Fermentation chamber water bath

[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.

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?

 

[SpeedYellow]

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.

 

[Skep18]

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.

 

[Trail]

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.

 

[rklinck]

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."

 

[BackAlley]

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.

 

[BackAlley]

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.

 

[SpeedYellow]

...
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.

 

[Skep18]

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.

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.

 

[rklinck]

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.

 

[jtratcliff]

Heat transfer is proportional to both thermal conductivity and temperature difference between the materials (dT/dt = -k dT/dx).

You just need to make the air colder in order to account for the poorer conductivity.

Thus a temp. control that cycles the freezer on and off as temps vary can be just as effective as a water bath at keeping fermentation temp stable. However the freezer will probably cycle more and use more energy for cooling the air.

 

[butterpants]

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."

Ahhh gotta love the specific heat of water!

I vote for this reply

 

[rklinck]

Heat transfer is proportional to both thermal conductivity and temperature difference between the materials (dT/dt = -k dT/dx).

You just need to make the air colder in order to account for the poorer conductivity.

Thus a temp. control that cycles the freezer on and off as temps vary can be just as effective as a water bath at keeping fermentation temp stable. However the freezer will probably cycle more and use more energy for cooling the air.

But you would need to actually be measuring the beer temp to get a constant temp with air. Considering that we all attach the probe to the outside of the fementer (even when insulated), we are not going to maintain a constant temp. A liquid immersion should be more constant because the heat will transfer from beer to water outside fermenter and the probe in the water bath would give us a better read on the temp inside the fermenter.

 

[SpeedYellow]

...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.
...

Not necessarily -- as an example, you can leave the probe hanging in the air, and set the thermostat differential to 0.5 degrees. Negligible swings in beer temp. And even if you use 3F differential, you'll probably see like 1F swing in beer temp. What exactly is wrong with 1F swing? Granted you can reduce this by adding a water bath, ceteris paribus, but again why?

The idea of fans & water baths is an engineered solution to a problem that doesn't exist. (and yes, I'm a mech eng.)

 

[Wynne-R]

I think the capacity of the freezer or refrigerator is generally adequate to control the temperature of the beer. I personally prefer water. My problem with air is that it is SLOW.

I think a lot of people seriously underestimate the time it takes to cool a warm fermentor with cold air. There will be gradients toward the center of the fermentor and the probe on the outside will be cooler than the inside. Once you hit steady state (cool it off) it should track fairly closely.

When the fermentation kicks in, it stirs things up pretty well, the temperature will be the same throughout the beer. The heat of the fermentation is not really a big deal if the fermentation is well controlled, it works out to be a few watts spread out over 30 - 40 hours.

 

[Skep18]

The idea of fans & water baths is an engineered solution to a problem that doesn't exist. (and yes, I'm a mech eng.)

...unless the problem is you don't have a dedicated freezer but do have an empty bath tub, which with many beginner and dare I say experienced brewers probably do have. (and yes, I am as well a ME)

 

[Trail]

But you would need to actually be measuring the beer temp to get a constant temp with air. Considering that we all attach the probe to the outside of the fementer (even when insulated), we are not going to maintain a constant temp. A liquid immersion should be more constant because the heat will transfer from beer to water outside fermenter and the probe in the water bath would give us a better read on the temp inside the fermenter.

Except that this has been repeatedly disproven and the delta is around one degree. Not trying to get all dogmatic on your ass, but this has been discussed to death.

With respect to the people who took issue with my claims that needing a water bath for thermal conductivity is absurd, allow me to clarify:

1) It is a matter of public record that refrigeration + temp controllers trump swamp coolers.
2) No one who is brewing five-gallon batches of beer has any problems hitting their desired temps with a properly configured fridge or freezer. Note also the success of CoolBrewing, which is a swamp cooler without the swamp.
3) I haven't seen anyone having problems with ten gallon batches/multiple five gallon batches/inuit tribes starting fires for warmth between the fermenters. Doesn't mean they absolutely don't happen (well, except for the last one)... but I'd be surprised if they did. Yeast being able to raise the temp by ten degrees is only an issue if the fridge can't go below target temp.
4) People brewing in gigantic 20-gal conicals may need to care about thermowells. These people will typically not be swamp cooling.

In conclusion, for typical batch sizes a thermistor on the outside is fine and worrying about the thermal conductivity of air is still absurd.

 

[rklinck]

Not necessarily -- as an example, you can leave the probe hanging in the air, and set the thermostat differential to 0.5 degrees. Negligible swings in beer temp. And even if you use 3F differential, you'll probably see like 1F swing in beer temp. What exactly is wrong with 1F swing? Granted you can reduce this by adding a water bath, ceteris paribus, but again why?

The idea of fans & water baths is an engineered solution to a problem that doesn't exist. (and yes, I'm a mech eng.)

Once the system reaches stasis, you are correct. But let's assume you put the fermenter into a chest freezer right after you pitch the yeast (as is typical). As the yeast start working, the create a lot of excess heat. This transfer quickly to the beer inside the fermenter. It does not transfer nearly as quickly to the air in the freezer (thus the general statement that the temp inside the fermenter will often bee 5 to 10 degrees warmer than the ambient air temp). So sure, your air temp will only fluctuate a little, because the compressor will kick on and cycle rather often. But, the liquid inside the fermenters will be considerably warmer. If the beer was at the temperature at the time you first put it into the chamber, it will spike considerably as the yeast start going and then cool down once the yeast slow down. Then you will get to stasis and the temps will remain constant.

