Friday, January 3, 2014

The Merits of Mineral Oil

A work in progress

I've been experimenting with oil-cooled computers.
It started with a basin and an unloved mother board, that worked out just fine.

Eventually I bought the $30 fish-tank and sneaked a bottle or two of mineral oil in with the groceries (the wife didn't officially sanction the project)

Dunking isn't a new thing (although many haven't heard of it) but most of the projects are done for the shock or the possibility of limitless cooling.

[quick note: mineral oil is totally safe on the solid-state components, don't mix moving parts or hard-drives.  The disks may appear to be sealed but they will have a small filtered port that equalizes the pressure in the disk, oil will get in that way]

[another note water is pretty safe on your solid-state components just so long as power is not applied, if you change your mind about oil-dipped hardware, it will take some time but you can wash it off, just let it dry for a month or more *I'm not responsible for your stuff.]

I too thought it was shocking, but I wanted to know how it worked.  Looking into the thermodynamics I learned a few things.
  1. Oil conducts heat well, better than air, not as good as water (or aluminum)
  2. Oil requires slightly more heat to increase the temperature by 1 deg than air per unit-mass
  3. Oil has much more mass per unit-volume .: holds much more heat per unit volume than air (still less than water)
A bit of envelope math showed that my 5-gallon fish-tank had the thermal-capacity of a bedroom or small office (10x10x8) or so.  The downside is the office/bedroom will exchange that thermal mass more easily than the oil.  The upside is all that waste heat is contained, and controllable.   This means by containing and controlling the fluid I control the heat as well.  Now I can decide/engineer a way to dump the heat.  I don't like fan noise, perhaps I use a large passive radiator then pump the oil through that.

The Motivation
I decided to write this journal because most of the information I found was fragmented and littered with inaccurate advice, or people assuming different motivations.  For myself, I wanted a modestly powerful computer that ran silent.  I've never bothered to overclock a PC, I don't spend top dollar to buy hardware, if I really needed that performance I'd spend a little more.

I'm also interested in the server application.  We've got some sever rooms where I work and they are horrible places to visit, I would hate to work in one.  There were some tests with oil-cooled servers that proved to be more efficient at controlling temperature.  Not only that but the rooms were quiet and normal room temperature (not freezing and windy).

It's not magic, the heat/energy must go someplace, but with a submerged system, where it goes is quietly controlled.  There were some other benefits like dustless and low-vibration that would likely mean hardware lives longer.

That's a bit down the road, but for now I'm curious how a computer responds to load and heat.

The Fan
One bump in the road I hadn't expected, the mini-power supply had a fail-safe in case the PSU fan was to fail.  I discovered this when the oil covered the PSU slowing the fan (increasing the current) and causing the PSU to trip and shut down.  The trick was first measuring the normal current of the fan, that was about 0.3 mA (if I remember right).  Then I put my finger on the hub slowing it down, the current rose to 0.4 mA and did not trip, but as I slowed it more and hit 0.5 mA the PSU tripped.  So I calculated the resistor value to simulate a 0.25 mA "fan" and replaced the real part with the simulated one.

The Tests
I ran a cron that uselessly calculates primes for 30 minutes of each hour (heavy CPU) then rests for 30 minutes.  Looking at the plots it looked like the system was getting warmer over time but not catastrophically.
I still monitor and plot the temperatures just for giggles.  You can see that it's running around 40 C and can get a bit warmer.  I run this cron on some of my air-cooled systems to get an idea of how they respond.
Normal monthly load (not the stress test)

Monitoring the systems I'm learning that each machine has a different thermal signature.
For instance the net-top does not get much hotter under load, but it runs pretty hot at idle.
The gaming machine runs much cooler all around, but fluctuates rapidly responding to small changes in  CPU load.

