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I have a computer outside its case. All the components are attached and working properly, the problem is that fans don't seem to provide good enough cooling when demanding programs such as high end games are run. The fans go crazy sometimes and the room with the computer gets increasingly warm especially with the door closed. I can't afford a commercial liquid cooling system so I thought I'd try to build my own.

My plan is to buy these things:

  • A small refrigerator
  • A plastic box big enough to hold the motherboard and the components attached to it
  • Enough oil to almost fill the plastic box

I'm going to submerge the computer in some form of oil. I'm not sure which kind yet. Since oil is better at absorbing heat than air is, while preventing freezing and water vapour on the electrical components it should be the perfect solution to keep the computer cool and running smoothly, even if I overclock it as much as I can.

The only two components that need to sit outside the fridge is the CD-ROM and the hard drive. I'm not sure the CD-ROM station is even necessary since the oil computer is going to be on the same network as my main computer so I can just transfer any files or share the CD station in my home network. However the hard drive being the only mechanically moving part might not fare too well in oil so I'll leave it dry on the outside of the fridge.

I'll bore a small hole somewhere in the fridge from where all the cords can come in/out.

Questions:

  1. What kind of oil should I use? I saw a video where they used mineral oil, but that's probably too expensive and they thought vegetible oil would go rancid (which it doesn't even after years in room temperature.)
  2. Do you have any tips I should keep in mind to avoid destroying my computer as much as possible?
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closed as not constructive by Dave M, KronoS, 8088, Joe Taylor, Nifle Jul 31 '12 at 10:02

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You don't want a fridge. If nothing else, the compressor will be just as noisy as a traditional fan setup (which can be had cheaper). You also don't want to use plastic, a plastic that'll hold up and not sag over time will be expensive. And for the love of goodness, don't use cooking oil. I also don't see any way that this will be cheaper than doing it right - if you're trying to save money this is a bad idea. That said, Puget does it right: pugetsystems.com/submerged.php –  Shinrai Jul 30 '12 at 19:58
    
Also, never mind that hard drives have moving parts, they rely on air pressure to operate properly. They won't work in a vaccum - they CERTAINLY won't work submerged. –  Shinrai Jul 30 '12 at 19:59
    
> they thought vegetible oil would go ranchid (which it doesnt even after years in room temperature.) Sure it does. I lathered some onto the bottom of my squeaky tilt-chair and in a few months, it was thick, sticky, smelly and just plain gross; it was the same with the squeaky screen-door even though we only used a little on that time. That’s why we bought a can of white-grease spray to lubricate the garage-door rails instead. –  Synetech Jul 30 '12 at 20:39
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Why is the computer outside of its case? Part of the point of a case is to force the air to flow across the components that are heating up. –  Zoredache Jul 30 '12 at 21:54
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possible duplicate of Cooling a server with oil bath –  Joe Taylor Jul 31 '12 at 8:52

3 Answers 3

the room with the computer gets increasingly warm especially with the door closed

Any cooling systems that just moves heat from one place in the room (your computer) to some other place in the same room is not going to address this. To do so you'd have to hang some kind of radiator outside the room to dump the heat elsewhere. Any active cooling system also generates more heat to add to the problem. Specifically, a fridge in a room heats the room.

Since oil is better at absorbing heat than air is

No, it's a better conductor of heat. You don't absorb heat, you move it from one place to another. You may be thinking of the "heat capacity" of various materials. This determines how much the temperature of a Kg of that material rises when you transfer a joule of heat energy into it. This isn't a help because you don't want your oil to get hotter and hotter. You want the oil to transfer it's heat to the air in the room.

Air also wins out because you can move it around faster than you can move oil around.

The cost of this movement of cooling fluid (oil or air) is even more heat. A fridge can never have an efficiency greater than 25 so for every 25 joules of heat you remove from your PC you add at least 26 joules to your room.

An 800W power supply running flat out produces 800 joules of heat per second. To prevent the PC (or it's oil bath) heating up you have to remove 800 joules a second, A fridge will mean you have to remove at least 832 joules a second from the air in your room.

The heat from your PC ends up in the air in your room, regardless of whether an oil-bath is an intermediary conductor, the way heat gets carried out of your room is primarily though air movement (unless you have aircon but that still requires the heat transfer from the PC via the air in the room).

I'm assuming your house is reasonably well insulated, if you live in a house made of steel or iron, bolt the PC to the wall.

