Hi all,
A couple of people have expressed an interest in seeing my recent build so I'm going to post up pics of the build in progress and some of the ideas and pitfalls.
I was knocking ideas around for some time on how to get sub zero temps and avoid problems with condensation. I know its possible to seal the motherboard to prevent this but I would hate to find I hadn't done an adequate job and have the build die on me.
So I came up with the idea of a sealed chamber which contains a cooling source and the main pc components being air cooled inside it. My thought process being that any moisture in the contained air would tend to condense out on the cooling source and as the pc components are not being directly cooled they would always be warmer than the surrounding air and so not attract condensation.
I took my ideas to run by the guys at the extreme overclockers forums thinking that was probably a good place only to find they have done similar things previously and call them chillboxes....oh well...just reinvented the wheel.
So lets crack on with the details....just to warn you...this is not a pretty build...its purely functional.
The cooling power comes from a 12000 btu window air con unit....that's 3.5KW of cooling!
Here she is before I took my screwdriver and hack saw to her.
Uploaded with ImageShack.us
This unit alone cost ?400....so this is not a cheap project.
You have to strip it down to expose the cold radiator...correctly called the evaporator or evap for short.
Uploaded with ImageShack.us
I was quite lucky with this unit, there is a nice gap between the evap and the rest of the unit and the entry and exit pipes come out of the top of the evap....all makes for an easier build.
Next is the building of the chamber, it obviously has to be insulated and absolutely crucially has to be sealed completely air tight.
Getting it air tight is quite a task, as you have to run so many cables through the chamber wall as everything except the mobo, cpu, gpu and ram has to be outside the chamber.
Every cable has to be individually sealed, including each cable in the 24pin atx power cable bundle otherwise air will enter between the cables.
An addition I made to my chamber, which is unique to my chillbox build, but I think quite important to help prevent air entry is an external expansion/contraction chamber to equalise internal and external pressures.
We've all experienced the suction effect you get when you close and try to reopen a fridge door, well that's because the air inside has contracted with the cold and is so sucking the door closed. If that pressure difference isn't equalised then it will tend to draw moisture bearing air into the chamber through any small imperfection in the seals.
Also if the air is at a lower pressure in the chamber that would also have an adverse affect on cooling efficiency.
Oh almost forgot...as a belt and braces approach to combat moisture I also have 2 large pouches of desiccant in the chamber.
My chamber is constructed out of 6mm acrylic to form the outer box and 50mm insulation board which forms the internal insulation box. Both boxes are independantly sealed and both seal via gaskets to the lid which is clamped on with webbing ratchet ties to provide a high closing pressure.
So just from this brief description I think you can gather this takes alot of work/planning/thought and quite an expense....add another ?400 for materials cable extenders etc etc etc.
Here's a picture of the box showing the evap and triple fan stack to the side. When the lid is on it also seals to the top of the evap and fan stack to make two chambers, one to the front and one to the back. This allows for a circular flow of air, the fans pushing air into the back chamber through the evap/rad into the front chamber where motherboard is housed.
Uploaded with ImageShack.us
And here it is with the mobo in place, you can also see the 2 large pouches of desiccant in the back chamber.
Uploaded with ImageShack.us
Here it is with the heavy duty lid on.....like I said not pretty....but functional.
The banister rail on the top is to convert the tension in the webbing into a closing downward force on the lid rather than just tending to crush the box.
Uploaded with ImageShack.us
And the crucial bit...the expansion chamber....or sac actually...lol
Uploaded with ImageShack.us
It's a space hopper connected via a 19mm breather pipe to the chamber...lol....like I said, I'm personally not too concerned about esthetics, I needed something which was able to accommodate volume changes up to 9 liters and maintain the integrity of the sealed chamber....this was ideal even if a little silly.
There's a few caveats I want to add for anyone considering anything similar.
Firstly safety.....don't forget that the ac unit runs on full mains voltage, and mine has a large capacitor in the circuitry that could potentially hold charge even when powered down.....it's easy to forget when your used to dealing with low voltage pc equipment.
Secondly... cost, the build isn't cheap, and the ac unit has a not insignificant power draw.
