Temperature stratification in conical fermentor

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kshuler

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Good morning everyone. Just thought I would report on something I noticed with my conical fermentor. I have an insulated conical, that has a peltier heating system, home made, but essentially similar to what the MoreBeer ultimate conicals have. Yesterday I chilled the wort to 59 while transferring to the conical, but I was using Thames Valley yeast, which ferments best at 59 to 72. As such, I wanted to heat the wort to 62 to start fermenting. So I turned on the heating system. After about 2 hours I came back. The temperature had changed only a little, but I felt the metal lid, and it was hot. I gave the fermentor a stir, and the temperature read 84! There was massively more temperature stratification than I would ever expect. I would have thought that there would be currents in the fermentor that would even out the temperatures, but it does not appear that such currents exist, or if they do, only very minimally.

So I let it cool and pitch at 64. As I have found the chillers work much better at holding temperature than changing it, I went ahead and turned on temperature control and went to bed. Woke up this morning to beer nicely in the 64 degree range, right where it should be. But then I decided to toss in a Tilt digital hydrometer so i could keep track of the gravity. It read 83 degrees! I pulled the temperature probe up from the bottom of the thermowell so it sat at the upper layer of the fermentor… it read over 78, as well! Again, there is significant vertical temperature stratification in the conical.

Has anyone else noticed this? It appears to be a thin layer of very hot wort, right at the top, and the rest of the wort seems to be held at the appropriate temperature. IS this something to worry about, as only about 5% of the wort is at this elevated temperature? Does the same thing happen with browbeats? What about with jacketed conicals?
 

bkboiler

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absolutely! my ferm chamber has the temp control thermal probe hanging from the top and i have a dial-thermometer at the bottom. There's also a ferm-ometer strip on the top of each carboy. There's easily a 5 degree difference between the top of the fermenter (yeast-heat production) and the bottom of the ferm chamber (where i can read the dial gauge).
 
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kshuler

kshuler

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I see. But of course, this was a HUGE 20 degree difference related to my fermentation control. I thought the warm wort would rise and suck in the cold and generate a little circular current. Apparently not. So when I document fermentation temperature, do I document the top or the bottom? What are the chances of getting fusels and esters from the small portion that was overheated? Should I worry about the quality of the batch (I guess only time will tell). I have used this setup in the past and have not noted any strange flavors, so I am guessing it is OK.

How to big breweries deal with this? I would think jacketed fermentor would do exactly the same thing, right (only opposite, with the cold collecting on the bottom)? Do they stir somehow?
 

dcbw

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A jacketed fermentor has a full jacket that goes around almost the whole thing including the cone. The glycol is thus able to cool or heat almost every surface and ensure constant temperature. No stratification because all sides are the same temperature.

The morebeer doesn't look like a real jacketed conical. Instead it appears to have heat and cool bands around the middle, and only neoprene insulation wrap on the cone and top. I doubt it can heat/cool as consistently as a fully jacketed glycol chilled conical.

In your case you might need to stir. Or get an upright freezer and put the conical in it.
 

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When fabricating my coil for my 40 gal fermenter I assured that it stretched from the 30 gal line all the way down to the 3 gal mark. This sits just above my sample port. I also assured there was plenty of space between my thermowell and the coil. I'm assuming that I should not see a stratification issue. I'll use it for the first time next week. I ordered another lid so that I can use CIP by installing a couple of the spray balls from Brewers Hardware.
 

stouttanksandkettles

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If you have the peltier chip attached directly to the conical, that would explain what is going on. The chips are 2"x2" and as a result, your heating or cooling will be concentrated there. And, with heating, heat rises so you will not see it affect the liquid temperature much below the height of the chip.

Even if you have a heat sink or aluminum block (we offer milled aluminum blocks that match our fermenters), the heat rising affect will always exist. So, for heating with a peltier chip, put it as low as you can on your fermenter. I think you'll see better/more consistent results that way. But I still wouldn't expect the chip to heat the liquid below without stirring or agitation.

In commercial breweries, fermenters are not typically heated, they are just cooled. The cooling jackets are designed to provide cooling throughout the tank by covering a fairly large surface area on the side and the cone.

