HW projects - Silent natural convection (fanless) liquid cooled PC

And now for something slightly different...


Some background:

The idea of this project was to construct a PC that would generate minimum amount of noise. Modern high end PCs generate huge amounts of heat that must be removed from the components, normally by using heatsinks and fans.

In the worst case scenario, the heat is removed from the components by using heatsink / fan combinations and after that the hot air is blown out from the case using another fan or by several fans. This kind of bad design results in having a case full of noisy fans and can quite often be seen in DIY rigs, whereas computers made by leading manufacturers usually utilise many kinds of air duct designs to blow the hot air out directly to reduce the noise and, of course, the amount of costly fans.

One solution to the fan problem is to use a liquid as a heat transfer medium circulated by a pump to a radiator outside the case where it is dissipated to the surrounding air by means of natural convection.

Info about natural convection can be found here:
http://en.wikipedia.org/wiki/Convection

Commercial watercooling systems have been on the market for a while now, and they might be quieter and more effective than direct fan cooling but usually the heat exchangers used in these setups still use fans to expel the heat from the coolant and are quite often used by overclockers for their high efficiency.

My old watercooled setup worked flawlessly for five years, but it still had a fan in the power supply and four slowly rotating fans in the radiator made from old Ford heater matrix. The fans were originally pretty silent, but after few years of 24/7 use they started keeping noise. Fans also gather a lot of dust inside the casing and to the components unless a filter is fitted. So, when the time came to upgrade I wanted to use the watercooling parts from the old setup and strip off all the fans from the new system, if possible.

Building the new system:

The first step was to get a proper case. The Antec P182 was quite affordable and had good sound dampening and anti-vibration properties. This is important since hard drives and CD/DVD drives might also be noisy. After this the Antec Phantom 500 power supply was selected, since it seemed to be the only available passively cooled PSU on the market (it actually has a small fan inside, but it turns on only if necessary and acts more like an overtemperature protection).

rad pipework

I assembled the DIY passive radiator, Eheim 1046 pump and Innovatek tank (tank-o-matic) to be a separate external module. The radiator was constructed from one large aluminium grill, two rounded aluminium corner pieces, some 2mm aluminium plate, four metres of copper pipe and fittings. The Innovatek water tank had to be "modded" because for some odd reason it generated cracks to the top part of the tube and started leaking after few weeks of use and I had to fix the end cap in place with silicone. I also fitted quick connectors and shut off valves to the coolant hoses to make the module easy to remove and reconnect.

Very little modding was made to the case itself since it was nearly perfect for my needs. Only few extra holes and a DIY switchpanel for operating the three pre-assembled fans (if necessary). To this day, there has been no need to put a single fan on. The PSU fan has not switched on either, so the system itself is totally silent. The pump impeller is the only actively moving part on the cooling system but it is silent because it has no bearings or brushes. The magnetically rotating shaft is lubricated by the cooling water itself.

The "noisiest" part of the system is now my second monitor, it is an old 17" CRT and keeps a slight humming sound =) .

UPDATE: 7.5.2008 - No more of that CRT hum, since it broke up. Replaced both old displays with two new 22" LCD flat panels. Totally silent now, but I think the old CRT had a better picture though...

I also relay modded the extension cord so that when I turn on the PC, the pump, monitors and audio amp also power up.

tapping the threads	pre-assembled rad	old Ford rad	semifinished rad

Coolant:

An ideal coolant would have low viscosity, high thermal capacity, be chemically inert, non corrosive and preferably be electrically non-conducting.

I was originally planning to use non conducting coolant, such as Fluorinert manufactured by 3M because I happened to have a liter or so of this somewhat expensive stuff that was scavenged from remains of old liquid cooled Cray T3E supercomputer. Unfortunately Fluorinert evaporates rather quicky, leaks easily having very low viscosity and because the chemical compatibility with all the materials in the cooling system (rubber O-rings, soft PVC tubing etc.) could not be fully confirmed, I decided not to use it.

The current coolant is just a 50/50 mixture of ethylene glycol (antifreeze) and distilled water. The purpose of the ethylene glycol is to reduce corrosion and to prevent the growth of algae.

Temperatures (during winter):

New convection rad
idle CPU 30C, GPU 35C, MOBO 26C, full overnight torture CPU 40C, GPU 55C, MOBO 28C
Old rad (for comparison)
idle CPU 26C, GPU 32C, MOBO 26C, full overnight torture CPU 38C, GPU 50C, MOBO 28C


Temperatures (during summer):

New convection rad
idle CPU 38C, GPU 40C, MOBO 28C, full overnight torture CPU 54C, GPU 58C, MOBO 28C


System specs: (nothing spectacular here)

ASUS A8R32-MVP Deluxe MOBO, AMD Athlon 64 3500+, Asus EN7600GT, 2GB RAM
Antec P182 case, Antec Phantom 500 Passive PSU, DIY Passive Radiator

---

UPDATE: The "waterblocks" picture got me the first prize (Sony DAV-DZ830 Home Theater System) in the Gates Unicoil photo competition. -> [ www.gates-unicoil.com ]

(click for larger image)



front view



side view



corner view



waterblocks



quick connectors and valves