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stewbacca6
19-03-2009, 08:27 PM
Hey everyone I am an engineering student and I wanted to try to turn a mini-fridge into a fridge/freezer where I could cool drinks to a state of a small amount of ice. So i was thinking of just a cycle between 31 degrees F and 33 degrees F, so when I pour my beer its about 10% frozen, nice and icy.
I don't know much about refrigeration but i thought it would be a fun project so I'm looking for a little guidance. I'm thinking about installing a bigger chiller, rig up some sort of temperature control and just start testing it. What do you guys think? thanks a lot!

Scramjetman
19-03-2009, 10:09 PM
Beer ( depending on alcohol content freezes at about -2.5C )

This is not an easy exercise as refrigeration requires a careful balance between a number of elements in the system. If you just go and change one element ( ie shove in a bigger compressor) there are all sorts of penalties that appear. To maintain the balance, a larger compressor requires a larger condenser to get rid of the extra heat. A larger evaporator is need to transfer the energy to the conditioned space and so on it goes.

To have your fridge go to a lower temperature requires more refrigeration power. Proveided you have the power to hit your lowest temperature requirement, it's just a case of resetting the thermostat up for normal operation when you are not in "beer chilling" mode

stewbacca6
20-03-2009, 12:22 AM
ok forgot about alcohol's lower freezing point. What about if I got a mini-freezer and rigged up a temperature control to constantly cycle between a degree or two below freezing temp and a degree or two above.
I guess my question is how are the thermostats set up in freezers? Could someone easily rig up something to power the unit for how i am describing. Aside from having a sweet beer fridge this is also a learning process for me about this subject.

The MG Pony
20-03-2009, 04:49 AM
You'd need a closed loop electrical thermostat with a custom programed hystarious.

most opperate with a 4 to 5 degree differance built in with no hystarious to smooth out the cycle.

you need to take steps to prevent short cycling the compressor too, this can be don via hot gas injection into the evap to precicely control the evap temp.

stewbacca6
20-03-2009, 10:34 PM
Is there a thread on the fundamentals of refrigeration I could read to understand what you guys are saying?

Toosh
21-03-2009, 09:03 AM
Is there a thread on the fundamentals of refrigeration I could read to understand what you guys are saying?

Hi Stew, Have a look at this

http://www.ishrae.in/DasBlogce/PermaLink,guid,700f674c-330f-4229-9284-0915578f267d.aspx

Norm :eek: