HELP WANTED: PC GPU and CPU minimum operating temperatures. 0 decibel refrigerated cooling.

[Nicholas Chandler-Yates]

Ok so I am thinking of building a Steampunk inspired PC to use for gaming and as a Steam Machine for the next generation.
the prime goal here is to make a 0 decibel system, no fans, pumps or other moving parts.

my Idea is to use a small 'absorption refrigeration' unit torn out of a chinese minibar.

If you don't know what absorption refrigeration is here is the rundown: It uses the condensation of ammonium and then absorption back into a liquid water medium to provide cooling. ammonium absorbed in the water is heated, changing it to a gaseous form, where it goes to the condenser plate, condenses and causes cooling, it then flows back down out of the condenser to the absorption liquid, is absorbed before being heated and starting the process again.

The point is, an absorption refrigeration unit is completely silent (no compressor like freon fridges). so i was thinking of interfacing the condenser plate directly with the heat sinks of the CPU and GPU, and the surrounding this condenser-cpu-gpu setup in a small insulated box made of styrofoam (with lots of desiccant added to the inside to stop condensation) and then wrapping this unit in several layers of plastic bags (airtight to stop condensation too). Before putting this unit in a custom made burnished copper case.
Then I plan on painting the existing pipes on the unit above with copper paint (and/or just wire wheeling them to take the paint off and show bare metal) and then building a separate unit housing the HDD, motherboard, PSU etc and mounting it to this whole setup.

My problem is that I've never built a PC before, so I have to wonder, Is it possible to isolate the CPU and GPU from the rest of the computer hardware like this (I don't want my motherboard in the fridge if I can help it, and the HDD doesn't like to get cold.), is there any other part of the computer that will need cooling, and most importantly will my CPU and GPU get TOO cold? Operating temp of the condenser plate is around 0 degrees C.

EDIT: I found a quote saying that motherboards work fine down to 0 C, and I don't think there is such a thing as a cable to connect a CPU to a motherboard to isolate them (unless I am mistaken in which case inform me) so keeping my motherboard, CPU and GPU (and associated heatsinks interfaced directly with the condenser plate) all inside the refrigerated-airtight-desicated unit is doable.

 

[SnowyGamester]

As someone who has years of experience with computers with plenty of repairs and builds under my belt I can't say I have the balls to try something like this and I especially wouldn't try it as a first build. That being said, I can't think of any real reason why it shouldn't work...the biggest issue would be getting the thing in there, making sure it has adequate contact with both the CPU and GPU, and all the while making sure there isn't any condensation build-up. Unfortunately there isn't really any way to separate the CPU and GPU from the rest of the case...there are riser cables that can be used to move a PCI card away from the board but having not used one I can't say how they may affect performance or potentially be bad for the GPU. You'll also need to track down a passive PSU...unfortunately having a quick look online they don't tend to be very powerful.

Regardless, as cool an idea as it is it will be a mess of a job.

 

[Nicholas Chandler-Yates]

As someone who has years of experience with computers with plenty of repairs and builds under my belt I can't say I have the balls to try something like this and I especially wouldn't try it as a first build. That being said, I can't think of any real reason why it shouldn't work...the biggest issue would be getting the thing in there, making sure it has adequate contact with both the CPU and GPU, and all the while making sure there isn't any condensation build-up. Unfortunately there isn't really any way to separate the CPU and GPU from the rest of the case...there are riser cables that can be used to move a PCI card away from the board but having not used one I can't say how they may affect performance or potentially be bad for the GPU. You'll also need to track down a passive PSU...unfortunately having a quick look online they don't tend to be very powerful.

Regardless, as cool an idea as it is it will be a mess of a job.

What is a passive PSU?
I was thinking of hooking up a heat sink to the GPU and CPU, and just having these heat sinks directly in contact with the condenser plate, If I have to I can do a bit of metal fabrication wok on the heat sinks, after all a heat sink is basically a block of metal, metal fabrication is a hobby of mine so this part is easy. For example if the condenser plate I find has metal baffles in it, I can cut grooves into the heat sink (cross grain to its own baffles) to marry the two together and use thermal paste to complete the join. I might even get lucky and get a situation where the grooves of the Heat sink will fit into the grooves of the condenser plate.

