Purchasing a freezer/controller...question:

[iamwhatiseem]

Next weekend I intend to purchase a small chest freezer (being sure to buy one large enough for two carboys)...and a subsequent temp. controller.
My question is...do the stick-on surface thermometers work well in this setup?
What is the relation between the air temp and the beer temp during the robust fermentation step?
In other words...let's say with an ale you want 66 beer temp during primary...what would you keep the air temp at?

Thank you for responding.

 

[TheDecline]

Its hard to do this calculation properly since there are so many contributing factors but lets give it a shot.

Quoting rocketman768 "Let's assume 5 gal (19L), 12 plato, OG = 1.050, and that all of the sugar is consumed. We have 19 * 1.050 * 0.12 = 2.394 kg of equivalent glucose which is 2394/180 = 13.3 mol. That means we are going to release 13.3 * 118 = 1,569.4 kJ. Assume that your fermentation is quick and it finishes in 24 hours. That means the average rate of energy release is 1,569,400 / (24*3600) = 18 W."

From there we get 18W = 61.4 btu/hr. 61.4 btu can raise the temp of 19L of water .81 degree C in one hour. which is about 19.5 degrees C in 24 hours. But of course you have a freezer absorbing that heat as efficiently as it can so despite all the math this basically comes down to how good your vessel is at transferring heat. If you have a fermenter made of copper or aluminium your actually beer temp will probably be close enough to your freezer temp that it doesn't matter. Stainless steel is about 12 times less conductive than aluminium and plastic is significantly less conductive than SS depending on how its made.

When I ferment a lager in my Blickmenn SS Conical I notice about 1 degree C differential between beer and freezer temp. Of course Im going by a temperature reading from the surface of the Conical and not the actual beer itself so its probably a bit higher. For what its worth, the small margins are not worth concerning yourself really. I would say if you are really concerned, just leave the probe for whatever temp controller you get to control your freezer unattached inside and whenever you put a beer in, just stick it to the side of the vessel. Good enough.

 

[Brulosopher]

I use Fermometers on all of my plastic carboys (Better Bottle). Last week I took a temp reading of my fermenting wort with a thermometer- it was spot on with the stick-on Fermometer. What I do is tape the temp regulator probe to some cardboard then tape that to the carboy, set my temp to where I want to ferment, and let it rip.

 

[iamwhatiseem]

Its hard to do this calculation properly since there are so many contributing factors but lets give it a shot.

Quoting rocketman768 "Let's assume 5 gal (19L), 12 plato, OG = 1.050, and that all of the sugar is consumed. We have 19 * 1.050 * 0.12 = 2.394 kg of equivalent glucose which is 2394/180 = 13.3 mol. That means we are going to release 13.3 * 118 = 1,569.4 kJ. Assume that your fermentation is quick and it finishes in 24 hours. That means the average rate of energy release is 1,569,400 / (24*3600) = 18 W."

From there we get 18W = 61.4 btu/hr. 61.4 btu can raise the temp of 19L of water .81 degree C in one hour. which is about 19.5 degrees C in 24 hours. But of course you have a freezer absorbing that heat as efficiently as it can so despite all the math this basically comes down to how good your vessel is at transferring heat. If you have a fermenter made of copper or aluminium your actually beer temp will probably be close enough to your freezer temp that it doesn't matter. Stainless steel is about 12 times less conductive than aluminium and plastic is significantly less conductive than SS depending on how its made.

When I ferment a lager in my Blickmenn SS Conical I notice about 1 degree C differential between beer and freezer temp. Of course Im going by a temperature reading from the surface of the Conical and not the actual beer itself so its probably a bit higher. For what its worth, the small margins are not worth concerning yourself really. I would say if you are really concerned, just leave the probe for whatever temp controller you get to control your freezer unattached inside and whenever you put a beer in, just stick it to the side of the vessel. Good enough.

Thanks!...I love the math!
Thanks to other folks comments as well.
Sounds like it is as simple as placing the probe against the vessel, set it to where I want it - and the temp. will be effective enough.

Thanks that helps.

 

[day_trippr]

[...]Sounds like it is as simple as placing the probe against the vessel, set it to where I want it - and the temp. will be effective enough.[...]

Almost right. You want to cover the probe with something insulative, so the probe isn't being affected by the air. I use an inch thick chunk of closed cell foam over the probe and pin that to the keg or carboy using a velcro strap I picked up at Home Depot.

The result is tracking within a half degree of the actual beer temperature. The only thing that works better is a thermowell...

Cheers!

 

[iamwhatiseem]

Almost right. You want to cover the probe with something insulative, so the probe isn't being affected by the air. I use an inch thick chunk of closed cell foam over the probe and pin that to the keg or carboy using a velcro strap I picked up at Home Depot.

The result is tracking within a half degree of the actual beer temperature. The only thing that works better is a thermowell...

Cheers!

Very close to what I was thinking of...I thought about the velcro tape and putting some thinsulate over it. I have an old jacket that has the insulation layer, I was gong to cut a piece out and double/triple up over the exposed area.

 

[Xpertskir]

You can do the probe taping method, or get this

http://www.williamsbrewing.com/THERMOWELL-FOR-PLASTIC-CARBOYS-P2596C100.aspx

I own one, and used to measure temps in the aforementioned way. The most important thing is controlling wort temp, not the air temp.

 

[BigFloyd]

I use STC-1000 dual temp controllers ($19 on Amazon) on my fermenter fridge, cold crash/lagering/yeast storage freezer (kept at 36*F) and on my keezer (39*F).

In the fermenter chamber, I simply tape the sensor to the bucket and cover it over with folded-over bubble wrap to insulate it from the air. In the keezer, the sensor lives in a jar filled with water.