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Why a mini fridge won't work.

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Old 03-15-05, 02:31 AM Thread Starter   #1
matttheniceguy
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Why a mini fridge won't work.


Fairly often someone comes up with the idea of using that old mini fridge to cool their computer (guilty of this myself). Unfortunately, without considerable modification to the fridge, there is no way this will actually work. The most common plan is to put a reservoir inside the fridge, and then water cool the computer with water that is chilled by the fridge. Another popular plan is to put the motherboard and its components directly inside the fridge. While this seems like a good idea at first, it just won't work. The reason for this is that the phase change system in the fridge can't cope with the heat load of a modern processor, let alone an entire system.

Lets start by looking at the heat load a mini fridge is usually under. A large mini fridge (3.2 cu ft) has a surface area of around 1.85 meters squared. Its walls are made of 1" styrofoam, with a metal or plastic casing. Assuming there is free convection on all surfaces of the fridge, and the fridge is at 4 degrees C in a 22 degree C room, the heat transfer out of the fridge is around 20 watts. (this value is probably a little high, I haven't counted a lot of the smaller thermal resistances)

When you put something in the fridge, this temporarily increases the load on the system. A good mini fridge can cool several liters of beer....err... water down to drinking temperature within an hour or so. The phase change systems inside these fridges do have the capacity to remove fairly large amounts of heat, unfortunately they don't have the capacity to do so continuously. The biggest problem with a mini fridge is its condenser. The condenser of a mini fridge differs quite greatly from the condenser of a standard phase change system for a computer. In a system made for a computer, the condenser is like a fairly large radiator, with a lot of surface area, and a good fan blowing across it. This allows it to dissipate a large amount of heat, while the fluid exiting it is barly above room temperature. The condenser on a mini fridge is generally just a series of pipes with very little surface area. To make things worse, it is usually built right into the side of the fridge, under the metal casing (feel your fridge when the compressor is on, one side will be warm). This consenser is not able to handle large heat loads for any sustained period of time, and will not generate very low temperatures.

If you have an old mini fridge laying around and you really want to use it to cool your computer, your only real option is to change the condenser. Once you are doing this work though, you may as well just make a direct dye system and get some real cooling going. The compressor from a mini fridge is usually big enough for a DD system, but be warned that these compressors are not made to run continuously so it will need some decent cooling on it, and it probably won't last all that long.

Edit: There are a lot of smaller coolers made for holding a 12pack or some lunch meat or whatever you want, that people will consider using because they are usually very cheap. These don't use a phase change system like larger mini fridges, but use a small pelt. These coolers have a lower cooling capacity than even a mini fridge does. They usually use a small (10-50 watt) pelt, with the hot side passivly (or sometimes) activly air cooled. They have no chance of working, even with considerable modification.

Last edited by matttheniceguy; 03-16-05 at 06:28 PM.
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Old 03-15-05, 09:25 AM   #2
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also big problems come into keeping the actual fridge air tight, expecially when using the door, and you can never illiminate all of the air inside.
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Old 03-15-05, 11:37 AM   #3
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1) Stuck.

2) I changed the title a bit to make it a bit more of an obvious draw to those thinking of doing this.

3) Anyone want to add their particulars of their attempt to do this? Some people find it easier to wrap their brains around why something will or won't work if they get an actual real world example.

4) Nice write up Matt.

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Old 03-15-05, 03:56 PM   #4
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Water fountian


I use a water fountian for my cooling and now I've been running this system for 3 weeks and It is awsome. But now I need advice, I have a old Toshiba stereo receiver for my amp and when the compressor turns on there is a moment that a static sound comes through the speakers .

The power for the computer is seperate from the compressor I have attached ground to all ,the stereo has only a two male end, how can I get rid of the static sound when the compressor turns on.

I installed a new power wire from the panel 300v for the compressor this was inspected by a expert.
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Old 03-16-05, 01:49 AM Thread Starter   #5
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Sounds like your talking about some sort of electrical interferance. I know my old Sansui amp goes Loco just before a cellphone near it will ring. It's probably some sort of high frequency put out by the electronics working the compressor which is messing with the preamp and getting amplified. I can't say I really know what I'm talking about here though.

