because heat has been absorbed by the 10 gallons of water and removed from the system twice. If you're coming down from 212 to, say, 60, then you will need a lot of cold water to accomplish that, while 30 gallons all at once mixed only gets to 81.5F not 60.

From : http://www.chemteam.info/Thermochem/MixingWater.html
Mixing water formula: Qh*(Th-Tf)=Qc*(Tf-Tc)
Where:
Qh = Quantity of hot water
Qc = Quantity of cold water
Th = Temp of hot water
Tc = Temp of cold water
Tf = Final Temperature

Simple logic can also get you there:
Assume the cold water is at 38, 100% exchanger efficiency and 10G as the wort volume.
Heat exchanging 10G of cold water with the 10G of wort will reduce the temp to (212+38)/2 = 125
Heat exchanging 10G of cold water with the 10G of already cooled wort will reduce the temp to (125+38)/2 = 82
Heat exchanging 10G of cold water with the 10G of further cooled wort will reduce the temp to (82+38)/2 = 60

This example requires 30G of 38 degree water to do the job and that's ALWAYS having 38 degree water as the heat sink. If you try to recirculate your cooling water, it won't be anywhere near 38 degrees and therefore will take much longer and you'll hit equilibrium depending on cold water volume so you may never hit your target. It would be initial cold water volume dependent.

The way I initially estimated a barrel size in my build was I treated the hot and cold temperatures as observations and then calculated a weighted mean using the volumes of water I expected to have at room temperature. It ends up being the same formula, so of course somebody already thought it through again. (Not that I came up with weighted means just applied them here.) Also in the background I'm pretty sure you need to consider the specific heat capacity to be equal for the two liquids. The link given by RoatanBill also seques into phase changes which I was beginning to consider concerning the ice and water needed for what I was saying was phase II. But I didn't have any info on the specific heat capacity of wort so I didn't get that far.

 

[Horseflesh Inferno]

Old argument and poster has not been here in several years. But the way it is presented in post #6 (below) assumes mixing that's what the formula assumes. The simple logic part is however a mistake in logic used to get you there. Using the three steps, RoatanBill has used the mixing formula at each step but at the next step, reintroduced the 38F water. If the answer of a final temp of 60 is correct, using 38F as the cold water temperature, we could solve the equation for Qc. So,
10*(212-60)=Qc*(60-38)
10*152=22QC
QC~69.1 gallons.

It could also be solved for Tf
10*(212-Tf)=30*(Tf-38)
2120-10Tf=30Tf-1140
3260=40Tf
Tf=81.5F

But neither leads to the answer as presented.
The 3 individual calculations are correct using the formula given but the problem was not specified in this manner, i.e. three separate recirculation (mixing) steps (RoatanBill assumes 100% heat exchange technically). It does suggest something interesting and that is that if you break the mixing up into smaller volumes, less water is necessary. Which is so because heat has been absorbed by the 10 gallons of water and removed from the system twice. If you're coming down from 212 to, say, 60, then you will need a lot of cold water to accomplish that, while 30 gallons all at once mixed only gets to 81.5F not 60.

The way I initially estimated a barrel size in my build was I treated the hot and cold temperatures as observations and then calculated a weighted mean using the volumes of water I expected to have at room temperature. It ends up being the same formula, so of course somebody already thought it through again. (Not that I came up with weighted means just applied them here.) Also in the background I'm pretty sure you need to consider the specific heat capacity to be equal for the two liquids. The link given by RoatanBill also seques into phase changes which I was beginning to consider concerning the ice and water needed for what I was saying was phase II. But I didn't have any info on the specific heat capacity of wort so I didn't get that far.

I was running formulas too and my calculations showed my setup probably wouldn't work. I didn't even build it for many years because of that until I was at a buddy's house for brew day and he did it. When I saw it worked I just went back to my original idea and built it. I think one of the things I couldn't calculate properly was the fact that the 10 gallons of roughly 35 degree water was going to stay 35 degrees for a long time. Even though hot water was circulating back, it would only melt the ice, but not warm up the water. The temperature of the ice was the variable that I couldn't properly calculate because I didn't know how. But after building it and using it I realized it worked far better than I originally even thought it would. By the time the kettle it empty the water is still cold with a few chunks of ice remaining.

 

[Deadalus]

I used to know how to calculate it, we did it in HS and college, but I couldn't remember the terms which frustrated the hell out of me. Then I also realized I would have to convert to metric and deal with mols. I knew I could get it into the 90s that was the easy calc so I did go ahead and build it too.

Heat of fusion is the part about where the temp stays stable, if you never got around to looking it up. Changing state from ice to liquid and vice versa. That's the name and part I had forgotten how to calculate. It was a total blank.