Cheers,

John
Stout Tanks and Kettles
stouttanks.com
Aluminum block for peltier chips
Instructions to make your own peltier cooling (or heating) system
 

sunny_jim

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Hello
Stratification can happen in several ways - adding yeast to the top of the wort is one way. The top ferments out and then the bottom finally has enough yeast to ferment. In multiple brew fermenters, pitching all yeast to the first brew is another way to assure stratification. An article was intended to be attached about the phenomenon. It was rejected as being over size limits. Contact me for more as needed.
Send me your e-mail if you wish and i will share.
Otherwise, if you are an MBAA member, you can see the whole paper on stratification in the Technical Quarterly. it is real, makes some lesser quality beer and the yeast don't do well next time pitched.
See http://www.mbaa.com/publications/tq/tqPastIssues/2008/Abstracts/TQ-45-2-0115.htm
Regards
 

DPBISME

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One wonders if this is one of the reasons that there seems to be an optimal shape for conicals... One would think the narrower the conical the more heat stratification there would be. I would think convection might be a bit more limited in a narrow one...
 

SplitHops

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Good morning everyone. Just thought I would report on something I noticed with my conical fermentor. I have an insulated conical, that has a peltier heating system, home made, but essentially similar to what the MoreBeer ultimate conicals have. Yesterday I chilled the wort to 59 while transferring to the conical, but I was using Thames Valley yeast, which ferments best at 59 to 72. As such, I wanted to heat the wort to 62 to start fermenting. So I turned on the heating system. After about 2 hours I came back. The temperature had changed only a little, but I felt the metal lid, and it was hot. I gave the fermentor a stir, and the temperature read 84! There was massively more temperature stratification than I would ever expect. I would have thought that there would be currents in the fermentor that would even out the temperatures, but it does not appear that such currents exist, or if they do, only very minimally.

So I let it cool and pitch at 64. As I have found the chillers work much better at holding temperature than changing it, I went ahead and turned on temperature control and went to bed. Woke up this morning to beer nicely in the 64 degree range, right where it should be. But then I decided to toss in a Tilt digital hydrometer so i could keep track of the gravity. It read 83 degrees! I pulled the temperature probe up from the bottom of the thermowell so it sat at the upper layer of the fermentor… it read over 78, as well! Again, there is significant vertical temperature stratification in the conical.

Has anyone else noticed this? It appears to be a thin layer of very hot wort, right at the top, and the rest of the wort seems to be held at the appropriate temperature. IS this something to worry about, as only about 5% of the wort is at this elevated temperature? Does the same thing happen with browbeats? What about with jacketed conicals?
I would do the simple thing, read temperature at the bottom of the conical for Lagers and the top for the ales. Sounds stupid simple but good luck trying to get it to regulate without an agitator which we don't want to do during fermentation anyway.
 

Mashinations

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There is absolutely active currents/movement when fermentation is taking place. Just want through the side of a carboy and it's pretty clear.

Other than the hydromotor you put into the beer at one point you really didn't say where/how any of these temperature readings were taken.

With any of the heating/cooling solutions that aren't a jacketed fermenter I agree with what someone else wrote - they are far better at maintaining temperature than increasing/decreasing. You're warming the air around the fermenter or in some cases the fermenter itself and you need to wait for the BTU's to be put in/out of the wort to wherever the temperature is being taken. There's always bound to be some carryover.

I'd be shocked if there was a 20 degree separation in the actual wort over what amounts to 18-24 vertical inches unless it was right at the point where you were heating the conical.
 

nogoer

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This is part of the reason why i shied away from peltier style temp control. Not only are they small, but they only sit on one side so the effectiveness of the heating or cooling isnt great and you'll have large temp swings just trying to go either way except maintain. I'm sure it takes a long time for the heat to radiate in a 3 dimensional space like that and it would be very difficult for that heat to move downwards as well. Your temp probe placement is key to getting enough temp control but not too much. If its too close it wont heat enough if its too far it will heat too much before it registers the proper temp.

Im not sure what your temp control setup is, but i use a heat and cooling controller and have a heat pad at the bottom of the cone. this way heat has to move up and has a longer distance to travel and create convection. My cooling is with interior coils placed in the middle vertically and spanning a few gallons worth of vertical space(its a chronical brewmaster version). Even in the middle of winter i al;most never need heat so i usually leave it unplugged and use cooling only.
 

