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Old 09-30-2013, 10:11 AM   #1
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Default Fermentation chamber water bath

Hi,

I use a deep freezer based fermentation chamber but I'm thinking that even with a fan, the air to carboy heat exchange is not enough to keep up with the energy being given off during peak activity of the yeast.

I was thinking that a water bath would be lots more effective, especially if I added a little aquarium power head to circulate the bath water. Thought it would be great for lagers since you could precool the bath to close to freezing on brew day and then only have to bring the wort down to 60 or 65.

Anyone tried this?

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Old 09-30-2013, 01:29 PM   #2
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Originally Posted by BackAlley
Hi,

I use a deep freezer based fermentation chamber but I'm thinking that even with a fan, the air to carboy heat exchange is not enough to keep up with the energy being given off during peak activity of the yeast...
Why do you think the freezer isn't cooling enough? If your freezer can get down to 35-50F, then it can most definitely keep up with fermentation. Sounds like you have a freezer problem.
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Old 09-30-2013, 02:35 PM   #3
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FWIW, I'm very new to brewing but given my engineering background, swamp coolers make me feel better. Carboy temps seems to match bath water temps (I keep mine in a bath tub) which can be quickly cooled by the degree very easily when you figure out what that is. For me, a frozen 3/4 full milk jug drops a couple degrees. Easy to maintain and watch and you have a huge thermal mass to avoid sudden swings with great heat transfer rate to control everything inside the carboy. Just make simple sense to me. I will caveat this by saying it can be a lot of work during the first few days of rapid fermentation, checking the water temperature all the time to be sure you're still at the ideal temp. That being said, my bath water never rises above 72F (room temp), even if left unattended, which is "safe" in the ideal fermentation temp limits of most (not all) ale yeast strands I use. Nonetheless, I tend to keep things from 66-68F.

Does this mean freezers/fermentation chambers are bad/ineffective? Probably not, but I have no idea, lol. I've never been so fortunate as to have one. With regards to accuracy of internal temps, water will transfer heat better than air; that's physics.

I don't think I'll get one either as people seem to think carboy temps can rise by up to 10 degrees different from whats outside the carboy at peak fermentation. In controlled chambers, people probably accommodate for this by lowering their temps by up to 10F, making everything kosher, which probably works. However, given the wort/carboy is submerged in water and churning internally during fermentation, I don't believe that 10 degrees applies to this situation. The heat transfer would just happen way to effective for this to be the case.

But alas, probably want to wait for some more experienced brewers to chime in.

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Old 09-30-2013, 02:48 PM   #4
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I have an entry-level mini fridge wired up to a $20 temp probe + controller, which I tape to the side of the carboy. Temps are always perfect, even for powerful fermentations.

I insulate the temp probe with a thin layer of foam mailer padding. Works great, and temps are set and forget.

The opinion that a fan or water might improve matters is absurd. My second cooler is a Cool Brewing bag, basically nothing more than a large, semirigid picnic cooler. Put carboy inside, toss a couple frozen 2-liters in with it, done. No pooled water, it's dry as a bone inside and holds temps for 12 hours at a stretch on hot days.

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Old 09-30-2013, 03:05 PM   #5
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As a matter of science a water bath will be more effective at controlling temps. Liquids are much better conductors of heat than air (e.g., it takes considerably more energy to change the temperature of liquid than the temp of air. This is why you can defrost meat better sitting in a sink full of water versus sitting on your counter exposed to air.

The yeast in the beer can put off a ton of energy (and heat). Dissipating that heat to the air around the carboy will take considerably more time that dissipating the same amount of heat to a liquid bath surrounding the carboy. So theoretically, if you could have your carboy immersed (at least to the level of the beer inside) in temp controlled liquid, that will control fermentation temps more precisely. The energy from the yeast will not be enough to really elevate the temp of the overall liquid mass.

As for the comment that a temp controlled freezer always works perfectly, I'm not so sure. A temp probe on the outside of a carboy (even covered with styrofoam) is not measuring the internal temperature of your carboy. I am willing to be that the temp in the middle of the carboy will be at least a few degrees warmer during peak fermentation. If the carboy were immersed in a liquid bath that is temp controlled on the other hand, the temps would be much more consistent.

That being said, few of us have room to build a temp controlled environment that then has enough room for a water immersion system. So we use chest freezers because they are "good enough for government work."

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Old 09-30-2013, 03:31 PM   #6
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Originally Posted by Kerin View Post
I have an entry-level mini fridge wired up to a $20 temp probe + controller, which I tape to the side of the carboy. Temps are always perfect, even for powerful fermentations.

I insulate the temp probe with a thin layer of foam mailer padding. Works great, and temps are set and forget.