Thirdly... heat pipe design heatsinks do not work with this set up...they use distilled water in the heatpipes as a working fluid/evaporant which obviously freezes and cannot move the heat as intended.
I use a solid copper Zalman 7500cu cpu heatsink.
My current graphics cards also have solid metal heatsinks but I can see a potential problem when I come to upgrade them as most graphics cards now use heatpipe or vapour chamber designs (which use the same principle). So if I can't think a way around that then I may be restricted in my gpu upgrade choice. Another point to note is fan design, fans must run on ball bearings not fluid bearings....the fluid freezes.
Fourthly....cooling efficiency, I've opted to use air cooling as it's simpler and cheaper, but aircooling components often operate at load with a 40 to 50 Deg C temp delta above ambient. I still have that same temp delta but of course operating from a -30Deg C baseline.
Other forms of cooling are more efficient and can reduce that delta considerably. I have colleagues over at the extreme overclocking forums that use similar systems but include water cooling. These require the use of alcohol/glycol/water antifreeze mixes which can attack some materials and cause leakage, this together with the fact it adds another layer of complexity and opportunity for failures is the reason I've steered away from that route at this time, but may have to go the water loop route if I can't solve the gpu heatsink problem.
Fifth....size and noise, my systen is 3-4ft long by 2-3ft wide, the compressor on the ac unit makes a noise. I have mine in a spare room and I game using headphones so the noise is not a problem for me.
This is still very much a work in progress for me and I'm looking at ways to make improvement.
I'm considering using a different gas in the chamber, one that cools more efficiently than air and so reduce the temp delta. Some refrigerant gases are 5X denser than air and at the same cfm flow have, I think, the potential to cool 4X more efficiently which would greatly reduce the temp delta above ambient.....but would not solve my longer term problem of gpu cooling.
In the longer term I'm considering something very different. I'd have two gases in the chamber. One would remain a gas at chamber temps while the other would liquify out to form a pool of liquid gas at the bottom of the chamber which the mobo would be laid flat in and submerged...this would effectively give me direct phase change cooling of the components which I could use without heatsinks and so also solve my gpu problem.
But that is for the future as I'd have to redesign my chamber.
A couple of people have expressed an interest in seeing my recent build so I'm going to post up pics of the build in progress and some of the ideas and pitfalls.
I was knocking ideas around for some time on how to get sub zero temps and avoid problems with condensation. I know its possible to seal the motherboard to prevent this but I would hate to find I hadn't done an adequate job and have the build die on me.
So I came up with the idea of a sealed chamber which contains a cooling source and the main pc components being air cooled inside it. My thought process being that any moisture in the contained air would tend to condense out on the cooling source and as the pc components are not being directly cooled they would always be warmer than the surrounding air and so not attract condensation.
I took my ideas to run by the guys at the extreme overclockers forums thinking that was probably a good place only to find they have done similar things previously and call them chillboxes....oh well...just reinvented the wheel.
So lets crack on with the details....just to warn you...this is not a pretty build...its purely functional.
The cooling power comes from a 12000 btu window air con unit....that's 3.5KW of cooling!
Here she is before I took my screwdriver and hack saw to her.
Uploaded with ImageShack.us
This unit alone cost ?400....so this is not a cheap project.
You have to strip it down to expose the cold radiator...correctly called the evaporator or evap for short.
Uploaded with ImageShack.us
I was quite lucky with this unit, there is a nice gap between the evap and the rest of the unit and the entry and exit pipes come out of the top of the evap....all makes for an easier build.
Next is the building of the chamber, it obviously has to be insulated and absolutely crucially has to be sealed completely air tight.
Getting it air tight is quite a task, as you have to run so many cables through the chamber wall as everything except the mobo, cpu, gpu and ram has to be outside the chamber.
Every cable has to be individually sealed, including each cable in the 24pin atx power cable bundle otherwise air will enter between the cables.
An addition I made to my chamber, which is unique to my chillbox build, but I think quite important to help prevent air entry is an external expansion/contraction chamber to equalise internal and external pressures.
We've all experienced the suction effect you get when you close and try to reopen a fridge door, well that's because the air inside has contracted with the cold and is so sucking the door closed. If that pressure difference isn't equalised then it will tend to draw moisture bearing air into the chamber through any small imperfection in the seals.
