I think this is different than the "should i air or watercool" thread, so I'll try to be as concise as possible, as I've found little to no info on this while googling.

For school, I'm about to submit a project proposal to the faculty for a render farm: The system itself will be 8-15 lower-end PC's linked together to a main computer to perform rendering operations for the art students. Render farms can get hot... the ambient heat caused by close to a dozen PC's can sometimes raise the operating temperatures to dangerous levels, especially on a system like this that will probably be utilized often by the hundreds of modelers at this school.

So, instead of individually-cooled systems which would possibly become a hassle in and of itself, I came up with the idea of placing all the systems into a fridge to keep the temps down. The thing I'm worried about most is the moisture in the air in normal residential refrigerators that could cause some very bad and very obvious problems. Unfortunately, most commercial applications either lack the storage space, are way too big, and they all cost more than a used car.

If anyone might have any ideas or suggestions for this project idea of mine, I'd be extremely grateful. Thank you.

Look into the server farms that are still out there/here.
Some have built a walkin cooler of sorts, basically using one or two units torn out of refrigerators.

Even a window mount ac would work for this in a wood framed and plexi glass or spare closet.
You'd still want to load each machine with a good fan systems, or strip them all the way down to bare.
No sheet metal sides, kinda like mini rack mount expossing
all componants but have a central network drive.
Exhausting the heat from the building may prove difficult.

The cheapest solution using new (under warrenty) equipment is, as mention above, a high efficiency domestic window AC unit.

As long as the Farm is in an enclosed space that is sealed and you're AC unit has a dehumidification function you should be fine. Keep the AC in recirculate mode to avoid fluctuating temperature and humidity levels.

If the farm is to be in a box or a closet then just rememebr to seal, seal, seal and insulate - you dont want your hard earned cooling going out the door so to say.

As for dust control, if the system is sealed you should have no trouble, if it is not possible to seal it pefectly then add a pressure boost fan at the bottom with a high effieciency filter. You need just enough power to make the door want to "gently" pop open. That means no dust or bugs will crawl into your farm through any small crack, opening, seams or unused pass throughs.

Hope that helps give you some ideas without breating the bank.

OH BTW .... that AC unit needs to dump its heat somewhere so dont forget to give it enough ventilation to do its job properly.