The opinion that a fan or water might improve matters is absurd. My second cooler is a Cool Brewing bag, basically nothing more than a large, semirigid picnic cooler. Put carboy inside, toss a couple frozen 2-liters in with it, done. No pooled water, it's dry as a bone inside and holds temps for 12 hours at a stretch on hot days.
Wow, "absurd", that's pretty harsh.

The fermentation is generating heat, sometimes lots of it. The transfer of that heat out of the wort/beer is limited by the temp difference between the wort/beer and the convection from the surface of the carboy/bucket to the surroundings. Since we're trying to control the heat inside the fermenter not just the surface of the carboy, maximizing the convection minimizes temp differences.

A fan helps that a lot and I was wondering if one could do better with a water bath placed in the freezer, much as an industrial fermenter can be jacketed in water or glycol.
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Old 09-30-2013, 03:34 PM   #7
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Why do you think the freezer isn't cooling enough? If your freezer can get down to 35-50F, then it can most definitely keep up with fermentation. Sounds like you have a freezer problem.
Sorry for the confusion..the freezer's able to make plenty of cold. What I'm wondering about is the rate that air, even blown by a fan can get the heat out of the fermenter.
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Old 09-30-2013, 03:51 PM   #8
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...
The opinion that a fan or water might improve matters is absurd.
To those of us who simply dial down the thermostat a couple degrees around peak fermentation, yes it's absolutely absurd. But for those folks who think turning down a knob is too difficult, then a fan or water bath would probably help get the wort closer to the fridge temp at the expense of time, effort, and possibly power costs.

A third solution is to run a low thermostat differential then insulate the probe to the carboy. In that case, a fan or water bath is again absurd.
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Old 09-30-2013, 03:58 PM   #9
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As a matter of science a water bath will be more effective at controlling temps. Liquids are much better conductors of heat than air (e.g., it takes considerably more energy to change the temperature of liquid than the temp of air. This is why you can defrost meat better sitting in a sink full of water versus sitting on your counter exposed to air.

The yeast in the beer can put off a ton of energy (and heat). Dissipating that heat to the air around the carboy will take considerably more time that dissipating the same amount of heat to a liquid bath surrounding the carboy. So theoretically, if you could have your carboy immersed (at least to the level of the beer inside) in temp controlled liquid, that will control fermentation temps more precisely. The energy from the yeast will not be enough to really elevate the temp of the overall liquid mass.

As for the comment that a temp controlled freezer always works perfectly, I'm not so sure. A temp probe on the outside of a carboy (even covered with styrofoam) is not measuring the internal temperature of your carboy. I am willing to be that the temp in the middle of the carboy will be at least a few degrees warmer during peak fermentation. If the carboy were immersed in a liquid bath that is temp controlled on the other hand, the temps would be much more consistent.

That being said, few of us have room to build a temp controlled environment that then has enough room for a water immersion system. So we use chest freezers because they are "good enough for government work."
I agree with this response. Both routes will get the job done.

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Originally Posted by SpeedYellow View Post
To those of us who simply dial down the thermostat a couple degrees around peak fermentation, yes it's absolutely absurd. But for those folks who think turning down a knob is too difficult, then a fan or water bath would probably help get the wort closer to the fridge temp at the expense of time, effort, and possibly power costs.

A third solution is to run a low thermostat differential then insulate the probe to the carboy. In that case, a fan or water bath is again absurd.
Absurd for homebrewing, maybe. Absurd from a physics viewpoint, not at all. However, recognizing this is indeed a homebrewing forum, I guess I'll leave this alone at this point, lol. I'm sure the method each person is using is yielding acceptable beer (according to their tastes) therefore to split these hairs is probably a waste of time.
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Old 09-30-2013, 04:00 PM   #10
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Originally Posted by SpeedYellow View Post
To those of us who simply dial down the thermostat a couple degrees around peak fermentation, yes it's absolutely absurd. But for those folks who think turning down a knob is too difficult, then a fan or water bath would probably help get the wort closer to the fridge temp at the expense of time, effort, and possibly power costs.

A third solution is to run a low thermostat differential then insulate the probe to the carboy. In that case, a fan or water bath is again absurd.
It might be "overkill" but referring to it as absurd is a bit obnoxious in my view. I'm not sure how effective a fan would be, but a water bath would definitely do a much better job of maintaining a relatively constant* temp. You are right that you can keep temps cool enough by simply lowering the air temperature but you are going to have much wider swings in the beer temp with air versus a liquid bath.

*I am not an expert on this, but I certainly understand that we will get the best results not only from keeping fermentation temps cool enough but also from keeping it relatively constant.
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