Air Conditioning - Miniature A/C Unit

Ok guys, I don't know wether this has been asked before (I hadn't seen a post) but here's what I'd like to do:

I'm too cheap to buy a new computer case. They're expensive and I could probably build one with a little help from gaffa tape. Anyway, the case is not meant for a P4 computer which requires lots of space for cooling.

What I'd like to do is either build or buy a small A/C unit that will blow (via ducts) very cool air over the internals of the computer. The air cannot contain moisture of any sort as this would lead to short's in the computer.

As far as I understand, a refrigerant cooled a/c doesn't leave moisture in the air does it? If not then...

Can you guys recommend a unit that would sit either to the side or on top of my PC, that would allow me to use some flexible ducting to pour air into the computer? If I cannot buy one, how would I go about building something like this?

Any help on this matter would be greatly appreciated.

Regards,
Twobit

The air may not contain moisture, but if you make the surrounding metal too cool you will produce condensation. A well working A/C unit produces plenty of water that must be drained away constantly. Computers don't need to run below room temperature at all. I'd say quit wasting your time on a refrigeration unit and provide for plenty of air flow through the computer. Make sure that you have plenty of air filtration that can be easily replaced to keep the dust to a minimum. Computer component heat transfer to the air from a layer of dust is the REAL killer of computers. It would be better to keep the air flow up and the computer clean than to try to reduce temperatures by providing 40 degree air from an A/C unit.

If you are a real die hard, there are solid state units out there today that get cold when you put DC to them. They are expensive and need plenty of amps to work. Look into going that route. High end computers use a closed loop water cooling system. A heat exchanger is mounted on the outside of the case. Water is circulated only to the microprocessor. That's the only component that needs the cooling.

then you are definitely not in the market for air conditioning it! And yes, air conditioned air by conventional methods is moisture laden by nature because the air has just been pulled across a wet cold coil. Good question though.

jughead,

A quick check came up with a case that costs $55.00: Cheap case (http://www.compwarehouse.com/computertowercasemonitor.html)
This would be a fraction of any type of cooling system that you could build.

As jughead said, a problem with making a computer cooler using an airconditioner, is that although the air that is discharged is dry, there is a likely possibility that the cold temperature of the air would cause condensation to form inside the case.

The issues here are a little misleading. Yes, heat is hard on computers. Operating them in a high heat environment will greatly increase the mean time between failures (MTBF) of the components. However, the components in question can operate at up to 100 degrees without much trouble at all. In order to maintain that nominal temperature (or below), you must dissapate a particular amount of heat (BTU's) per component. As long as that amount of heat is transfered to the surrounding air and is carried away the temperature of the component will never rise. Heat always flows from what's hot to what's not. That is, heat flows from hot to cold, assuming no other outside influences. The amount of heat that flows depends greatly on the temperature difference between what's hot and what's (in a relative sense) cold. This is the ideal case. You can influence the amount of heat transfer greatly by providing insulation between what's hot and what's cold. In some cases even a small layer of insulation may have a large effect on the heat transfer. Consider a thin layer of dust on the top of a chip. Dust can trap and stagnate air. That air can and will act as a thin layer of insulation. Heat transfer will be inhibited and chip temperatures will rise. Now, to compensate, one has the tendency to think: "I'll just keep the components cool by providing 40 degree air to the components". Since the difference in air temperatures is increased, you will, in fact, increase the heat transfer and keep the temperatures below the red line, until you get more insulating dust.

From my personal experience recently; My Dell dimension 8200 has two small muffin fans running inside. One in the power supply and another inside the computer. The power supply fan had quit and I didn't notice it until I installed a new USB board a couple of months ago. Now, I know enough to do regular maintence on electronic equipment from long experience on the job, but often ones own equipment at home goes lacking from the same treatment one give the equipment at work. Not only did I find the fan not working, but I found a thick layer of dust clogging up the fan intakes and a great deal of dust coating the components themselves. My solution was to remove the computer to the garage where I could blow the whole thing out with compressed air. The fan was replaced and the now dust free computer is running much cooler, I'm sure. I've worked on ships as an electronics officer where the installed computers are a mission critical devices. There, each computer has a small piece of filter material installed across each fan air intake. That filter is checked each month as part of the regular preventative maintenance schedule.

The moral of the whole story above boils down to the following: one can either enhance the component heat transfer by increasing the temperature difference (providing cooler air with a mechanical A/C unit) or one can remove the insulation (dust) from the components to get a simular result. The choice is up to you.

Im with GregH get a new case. Tiger Direct has all kinds.
Also check the heat sinks you have there. I put a bigger heatsink and fan in then another fan on the case . Chip temp dropped over 60oF. Like said dont blow AC air into it.
On some very large set ups with PC we have set them up that the room had AC in it and the air returns to the units where like under the PC are right by them.


ED ;)

About five years ago I was on a ship down south where it was hot outside. A salt water leak had developed over a control unit for a chilled water circulating pump. The control unit was damaged and needed parts. As a result, the temperature inside a room containing about 12 PC's was between 115 and 120 degrees. The room was that way for about 2 weeks until we could get the circulating pump back working again. You know, not one of the Gateway computers ever crashed. They've probably been replaced with newer, better, models by now, but the high temperatures didn't seem to do them much damage .

This is somewhat of a joke. Is this a test? Obviously a new case is the only practical answer, but a Peltier cooler is the answer you're looking for. There are models made specifically for CPU cooling. They are used in situations like the one you initially described where proper air circulation can't be achieved or where CPU temp is greater than can be dissipated by air alone (overclocking).

Did I pass? :D

Doug M.

No I don't think you passed Doug.

I think that maybe we didn't offer twobit a solution fast enough and his/her processor burnt up. :D

Yea, there's ready made stuff out there that's designed specifically for computers, but by the first post the guy was too cheap to buy one. It would cost him more to try to rig up something on his own especially since he had to ask how.