Today's lesson: Thermodynamics 101

[Tex Arcana]

Or: How To PROPERLY Cool A Computer in 20 Easy Steps pics

So, for today's lesson, we will learn the basics of cooling a computer.

Simply put: cool air in, hot air out. Since the first law of thermodynamics states that temperature "flows" from hot to cold, this is critical to keeping our rigs cool. Especially in these times, when you can fry an egg on our CPUs and GPUs.

So, what's one to do?? In my case, get a good case(hurr), and then do things to it to improve the flow of cool air in and hot air out.

To wit, my riglet:

As you can see it's a nice CoolerMaster 640(iirc), with some nice features such as open flow, big 120mm variable speed fans, and plenty of places to put said fans.

Airflow:

Pretty good, if you ask me. There's a fan behind the processor as well, nice feature of this case. Also, the white "X" means I closed that particular vent, because with it open it just pulls cool air in and right out, instead of forcing the flow to go over components.

Now, the best way to air cool a processor is to get the coolest air possible to the HSF; and the best way is to run a vent from the HSF right to the outside of the case.

Which I did:

Yep, some 6" dryer duct, a 4" PVC toilet flange, and some black spraypaint.


The rig as it sits before the mod:

You can see the side fan that's over the vidcard and "southbridge", and the CPU HSF thru the side panel vents:

Closer look of the HSF:

Mmmmm, i7-920 goodness, despite the stock HSF:

You should be able to figure what's coming next, but wtf, I'll detail it:

The freshly painted duct and flange, ready for installation:

The duct going onto the HSF:

Perfect fit!

The flange in place, to be fastened to the side cover:

Ready for installation. It's kinda obvious that the duct will pull cool air from the outside, directly to the HSF:

I know, some of you will say this isn't new... and you'd be right, I've seen machines from the mid-90's that had ducts like that from the factory. But that's not the point; the point is that we spend so much time with uber-coolers and watercooling, yet we forget one of the basic tenets of cooling, which is to make damn sure that the air going in and thru is as cool as humanly possible.

I think this qualifies.

Side panel with the flange installed:

Flange in place, fits nicely, and the paint on the screws even looks nice:

Side panel installed, duct on the flange:

View of the duct thru the back panel vent:

One complete HSF duct, ready for action:

The only "problem" with this is the other side panel fan's header is on the mobo next to the heat sink for the power control chips, near the back of the case, and it's a bitch to connect even without the duct. I should make an extender wire to make the job easier, but I shouldn't have to get inside there anytime soon.




And there you have a rig properly cooled. If any fans fail, there will be enough flow to keep operating, albeit at reduced efficiency.

The resulting airflow diagram:

Please forgive the shitty iPhone pics and shitty Paint.net diagrams, but I think you see the point, that the airflow is superior in this system and will ensure its reliability for a long time.

If I ever do get to upgrade, I'll probably do something like this:

Instead of the fans on the cooler tower, leaving a hotspot in the middle where the fan hubs are, by remotely locating the fans to the case body at either end of ducts, I get uniform airflow over the cooling fins, and ultimately superior cooling--and, if a fan fails, or both, it'll still work thanks to convection.

Thus concludes today's lesson on thermodynamics, your computer, and you.

Any questions?

 

[pi3]

Any questions?

Do you hold and "advanced" degree from Liberty University because this is a funny sentence:

Simply put: cool air in, hot air out. Since the first law of thermodynamics states that temperature "flows" from hot to cold, this is critical to keeping our rigs cool.

Um... no. The first law deals specifically with conservation of energy. You're thinking of the second law which states (basically) that in a closed system entropy tends to increase over time. One formulation of the second law is the common observation that heat energy will not flow from areas of low concentration to high unless work is applied.

Other than that, good job cooling your riglet.

 

[thehybridfrog]

Or: How To PROPERLY Cool A Computer in 20 Easy Steps

20 Steps is not easy for what you did. I have a few of those plastic funnels that Dell sells with their computers from home and work that if I ever thought about it I guess could be good for a situation like this. On the other hand 230mm fan on the side of my sniper.

