Air conditioned case

I had been thinking about building an air conditioned case for awhile now. Last week I was at Lowes and seen a 5000 BTU, small window unit for $98. Figured I buy it and see what it does. If it's no good for cooling down a PC, I can use it in my small shop office.

So, over the weekend I did some tinkering and came up with a temporary setup that more or less shows 5000 BTU's is not enough cooling for a whole computer enclosure. It works, but even recirculating the chilled are back into the evaporator, it only drops about 5 to 7 degrees F. below ambient room temps of 74 F. It's been running for about an hour right now, and I see the inside case temps are 69 F.

Anyone doing anything like this? If so, how many BTU's would it take to cool an entire computer running an FX-8150 overclocked to 4.5GHz?

-Rodger

Depends on video cards too.

EDIT: Oh, didn't see your sig since it's on mobile. Let me see if I can do the calculations.

Hey, just looked my evaporator and seen it was iced up! Evidently, I need to let some ambient room air into the evaporator. This is better now, at 57 F. and dropping. Could be interesting...

-Rodger

Knufire said:

Depends on video cards too.

EDIT: Oh, didn't see your sig since it's on mobile. Let me see if I can do the calculations.

Click to expand...

Sorry, got a bit excited to see temps dropping... Hey, that would be a big help to know if this is too small a unit to spend too much time on.

About 600W of heat on that computer (pretty big overestimate to be safe, just plugged your system into the extremevision PSU calculator). 1000 BTU is about 300W of heat, so a little bit more than 2000BTU would keep the case air temperature the same when fully loading your system. Heat capacity of typical room air is about 0.00121 J/cm^3K. What that means is that you need .00121J of energy to lower a cubic centimeter of air down 1K, which is the same as 1C. Based on the Newegg dimensions, your case volume is about 58 461.2113 cubic cm (again overestimating because there's stuff in the case), so about 71J of energy to lower the temp 1C. Watts a J per second, so 71W would lower 1C every second, so another 1000BTU should be about 4C. This is on top of the 2000 needed to maintain temp, so a 5000BTU unit should be lowering about 12C? That's a pretty big overestimation since I started with a pretty high heatload of your computer and the volume calculations were based on an empty box the size of your case.

Past that, no idea how to figure out the equilibrium. If it stops at 12C below your room temp, I'd be pretty surprised that I was right. xD

Knufire said:

About 600W of heat on that computer (pretty big overestimate to be safe, just plugged your system into the extremevision PSU calculator). 1000 BTU is about 300W of heat, so a little bit more than 2000BTU would keep the case air temperature the same when fully loading your system. Heat capacity of typical room air is about 0.00121 J/cm^3K. What that means is that you need .00121J of energy to lower a cubic centimeter of air down 1K, which is the same as 1C. Based on the Newegg dimensions, your case volume is about 58 461.2113 cubic cm (again overestimating because there's stuff in the case), so about 71J of energy to lower the temp 1C. Watts a J per second, so 71W would lower 1C every second, so another 1000BTU should be about 4C. This is on top of the 2000 needed to maintain temp, so a 5000BTU unit should be lowering about 15C? That's a pretty big overestimation since I started with a pretty high heatload of your computer and the volume calculations were based on an empty box the size of your case.

Past that, no idea how to figure out the equilibrium. If it stops at 15C below your room temp, I'd be pretty surprised that I was right. xD

Click to expand...

Interesting.

Running Prime95 as I type this. Seen case temps go down to about 55 F. and seem to hold there, so thought I try some stressing and watch temps. Started with the CPU at 20C., cores about 2 to 6C. Case was 55 F. in the upper most corner away from the chilled inlet air.

Been running for 15 minutes now. CPU temp will go to 72C and then CPU throttling starts kicking in. It progressively lowers the multiplier until the CPU gets to 1.8 GHz (normally runs at 4.8 GHz.) Take only a few seconds and comes back to 4.8 Ghz. with 50 C. CPU temp. Core temps max at 67~68 C.

Running Prime95 I see case temps have risen to 60 F. with ambient at 74 F. That's still 14 F. lower then it would be running. I need a better CPU cooler.

-Rodger

I would like to see pictures of how you have the chilled air going into the pc. Maybe then others could chime in on how you could improve the air flow of the cool air into the pc. I have a 10kbtu ac and it is just for the room and when I turn on the ac my pc cools down quite a bit so I dont see why your cpu is throttling down when you have the ac hooked straight to the pc case. More heads are better then one.

Well, seems the above is where this computer is at right now. I should mention that this is all in a temporary cardboard enclosure. The AC unit had it's case removed and I made a tight case around unmodified parts. I redirected the chilled air up and there is another cardboard case built above the AC case. It is isolated from the AC case by some 1/4 foam art board, which is what this case is made from. The only exhaust out of this case is a bit though the GPU and a single 5" hole cut to allow air to pass down into the AC case, right on top of the compressor to help cool it down. This air then moves around the side of the case, back to the front evaporator and also rearward to the condenser. What I was trying to do was somewhat cool down the heat exhausted to a manageable level, as I am not venting any heat outside. I also wanted to recirculate the chilled air, but as it turned out that was what cause the evaporator to frost up. I'm sure that there is a better way to do this, I have to do some searching and head scratching.

So, it seems it would cool this computer down after all. I do need to look at a custom water cooling setup though as this H80 isn't strong enough for the heat this CPU generates.

Thanks for working out the calculations Knufire. I'm going to look at some better CPU cooling options and see where this leads.

-Rodger

Richierichdolla said:

I would like to see pictures of how you have the chilled air going into the pc. Maybe then others could chime in on how you could improve the air flow of the cool air into the pc. I have a 10kbtu ac and it is just for the room and when I turn on the ac my pc cools down quite a bit so I dont see why your cpu is throttling down when you have the ac hooked straight to the pc case. More heads are better then one.

Click to expand...

I believe it's the Crosshair IV Extreme that's throttling down the CPU. This board's BIOS is pretty hacked up, just to allow the FX series to run on it. I'm waiting for the CHV-Z to be released and will be upgrading then. That should resolve the throttling issue.

As I already posted, I need better custom CPU cooling now. I'm pretty sure I could stay under 60C. with the right setup in this case, or the real one I'll make if this all seems worthwhile.

Let me take a pic or 2 and I'll post it.

-Rodger

Here are some pics, just done with the cell phone, so might need a bit of interpretation.

Pic 1 - Whole case shot with the Noctura D-12 installed.
Pic 2 - Close up of the motherboard, and D-12.
Pic 3 - Close up with the H80 installed - Note the chilled air inlet on the floor.
Pic 4 - Chilled air diverter into the H-80.
Pic 5 - Another Whole case shot.
Pic 6 - Another inside case shot - Note the 5" exhaust port into the top of the AC box.

-Rodger

Well, been where I've never been before on this rig...



-Rodger

You show great promise. Ever thought about benchmarking?

Bobnova said:

You show great promise. Ever thought about benchmarking?

Click to expand...

Ah gee, now I'm blushing...

The brotherhood of the ducktape / crazy benchers would be a welcome place for you. Hacking together what you have around on a whim for a performance increase is something that tends to happen a fair amount when we get moving.

TsunamiJuan said:

The brotherhood of the ducktape / crazy benchers would be a welcome place for you. Hacking together what you have around on a whim for a performance increase is something that tends to happen a fair amount when we get moving.

Click to expand...

Yeah, maybe it would if I had any regular time. I can only do things in spurts when I have a lower workload. I'm trying to stay away from work more, but it keeps calling me back. Maybe if I could retire again, it would stick better. I appreciate both the invites though.

-Rodger

Don't worry, we'll be here. Lurking. Constantly

I have actually experimented with this before and the best way I found was to first place the AC above the PC case as cold air drops much easier than it rises. Secondly place a dryer vent hose on the ac outlet using duct tape of course then tape off the rest of the outlet vent so all your cold air goes through the hose. Tape the other end to your side fan vent (close off any gaps with tape again and viola. It's actually quite effective. I used to do it all the time when I overclocked (before I got single stage) by placing the end of the hose directly on the HSF.

Dang! 5.2GHz on an FX8150? Bad *** bro!

OptyTrooper said:

I have actually experimented with this before and the best way I found was to first place the AC above the PC case as cold air drops much easier than it rises. Secondly place a dryer vent hose on the ac outlet using duct tape of course then tape off the rest of the outlet vent so all your cold air goes through the hose. Tape the other end to your side fan vent (close off any gaps with tape again and viola. It's actually quite effective. I used to do it all the time when I overclocked (before I got single stage) by placing the end of the hose directly on the HSF.

Click to expand...

Appreciate the advise. I'm trying alot of stuff. Right now I need to figure a way to recirculate a higher percentage of the chilled air, without freezing the evaporator. In my initial testing, without a computer installed, I was able to reach 25 F. and no frost. By necessity, the design had to change to fit the computer, so now I am considering what else to try to get good recirculation with minimal or no frost.

I will also need a custom water cooler to keep CPU temps lower during stress tests/benchmarking.

-Rodger

DieselDawg9 said:

Dang! 5.2GHz on an FX8150? Bad *** bro!

Click to expand...

Thanks alot.

Been trying hard to just reach 5Ghz for the past year or more. Nice to see it was possible using a motherboard not even designed for FX processors.