Alexspeers

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Rather than fill this check out: MBAA TQ vol. 45, no. 2, 2008, pp. 115-120. A wonderful. article by David Kapral.

This is usually only an issue for them when 2 or more brews are added and new denser brew 'slips' under the actively fermenting one.

If you have an active fermenter and just 1 brew I would not expect to see this as CO2 should 'rouse' the ferment.
 

richmke

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I thought the warm wort would rise and suck in the cold and generate a little circular current. Apparently not.
It appears to be a thin layer of very hot wort, right at the top, and the rest of the wort seems to be held at the appropriate temperature.
The wort right by the heating element will be the warmest. As it warms, it will start to rise, and be displaced by cooler wort around it (convection).

If the heating element is near the top, then only the top layer will be heated, and it will take a lot of time for the cooler wort below to heat (conduction).

If the fermentation is generating more heat than is being lost, then the fermenting wort could pick up additional heat (top warmer than by the heating element). But, then you shouldn't need the heating.

If you say it is "hot" at the top, then I suspect your heating element is near the top. Try to put the heating element as low on the fermentor as possible.
 

anchornm

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I now use stainless milk cans with 2" tri-clover necks.
I submerse them in cold water, and use an inkbird type device to turn on a pond pump when the temp goes too high. The rig has three chambers, and three pumps, which all overflows return to a cooler full of blue ice.
I monitor the jacket, not the wort.
I set the jacket at the low target for the yeast, but do not pitch the yeast until the next day (Aussie No Chill), everything is equilibrated by then. After the primary, I pump it to the second milk can (using CO2) that is kept at the high limit of the target yeast. I let it rest outside the bath for 24 hours to diacetal rest.
After the secondary, I transfer to kegs, and hold at cellar temp for 2 weeks or so. Depends how busy I am. The kegs are topped up with 12PSI CO2 daily. When they go into the kegerator, it cold crashes, and just keeps getting better until it goes dry...
I lose two transfers of trub (about 1/2"). I never harvest yeast. I harvest starter...
 
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kshuler

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Wow, thanks for the thorough input. I'll explain the system a bit more. I use a Stout Tanks and Kettles 7.3 gallon fermentor, and I actually bought their milled aluminum blocks for this, as it was too much of a pain to get them milled. I have a controller that supplies current for either heating or cooling described here that powers two peltiers (9 amp each), and runs off an Auber PID. The entire conical, other than the top, is insulated in 3/4" neoprene, and the aluminum block has its own neoprene covering so the fans blowing do not decrease their effectiveness. I have a 1.5" tri-clover T, with a thermowell going into the wort (offset to one side-- I keep it as close to the aluminum block as possible, which is about 1.5-2 inches) and a blow off tube coming out the side. In addition, I have a Tilt hydrometer floating in the fermenting beer. I have the aluminum block mounted as low as I can on the fermentor, so it is not touching the stand and only heats the conical fermentor.

The temperature controller has an RTD probe down the thermowell, and usually I send it all the way to the bottom so it is about 6 inches under the fermenting beer. It reads the temperature there. I have tried several positions. Initially when I started it, the thermowel was on the opposite side of the fermentor from the aluminum heating/cooling block. But when things weren't heating up, I moved the location to the side closest to the heater... there was, to my surprise, no significant change. When compared to the temperature of the TILT, however, it was VASTLY different. This led me to pull up the RTD in the thermowell but about 4 inches and that's when the temperature registering on the controller started to rise VERY rapidly.

I just looked at the data from the tilt. At 19:09 it read 59 degrees. This rose rapidly and peaked at 20:54 at 93.7 degrees. But when I measured with the RTD in the thermowell, the temperature at the bottom continued read 59. When I switched it to the other side (closer to the aluminum block) at read 60.8... so it was certainly a little bit higher. But when I pulled it up 4 inches, it was 84 as read by the thermowell RTD.

Once active fermentation started and the beer was churning, I checked again and there was no significant difference. But it has slowed now, and it once again seems to be showing thermal stratification.