My guess would be that the best way to stop it would be to move the amp and compressor further appart, or maby make some sort of sheilding. If it is only when the compressor is starting, it probably isn't worth doing anything about.

What is water fountain cooling? I'm not sure what you mean, some sort of bong? Is the compressor cooling the computer somehow, or are you just talking about a fridge by your system.
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Old 03-16-05, 06:17 AM   #6
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Quote:
Originally Posted by matttheniceguy
.......Lets start by looking at the heat load a mini fridge is usually under. A large mini fridge (3.2 cu ft) has a surface area of around 1.85 meters squared. Its walls are made of 1" styrofoam, with a metal or plastic casing. Assuming there is free convection on all surfaces of the fridge, and the fridge is at 4 degrees C in a 22 degree C room, the heat transfer out of the fridge is around 20 watts. (this value is probably a little high, I haven't counted a lot of the smaller thermal resistances)
...
My all-purpose tool(Kryotherm) would put it ~30w for Polyurethane insulation.
Just rough checking numbers.
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Old 03-16-05, 07:04 AM   #7
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Ok that worked moving the amp away from the system. Waterfountian cooling is basically a fountian something like in a university or like that. It has all the things for a great chiller. It has a compressor a canister for water, and a nice rad for cooling the gas.
I now know why they say never drink out of a waterfountian ,when I cut the top off the canister you would not believe the stuff in it.

If anyone ever gets a chance to get one than grab it up it is so far perfect for a chiller
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Old 03-16-05, 07:04 AM   #8
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What about.... a full sized fridge? Or maybe a freezer? Seems like it could keep it much colder in a freezer, and the heat comming from the comp would keep any liquid from actually freezing.
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Old 03-16-05, 07:17 AM   #9
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Quote:
Originally Posted by PCGUY112887
What about.... a full sized fridge? Or maybe a freezer? Seems like it could keep it much colder in a freezer, and the heat comming from the comp would keep any liquid from actually freezing.

It would probably work better, but the heat of the computer would still put a constant load on the system and the condensor and its fan would probably not be able to keep up.

If I had a fridge laying around that I could use its parts, I would probably just get a nice condensor and fan on it, and while I am at it, make it direct die anyway.

That is if you don't plan on using the fridge/freezer any time soon.

EDIT: I might add that some condensors are incredibly massive on the bigger units, like the whole back side. Although, they don't really have any fins or coils, it is pretty much just a really long tube coiled around. Without any fins of some sort or active airflow, under load it could probably heat up over time.

Preferably for a direct die setup, I would think a window AC unit would do the job much better as it is designed to run more constantly than a mini-fridge or even a normal fridge.

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Old 03-16-05, 07:21 AM   #10
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You should also mention the fact that many minifridges do not even run with compressors, they use TEC's which makes them even less powerful for PC cooling.

Nice job Matt, I think this is a good idea for a thread in here, as I've seen these minifridge questions come up since I first joined.

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Old 03-16-05, 07:24 AM   #11
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Quote:
Originally Posted by I.M.O.G.
You should also mention the fact that many minifridges do not even run with compressors, they use TEC's which makes them even less powerful for PC cooling.

Nice job Matt, I think this is a good idea for a thread in here, as I've seen these minifridge questions come up since I first joined.

Really? TEC's? I am pretty sure most do use compressors though.

Are you talking about those little ones you can put in a car and stuff or like a 4 and a half by 3 feet type of minifridge?

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Old 03-16-05, 08:06 AM   #12
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Many use TEC's, especially the ones you can get for really good prices that I've seen people think about using for this purpose.

I'm talking about the kind that will hold a gallon of milk, a 12 pack, some lunchmeet, along with some other odds and ends.