The Oil-PC (an old shuttle stripped down to the frame) has a much more stable profile.
The system can only release heat from the walls of the fish-tank (less than optimal).
When the Oil-PC comes under load it will jump and level off at the high-temp.  Going back to idle the CPU cools quickly to idle-temp and holds there with little fluctuation.

The Ooze
So I had a "great" idea to mix phosphorescent powder with the mineral oil.  I got about 5g of blue/green powder.  The mixture tested to be non-conductive, and it glowed nicely but it wouldn't stay in suspension.  The result was glow-in-the-dark "dust" at the bottom of the tank.  So I'm not going to do that again.  I had hoped that I could get the oil to "glow" from within but even when the powder was still suspended it just looked like dusty specs floating in oil.  Not the "secret of the ooze" I was hoping for.

What's Next?
I'm looking at methods to build a custom tank for my gaming system.  I'd like have a bit better presentation and cable management .

I finally got around to connecting up a pair of radiators to a 50gph fish-tank pump.  I picked the pump mostly for dimensions and hoped for the best.  I bought some surgical tubing (10') and connected everything up.  It was less than impressive.  The flow rate was there but unimpressive.  I left it running and did not observe any significant changes.  After a few days though I noticed the hose detached itself from the pump.  I went to re-attach it and noticed it was now entirely too large to fit snugly over the diameter.
I figured the warm oil bath caused the rubber to expand, luckily the pump came with a larger diameter attachment and it fit again.  Until I noticed the oil now had an odd yellowish tint.  I worried the heat was dissolving part of my computer, until it dawned upon me... Surgical tubing is the same sort of sickly yellow color.  So I Googled surgical tubing and mineral oil and I was reminded that mineral oil has a nasty habit of damaging latex condoms!  Egads!
So note to self, latex and mineral oil don't mix, or rather they mix all too well.

The Myths
So I want to keep a running summary of the myths I read on posts and what I've experienced with them

  1. It will damage hardware:
    • No.
    • Also no fish, don't be silly.
  2. It's too messy to deal with
    • If you are not prepared it will be messy.  It's not so bad getting your hands messy, quite good for the skin!
    • If this becomes a big thing for me I suspect I'll build a hanger that I can suspend the hardware while I replace parts allowing the oil to drip back into the tank without making a mess.
    • So yes, it's a bit messier, but I wouldn't recommend it for a laptop, but perhaps a server that you keep in the dungeon.
  3. It's not as good as water-cooled:
    • Yes the thermal conductivity isn't as good.  If you aren't overclocking or worried about catastrophic temperatures then it's quite good.  
    • Oil is better than water for submersion!
    • It really depends on how you engineer the system.  My next rig will test means to transfer heat out of the system.
  4. Post-submersion connections:
    • I have had no trouble connecting video-cards, USB, PS/2 or any connectors after dipping or while submerged.  It does take some care to remove oil from my hands but otherwise it's fine.
  5. Upgrades are impossible
    • Messy yes, impossible no.
    • If you are lazy like me, you could just dip your arm into the tank and swap out the ram or a video card, it will make a connection, just let your arm drip and have a towel ready.

Oil Drilling... er mining

So I replaced the tubes with nice clear vinyl tubing which was useful for locating and eliminating bubbles.  The bubbles acted like blocks in the oil flow, a stronger pump would have handled things better.
With the radiators and pump I wasn't able to "over heat" the system with any amount of CPU use.  I decided to mine litecoins to heat-stress the oil, they don't quite make money, but it feels more productive than tossing primes into /dev/null.

For a bit I added a GPU (too old to mine bitcoins) and it added tons of heat.  It was an old card that had the fan burn out from dust.  So now the bare chip radiates heat into the oil.  In fact you can see the distortion in the column of hot oil streaming off the chip.

I picked up a block eruptor (small bitcoin mining ASIC)  for cheap.  Its a little USB device, 333MHash/s but it gets pretty hot.  Before I dunked it I tested it by attaching a CPU heatsink to the back.  It was awkward but kept the device from getting too hot to handle.