Using oil to "absorb" heat

If you live in Alaska, you could put your PC in a 55 gallon oil drum and leave it outside in the snow when you are not using it, when you want to play Crysis-5 You fork-lift the drum into your room. The oil is at say 5C (you may need to wait a few hours for everything to thaw to a usable state) and your room is at 20C, we can calculate how many joules the oil can "absorb" before its temperature reaches 20C and you need to stop playing and move it outside to cool off again. I'm too lazy to do the maths right now.

Conclusion

An oil-bath cooling system is a fun demo but it isn't a cheap or convenient solution to a hot PC and certainly won't help if your room is uncomfortably hot.

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The fridge on its own wouldnt create much heat unless something very warm is put inside it. Keep in mind the oil inside the fridge would be at like 5C when the computer is turned on, so not only will it take a long time to heat the cool oil up, but also its being continuously cooled all the time from the fridge. –  user11177 Jul 30 '12 at 23:58
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@pittler you don't understand how a refrigerator works... Start with an empty room at some temerperature. If you put an empty fridge in the room, the inside of the fridge will be cold, the outside will be hot (or at least warm) because the fridge is pumping heat out of the inside. The room will get hotter than it was without the refrigerator because of the energy consumed by the fridge's compressor motor that's doing the work of pumping heat from inside the fridge out into the room. –  Ward Jul 31 '12 at 5:37
    
Then, add a heat source - a PC. It doesn't matter where you put it - inside the fridge or just in the room - the room will get even hotter. The heat generated by the PC gets into the room one way or another, regardless of whether it's in the fridge or not. All you're doing by putting the PC in the fridge (with or without oil bath) is removing the heat from the immediate vicinity of the PC. –  Ward Jul 31 '12 at 5:40
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@user1117: Cooling is overbalanced by heating. Every joule of heat removed from the interior of the fridge is added at the exterior of the fridge. In addition to this, the fridge consumes electricity which is all converted to heat. This may help a PC inside the fridge but it makes the room hotter. The hotter the room, the harder the fridge has to work, the harder the fridge works, the more electricity it consumes and the hotter it gets. –  RedGrittyBrick Jul 31 '12 at 9:50

As things are, there's very few scenarios where oil immersion cooling would be good, outside experimentation.

I have a computer outside its case

While it sounds like a good idea to run a system outside a case, cases are designed for airflow to assist in cooling. It's not just something to hang lights off.

I can't afford a commercial liquid cooling system

There's ones that cost about as much as good quality air coolers. You shouldn't need liquid cooling unless you're overclocking. Most practical immersion cooling systems I have heard of use exotic fluids, or pumps, despite what Wikipedia says. You're just - at best - going to switch from moving liquids across a closed system, to moving it from an open system.

I'd note a cheap case or a basic self-contained watercooler should both cost less than a fridge.

Before you go anywhere, you need to have a firm understanding of the two main processes of cooling a computer - conduction and convection. Metal is a good conductor of heat, and moves heat readily. Air is a crappy conductor of heat, but can flow very easily, so some heat is lost due to heat itself. Fans and cases speed this up by forcing convection by blowing and shaping airflow away from where you want the heat.

Submersion cooling has a few problems. Firstly, liquids are much thicker fluids than air - so while some convection and conduction will occur, it's harder to force convection to happen - water coolers get around this by having a large radiator, and a large surface area to shed heat. You need to select a fluid that won't conduct electricity - cray used inert flourocarbons, but what the only commercial system I know of from puget systems uses mineral oil - so thats probably the best option. Tom's Hardware used vegetable oil, but this wasn't tested in a longer term test.

You will need a pump to circulate the oil, you will need a radiator to remove heat - unless of course, you want to risk deep frying a computer in oil. In essence, you're spending a lot more time and energy than getting a cheap case or watercooling. Mineral oil will very likely also eat away at anything made of plastic eventually, so.. I wouldn't rely on this for my daily driver system. Oddly I don't think mineral oil degrades that fast so that would be the LEAST of your worries. I'd even consider that lower than cancer.

Considering you are running it in a fridge you will also test if the coolant hardens under low temperature - many organic oils do this, and work out how you're actually going to get power and IO into the fridge. Test the oils alone - check conductivity, see if they eat sacrificial cables (for science!), and things like that before you decide.

This sounds like fun, but not very practical.

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Skip the idea with the fridge. The oil cooling is enough and the fridge doesn't have enough power anyway.

Don't use mineral oil, it's organic and will change over time. Use a synthetic oil instead.

I cannot tell you what the oil will do with the mainboard and the other PCBs in the long term.

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