recirculating counterflow chilling water?

[DolfoMan]

Alright everybody; so I'm in the process of rebuilding my brew system and I've been thinking of ways of making things as simple and self contained as possible. I've been seeing a lot of info recently on people recirculating their chiller water with a simple water pump to save water. I love the idea, but I have a counterflow chiller instead of an immersion chiller, has anyone had any success with doing this recirculation with a counterflow? Is it any different from doing it with a coil? And most importantly, how do you keep your water supply cold? The exit water with a counterflow is always so damn hot, its hard to imagine the supply will stay cold long enough.

 

[doomy86]

A counter flow chiller is already very efficient, you won't gain a lot by recirculating. You could lower the flow rate and use the hot water for cleaning afterwards.

 

[govner1]

Alright everybody; so I'm in the process of rebuilding my brew system and I've been thinking of ways of making things as simple and self contained as possible. I've been seeing a lot of info recently on people recirculating their chiller water with a simple water pump to save water. I love the idea, but I have a counterflow chiller instead of an immersion chiller, has anyone had any success with doing this recirculation with a counterflow? Is it any different from doing it with a coil? And most importantly, how do you keep your water supply cold? The exit water with a counterflow is always so damn hot, its hard to imagine the supply will stay cold long enough.

I use a CFC & once the ground water temp rises above 75°F I use a pump ( from HF) to recirculate my chilling water. I usually need to add 1-2 bags during the process.
I do empty the initial "hot" water into a 10 gal barrel & add SanClean for general cleaning.
I'm also recirculating/whirlpooling into my BK. Once my Thrumometer reads at my target temp I fill my fermentors.
As someone stated above, you should use your pump outlet ball valve to control the wort flow rate to improve your chilling rate.

 

[Drumminguy81]

I experimented with this using a sump pump and a plate chiller. I got a large cooler and filled it with ice and water and recirculated. It worked ok but doing 10 gallon batches I found that all the ice was melted and water so warm that it wouldn't chill enough. Also found that buying 2-3 bags of ice every brew was annoying and pricey. I have since gone to much larger batches and use ground water. When the ground water is too warm I have a glycol system that I can turn on with a second plate chiller to pre chill my ground water. Im able to chill 22 gallons from boil to 70* in one pass in about 20 min. Hope that all makes sense.

 

[govner1]

To clarify, I use ground water initially and whirlpool/chill as low as that will get me. I save this water for cleanup & for watering herb & flower beds. This will usually get me to about 80°F or a little lower. Then I switch to my pump & ice water to complete my chill. I recirculate this water.

 

[RoatanBill]

If you're coming down from 212 to, say, 60, then you will need a lot of cold water to accomplish that.

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.

 

[govner1]

Having 38°F water is a miracle in my area!!!

 

[RoatanBill]

Having 38°F water is a miracle in my area!!!

I picked that value (38) because it's the standard refrigeration temperature.

My post actually was geared towards having a chiller available of some sort. A real glycol chiller would be below freezing.

Point is, if you try to recirculate the output back to the input, you're defeating the purpose. I realize people recirculate the wort back to the BK for multiple passes through a chiller using many times the BK's liquid volume in cooling water to accomplish the task. That's pretty wasteful of fresh water and since I live on an island I'm cognizant of NOT wasting water.

My example shows that under somewhat ideal conditions it takes a large quantity of cooling to bring the wort to pitching temperatures. There's simply no way around that physics reality.

 

[govner1]

It's difficult for me to whirlpool w/o recirculating back into my BK. I also try and conserve my water as detailed earlier.

 

[DolfoMan]

Thanks for all the input everyone. Looks like even with conserving water in mind, it doesn't seem worth it to recirculate the water. I may build a chill box for the water between the ground water and the chiller instead to get the water as cold as possible before it exchanges heat with the wort.

 

[beermanpete]

I am working on setting up a closed system for the chilling water. From what I can tell it should work well as long as the wort and cooling water are only run through the heat exchanger once, the flow rates are low enough, and the cooling water is colder than the desired output temp of the wort. RoatanBill's example is misleading because it assume the two fluids are combined which does not allow the coolant to become hotter than the cooled wort. With an isolated system and counter flow the coolant can be heated to nearly the original wort temperature and almost all of the heat in the wort can be transferred to an equal volume of coolant.

I have been following Dave Miller's article as a guide:
http://brewlikeapro.net/heatexchangers.html

I will be testing it out on a 5 gallon batch in a few days.

 

[Owly055]

Use your water by running it into the washing machine, or to bath, or something else, and plan your brewing around utilizing the water..... flush your toilet with it, water your house plants, use it for clean up and / or for washing dishes............ It's absurd to burn electricity to make ice for chilling water for your counterflow chiller...... a waste of money!

