Air conditioning...

[Rob Cork]

Just discovered the real benefit of lower ambient temps for myself - my room at college has a patio style door out onto the walkway outside, and I opened this to let some fresh air in. Being England and winter, it's pretty cold outside, probably only a degree or two above freezing. What I found was chipset temp down from 26C to 14C, and cpu core temp down from 41C to 31C - at 2.2V!!! This got me thinking about some way to cool the air coming into the case - ducting isn't really an option cos I can't leave my window open when the room's unoccupied, and I need the comp to be portable. Here's an idea I came up with:

Slimline radiators over the intake fans, run from an independant inline water loop, with a 'chiller' before the radiator (suggested by Azz ) - a waterblock with a peltier and hsf on to cool the water passing through. This way the radiator is kept nice and cold - and hopefully cools the air coming through by a good few degrees. I'm curious whether anyone else has tried something similar, and how effective it might be at cooling the air - if it's only a degree or two different it's probably not worth the money for the extra watercooling kit.

I'm planning on building a shiny new rig in the summer when I have loads of time on my hands, and I'm thinking if including this idea in the design. Anyone think it's worth it?

 

[Big Mike]

I think condensation would be a serious concern with this setup unfortunately...

 

[Metaxas]

Condensation would MOST definatly be a HUGH concern in that rig. Running the inside of your case below ambient temp presents condensation dangers..which could lead to all out disaster. However, I have been looking into ways of overcoming this, because I would like to duct A/C air through my case, and reduce ambient temps year round. What about coating the boards with something, like silicon, but then again, doing that would trap the heat on the board itself right? Hmmmmmmmm....that's a toughie.

 

[merlins_wraith]

hmmm ... working on this very problem as we speak .... although the temp is nice and chilly outside right now ... living in the southeast US ... i am worried about the condensation issue in about 3 months ... this is the system as it currently sets .... give me feedback if you feel so inclined ....

1) i am running an automotive transmission radiator in the front bottom of my HX08 case ... i have piped rs-12 refrigerant (6 oz can mounted in the bottom of my case) running one way through the radiator ... and have plugged the other end with a bleed value ....

2) i am running two 85 cfm fans behind the radiator .. one that is directly ducted to the top of the heatsink fan ... the other that blows undirected into the case

3) i have constructed a small catch pan below the radiator to remove the water that drips off the radiator ...

4) i have installed a two outlet fanbus so that i can adjust - ' on the fly ' to make sure that there is more out going air than incoming air ...

5) i have installed a two temp heat probe ... one for room temp and one for radiator temp to monitor the difference between room and case temp
------
in the process of developing an in line value and pressure gauge in order to regulate the cooling and pressure in the radiator .... currently i have to bled the system about 3 times per day ... way too high maintenance .... also working on pics - right now the system is installed on a my k62 system (now running at 16 degrees C) so that i don't turn my duron system into an overweight keychain ....

'do or do not there is no try'
duron 700 @ 980 kt7 raid
k62 550 @ 700 (instable paper weight)

 

[Rob Cork]

Thanks for replying guys - I hadn't thought that condensation would be an issue, as i wouldn't have expected the air to cool that much, but I guess it would be risky. There didn't seem to be any condensation problems with the really cool air from outside, but I suppose that's cos it's pretty dry at that temp. Cooling air from room temperature to low temps probably would give some condensation - coating the components in some silicone-based spray sealant might work, but that might act as an insulator, negating the benefit of cold air. Clearly more thought needed here, thanks for the help

 

[Eriksson]

Rob Cork (Jan 17, 2001 06:42 p.m.):
Just discovered the real benefit of lower ambient temps for myself - my room at college has a patio style door out onto the walkway outside, and I opened this to let some fresh air in. Being England and winter, it's pretty cold outside, probably only a degree or two above freezing. What I found was chipset temp down from 26C to 14C, and cpu core temp down from 41C to 31C - at 2.2V!!! This got me thinking about some way to cool the air coming into the case - ducting isn't really an option cos I can't leave my window open when the room's unoccupied, and I need the comp to be portable. Here's an idea I came up with:

Slimline radiators over the intake fans, run from an independant inline water loop, with a 'chiller' before the radiator (suggested by Azz ) - a waterblock with a peltier and hsf on to cool the water passing through. This way the radiator is kept nice and cold - and hopefully cools the air coming through by a good few degrees. I'm curious whether anyone else has tried something similar, and how effective it might be at cooling the air - if it's only a degree or two different it's probably not worth the money for the extra watercooling kit.

I'm planning on building a shiny new rig in the summer when I have loads of time on my hands, and I'm thinking if including this idea in the design. Anyone think it's worth it?

1 Lets look at the condense problem. If you manage to blow 'cold' Air into your case, that is ok. The only thing that happens inside your case is that the cold air warms up. There in no condense involved in this process.

Your condense point is the radiator outside your case. The ambient air will cool down going thru the element, and condense will accumulate on the radiator element. This can be dealt with. The only risk is that droplets are sucked into the case from the radiator. This can be dealt with too.

If you are interested you can study Air conditioning solutions for buildings, this problem is common in cooling situations.

In the case you manage to get enough cooling, you might see condense on the outside of your case

2
Using peltiers to manage the cooling of incoming Air is not easy to do. Lets check the 50 cfm case.

50cfm = 0,024m3/s and air is approx 1,17kg/m3 and specific heat is 1,05 kJ/kg .

That is you are pumping 0,024x1,17= 0,028kg of air into your case per second. To reduce the temp by 1c degree you need 0,028 x 1,05 = 0,0295 kJ/s or in other words 295W of cooling power per centigrade.

Now this is one ugly figure to look at dont you think. I dont know how much Air flow is needed to cool down your case, but tis Idea is obviously [H]ard do deal with.

 

[Rob Cork]

Thanks Eriksson, I can just about follow that reasoning and maths - I'll assume it's right That's definitely a lot of power needed, I'll probably have to scrap this idea as impractical, but I'll keep thinking. If only there was a way to get low ambient temps without freezing to death yourself. Hmmm...