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Author Topic: Immersion Chiller Design  (Read 2884 times)

Offline Saccharomyces

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Immersion Chiller Design
« on: November 23, 2020, 02:23:01 pm »
A chiller is one of the last things I need to build or buy before I can get my new brew house up and running.   I used immersion and counterflow chillers in the past, all of which I built. If chilling wort in the least amount of time using the least amount of water and while remaining relatively easy to clean was important, counterflow was the obvious choice before JaDeD started to produce outside of the box immersion chillers.  Yesterday, I started to think about JaDeD's claims.  It is obvious that the Hydra chills wort faster than a single 25' coil of copper tubing of the same diameter.  It does so by increasing the volume of coolant and the amount of surface area that is in contact with the wort.   However, one thing that it does not do is increase the surface area to volume ratio and that is what makes a chiller truly more efficient, especially as Delta T grows smaller.  By more efficient, I am not talking about speed of cooling.  I am talking about the amount of heat being being draw off by the coolant per unit of volume.  Time in heat exchanger only becomes important as Delta T grows smaller.   A 50' immersion chiller is not more efficient than a 25' chiller when Delta T is large because temperature equilibrium is reached fairly early.  However, as Delta T grows smaller, a 50' immersion chiller is more efficient than a 25' immersion chiller because the coolant has longer to sink heat from the wort; however, it does so at the cost of time.

With that said, the Mantis is truly a more efficient immersion chiller than a single 25' coil of 3/8" copper.  Here is why:

25’  3/8” copper tubing chiller

Surface Area = 300” (25 feet) * 0.375 * 3.14 = 353.25 sq. in.
Volume = 300” (25 feet) * 0.1875 ^ 2 * 3.14 =  33.12 cu. in.
Surface Area-to-Volume Ratio = 353.25 / 33.12 =  10.67

2 x 25’ 1/4” copper tubing chiller

Surface Area = 300” (25 feet) * 0.25 * 3.14  * 2 = 471 sq. in.
Volume = 300” (25 feet) * 0.125 ^ 2 * 3.14 * 2  =  29.44 cu. in.
Surface Area-to-Volume Ratio = 471 / 29.44 =  16

As one can clearly see, a 2 x 25 x 1/4” copper tubing chiller is 1.5 times more efficient in terms of surface area to volume than a 25’ 3’8” chiller for any given volume of water.  That is not as important when Delta T is large, but it conserves water when Delta becomes small.   We have all seen an immersion chiller drop wort from boiling to around 150F quickly.  From that point, cooling speed slows as Delta T become smaller.   The only way to increase thermal transfer is to slow down coolant flow or increase the length of the chiller.   However, there is another way; namely, increase the surface area to volume ratio.  Turbulent flow through the chiller will allow for better heat transfer for any given surface area to volume ratio, but the limiting factor will be how small can we make Delta T before we reach diminishing returns with respect to coolant usage.

« Last Edit: November 23, 2020, 03:24:06 pm by Saccharomyces »

Offline denny

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Re: Immersion Chiller Design
« Reply #1 on: November 23, 2020, 02:29:05 pm »
with my water and a Hydra I can get 6 gal. from boiling to 60F in 6 minutes
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Offline ynotbrusum

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Re: Immersion Chiller Design
« Reply #2 on: November 23, 2020, 03:14:14 pm »
with my water and a Hydra I can get 6 gal. from boiling to 60F in 6 minutes

Yep, my Hydra works quick enough and when I need to go below my well water temperature (about 56F), I can run a pump with ice water with my old immersion coil recirc'ing to push it below water tap temp.  In the winter, I just set out a 5 gallon bucket the night before brew day and use it for the ice water bath.

I rarely use a counterflow anymore for these reasons...and I just bought a CuSS brand specially made for my Foundry.  It is really slick.
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Offline Saccharomyces

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Re: Immersion Chiller Design
« Reply #3 on: November 23, 2020, 03:30:43 pm »
with my water and a Hydra I can get 6 gal. from boiling to 60F in 6 minutes

The Hydra works well as it does because of the increased volume of water and short exit time, not because it is more efficient in terms of heat transfer per volume of water.   Water volume increases with respect to surface area. That is okay.  However, there is no denying that the Hydra does not reduce water  volume.  It just reduces time.  I would like to design a immersion chiller that is efficient with respect to water consumption as a well-designed counterflow chiller.  A counterflow chiller always has a low Delta T exit-wise with a high Delta T entrance-wise, which translate to maximum heat exchange.
« Last Edit: November 23, 2020, 05:10:46 pm by Saccharomyces »

Offline denny

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Re: Immersion Chiller Design
« Reply #4 on: November 23, 2020, 04:11:42 pm »
with my water and a Hydra I can get 6 gal. from boiling to 60F in 6 minutes

The Hydra works well as it does because of the increased volume of water and short exit time, not because it is more efficient in terms of heat transfer per volume of water.   Water volume increases with respect to surface area. That is okay.  However, there is no denying that the Hydra does not reduce water  volume.  It just reduces time.  I would like to design a immersion chiller that is efficient with respect to water consumption as a well-designed counterflow chiller.  A counterflow chiller always has a lot Delta T exit-wise with a high Delta T entrance-wise, which translate to maximum heat exchange.

Having a well, water consumption is not something I worry about.  Clay at Jaded is very aware of water consumption. You might want to speak with him bout the subject as it relates to their chillers.
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Offline BrewBama

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Re: Immersion Chiller Design
« Reply #5 on: November 23, 2020, 04:28:25 pm »
It doesn’t matter to me why the Jaded Hydra works as well as it does. The fact remains it works ...and very fast.

I reserve the hot water that comes out of the IM that would otherwise go down the drain for cleaning.

Once the wort is ~100*F I change the circuit over to an ice bath.

So, the only waste is the 3-4 gal of what was ice water. I just figure that’s the cost of doing business.


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Offline purduekenn

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Re: Immersion Chiller Design
« Reply #6 on: November 23, 2020, 04:54:37 pm »
Jaded hydra is a great chiller. It chills to ground water temp from my municipal water temp in 6-8 minutes.

Offline kpfoleyjr

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Re: Immersion Chiller Design
« Reply #7 on: November 23, 2020, 08:40:10 pm »
When I moved from propane to electric, I bought an “ElectricChair” stand from JaDed that lifted the bottom of my existing Hydra off of the electric element on the bottom of the boil kettle.  The result was that it exposed a couple of the loops on the top part of the Hydra when brewing a 5-gallon batch in my BrewBuilt 10-gallon BK, and it takes a little longer to cool down a boil.  I usually brew 6-gallon batches now when I can, which helps immerse more of the Hydra.  I looked into using a curved heating element that would be out of the way, but it was recalled before I got a chance to use it and I returned it to MoreBeer; still waiting on the replacement.

Offline Richard

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Re: Immersion Chiller Design
« Reply #8 on: November 23, 2020, 10:34:05 pm »
I use an immersion chiller and "waste" almost no water. I have a small lunch-sized cooler that I put in the left side of my 2-compartment sink. In the cooler is a submersible pump that pumps water through the chiller. Once the pump is started I flow enough water from the sink spigot into the cooler to keep the water level over the pump. The output water goes to the other side of the sink, and the first and hottest water is saved for cleaning up later. When that sink gets full I put the discharge water into buckets that get saved for watering the landscape and house plants. When the wort temperature gets down to 120 or so I add ice to the cooler to increase the delta-T of the water in the chiller. When the discharge water is cooler than my tap water I put the discharge water back into the cooler and stop adding tap water, making it a closed system. The only water that goes down the drain is a bit lost when I change buckets. If I have someone to help me with the change there is absolutely no water lost.
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Offline kramerog

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Re: Immersion Chiller Design
« Reply #9 on: November 23, 2020, 10:56:19 pm »
Sacch, yes, the Hydra is very fast because it has 3 parallel coils resulting is very high coolant flowrates. It is like bringing a cannon to a gunfight. For a coolant efficient design, the two most important factors are the area and the degree of convection in the wort (it doesn't take that much flow to get turbulent flow within a small pipe). Initially during cooling, it is possible to get a decent amount of natural convection from the difference in density of hot wort and cool wort and the wort temperature drops quickly, but as the temperature delta goes down natural convection essentially disappears.  Forcing convection of the wort by stirring (either manually or using a mix stir), pumping the wort or moving the cooler in the wort (as shown in some Jaded videos) keeps rate of heat transfer high. In other words, area is important but surface area to volume of pipe not so much.

