[shadk]

Anyone use the freezer part of a fridge as a glycol chiller?  I’m think of putting a closed vessel with glycol mixture.  Ad a pump outside fridge and run hoses to my catalyst coil with inkbird temp control to run pump.  Thoughts?

[HopDen]

Anyone use the freezer part of a fridge as a glycol chiller?  I’m think of putting a closed vessel with glycol mixture.  Ad a pump outside fridge and run hoses to my catalyst coil with inkbird temp control to run pump.  Thoughts?

I know next to nothing about refrigeration but how I made my DIY chiller was by using a 5k BTU window AC. Search youtube and there are a few videos that pop up. If you're interested.

[shadk]

I did see that but I was thinking about simplifying things.  I use the refrigerators or my beer storage but then had an ah ha moment with unused freeezer. Let’s put 3-4 gallons of glycol water in freezer then attach a pump. 

[HopDen]

I did see that but I was thinking about simplifying things.  I use the refrigerators or my beer storage but then had an ah ha moment with unused freeezer. Let’s put 3-4 gallons of glycol water in freezer then attach a pump.

Give us an update when you have it running. Post a video or pics. I would like to see how you configured it

[MNWayne]

Sounds like a brilliant idea.  No idea how to even begin figuring out the math on this, so I'd put as much liquid volume in the freezer as could reasonably fit (gotta maintain some circulation space).  That way you have plenty of (negative) thermal mass to do big projects like a cold crash.

[BaseWerks Brewing]

How big of glycol volume will you be able to have?  How big of batches do you brew? 

I tried to use a mini fridge to keep my chill water cold for 10 gallon batches and in my experience it just didn't work.  Air to liquid temperature transfer is very slow.   I ended up going the DIY chiller route with a window AC unit after the refrigerator crapped out shortly after I tired it.  The DIY chiller works really well.

It could work if you have a big enough volume of liquid so you have enough thermal mass to compensate for the low temp transfer between liquid and air.  Someone much smarter than me with formal education in thermal dynamics could calculate the volume you would need for your batch size.  If you can get the glycol in direct contact with the cooling element in the freezer you would have much better luck. 
I would maybe try looping some copper tubing around the freezer element to get some direct contact with the element and improve the efficiency of the freezer to chill the liquid.   

Summary, in my experience it didn't work but if you do some things differently maybe you can succeed where I failed. 

[Wilbur]

I've thought about this a bit, I have a minifridge that I straightened out the freezer portion and have thought of putting a reservoir around that.

For what you're talking about, increasing the reservoir size will help. I'd also think about running the return through a radiator to try and draw as much heat out before it returns to the reservoir. I'd also try and separate the supply and return as much as possible so you don't start pulling warm return fluid out with your pump. Physical distance or a baffle in between the supply and return ports could help.

[MNWayne]

I can see where a mini fridge would not provide a large enough negative thermal mass.  A full size freezer MIGHT hold enough cold liquid for a 5 gal batch, again, I have no idea how to approach the numbers to justify even trying this.  Here's some dumb math.  If you are chilling 5 gallons of wort and you have 5 gallons of 30F water in the freezer, and your target wort temp is 60F, then if your beginning wort temp is 90F, you should make it.  The only way you can increase the cooling capacity would be increase the size of the (negative) thermal mass, and/or ditch the convective cooling of the glycol and work out a way to immerse the cooling coils from the fridge unit into the glycol itself.  I went the way of the converted window air conditioner and it works great.

[chinaski]

I wonder if it would end up turning on your fridge's compressor way more than it's designed for by constantly bringing in some heat into the freezer compartment? Not sure how fridge thermostats work.

[BaseWerks Brewing]

work out a way to immerse the cooling coils from the fridge unit into the glycol itself.  I went the way of the converted window air conditioner and it works great.

MNWayne - Yes, I agree. I believe that is the biggest reason the DIY AC chillers work so well as compared other non-direct options.  I haven't broke down a purchased glycol chiller, like SSBrewTech, but I figure they go about chilling the glycol in a very similar way.

[SCBeerDude7]

You could make your own extremely efficient glycol chiller out of a mini fridge, freezer, or a wall unit.  All you need is some refrigeration knowledge, an EPA Section 608 license, and know how to braze.

Purchase a cheap refrigerator or freezer.


Purchase a heat exchanger.



Then the fun part:
Evacuate the refrigerant.
Destroy the fridge/freezer cabinet.  You don't need the cabinet part of the unit, because you will have refrigerant cooling the glycol or other liquid coolant directly.
Remove the evaporator coil.
Braze the cap tube from the fridge/freezer into the heater exchanger.
Braze the suction line for the fridge/freezer to the other side of the heat exchanger.
Consider adding a suction line accumulator (optional).
Connect your hoses to the heat exchanger for the liquid coolant.
Pull a vacuum to 5 microns.
Recharge the system with refrigerant.
Insulate the heat exchanger very well.
Connect your temp control, inkbird or otherwise to turn on both the compressor and water/glycol pump when cooling is called for.  Alternatively you can have the inkbird or other control turn the compressor on for cooling and leave the water/glycol pump to run continuously.
You will not need the original thermostat built into the fridge/freezer, because your using a seperate control with a temp probe in the fermentation vessel.  Hopefully you'll be using a thermowell.

Overall the package will take up much less space than the original fridge/freezer, because your only using the refrigeration system from the mini fridge/freezer and not the cabinet.  A 4 cuft or 5 cuft fridge or freezer unit should work nicely.

Benefits:
- Very low footprint.
- Refrigerant directly cools the fluid.  Much more efficient and fast.  Much better than coiling a tube inside a fridge/freezer cabinet for water/air heat transfer or coiling a tube against an evaporator coil.
- Save money instead of buying a pre-made glycol chiller system for thousands of dollars.

Source:
That would be me.  EPA Section 608 Licensed.  Many years of experience in refrigeration working for a medical devices manufacturer of scientific fridges, freezers, ultra-low temp freezers (cascade systems), and cryogenic tanks.

EDIT:  Just remembered.  If the mini fridge/freezer has the condensing coils embedded in the side walls you won't be able to destroy the cabinet.  There are units out there, typically referred to as "built in" units, that have the condensing coil and fan located at the bottom rear instead of being foamed in the side walls.  One of those would be ideal.  They usually have a vent under the door.  Here is an example:
https://www.amazon.com/Summit-Appliance-ADA302RFZ-Undercounter-Refrigerator-Freezer/dp/B08RR661ZK/ref=sr_1_3?dchild=1&keywords=built+in+undercounter+freezer+manual&qid=1612994270&s=hi&sr=1-3

[SCBeerDude7]

I posted a DIY fermentation chamber that I recently built to the "Pimp My System" section of the forum today. 
It's not for glycol chilling, but instead for controlling fermentation temp. 

The premise is similar though in that it involves modifying a pre-built unit.