Interestingly, this comes up as I am doing a no boil / no chill brew.... I've done several, and it DOES work. That said, I have essentially free unlimited well water that is very cold any time of year. Pumping costs are laughably low. Maintenance is almost zip. I replace a pump every 30 years or so, a pressure switch ($20) every 4 or 5 years, and knock on wood, the pressure tank is well beyond 30 years. The well does not belong to me, but I've used and maintained it for many years, and my neighbor uses it a few months a year to water livestock....My electric bill goes up about $30 those months. Someone else put the well in, I maintain it, and spend perhaps $150 dollars a year over the long haul. He's happy......... I'm happy. The $6K that it cost to sink the well (estimated) was spent long before I came along....... One hand washes the other. He helps me....... I help him......in various ways, everybody gets along. Life in rural Montana. Good people, good neighbors, good friends. We each know the other is there, no questions asked when we need help. That's the way it should be, and always has been out here.


H.W.

 

[RoatanBill]

beermanpete:
It makes absolutely no difference if the liquids are combined or not. It's a function of the energy transfer only. My example tried to show how much cooling water would be required given the stated optimistic assumptions. Your last sentence is true enough and IS exactly the same as my example in terms of heat transfer.
I provided a web site to visit and the actual formula to do the calculations.
The heat exchanger isn't 100% efficient, so my example underestimates the amount of cooling water required in a real world situation.

 

[Owly055]

It takes minutes only, and not much water to chill to 175. There is absolutely no reason to fast chill much below 180....... except time. Chill to 175, and put into your fermenter, and set it in a cool location..... pitch yeast tomorrow.
By doing this you save water and energy, and add an additional sterilization phase.

As our national half wit would say: "It'll be beautifully efficient, and beautifully sterile, and you will be beautifully covered while making beautiful home brew for your beautiful friends and family".

Is that a beautiful idea or what?
H.W.

 

[dlettow]

What I sometimes think about, and wonder if anyone has tried, is creating a closed system for reusing chiller water. Basically, two 30 to 50 gallon barrels. To chill, pump water from tank A, through chiller, and into tank B. The water in tank A would be ambient temp. B would fill with hot water so as not to raise the temp of A during the process. Then between brews, the water would cool back to ambient and could be reused. Virtually zero waste!

This would take a fair amount of space, and the tanks need solid foundational support because of the weight. However, those of us who brew in our basements might be able to accommodate this setup. Ambient temp in my basement is between 50 and 70 depending on time of year.

 

[lucianthorr]

After one or two experiences with a garden hose going AWOL in the middle of my kitchen, I did something similar and it actually worked pretty well.
I'd start with one brew-bucket with an 8lb bag of ice and tap water on the kitchen counter going down to my plate chiller on a chair which would then empty out into a second brew-bucket on the floor. When the bottom bucket filled up, I'd swap it out for a third empty bucket and pour the bottom water back into the top and as the ice would melt, I'd drop another bag in.

It usually took about 4 bags of ice to chill 5 gallons and it was definitely a clean process.

 

[dyqik]

If you're coming down from 212 to, say, 60, then you will need a lot of cold water to accomplish that.

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.

That's true for an immersion chiller or for recirculating CFC with recirculated wort, but with a non-recirculating CFC (incl. plate chillers), the outlet water can be a lot hotter than the outlet wort temperature, because it's not a case of bringing the mass of cooling water into thermal equilibrium with the mass of hot wort. It's a true heat exchanger rather than a "mixing" type process.

At painfully low flow rates (which you'd never use in practice) or with a very large CFC area, you can cool 10 gal of wort to within a degree or two of the inlet cooling water temps, using only 10 gal of cooling water. The cooling water is output just a degree or so below that of the inlet wort. At somewhat more realistic flow rates with a good CFC, you might take 20 gal of 40F water to cool 10 gal of wort from 212F to 60F, and end up with 20 gal of ~130F water.

However, if you recirculate the CFC cooling water, then the inlet temperature rises, and it's not as "efficient" (except you are keeping the water, so efficiency doesn't apply). However, if you have a big reservoir, the temperature rise is small. If you recirculate the wort as well, then it's a mixing type process, and your math does apply.

 

[RoatanBill]

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.

 

[beermanpete]

RoatanBill,

You seem to be neglecting the capability of a well designed counterflow heat exchanger. With this arrangement an approach temperature of 2°C to 10°C is common. See this website for an example: http://www.alfalaval.com/increase-efficiency/products/compact-heat-exchangers/

With this type of heat exchanger the wort can be cooled to pitching temperature with an equal volume of water that is cooler that the target temperature by no more than the approach of the heat exchanger. If the coolant is cooler still the volume of coolant required is less that the volume of wort to be cooled.

Peter

 

[dyqik]

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.

No, you don't understand counterflow and plate chillers. They don't work by bringing one thermal mass into equilibrium with another, which is what your calculations represent, regardless of whether the fluids actually mix or not (the thermal calculation is the same whether or not the fluids mix if you assume 100% efficiency in the thermal contact). Immersion chillers are fundamentally different to counterflow type chillers, because they are cooling the whole wort mass at once, rather than incrementally cooling tiny portions of it with a tiny portion of the cooling water. Your math is for (repeatedly) bringing two thermal masses into equilibrium, not for heat exchanging.

