Extreme Water-Cooling Using Refrigeration

Detailed article to adapt a “cube” fridge for watercooling. — Nicholas F. Singh.

The final product – my modified “cube” fridge.

Foreword

A couple months ago, I made my own water-cooling system from a custom-milled copper block and piping, soldered together in my basement. The copper block had 5 holes drilled through it length wise, and the 2 pipes on the side were machined to fit the exact curvature of the block. This design, I felt, would be the most efficient due to the fact that a very high volume of water can be passed through the block at a slightly lower speed than normal – the ideal condition for heat transfer via water.

I placed this block on top of my 1.33 GHz Athlon, 266 MHz, and secured it down with the decidedly crappy clamp I got from Danger Den. Careful – that thing is an outright socket lug killer! I snapped off 3 of my lugs before I got the hang of this dumb thing. Epoxy anyone?

I decided to put my water input/output points where my power supply was originally mounted. I decided to cut out the upper portion of my case, move my power supply up, and design a custom plate to cover the hole left by the supply and hold the barb-hose fittings. The size of my massive “old school” Gateway 2000 case allowed for this.

After measuring, drilling, and threading up a storm, I got two ½” brass male hose-to-barb fittings into the custom plate, which were secured down by two ½” conduit locknuts.

I then simply ran two reinforced hoses out to a crappy Rubbermaid water reservoir with a fish tank submersible pump. Needless to say, the water got very hot, very fast. I always knew I’d try to upgrade this cooling setup, and Christmas Break was my opportunity to go nuts.

The focus of this article is not on the design of the water block, but rather the method by which I used a small refrigerator to super-cool my system’s circulating water.

Section 1: Selecting the refrigeration unit

Three words: Size, Size, Size.

That’s all that matters when it comes to selecting your refrigerator. The smaller the better, because you will move it around a lot when drilling holes and while testing for water leakage. And also, if you’re like me, you don’t have the much room for a massive fridge next to your computer! In addition, the smaller they are, the less expensive. This is not always the case, though. I suggest getting an older one with dimensions around 19″ cube.

I got mine on eBay for $20. It had a big dent in it as you can see, but I could care less. Aye, as long as it works! Unless you’re finicky about the cosmetic condition of everything in the vicinity of your PC, and unless you’re loaded with money, don’t bother buying one new – you’ll spend enough on the parts for this cooling design! (New mini-refrigerators can cost upwards of $100)

Section 2: Refrigerator Mods

My design calls for two ½” hoses to circulate water through the unit. I cut two 5/8″ holes in to the left side of the fridge about 4 inches apart. The width between holes isn’t that important, but I suggest you cut from the inside out. As you’ll see in the next picture, the ice cube tray and temperature controls can get in the way of your drill. If your holes are too high, you’re going to have a tough time in the future.

This drilling will create a bit of a mess due to the foam core, so do this outside or in your basement. Use a rotary tool to clean up the jagged edges of the outer metal casing, or take a round file to it. It will need to be smooth, so do a thorough job of it. And, WEAR SAFETY GOGGLES. You’ll be thanking me when little scraps of metal clank up against your goggles as you drill.
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Nicholas F. Singh

Section 3: Fitting Assembly

Next, I set out to create an assembly that would allow me to screw on two hoses to the outside and have two barb connectors available on the inside. Sounds simple, but you have to remember that there is about ½ inch of insulation to deal with, and you can’t screw on a hose-to-barb fitting directly onto the flimsy outer metal casing!

Whip out your ruler, and measure the distance between your two holes. Then cut two aluminum reinforcement sheets to distribute the pressure of the fitting assembly along the inner and outer edges of the fridge. For this design, you’ll need:

• Two ½” brass nipples
• Two 5/8″ brass couplers
• Two ½” male hose-to-barb fittings
• Four ½” conduit locknuts
• One sheet metal plate, with Two ½” threaded holes
• One sheet metal plate, with Two 5/8″ UN-threaded holes

The parts are pictured below, along with the final fitting assembly:

DO NOT TIGHTEN EVERYTHING YET!

Only tighten the partially assembled parts you see on the top of the left image (above). Be sure to use Teflon tape thread sealant on all joints, or you will have leaks.

Take the plate with the threaded holes and screw in both nipples. Then tighten on the couplers and the conduit locknuts on the opposite side. Tighten these as much as you can, because you won’t get a second chance without a lot of work!