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Old 03-16-05, 03:08 PM   #13
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Mini Frg or fountian or fish tank


Myself I think that a fridge is lot of work for a water chiller although if someone really wants to, it shall be done. I think that a water fountain is a good thing for this. A water fountain is built for water cooling but you may even try water chillers by aquarium suppliers and put the chiller in the fish tank then get some fish and put them in the fish tank, what a great conversation piece for friends. The mini fridge idea is not so good like said before a mini fridge would not take the constant heat, I had a lunchbox, which was a cooler, and it lasted 3 weeks what a waste of 70 dollars.
http://www.aquadirect.com/
This is the kind of thing I was talking about and donít forget to buy the fish tank and fish.
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Old 03-16-05, 03:33 PM   #14
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A water fountain may be better designed for this because its condenser isn't like a fridge where you mainly have a large fanless coil of tubes. I still think a modified window AC unit is the best way to go though. It is designed to run more constantly than a fridge or even a water fountain.

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Old 03-16-05, 03:38 PM   #15
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Quote:
Originally Posted by @md0Cer
A water fountain may be better designed for this because its condenser isn't like a fridge where you mainly have a large fanless coil of tubes. I still think a modified window AC unit is the best way to go though. It is designed to run more constantly than a fridge or even a water fountain.
Got a link or some pic of a AC unit
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Old 03-16-05, 04:13 PM   #16
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Good job Matt. This should prevent a lot a people from having to learn the hard way.

The best a fridge can do for you is to give you a few minutes to benchmark your computer at speeds that you cannot normally sustain. I accomplish the same thing by dumping ice in my oversized res.

I think the root of the problem is that many people think only in terms of temperature whereas they should be thinking in terms of power and thermal resistance.

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Old 03-16-05, 05:38 PM   #17
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Quote:
Originally Posted by LabRat23
Good job Matt. This should prevent a lot a people from having to learn the hard way.

The best a fridge can do for you is to give you a few minutes to benchmark your computer at speeds that you cannot normally sustain. I accomplish the same thing by dumping ice in my oversized res.

I think the root of the problem is that many people think only in terms of temperature whereas they should be thinking in terms of power and thermal resistance.

I overcome the problem of thermal resistance by 3 methods, first was to wash my mainboard and componts with electric motor cleaner, than I use a silcon spray {none conductive} sprayed the main board and vcard and sound card, then I use a dielectric greese and gooped it all over the socket pins put the processor in than smeared it about .25 inches thick over the processor and around the whole area of the processor slot, did the same thing to the video card with the die greese. I went to the barn and got a cup full of lye and sprinkled it around the bottom of the case but not on any componts. Did a moisture test and was in the dry range. Not bad for a rookie. Power was an issue I had to buy a new power supply and mount it in the box, that runs the arogate display monitor and that supplies the water pump and a few cools lights and temp sensors, this was a way for me to monitor the system when the system was shut down. Then I had to run a new wire to the panel for the compressor for it is 120 V AC.

The compressor turns on about ever 2 hours when I play games, it is on less than a minute, if the room is hot it runs for 3 mins. If I don't use the computer it hardly comes on. So people do think of the more important parts like moisture or thermal resistence

Last edited by gomerpile; 03-16-05 at 06:06 PM.
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Old 03-18-05, 12:24 AM   #18
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Quote:
Originally Posted by gomerpile
Got a link or some pic of a AC unit

Not at the moment. I could dig around and look for some. I remember once seeing a whole slew of pics taken by someone who modifed their window AC unit for direct die cooling.

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Old 03-25-05, 11:23 AM   #19
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I'm quite new to the alternative cooling concept, however, from a beginner's standpoint, one of the problems I can foresee is condensation...for instance, with a mini-fridge, opening the door for any reason would allow ambiant air and moisture into the space, which seems like it would invariably condense on the surfaces of the components....am I off base in assuming this?
is condensation an obstacle or consideration in any of these extreme cooling methods? if so, (and i cant see how it would not be,) how is it dealt with?

Also, thanks for this thread....this was an idea I had while brainstorming, you saved me a lot of time.

Edit* After reading a sticky i see that insulation is the solution...although it is difficult to picture a practical real-world method of insulating for me, having never seen a system utilizing it..
lots to learn..

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Old 03-25-05, 12:17 PM   #20
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Quote:
Originally Posted by gomerpile
Got a link or some pic of a AC unit
Here's one for a wicked chiller system but it's a long thread. Be warned Just click here
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