I will probably just skip all of this and just get some solid blocks of copper and make my own heat sink, (its not really that hard, all I need is a hacksaw, drill, grinder etc), allowing a 'perfect' marriage between the condenser plate and the heat sink, and additionally cut some grooves in the sides for air cooling (after all it is still inside a fridge).

as you can see the fabrication work I am pretty comfortable with. With the computer stuff, not so much.

Condensation, believe it or not, is pretty much a nonissue if it is built properly, just make it an airtight unit and put plenty of desiccant inside. (no condensation if there is nothing to condensate)

the real thing I am worried about is whether the heat output from a CPU and GPU working hard would be more than the amount of cooling provided by the unit. If so this could be a big issue. I doubt very much that I could find figures for these numbers, given that I'll be using a cheap chinese refrigeration minibar unit, so I might just have to roll with it and see how it goes. I dunno how much heat a high end GPU and CPU output.

EDIT: Considering that the minibar refrigerator will probably only cost me about 60-100 USD, I might actually SAVE money, given that I won't need fans, and that I'll be building the case myself. However these savings will quickly disappear when I buy a couple blocks of copper and buy the copper plating for the custom housing. I thought about it and I could just make the housing slightly bigger than the refrigeration housing, allowing room for the Hard drive and PSU.

quick question, does a PSU heat up a lot? I note that the one on my laptop does a bit.

well on second thought, if the refrigeration unit is pretty powerful compared to the heat output and I don't insulate well enough, I could run into problems with condensation on the OUTSIDE of the refrigeration box (the inside is moisture free but if the outside gets chilled it will condensate on the outside). However I will know if this is an issue before I start building the housing unit, so I can change my plans for the design of the metal housing accordingly.

 

[SnowyGamester]

A passive PSU is a PSU that doesn't have it's own built-in fan...a PSU generates a fair amount of heat so most have one (and hence aren't silent). Admittedly I haven't researched it thoroughly but at first glance I didn't run across any that supplied more than 500W of power which is adequate for most machines but I take it you're building something fairly powerful so finding one that does the job may be an issue. Also expect your hard drive to make a bit of noise as it has moving parts. As for whether the refrigeration unit will be enough to draw the heat from the CPU and GPU...it's not really the done thing so yeah I doubt you'll be able to work it out without actually going through with it. My advice would be to get everything assembled using stock parts, make sure everything is working correctly and then fit the refrigeration and try it out, watching the temperatures and making sure they stay within safe ranges.

 

[Nicholas Chandler-Yates]

You'll also need to track down a passive PSU...unfortunately having a quick look online they don't tend to be very powerful.

OH OK, so most PSUs need to be cooled as well? what kind of wattage would you recommend for a PSU in general? I see that passive units (ones without fans tend to be significantly less than 500w.

Depending on how powerful the refrigeration/heat-output ratio is I could always drop the PSU into the refrigeration compartment as well.

EDIT: wow you ninjad me good

 

[Nicholas Chandler-Yates]

I didn't run across any that supplied more than 500W of power which is adequate for most machines but I take it you're building something fairly powerful

I am not actually going for super powered, my MAX budget for this is somewhere around the $1500 mark, but would prefer to spend $1000 at most.

Not sure yet what that will get me, but any suggestions (or suggestions on good places to look for this info) would be welcome

 

[SnowyGamester]

You could refrigerate the PSU however that won't exactly increase the power output...you could potentially get a more powerful one, disassemble it, remove the fan and hope the refrigeration can handle it, the issue with that being there isn't any easy way to monitor the PSU temperature so it may overheat and burn out without warning which could also damage other parts which is less of an issue with the CPU and GPU as you should be able to monitor their temps and power off if you run into an issues. As for how powerful it needs to be, it depends entirely on what it needs to power.

