speeding up cooling in side-by-side fridge

[twd000]

I have converted a side-by-side refrigerator. The compressor is controlled by one STC-1000, and a 3" PC fan in the wall passthrough is controlled by another STC-1000. Kegs in the left side, carboys on the right.

It seems to control temperature within an acceptable band, but the speed is excruciatingly slow. When I put a full 6 gallon carboy on the fridge side, it took almost 48 hours to cool from 35 C to 5 C. Not too much of a surprise, since it is basically weak convection from the PC fan driving the temperature exchange.

So I was thinking of building a forced cooling loop to crash cool wort/beer. I would put a 1-gallon reservoir of glycol/water mix, mounted above the evaporator fan (coldest place in the freezer). Hook up a cheap Harbor Freight pump and some flex tubing run through the wall passthrough. Flex tubing would connect to a double-barrel copper pipe, with a U-joint at the bottom. A basic closed-loop heat exchanger.

Do you think this will work? Is there any health risk or yeast mortality when leaving copper in the wort for extended periods of time?

 

[audger]

Is there any health risk ... when leaving copper in the wort for extended periods of time?

yes. copper poisoning. fermented beer is acidic enough to cause copper to break down and be dissolved into it. its ok for use durring brewing, but not for finished beer. you will need stainless steel if you want to do this.

When I put a full 6 gallon carboy on the fridge side, it took almost 48 hours to cool from 35 C to 5 C. Not too much of a surprise, since it is basically weak convection from the PC fan driving the temperature exchange.

the fan isnt the problem, its the heat transfer medium... aka. 'air'. air has such a low thermal density, that it takes a long time to move heat from the carboy into the evaporator coil (which is where the heat is being absorbed into). putting a piece of copper (or steel) with coolant running thru it inside the carboy would definately speed up cooling.

however- instead of air being between the carboy and evaporator coil, its now standing between the coolant and the evaporator coil. you just moved your problem to another area. the only way to offset that, is to use a larger coolant resevoir and let it chill over time.

 

[twd000]

yes. copper poisoning. fermented beer is acidic enough to cause copper to break down and be dissolved into it. its ok for use durring brewing, but not for finished beer. you will need stainless steel if you want to do this.


the fan isnt the problem, its the heat transfer medium... aka. 'air'. air has such a low thermal density, that it takes a long time to move heat from the carboy into the evaporator coil (which is where the heat is being absorbed into). putting a piece of copper (or steel) with coolant running thru it inside the carboy would definately speed up cooling.

however- instead of air being between the carboy and evaporator coil, its now standing between the coolant and the evaporator coil. you just moved your problem to another area. the only way to offset that, is to use a larger coolant resevoir and let it chill over time.

This link seems to indicate that copper is mostly resistant to acidity, and only a big problem when in contact with another galvanic metal. I would have rubber flex tubing touching the copper.
http://corrosion-doctors.org/Food-Industry/Beer-corrosion.htm
Of course, I could try to do this with stainless, but I imagine the fittings would be harder to find. Actually it would be best to bend a tube so no fittings are required.

I agree that the air is the limiter here. Which is why I would mount the reservoir directly above the evaporator fan. That air comes out well below 0 C at a good pace, so hopefully I would be able to recool the reservoir quickly.

 

[Huaco]

Umm... every time I sanitize my IC in boiling wort and then use it to cool the wort, it ALWAYS comes out nice and shiny... I did not scrub it, It was scrubbed by the wort. That outer most layer of copper had been dissolved into the wort and is OK in that amount, however, if you leave the copper in there for weeks or months... that is a different story. A LOT of copper will have dissolved into the beer by that time.

 

[twd000]

Gotcha - I'll go with stainless tubing if I decide to pursue this idea

 

[DogTail]

If you're going to go to this much trouble why not make a bath that the carboy can sit in and have your copper with circulating glycol in the bath? This will give you a liquid medium that provides fast heat transfer and minimal interaction. Also this way you will avoid any possibility of contamination and there are no worries about having to remove anything but the carboy from the fridge; the system can always stay in place and just activate the glycol pump when you want to chill in a hurry. IMO you should try to avoid putting anything other than hops or flavoring in any carboy.

 

[twd000]

If you're going to go to this much trouble why not make a bath that the carboy can sit in and have your copper with circulating glycol in the bath? This will give you a liquid medium that provides fast heat transfer and minimal interaction. Also this way you will avoid any possibility of contamination and there are no worries about having to remove anything but the carboy from the fridge; the system can always stay in place and just activate the glycol pump when you want to chill in a hurry. IMO you should try to avoid putting anything other than hops or flavoring in any carboy.

Yeah that was my original thought, but the width of the fridge side is only 17", and I couldn't come up with anything that would fit in there. My Rubbermaid tub that I used as a swamp cooler has sloped walls that go out to 22"

 

[DogTail]

You could always make a tub out of mdf and get some heavy duty real thick poly and line it to ensure it does not leak... it would not have to be more than maybe 8" high to get really good heat transfer

 

[drkwoods]

I had the same exact problem with my fridge. I up'd the Fan Size to 6" and added a (Simultaneously controlled) Second fan at the bottom pushing air from the bottom of the fridge back into the freezer side.. this fixed it for me.. I also noticed there is a flow return port near the bottom between the sides. When I opened that I got improvement but went ahead and added the extra fan into the system.

 

[twd000]

I had the same exact problem with my fridge. I up'd the Fan Size to 6" and added a (Simultaneously controlled) Second fan at the bottom pushing air from the bottom of the fridge back into the freezer side.. this fixed it for me.. I also noticed there is a flow return port near the bottom between the sides. When I opened that I got improvement but went ahead and added the extra fan into the system.

Interesting. The upper opening with the 3" fan is only about 2"x4" - do you still think a 6" fan would improve cooling? I opened the lower port (removed grate) but don't have a fan down there yet.

 

[twd000]

Now I'm wondering whether others have their fans set to "push" or "pull". My fan in the top port is set of the freezer side, to push air into the fridge side. When I put my hand on the fridge side, it is a pretty weak airflow. Think it would make a difference to put it on the freezer side to pull air through?

Also has anyone come across and electrically actuated damper? There are times when I want to isolate the tow sides as much as possible, and it would be nice to limit the amount of bleedover through the fan port.