Using water immersion should lead to quicker heat transfer to a much larger thermal mass, leading to a much smaller spike in temps in the fermenter.

 

[Polboy]

I build one over a year ago, here is a thread from work in progress (for summary look at post 17 and 18):
https://www.homebrewtalk.com/f51/office-water-cooler-temp-control-289108/
Now i use heavy duty 27gal size tote and its perfect for 2x 6.5gal carboys. I can set any temp in 57-90 F range and walk away, it take some time to cool down but when it does it keep it perfectly. If i find time i may insulate the whole thing to cool it faster and lower

 

[BackAlley]

Wow...this thread ended up being a lot more controversial than I had expected. Actually I didn't expect it to be controversial at all!

My chest freezer (which I adopted) has plenty of room inside but it can actually only fit one carboy. So for me, plopping the carboy into a water bath didn't really seem that complicated, and if all it did was reduce the rise due to ferment activity, it seemed worth it.

 

[Trail]

Once the system reaches stasis, you are correct. But let's assume you put the fermenter into a chest freezer right after you pitch the yeast (as is typical). As the yeast start working, the create a lot of excess heat. This transfer quickly to the beer inside the fermenter. It does not transfer nearly as quickly to the air in the freezer (thus the general statement that the temp inside the fermenter will often bee 5 to 10 degrees warmer than the ambient air temp). So sure, your air temp will only fluctuate a little, because the compressor will kick on and cycle rather often. But, the liquid inside the fermenters will be considerably warmer. If the beer was at the temperature at the time you first put it into the chamber, it will spike considerably as the yeast start going and then cool down once the yeast slow down. Then you will get to stasis and the temps will remain constant.

Using water immersion should lead to quicker heat transfer to a much larger thermal mass, leading to a much smaller spike in temps in the fermenter.

I'm not disagreeing with you on theoretical grounds - obviously more thermal conductivity is a good thing, all else being equal, as is a greater quantity of thermal inertia when fermentation starts. Also obviously, air will move heat less effectively than water. But in practice I've NEVER found that the limiting factor in my fermentation temp control was the fridge. I've sloshed, rolled, peered, and poked, and I've never seen my temps reflect that the inside was dramatically warmer than the outside.

Lower heat transfer itself is not a problem. Insufficient heat transfer is an issue, and one I haven't encountered with either of my air cooling systems.

 

[SpeedYellow]

Once the system reaches stasis, you are correct. But let's assume ...

Agreed. The point I made earlier was that this peak-fermentation-spike can be handled by (1) turning the t'stat knob down a few degrees for a couple days, or (2) insulating the probe to the side of the fermenter. Either seems simpler than engineering a fan or dealing with a water bath.

But that's the nature of brewing, eh? Some of us like simple stovetop kitchen brewing and others like to engineer elaborate brewing control systems. There's no right or wrong; just different philosophies.

 

[BackAlley]

OK, a sort of related question then. To date, I've been controlling the ambient air temp in the freezer. It appears the preferred way to control ferment temps is to attach to the side of the fermenter, insulate the outside so that it's reading as close as possible to the wort temp.

What happens though if say my wort is at 68 and I want it to be 66. It's obviously going to take a couple of hours, meanwhile the freezer's running because the controller is asking it to. Does it get down to deep freeze temps at which point the freezer's own thermostat shuts it off? I'm probably missing something simple here.

 

[SpeedYellow]

OK, a sort of related question then. To date, I've been controlling the ambient air temp in the freezer. It appears the preferred way to control ferment temps is to attach to the side of the fermenter, insulate the outside so that it's reading as close as possible to the wort temp.

What happens though if say my wort is at 68 and I want it to be 66. It's obviously going to take a couple of hours, meanwhile the freezer's running because the controller is asking it to. Does it get down to deep freeze temps at which point the freezer's own thermostat shuts it off? I'm probably missing something simple here.

Yes, exactly right. If your probe is measuring the liquid temps, then the freezer air will drop down to 0F or whatever when it's told to run. BUT simply taping the probe to the fermenter and using a little "insulation" isn't really measuring beer temp; it's somewhere in between air and beer, and depends on your insulating job. So the freezer air probably won't really drop to 0F or whatever. But that's immaterial anyway.

Also, this idea of insulating the probe to the fermenter ONLY makes sense if your t'stat differential is low. If you use a Johnson analog t'stat (fixed 3.5F differential) you'd want to leave it in the air or suffer 3.5F swings in beer temp. So only insulate the probe to the fermenter if you can reduce the differential to 0.5 or 1F. I suspect many folks don't understand this.

 

[BackAlley]

Also, this idea of insulating the probe to the fermenter ONLY makes sense if your t'stat differential is low. If you use a Johnson analog t'stat (fixed 3.5F differential) you'd want to leave it in the air or suffer 3.5F swings in beer temp. So only insulate the probe to the fermenter if you can reduce the differential to 0.5 or 1F. I suspect many folks don't understand this.

I'm using an STC-1000 so I can do that.