Fermentation Chamber, Swamp cooler-ish. Input please.

[vraftsman]

So I want to build a fermentation chamber and I have the same idea as a lot of people here to basically build a mini fridge into a larger cabinet to cool, and I have several different ideas of how to heat it. Currently I have been using an old school electric blanket (the kind that doesn't safety shut off when the power is killed) on a PID-SSR controller. I plan to continue using the PID to control the heater, but change to an element style and set the alarm temp accordingly to turn on the refrigerator. I already have the controller built, just haven't been using the cooling end of it.

What makes my plan unique, I think, Is that I want to build a water bath into the lower portion of the chamber. My theory is that since air has a low thermal mass, it is susceptible to larger temperature swings. If I put several inches of water in the bottom of the chamber I have a large thermal mass that both stays at temperature and resists the change of an exothermic carboy during early fermentation. Not to mention better heat transfer being in direct contact with the carboy. This is based on the swamp cooler method used by many, just more precisely controlled.

Has anyone done this before? thoughts on if it's worth the effort? I'm leaning toward a submersed heater vs an air heater, thoughts?
Thanks in advance for your input!

 

[Stealthcruiser]

Watching.

 

[djt17]

If it's just thermal mass you are looking for; try lava rocks &/or bricks. It's what I use in my smoker's if I need more thermal mass.

 

[vraftsman]

If it's just thermal mass you are looking for; try lava rocks &/or bricks. It's what I use in my smoker's if I need more thermal mass.

Good input, I think this should help make most temp chambers a little more efficient, (full fridge is more efficient than an empty one.) Especially for someone who has a habit of opening it a lot. And bricks are easy to come by and don't spill.
I still think the direct contact of the water, (24x greater thermal conductivity than air,) to glass will make the biggest difference, most stable temperature.

Heat transfer: Thermal Conductivity: Air=0.024, Water=0.58, Brick=0.6-1.0
Related to thermal mass: Specific Heat(kJ/kg.K): Air=1.005, Water=4.19, Brick=0.9

 

[MindenMan]

I have a question, where do you plan on putting the sensor, and are you planning to use glass carboys? Your plan isn't terribly bad, and I did something similar initially.
If you put the sensor on the carboy, the water will overheat the carboy a few times until the temperatures settles down

 

[vraftsman]

I have a question, where do you plan on putting the sensor, and are you planning to use glass carboys? Your plan isn't terribly bad, and I did something similar initially.
If you put the sensor on the carboy, the water will overheat the carboy a few times until the temperatures settles down

I plan on attaching the probe to the carboy as you mention.
Why did you switch from that method? was it not working for you or just not worth everything being wet? And what did you switch to?
What kind of controller were you using? I have a PID that I am hoping is smart enough once an autotune cycle is run to keep it from overshooting too much. Thanks for the input and it'd be great to hear a little more about how you built yours.

 

[rnm410]

Maybe this will be of help, it is a macro enabled workbook so it will require MS Excel to run.
Shared through onedrive: Simple Non-Evaporative Swamp Cooler

If this is an issue for the site, I can disable macros and allow to run through the browser.