A few tips on immersion cooler design, putting the tubes next to each other reduces the effective surface area.   A coil design is good for inducing natural convention.  Generally, commercial immersion coolers are not optimized for kettle size.  If I had to make another immersion cooler I would probably do two coils of 25 feet length close to walls of the kettle (for a 10 gal batch) from the bottom and close to the top of the normal wort level to maximize natural convection and so it would be easy to put a mix-stir in the middle.

Offline pete b

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Re: Immersion Chiller Design
« Reply #10 on: November 24, 2020, 07:02:57 am »
Sacch, yes, the Hydra is very fast because it has 3 parallel coils resulting is very high coolant flowrates. It is like bringing a cannon to a gunfight. For a coolant efficient design, the two most important factors are the area and the degree of convection in the wort (it doesn't take that much flow to get turbulent flow within a small pipe). Initially during cooling, it is possible to get a decent amount of natural convection from the difference in density of hot wort and cool wort and the wort temperature drops quickly, but as the temperature delta goes down natural convection essentially disappears.  Forcing convection of the wort by stirring (either manually or using a mix stir), pumping the wort or moving the cooler in the wort (as shown in some Jaded videos) keeps rate of heat transfer high. In other words, area is important but surface area to volume of pipe not so much.

A few tips on immersion cooler design, putting the tubes next to each other reduces the effective surface area.   A coil design is good for inducing natural convention.  Generally, commercial immersion coolers are not optimized for kettle size.  If I had to make another immersion cooler I would probably do two coils of 25 feet length close to walls of the kettle (for a 10 gal batch) from the bottom and close to the top of the normal wort level to maximize natural convection and so it would be easy to put a mix-stir in the middle.
I never thought of using my mix stir when chilling. Thanks for bringing it up, it seems obvious now. That with the fact my water is cold, coming from an almost 400' well, should get me cool even faster.
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Offline dls5492

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Re: Immersion Chiller Design
« Reply #11 on: November 24, 2020, 01:28:47 pm »
My Hydra chiller from Jaded Brewing is Awesome. Worth every penny!
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Offline Semper Sitientem

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Re: Immersion Chiller Design
« Reply #12 on: November 24, 2020, 04:13:55 pm »
Just to pile on, I have a Mantis and it’s one of the best purchases I’ve made for my addiction.
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Offline Saccharomyces

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Re: Immersion Chiller Design
« Reply #13 on: November 24, 2020, 09:27:24 pm »
I went with the CuS.S version of the Mantis.  I plan to use the utility sink faucet in my garage as my water source.  I shut off my hose bibs and put away my hoses in the winter.  Plus, the reason why I went through the trouble to run 4-wire 240V/30A service to my garage is because I want to be able to brew with garage door shut. As I mentioned above, the 2 x 25' 1/4" coil design is 1.5 times more efficient than any 3/8" tubing-based chiller in terms of surface area-to-volume ratio.  That is the reason why it will outperform the Hydra when restricted to a 2 gpm water source.

Offline erockrph

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Re: Immersion Chiller Design
« Reply #14 on: November 25, 2020, 08:43:57 am »
Anyone here use a Scylla (or any other Jaded chiller for that matter) in the 6.5 gallon Anvil Foundry? That is one part of my system that could use some improvement. Given that I brew in my kitchen, and I have no way to connect my faucet directly to my immersion chiller, I am stuck sticking my faucet in a 5-gallon bucket that has a pond pump inside it to run my chiller. Despite having relatively cold tap water (low to mid 50's F), it still takes longer than I'd like to chill down to pitching temps. I'd love to knock 15-20 minutes off the end of my brew day.
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