The math for a counterflow heat exchanger can be found at http://web.mit.edu/16.unified/www/SPRING/thermodynamics/notes/node131.html

It's significantly different to the process you describe. In particular, the outlet cooling water temperature can be within a few degrees of the inlet wort temperature, and a lot hotter than the outlet wort temperature, so you can end up exchanging all the heat to be removed from the mass of wort to an almost equal (slightly greater because of inefficiencies) mass of coolant. Graphically this is shown in the plot of temperatures against position along the CF heat-exchanger from the Alfa-Laval link above:

The presence of the temperature cross is the critical difference to an immersion chiller or a recirculating CFC set up, and to cooling by bringing thermal masses into contact.

 

[RoatanBill]

I believe this thread concerns RECIRCULATING chill water. If you recirculate the water you eventually end up with the equilibrium case. Any advantage a technology provides on the first use of a molecule is negated on that molecules second use as it is now hot.

 

[beermanpete]

Sort of. The original post asks about recirculating the cooling water as a water saving method. The discussion that followed includes a variety of solutions. My first post is very clear that neither the coolant nor the wort are recirculated to achieve the predicted result. Our difference of opinion about the physics seems to be based on a disconnect about what we are discussing. The only way to get an acceptable result while recirculating the coolant would be to use a larger volume of water and ice (your point) or an active chiller (refrigeration).

 

[dyqik]

I believe this thread concerns RECIRCULATING chill water. If you recirculate the water you eventually end up with the equilibrium case. Any advantage a technology provides on the first use of a molecule is negated on that molecules second use as it is now hot.

We (me and beermanpete) are both talking about non-recirculating CFCs. Yes, if you recirculate the cooling water, you are effectively merely bringing the reservoir of cooling water into thermal contact with the wort and allowing them to equilibriate. This is the same as for a recirculating immersion chiller etc.

However, relevant to the OP's desire to reduce water usage, non-recirculating CFCs need a lot less water than recirculating chillers, _if_ you run them slowly enough that the thermal resistance of the wall and film layers at the wall isn't limiting you and you get a significant temperature crossover. And you end up with a nice bucket of hot water to clean up with...

 

[cmcquistion]

When I first read the title of this thread, I thought you were referring to recirculating the WORT and using a counter-flow chiller, not the cooling water.

I use my counter-flow chiller and re-circulate in the kettle, rather than doing a one-pass cooling with the counter-flow chiller.

I simply added a second valve to my boil kettle and I go out of the kettle, into a pump, out of the pump, into the CFC, then past a T-valve and back into the kettle. This allows me to do a hot-whirlpool in my kettle for late addition hops, before I start running the water.

My total cooling water usage is about 15 gallons or so and it take 10-20 minutes to chill, depending on ground water temp and how much I'm cooling. I'm very happy with my setup. My kettle is an electric BIAB system that I designed and built and the whole system is contained on one 30" wide cart.

 

[SevenOaks]

When I first read the title of this thread, I thought you were referring to recirculating the WORT and using a counter-flow chiller, not the cooling water.

I use my counter-flow chiller and re-circulate in the kettle, rather than doing a one-pass cooling with the counter-flow chiller.

I simply added a second valve to my boil kettle and I go out of the kettle, into a pump, out of the pump, into the CFC, then past a T-valve and back into the kettle. This allows me to do a hot-whirlpool in my kettle for late addition hops, before I start running the water.

My total cooling water usage is about 15 gallons or so and it take 10-20 minutes to chill, depending on ground water temp and how much I'm cooling. I'm very happy with my setup. My kettle is an electric BIAB system that I designed and built and the whole system is contained on one 30" wide cart.

This sounds just like I am contemplating. cmcquistion, can you post a photo of your setup?

 

[matchrocket]

When I lived in AZ, I threw 40 - 60 lbs of Ice in the HTL (Depending on the ground water temp at the time) and pumped water through my plate chiller, then back to the top of the HLT over Ice until my rack was complete.

I had no issues taking 10.5 gallons from boiling temp to pitch temp before the ice was melted. The left over water was then heated to be used for cleaning.

I dramatically reduced my water usage in this way. Now that I live somewhere where I have usable groundwater temps, I don't do it as I am, frankly, to lazy.

I have a HERMs setup, and I Didn't use the coil. Restricts flow to much to get the volume I wanted for efficient operation.

 

[cmcquistion]

This sounds just like I am contemplating. cmcquistion, can you post a photo of your setup?

Sure.

 

[Rcbandl]

Being in Florida our ground water is 70-80+ so i recirculate with the groud water to around 100 then use ice water recirculating with a 2nd pump to bring it to pitching temps. The ground water i use goes to cleanup, plant watering and any other use so its not completely wasted

 

[Barley_McAle]

I use an immersion chiller and I supply it with city water run through a Coleman cooler full of frozen water. I bought ice from a local store until I started to freeze water in those bottles you see in every store. You know, drinking water in small plastic bottles. I can't keep as much in my freezer because of the space those bottles occupy but it saves me so much money to use them instead of buying the ice it's well worth it. It works so much better to cool your wort with very cold water than to cool it with cool water that comes from your water supply. It uses some to wash through the cooler and become cooled to nearly freezing temperature but it's a lot better than running cool water from a city water supply. You will run a few gallons through the tubes but you will use less than you would if you didn't have the ice.