Perhaps I need to set up a system that will rouse the yeast with CO2 from the bottom.
 

Mashinations

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This led me to pull up the RTD in the thermowell but about 4 inches and that's when the temperature registering on the controller started to rise VERY rapidly.

I just looked at the data from the tilt. At 19:09 it read 59 degrees. This rose rapidly and peaked at 20:54 at 93.7 degrees. But when I measured with the RTD in the thermowell, the temperature at the bottom continued read 59. When I switched it to the other side (closer to the aluminum block) at read 60.8... so it was certainly a little bit higher. But when I pulled it up 4 inches, it was 84 as read by the thermowell RTD.
A lot more information to go on - that helps. So the only time you're getting what you believe is a "Significant" temperature difference is when you pull up the RTD. I suspect you're pulling it up onto the section of thermowell that is surrounded by air - not beer. That air temperature could be quite a bit higher than the beer temperature.

I use a similar thermowell method but on a conical that's in an upright freezer with 2 heating pads in it. Thermowell temp sitting comfortably at 68 and when I open the door to the freezer the air surrounding it can be well over that temp.
 

JasontheBeaver

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Interesting thread because I've been looking at buying a 15 gallon conical with a very similar setup to the OP and it kept nagging at me that stratification might be a problem.
I like the heating pad around the base cone area solution for heating, but usually it's cooling that I'll need so that's more important.
I wonder if there's a small, simple stirring device that could be installed through a tri-clamp port to just gently move things around?
 

Mashinations

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Interesting thread because I've been looking at buying a 15 gallon conical with a very similar setup to the OP and it kept nagging at me that stratification might be a problem.
I like the heating pad around the base cone area solution for heating, but usually it's cooling that I'll need so that's more important.
I wonder if there's a small, simple stirring device that could be installed through a tri-clamp port to just gently move things around?
Upright freezer is what you want. I put tape the heating pads to the inside of the freezer (not onto the conical) so whether it's heating or cooling it's adjusting the temperature of the air around the conical. Using an upright freezer also allows you the ability to do a lager - something you can't likely do with a Peltier system.
 

Wobbegong

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Very interesting stuff being shared here. I was concerned with variables in temp when contemplating my method. It makes sense that a larger surface area of heating/cooling contact would result in more consistent temp readings at various levels within the fermenter. I've tested my setup with water in the fermenter and find little to no variation in temp when cooling. I do get readings that are a couple degrees warmer up top when set up to warm, but nothing mere than 2 to 3 degrees. When set to lagering temps, I get very accurate and stable results top to bottom. The ability to adjust my cooling/heating liquid temp with extreme accuracy helps though.. :rockin:

Conical.jpg
 
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kshuler

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A lot more information to go on - that helps. So the only time you're getting what you believe is a "Significant" temperature difference is when you pull up the RTD. I suspect you're pulling it up onto the section of thermowell that is surrounded by air - not beer. That air temperature could be quite a bit higher than the beer temperature.
I would agree with you, but the TILT hydrometer, that is literally floating at the surfaced sends temperature and SG via bluetooth to my phone reads even higher than the temperature controller. Now, it is my first time using this so I don't really know how accurate it is at this temp. It held pretty steady and agreed with my calibrated thermometer in a glass of water at 65 degrees in the house though.

I will say that this is the first time I have used this setup for heating and had always used it on the cooling cycle until this brew... possible I had warm beer fermenting with a cold area the bottom of the cone. Would stirring have nay negative side effects, if I could figure out how to rig a sterile stirring mechanism to the fermentor?

I had thought about possibly rigging an aquarium chiller to the fermentor and trying that, but it would require some new expensive acquisitions... Has anyone checked the temperature on a long thermowell to see if they can detect temperature stratification? It isn't an issue once the beer starts to really get going, but when it is not churning I am worried that this will affect the beer.
 

anchornm

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I live in New Mexico, and temperature control almost always means trying to keep the fermenter cool. The original poster lives in Seattle, and the problem is different. IMHO, the shape of the conical accepts temperature contributions from the ambient air at different rates(depending on the position). Another major factor is that (if) you use gravity to move the beer, that requires the bottom of the conical to be above the top of the next tank. A simple homebrew setup says that the conical would have to be 3 feet off the ground to gravity dump into a keg. That means the top is at 7 feet (even with a fastfermenter). Getting 50 pounds of beer to the top (initially) is not my idea of fun. I can't imagine that a half barrel system would be any better. Sure, that means pumps, PBW, and difficult sanitization. If it were me (in Seattle), I would accept the room temperature as a godsend, and just change recipes and yeast to suit the seasons. It has worked in Europe for 1000 years.
 

stouttanksandkettles

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There are two different applications being discussed in this thread: heating and cooling.