 

[SnowyGamester]

I am not actually going for super powered, my MAX budget for this is somewhere around the $1500 mark, but would prefer to spend $1000 at most.

That will get you a pretty powerful rig...the one I'm running is fairly high end and cost less than that to put together.

 

[Nicholas Chandler-Yates]

Yeah the only thing i am actually worried about is if there is more heat being generated than cooling being generated. the larger the Cooling:Heat ratio is, the faster diffusion of heat away from the CPU and GPU will occur, however, the Cooling:Heat ratio MUST be greater than 1 (more cooling than heat) or else the computer will start to heat the refrigerator, instead of the other way around.
Cooling:Heat ratio more than one would result in the temperature in the insulated unit slowly *falling* after the machine is turned on until it reached some equilibrium temperature with heat loss through the insulation, or else reached its maximum low temperature operation. The actual temp of the CPU and GPU would depend entirely on how fast the heat could be diffused away from them into the ambient cold area.

Conversely a Cooling:Heat ratio less than one would mean that when I turned on the machine the temp in the fridge would slowly climb inside the insulated unit nearly indefinitely, resulting in severe temperatures. Like putting a heating element into an insulated box (essentially an oven) which results in a temperature of the whole system well above the ambient room temperature. (not good)

if I was a betting man, and I am if I plan on building this, I would think that the Cooling:Heat ratio would be well above 1, however there is a chance that I could be wrong. If so... its not really that big of a deal, I can always just use the components that I bought and build a normal PC.

I can do preliminary testing for this as well. After buying the refrigeration unit, I can chuck the motherboard, CPU and GPU inside the fridge and run a demanding program of some kind to simulate max power output, and put a thermometer inside the fridge and see what happens to the temperature. (as long as it stays below ambient room temp I am golden)

 

[Nicholas Chandler-Yates]

I did some research into heat output, and a very high end PC can draw as much as 500watts of power (average not max) when working hard, since almost all of this energy is converted to heat, and almost all of the heat is generated in the GPU and CPU, and because BTUs = Watts x 3.412. There are 1700 BTU/per hour being generated.
A lower end gaming PC will use as little as 150watts on average, resulting in about 500BTUs/hour of heat.

The COP (coefficient of performance - BTU moved/BTU consumed) for absorption refrigeration is
typically from 0.5 to 0.7*. The COP of a typical compressor refrigerator operating
under ASHRAE standard conditions is between 2.5 and 3.0.
http://geoheat.oit.edu/pdf/tp51.pdf

Absorption Mini fridges run on 60-100 watts of power, therefore they consume up to ~300 BTUs of power. with a COP of .7 this results in about 210, BTU/hour of heat being moved from the inside to the outside. Meanwhile a compressor fridge running on the same wattage with a cop of 3.0 would produce 900 BTUs/hour of heat moved, however in practice they simply have a lower wattage and the output is the same.

I found another article about using dorm fridges to cool aquarium tanks in the summer months.
http://www.beananimal.com/articles/dorm-fridge-aquarium-chiller.aspx

Mini refrigerators come in various sizes with compressors rated between 1/20 Horsepower and 1/8 Horsepower. As we noted above, the horsepower rating is pretty much meaningless and is only applicable if we care about the efficiency of the overall system, that is how many Joules of heat can be moved per Joule of energy consumed by the chiller. The average cooling capacity of a dorm fridge is somewhere around 150 BTU/hr, that is, it is capable of moving 150 BTUs of heat in 1 hour, regardless of how efficient (or inefficient) it is in terms of energy usage. For the purposes of comparison, a small window air conditioner can move 5,000-8,000 BTU/hr! If you step up to a mid size unit (the neck high models) they will be closer to 500 BTU/h.
Stop! That is not the whole story! The dorm fridge uses about 30% of its capacity just to keep the interior cool!
So lets put those numbers to work, shall we! We will take a target 75 Gallon system and model it with a decent 250 BTU/hr small refrigerator. Remember that 250 BTU/hr refrigerator will be able to devote about 175 BTU/hr to cooling the tank, the rest is wasted due to the design of the refrigerator!