Now, take this partially assembled half and insert the couplings into your refrigerator holes as seen below. If you’re confident of the fit, you may want to epoxy it to the case, but it shouldn’t be necessary. I do suggest you get some expanding foam to fill in the spaces around the couplers. It’ll cut down on cold air leakage, and will also serve to stabilize and secure your fitting assembly. I used “GREAT STUFF Minimally Expanding Foam.”

Now, place your other plate up against the holes inside the fridge, and screw in your two barb/locknuts as shown below. Since the holes on this side of the plate are unthreaded and slightly larger then the brass threads on the fitting, the metal plate gets pressed up against the walls of the fridge as you tighten the barb fitting. If you cannot tighten the barb any further and the plate is still not flush against the inner wall, tighten the locknuts to your liking.

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Nicholas F. Singh

My design calls for a medium-size water reservoir to be used with a submersible pump. Since I know the water in the reservoir will not be cooled fast enough to keep up with water circulation, I decided to implement a dual-coil radiator inside the fridge.

How do I justify using this? Well, inside the fridge, the water will be cooled just like, say, a (1) pitcher of juice or a (2) can of pop. If left there long enough, either container will become equally as cold, right? Right. However, it will take longer for the pitcher of juice to drop down to a certain temperature than would a can of pop. Why? Because the ratio of the surface area of the juice container to its volume is lower than that of the ratio of the pop can’s surface area to its volume.

Now, take this analogy and apply it to our situation. Obviously, the water in the reservoir would incrementally heat up due to the incoming warm water from the processor heat discharge (not to mention the heat generated from the submersible pump). Water near the center of the reservoir would never have enough time to be cooled sufficiently before it is pumped back to the processor.

Implementing cooling coils gives a very large surface area to volume ratio, which is exactly what we are looking for. Using two coils simply adds icing to the cake; it doubles the system’s effectiveness, since the water flux going through each would be cut in half. This, in turn, doubles the amount of time for heat to be dissipated into the copper tubing.

Now, the first step to realizing this idea is to actually create the device that would split the incoming water into two separate coils. Sounds easy, right? Well, not really. I decided to take the incoming ½” water source and split it to two ¼” channels. That’s a tricky conversion, as I found out! You’ll need the parts listed below, some of which are depicted in the left image below. The final assembly is also shown on the right. Again, be sure you use Teflon thread sealer! All the copper joints will need to be soldered together, so be sure you have your torching skills honed.

• One brass ½” barb to male hose fitting
• Three brass ½” nipples
• One copper ½” female hose to pipe converter
• About half a foot of ½” copper pipe
• One ½” copper “T” splitter
• Two brass ½” compression pipe to ½” female hose fitting
• Two brass ½” female hose to ¼” pipe compression fitting

I tied some flexible aluminum bracing around the splitter and hung it from the ice cube rack with some wire. No fuss no muss. You can hang the splitter any way you want though, just as long at it lines up well with the input water port. I suggest using flexible hose to connect the two barbs so the thing can move around without breaking any lines.

Nicholas F. Singh

I won’t go into too much detail on this one, because you can do it however you want, and it’ll have comparable performance. I just wanted the coils to look pretty, and to remain spaced securely.

All you’ll need is 20 feet of ¼” copper tubing. Cut it in half, and start winding it around whatever you feel best suits you. I used a wide bottle of Ragu’ Spaghetti Sauce, Garden Style. I then made a makeshift support bracing for the coils by first inserting wood spacers between coils, and then tightening the 40 support screws on the structure. Like I said, I don’t want to go into details, but if you want to use my general design, go for it!

Don’t forget to clean up your huge mess, buddy!

Well, that’s pretty much it! The rest is just a matter of connecting all the pipes together and adding a reservoir and pump of your choice. Here’s what the final product looks like, along with a photo of my setup:

This extreme water-cooling project of mine took about a week to complete, after all my planning was done. I would advise that you not attempt this project if you don’t have all the proper metalworking tools readily available. Especially threading tools! This project isn’t for the faint of heart, or the economically challenged. Little things add up – especially all the brass fittings. I easily spent over $150 on materials alone.

It you are interested in creating the ULTIMATE water-cooling device, this is the only way to go. Just imagine being able to cool your peltier down with water that is always on the verge of freezing – Great, aye? Heck, you don’t really even need a pelt at these temperature – just put the water block directly on the processor and you’ll get the performance of a “normal” pelt device.

And, you’ll have bragging rights for quite some time – not to mention a handy place to store a couple cans of pop.

Please email me with any of your questions/comments – it would be great to hear from you!

Nicholas F. Singh