Out of Pod Experience

why build a passive one? would not making passive massive copper tube be better?

From what I understand, a passive-liquid cooling system would be very hard to build efficiently.

What you'll need is some way to ensure constant flow over the CPU, could be convection driven, but at 30C, you're not going to be getting much flow. You also need a way to dissipate all the heat that the water pulls off the CPU. Again, if you don't want to buy a radiator, you'll need a holding reservoir with a fairly large surface area in order to dissipate as much heat as possible, as quickly as possible. In that case, your lower limit of temperature is theoretically the room temperature. However, at temperature differences of about 10C(assuming room temperature is about 20C), your convection flows are going to be very slow. With slow convection--> low volumetric flow, ---> not much heat transfer---> higher temperature on your CPU.

Which, actually will lead back to higher flow rates, more heat transfer, and therefore lower CPU temperatures... haha. The system would be self-regulating, up to a certain point, however I am VERY skeptical that it could keep a CPU at 30C under load without a pump.


I could design a passive system without much trouble, but without some fairly detailed, time consuming mathematical stuff, I couldn't give you any idea of how practical it would be. And I think your reservoir would need to be significantly bigger than an empty 2 liter. Off the cuff guess- several gallons.


If you're planning on gaming for long periods of time, you'd need to calculate exactly the flow rates through your piping, the heat transfer from the CPU to the coolant, the rate of heat dissipation from the coolant reservoir. There are probably a couple variables I'm forgetting. You'd also need to be in a stable climate controlled room, because seasonal variations in room temperature would affect how much heat can be dissipated from the reservoir.

My recommendation - don't go passive.


Honestly, you don't need to buy the flashy built-for-purpose pumps and radiators, if you can build them yourself, you can probably save a bunch of money, while getting something that doesn't look as good.

Edit: If you buy/build a radiator, it's much easier, and may actually be practical.

Disclaimer: I'm studying electrical/computer engineering, not mechanical. I've taken a few classes that have dealt with thermodynamics, but I'm not an expert. if a Mech person can add something or correct what I've written that would probably be good.

I am building myself a water cooled system. Currently my focus is only the CPU as the heat blocks haven't changed much in regard of fitting. (perhaps I am wrong, but look at video card heat sinks, they got a new one out every time a new video card is put on market... waste of money)

Ok i guess, video cards do change over time and I tend to think that the AM3 and LGA 1155 bolt patterns will be around for a while. Cooling the CPU via water cooling is a good idea in an age of 250W chips.

Anyways, I am trying to make a passive setup, without using a Rad as a way to cool the water. More of a holding tank that will contain X amount of water, with an aeration system going through the water to help draw heat out of the water.


If you are trying to do something with no pump, its not going to work. If you wanted to do something with a drop tower to do something more passive, its not going to work well. Fans, even slow ones, are exponentially better. I am thinking that using a PVC pipe stuffed with fishtank bio balls and using a 200mm fan to pull air up while water trickles down.

The question I have for just a CPU block, how much water you guys think I would need to successfully setup a passive water system, that would be able to keep the water at a 90 degree (30 Celsius) temps under load?


Most blocks are fairly good but a few are exceptional. I would go over to the [H]ardOCP forums and look at what other people are doing. I would suggest an EK copper waterblock(somepeople think their nickle block is flawed) or even the swifttech one that's on newegg isn't half that bad.
http://www.frozencpu.com/cat/l3/g30/c85/s139/list/p1/Liquid_Cooling-Water_Blocks_CPU-CPU_Water_Blocks_-Page1.html

My idea is to make an acrylic box that will hold roughly 2 liters of water, (Im even of thinking of recycling a 2 liter coke bottle).
I love ghetto mods but i would throw a silver shaving in there as a biocide. Residual stuff may encourage growth. Note that all your options where water is exposed to open air, you need to be really ontop of your maintenance. Not to mention you are going to rust out the fins of you waterblock due to electrolysis.

The question comes down to would that be sufficient amount of water to allow cooling to occur at a fast enough rate (including air bubbles running through the water) to keep a system cool enough alone? Or am I stuck just forking over more money for this overly priced computer stuff. Im not cheap, but for a stupid water pump for this application they want 60 bucks, when I can go to a local hardware store and get it for 20-30 bucks. Over inflated pricing ftw =T'

The pumps you see, like the swiftech 655 or the 35x are both good pumps that are made for long life and low noise.

but to answer your question on how much of a flow you need, well we would have to talk specifics, tell me what processor you want to use and what kind of overclock you want to have. After that tell me what pump you are going to use. If you use one of the before mentioned ones your GPM is roughly 4 or 5. Then its down to trying to figure out the size of the drop tower or the max wattage of what you can extract from the waterblock.

I don't think there's an easy way to sustain cooling with what the OP has in mind.
Water needs to evaporate (aka change phase) in an open system, you'll still need to fill up periodically (which will become a real hassle long term).
(it's the basis for the so called Zeer pots - Google around for videos
here's another good informative link on Zeer pots - http://practicalaction.org/zeerpots)

For closed systems, it's already been answered by the few posters above.

Personally, if you're doing DIY cooling, might as well go all the way.
Do it with a (cheap) car radiator and pump.

Quick Google:

http://www.xtremesystems.org/forums/showthread.php?189928-Yes-Another-Car-Radiator-Thread....Major-56K-Warning!
(holy crap, he really went big)

http://www.instructables.com/id/Computer-liquid-cooling-with-Car-parts/?ALLSTEPS

http://homegardensupply.kitchenpopular.com/cool-computer-cooling-with-car-radiator-extreme/
(using an aquarium pump)

http://photonics.engr.uga.edu/watercooling/index.html
(water cooling 101 - very informative)