I have done both with my conical.

I have not seen a stratification issue with cooling. The aluminum block mounts onto the straight side of the fermenter and then the cooled wort drops down into the cone pretty well (e.g., the warmer wort in the cone will rise up to the straight side, where the cooling is going on, keeping the temperature relatively even throughout).

I have tried heating water using the peltier chip as a test, and I also noted that the temperature was high at the top and low at the bottom of the fermenter. This is because the aluminum plate is up on the straight side of the fermenter and when it heats, the cooler wort down below gets trapped down there (because heat rises). The thermowell is also down near the bottom of the aluminum block, so it is sensing cooler wort and continues to tell the peltier chip to heat. As a result, you get stratification.

I think the point is that the peltier chips on the straight side of the tank will do a nice job for cooling the wort. But for heating, the wort needs to be agitated or else the peltier chip needs to be located down low in the tank in the cone area. This would require a totally different aluminum block because the curvature of the cone is different than the curvature of the straight side. Or, it may be possible to mount a chip to the cone with a lot of thermal paste to fill in the gaps...perhaps.

For me, I haven't had much of a need to heat my fermenter, so the peltier chips work great for my application.

I hope this adds a bit of clarification to the thread.

Cheers,

John
Stout Tanks and Kettles
 
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kshuler

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Thanks, John. I do love my Stout Conicals!

When summer rolls around and I have to switch to cooling, I'll try it then and see if I notice any stratification when cooling.

Klaus
 

sunny_jim

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Good morning everyone. Just thought I would report on something I noticed with my conical fermentor. I have an insulated conical, that has a peltier heating system, home made, but essentially similar to what the MoreBeer ultimate conicals have. Yesterday I chilled the wort to 59 while transferring to the conical, but I was using Thames Valley yeast, which ferments best at 59 to 72. As such, I wanted to heat the wort to 62 to start fermenting. So I turned on the heating system. After about 2 hours I came back. The temperature had changed only a little, but I felt the metal lid, and it was hot. I gave the fermentor a stir, and the temperature read 84! There was massively more temperature stratification than I would ever expect. I would have thought that there would be currents in the fermentor that would even out the temperatures, but it does not appear that such currents exist, or if they do, only very minimally.

So I let it cool and pitch at 64. As I have found the chillers work much better at holding temperature than changing it, I went ahead and turned on temperature control and went to bed. Woke up this morning to beer nicely in the 64 degree range, right where it should be. But then I decided to toss in a Tilt digital hydrometer so i could keep track of the gravity. It read 83 degrees! I pulled the temperature probe up from the bottom of the thermowell so it sat at the upper layer of the fermentor… it read over 78, as well! Again, there is significant vertical temperature stratification in the conical.

Has anyone else noticed this? It appears to be a thin layer of very hot wort, right at the top, and the rest of the wort seems to be held at the appropriate temperature. IS this something to worry about, as only about 5% of the wort is at this elevated temperature? Does the same thing happen with browbeats? What about with jacketed conicals?
 

sunny_jim

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Hello. Stratified Fermentations do happen in the industry. It happens particularly when adding unyeasted wort to an ongoing fermentation. The fresh wort pushes the active fermentation upwards past the RTD. Below the RTD is wort with about 4MM cells/ml. Above the RTD the "other fermentation" is out of control, and remains so until the lower fermentation hits about 12 MM cells/ ml . That takes about 24 hours.....then, the fermenter contents "turn" the temperature drops and you have a 3rd fermentation that is not very good. Please see my article in the Technical Quarterly, Volume 45 no. 2, 2008 that explains this in detail...and provides solutions. Contact me if you need more. David Kapral
 
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