This is similar to my own calculations 175btus vs 210btus. Either way, not NEARLY enough to offset the production of 1700BTUs per hour of heat from the high end gaming PC or 500BTUs/hour from the low end gaming PC.

Cooling:heat ratio is far less than one, meaning that this won't work.

Well I am glad I did the math (YAY MATH), just goes to show how massively problematic heat generation for PCs is.

Hell even the average freezer (compression) uses about 300-500 watts of power, being optimistic and assuming a COP of 3 this still only results in 900 BTUs/hour of cooling. Literally if you put your high end gaming PC in your freezer, it will DEFROST your freezer and turn it into an oven if you wait long enough under high computational load.

 

[Nicholas Chandler-Yates]

Looks like I am going to have to look into water cooling methods, although these can't result in a cryogenic system ...

it seems that to make a cryogenically cooled PC you would need to have a very high powered fridge/freezer, or else use an AC unit. This would not be quiet, nor space efficient.
it would be cool to use some vintage moped or motorcycle radiators (along with fans) and a water cooled system to create a steampunk styled machine.


some images of vintage radiators.

Give up on making a 0db system. unless the radiators can work without fans.

 

[Nicholas Chandler-Yates]

Alternatively... just throwing an idea out there, I could make a water cooled system with NO radiator, and rather just a large acrylic reservoir, then take a couple of aquarium air pumps and pump massive amounts of cool air through the reservoir to exchange heat. (after all millions of tiny air bubbles have way more surface area than any radiator.) It wouldn't be quiet, but it would look awesome.

I want it to look and feel like a low tech answer to a high tech problem.

 

[AWAR]

Pretty ambitious stuff around here.. But I'm not sure what sort of thing you want to do: A 0db system, or a uniquely styled/cooled PC?
If you simply want a completely silent PC it is very much possible, unless you want crazy performance out of it.
There are passive CPU coolers: image, passive PSUs as snowy said or these RM series that activate the fan only at >40% usage.
Water cooling is almost completely silent too, if you use low noise Noctua fans and have a soundproof case.

 

[Nicholas Chandler-Yates]

Pretty ambitious stuff around here.. But I'm not sure what sort of thing you want to do: A 0db system, or a uniquely styled/cooled PC?
If you simply want a completely silent PC it is very much possible, unless you want crazy performance out of it.
There are passive CPU coolers: image, passive PSUs as snowy said or these RM series that activate the fan only at >40% usage.
Water cooling is almost completely silent too, if you use low noise Noctua fans and have a soundproof case.

Both. My current idea is to build the case myself entirely out of bent and soldered copper tubing, with parts of the sides of the case made directly out of flat copper radiators (vintage or otherwise). Also I have a pretty unique idea using a water/water heat exchanger. Essentially part of the design will incorporate something like this:

It exchanges the heat in the inside coils of copper tubing with the water flowing through the canister. The water flowing through the canister will come from the water mains and will drain off to a garden hose that will water my veggies or my fruit trees.

Ill test it out running completely passively, there is gonna be an insanely long tubing run and with the radiators as well it might not need any additional fans to keep it cool even without the water/water system. I am planning on having fans if necessary tho, but a switch to turn them off when i run the water cooler, as they won't be necessary. I might get a non-passive PSU and hook it up to the water cooling system somehow.

In this way I would have a (nearly) 0 db system (water pump excepted) when running passively or with the water/water exchanger.

 

[AWAR]

-snip

It sounds a bit crazy to be honest but if you feel you can pull it off then by all means, go for it. You'll need at least an aftermarket water block as it will be pretty hard to manufacture one yourself. My only suggestion is to try it with junk/cheap hardware first. Frying a $300 component won't be much fun..

There are also better places you can get ideas from than the escapist advice forum. Try Hardforum. They have lots of experience in this sort of thing.