Also if the air is at a lower pressure in the chamber that would also have an adverse affect on cooling efficiency.
Oh almost forgot...as a belt and braces approach to combat moisture I also have 2 large pouches of desiccant in the chamber.
My chamber is constructed out of 6mm acrylic to form the outer box and 50mm insulation board which forms the internal insulation box. Both boxes are independantly sealed and both seal via gaskets to the lid which is clamped on with webbing ratchet ties to provide a high closing pressure.
So just from this brief description I think you can gather this takes alot of work/planning/thought and quite an expense....add another ?400 for materials cable extenders etc etc etc.
Here's a picture of the box showing the evap and triple fan stack to the side. When the lid is on it also seals to the top of the evap and fan stack to make two chambers, one to the front and one to the back. This allows for a circular flow of air, the fans pushing air into the back chamber through the evap/rad into the front chamber where motherboard is housed.
Uploaded with ImageShack.us
And here it is with the mobo in place, you can also see the 2 large pouches of desiccant in the back chamber.
Uploaded with ImageShack.us
Here it is with the heavy duty lid on.....like I said not pretty....but functional.
The banister rail on the top is to convert the tension in the webbing into a closing downward force on the lid rather than just tending to crush the box.
Uploaded with ImageShack.us
And the crucial bit...the expansion chamber....or sac actually...lol
Uploaded with ImageShack.us
It's a space hopper connected via a 19mm breather pipe to the chamber...lol....like I said, I'm personally not too concerned about esthetics, I needed something which was able to accommodate volume changes up to 9 liters and maintain the integrity of the sealed chamber....this was ideal even if a little silly.
There's a few caveats I want to add for anyone considering anything similar.
Firstly safety.....don't forget that the ac unit runs on full mains voltage, and mine has a large capacitor in the circuitry that could potentially hold charge even when powered down.....it's easy to forget when your used to dealing with low voltage pc equipment.
Secondly... cost, the build isn't cheap, and the ac unit has a not insignificant power draw.
Thirdly... heat pipe design heatsinks do not work with this set up...they use distilled water in the heatpipes as a working fluid/evaporant which obviously freezes and cannot move the heat as intended.
I use a solid copper Zalman 7500cu cpu heatsink.
My current graphics cards also have solid metal heatsinks but I can see a potential problem when I come to upgrade them as most graphics cards now use heatpipe or vapour chamber designs (which use the same principle). So if I can't think a way around that then I may be restricted in my gpu upgrade choice. Another point to note is fan design, fans must run on ball bearings not fluid bearings....the fluid freezes.
Fourthly....cooling efficiency, I've opted to use air cooling as it's simpler and cheaper, but aircooling components often operate at load with a 40 to 50 Deg C temp delta above ambient. I still have that same temp delta but of course operating from a -30Deg C baseline.
Other forms of cooling are more efficient and can reduce that delta considerably. I have colleagues over at the extreme overclocking forums that use similar systems but include water cooling. These require the use of alcohol/glycol/water antifreeze mixes which can attack some materials and cause leakage, this together with the fact it adds another layer of complexity and opportunity for failures is the reason I've steered away from that route at this time, but may have to go the water loop route if I can't solve the gpu heatsink problem.
Fifth....size and noise, my systen is 3-4ft long by 2-3ft wide, the compressor on the ac unit makes a noise. I have mine in a spare room and I game using headphones so the noise is not a problem for me.
This is still very much a work in progress for me and I'm looking at ways to make improvement.
I'm considering using a different gas in the chamber, one that cools more efficiently than air and so reduce the temp delta. Some refrigerant gases are 5X denser than air and at the same cfm flow have, I think, the potential to cool 4X more efficiently which would greatly reduce the temp delta above ambient.....but would not solve my longer term problem of gpu cooling.
In the longer term I'm considering something very different. I'd have two gases in the chamber. One would remain a gas at chamber temps while the other would liquify out to form a pool of liquid gas at the bottom of the chamber which the mobo would be laid flat in and submerged...this would effectively give me direct phase change cooling of the components which I could use without heatsinks and so also solve my gpu problem.
But that is for the future as I'd have to redesign my chamber.
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