So obviously I had to dunk the mining ASIC.  I decided to remove the useless and power-hungry GPU and cut off the CPU-mining.  Immediately the temperature drops.  I don't have a way to measure the exact temperature of the ASIC but I can guess it's near enough the average temperature of the mobo sensors I use to plot my temperatures.  The ASIC does report a temperature but I'll have to see how accurate it is.

Update 2013-12-31:
I got a IR thermometer for Christmas, so I can now get some measurements!

  • Tank-wall = 43C
  • Oil = 50C
  • Ambient =16C
  • Air-cooled BE (333MH) = 80C (hot!)
I'm now running a Block Erupter Blade (10GH) in the oil bath.  I've moved the smaller Block Erupters to an air-cooled position on another server.  Last I've got one BFL Jalapeno in a standard air-cooled position (not enough room to dunk it!)

Minor Issue
I have noticed that some of the PVC insulated cables (like on a keyboard) that are submerged got stiff and brittle after some time in the bath.  Not an issue while soaking but they failed pretty easily with normal use.  I'm not certain what the insulation is made of, but PVC is supposed to be inert with mineral oil.  I'll update if I ever figure it out.


  1. I was having problems with the Google+ comments. It wouldn't let me respond/interact. As I expect questions and comments, that defeats the point of the blog.
    Therefore, I've downgraded the blog back to normal comments. If anyone knows of a good tutorial or could explain the Google+ comment system to me I may swap back.
    As you can tell, I'm new to this whole blog thing.

  2. I wish i could help with that i'm not a blogger myself, I did want to ask a couple questions concerning your system and the one i'm working on putting together.

    One of which is what gph pump were you using, another was what is the capacity of your reservoir in actual contained mineral oil?, i'm looking at possibly putting a radiator in and fanning that for a direct cooling source tho still ambient temperature exchange not a direct cooling source, I've also contemplated buildling my computer into a minifridge, however i'm not sure that would be even close to doable unless it was a submerged computer due to the moisture present.

    1. Rio 450 GPH pump I got on amazon
      You might not need to be so aggressive in the cooling. I've got easy stability with passive radiators. A pair of Explorer steering-fluid coolers works really well.

  3. also you mentioned trying a phosphorous powder, have you looked at a product like this?

    i'm not sure about the incorporation into an oil based product though but if it was incorporable.... i will be checking that out in my system.

      so I'm thinking a table like this, would give you a REALLY awesome oil-cooled setup. Leave out all the fans, and run the plumbing though the back. You could even do some cool lighted "exchanger" in the middle

  4. I think this might work for making a more interesting fluid

  5. PVC parts - According to:
    PVC + Mineral Oil is not recommended above 60C. So I'd target keeping your system below 60C to prevent PVC rot. I suspect that's what happened to my USB connectors.

  6. Curious about a similar build for a cool factor. Considering taking an old laptop I have laying around and "dipping" the hardware (minus the HDD) into a mineral oil filled aquarium to use as a media server/netflix streaming device. It is by no means a high end/gaming rig and seems to have minimal fans/cooling in its stock case.

    My question - do you think the low heat from the low spec hardware and relatively light use (no gaming etc) would be safely managed in just mineral oil (no pumps, radiators etc)? Every build/guide I see on mineral oil PC's assumes you are using high heat, modern hardware,, overcloked and running modern games so says you need a radiator to disperse the heat.

    Any thoughts for someone who has actually done a basic mineral oil build is appreciated!

    1. Look at the power supply, but I can't believe it would be much higher than the system in this article.
      I'd be interested to how the display holds up. I think you'd be required to have an aquarium screen saver running.

  7. So this thread is a little old but I still have to ask? Any lessons learned to add to this? I am in the process of turning my HTC into a mineral oil pc due to quietness and ability to have the cooling at a remote point (outside of enclosed cabinet). I have to build a top box to hold my DVD drive, and a few harddrives and then I can get to work.