First law of thermodynamics states that energy can only be transformed and cannot be created or destroyed. You're more dealing with convective flow maybe? I'm not sure either really.

 

[cyclone3d]

Get rid of the fan grills (air flow restrictors) and you will run even cooler.

 

[pi3]

Get rid of the fan grills (air flow restrictors) and you will run even cooler.

Is a 1-2°C drop in case temperature worth the risk of sucking insects, small pets or fingers into your computer?

 

[Justintoxicated]

That duct looks like would block airflow from your missing fan in the120mm rear fan area. Another thing to keep in mind is that blowing air up from the bottom of the case could, allow excessive dust to enter the case depending on it's location. (Yes heat rises but there are other things to consider)

 

[rickss69]

Here is the only proper way to cool your pc...

 

[weuntouchable]

Did you take before and after temp readings to see if all of your work made a significant change in temps? Otherwise you pretty much just did a howto put a cooling duct into your case.

 

[cyclone3d]

Is a 1-2°C drop in case temperature worth the risk of sucking insects, small pets or fingers into your computer?

In a word.. YES! This is the [H]ardForum.

It really can make more than a 1-2c differerence depending on your particular case.

As for sucking small pets into the case... ummmmm if you let your mice or similiar roam around then you have other issues.

Also, I don't think it would really "suck" things into the case.... maybe extremely small insects, but unless oyu have a full on turbine fan that can actually create a lot of "sucking force", you really aren't going to be sucking anything into the case per se.

 

[Tex Arcana]

Y'all are right: I forgot my thermo lessons. Good catch. Still, made for a neat title for what was essentially a bit of pimpin'.

I thought I had mentioned it, but when I first set this up about a year ago (I fuckin work for (b)Lowe's, I rarely have time for anything but working or sleeping), I saw a 10degF drop on all four cores, so I figure it was worth it. This was really just me painting the bits and putting them back in, and documenting it--it cost all of maybe $5, I already had the duct left over from a dryer installation, so I went for it.

I think the riglet tried to suck one my my pugs into it, but the grilles saved the day!

I really just did this to prove something to myself and others, that the best source of cooling air had to be outside the case; it seems to me that watercooling that uses hot air from inside the case is a real waste of water cooling, not to mention the tower coolers that keep recycling all that hot air.

I'd love to watercool, but I'd want to do the same thing: isolate the cool intake air from the hot exhaust air. I think the next mod will be as I diagrammed: tower cooler with some duct and the fans mounted on the case at the intake and exhaust ends.

 

[Tex Arcana]

That duct looks like would block airflow from your missing fan in the120mm rear fan area. Another thing to keep in mind is that blowing air up from the bottom of the case could, allow excessive dust to enter the case depending on it's location. (Yes heat rises but there are other things to consider)

So far, what I've observed is that the air is pretty much going around the duct, and still being pulled out the top. If anything, the area directly below the CPU might be seeig some flow stalling there, but I doubt it. I thought about putting a shield beteen the duct and the top corner, spaced about 1-2" off the components on the mobo, to help guide the air down and around, with some (more?) going across those components above the CPU, and then out; but so far I haven't needed it.

One thing everyone has missed, is the fact that there's a fallacy in my theory (besides my liberty university fuckup): the CPU cooler is exhausting into the case, which doesn't help much. However, using a tower cooler/ductwork will solve that dilemma.

 

[BillParrish]

Nicely done, people can quibble all they want. A ducted source of cool air is a huge improvement for CPU cooling and that is that. Why the side mounted vent has disappeared is a mystery to me. Widely used in the P4 days you could hardly buy a case without one. A cheap accessory that could easily be removed if not needed. /shrug.

One thing everyone has missed, is the fact that there's a fallacy in my theory ... the CPU cooler is exhausting into the case, which doesn't help much. However, using a tower cooler/ductwork will solve that dilemma.

Note that the exhaust (see your "The resulting airflow diagram:" pic and the small red arrows) of the stock downward blowing cooler is designed to provide airflow over the CPU voltage regulation circuitry around the CPU socket. These power using/producing components are arranged around the socket both for layout/routing reasons and to take advantage of the "blow-by" of the stock coolers wash of air.

Keep in mind that while a tower cooler would help "direct" the exhaust either "out the back" or if orientated "North/South" as many of us have tried with success, up and out the top of the case if a fan is installed in the top of the case, a tower cooler typically eliminates this airflow over the CPU socket area components. A tower cooler in many instances shoots the exhaust over the top of those components/heat-pipe instead of directly at them and actually will increase the operating temp of the components in the area which is a bad thing for the filtering caps etc. Many times the clock chip is in this area as well. People who both Water Cool and Overclock have to pay particular attention to this as there is no active air movement in the area at all.

All I am trying to say is that it is important (and critical if OCing) to ensure these components and their related heatsinks/heat-pipes continue to receive active airflow and take that into account when implementing ducting or provide an additional fan, whatever.

Your design as it stands is about the best that can be done with the stock fan, should be a great help and does not cause the problem mentioned above but instead by providing the stock fan with cooler ambient room air will decrease the exhaust air temp washing those components with somewhat cooler air. A very good thing in high performance situations.

Moral of story and the point of this post is to remind people to not forget to ensure their CPU socket area components/heat-pipe have active airflow and with the application of a tower cooler or water-block, or ducting it is very wise to pay close attention to this for long term reliability and stable OCing at high power levels.

Nice post. It truly is all about airflow airflow airflow airflow, how much and where it goes.

 

[BillParrish]

Oh and if I may I want to use your excellent pics to show something I found out the hard way and while it seems obvious I think a lot of people miss it when buying a case.

Look at the last pic of the original post. The one with the full side on shot. Notice the lower HD bay. It almost completely eliminates any benefit from the lower front fan. This is very bad and the video card does not help as it is very long as are all the "big boys" these days and acts as an air dam for what air does get in the lower front. The entire lower 1/2 of the case is starved for air and if not for the OP installing the second side panel fan astronomical GPU temps would likely be the result.

I despise and will never buy again a sideways drive cage like that shown in the pic. as is it is crap for airflow and if fully populated with drives it is even worse. It does not even work well at cooling the drives and does almost nothing for case airflow. I took mine out and "swiss cheesed" the fan side with 3/8 holes which helped the HD's a bit but not much else. The old style "el-cheapo" case design was better in all respects except looks. I guess in mini-towers space to install and remove the drives in conjunction with a large video card is an issue too. But if you are putting a high performance computer in a mini-tower you deserve to have to deal with a lot of issues .

 

[Plumber4life]

I know a plumber who would be pissed looking for his drain lol.. props 2 ya

 

[Tex Arcana]

Good catch, Bill, and you're right: Asus documentation states clearly that the components near the HSF must get flow from the HSF to cool properly, and they even included a small fan to attach to the cooling fins near the CPU in case a non-stock HSF is used.

If I even do the tower design, I'll have to put a second blowhole fan in, and perhaps bleed some air from the intake duct to wash the chipset components. I could also open up one or more of the card slots to bring in more airflow in that area.

You may not be able to see it, but I have my hard drives spaced one bay apart, and set where they are in the wash from the bladed sections of the front fan, which makes for improved airflow. On my old Dell XPS (2003 p4), that fan was only 80mm, so I flipped the lower drive over so the circuit boards got the majority of the airflow, which helped along with keeping them spaced a bay apart.

The vidcard isn't as big a problem because the side fan right above it, as well as the fact it doesn't completely close off the case, so air flows fine past it.

Thanks for the props... would'ja mind putting your posts in the thread I made in Casemodding, cuz I think they're about to go for each other's throats in there. <_< >_>

 

[Tex Arcana]

I know a plumber who would be pissed looking for his drain lol.. props 2 ya

It's my wife that's pissed, the toilet STILL isn't fixed!

 

[BillParrish]

Just a note, my post was not critique of your system specifically, I think you are doing a great job with it. As with your post, my comments are an attempt to help the new guys with the "tricks of the trade" - thats all.

Posts like yours with the excellent pictures and good ideas foster discussion and information to the benefit of all (which is what I like to think this place is all about and I find it almost impossible not to toss my 2 cents in) So again, good stuff. Carry on!

Better get cracking on that plumbing or CPU temps will be the least of your worries.