Howdy all,

After a conversation with Mattarnster from the forum on MSN, I thought it might be a nice idea to talk about air flow in your system.

A lot of people don't think about air flow when they build their system. They just think "oh, it'll probably get a bit hot with all these hard drives, graphics cards and other PCI cards in, lets whack a fan in the back so it can keep it cool". But sticking a fan in the back isn't a simple solution, as its all about air flow.

In order for hot air to be exhausted from the system, you have to replace it with fresh air from outside the case or its not a very effective cooling method. To demonstrate how air flow in a typical system should look, I have created a quick diagram.



Fresh air should always enter through the front of the case, and hot air exhausted at the back. That way you're not pulling in hot air again which you've just exhausted from the system. As you can see I've indicated the PSU fan, a system fan, graphics card fan, the CPU fan and a single fan at the front of the system.

Most systems that have a fan at the front have a huge 12cm fan which runs quite slowly, but still pushes a lot of air. They also blow air over the system hard drives which are directly behind it in most cases. This keeps them cool with ease and then this air goes into the case where it replaces the hot air being expelled by the smaller, more in the region of 8cm (as most are), fans at the back of the case. My server and my desktop PC both have the setup you see in the diagram and it works extremely well.

When I bought my server and desktop cases, I deliberately made sure there was a fan on the front so I could have one to blow air over my hard disks. Since cooling them with either a fan in the case or one that attaches to the hard drive itself, I've not once had one of those disks fail. Coincidence or not, I can't confirm.

You have to remember, heat is the biggest killer of hard drives and all electrical components. Don't cut back in any way on the cooling of your hard drives, or you'll easily shorten their life span. You should aim to keep the temperature of your hard drives under 30 degrees Celsius. Anything higher isn't good for it. Why you might ask? Heat makes the disk platters expand and contract, and when this happens you run the risk of the read/write head hitting the disk and causing a head crash. Just remember how far away that read/write head is from the disk, its microns.

You can monitor your hard drive temperature if you have S.M.A.R.T enabled, which all modern hard disks support. If you run a RAID array however, S.M.A.R.T data doesn't get passed to the controller unfortunately. You can monitor the temperature with a program such as SpeedFan, which reads the raw S.M.A.R.T data and gives you it in a form you can understand (Celsius!). Its a nice program and can give you other system temperatures too.

The lower your temperatures, the better! But remember, trying to get your system lower than the temperature of the room is impossible, no matter how much you try, and believe me, people try!

I hope this gives some insights into the air flow in your system and how you can improve it. Its certainly worth it if you like the data on your hard drive, and don't like to replace failed components. It only costs a few pounds/dollars/euros to buy a system fan or two and get the air flow in your system moving!

EDIT: Quick addition mrpijey has just mentioned to me that I totally overlooked... Cabling! If your cabling is messy, it will obstruct the airflow considerably and this will keep the system warmer than it should be. Try and use round cables rather than flat, and use cable ties for permanent setups, tying them out of the way at the back of the case and out of the way of the air flow.

Something that should be pretty obvious but also often ignored is the placement of the computer. Don't put it where sunlight can shine on it directly. Also don't put it any near heat radiators or other sources of heat. Be sure to put the system where it has plenty of fresh air to use and not let it re-use heated air (such as in a cabinet etc).

If you use it in a cabinet also put enough fans (and the right airflow) in the cabinets.
But the best way is, that the back of the cabinet is open.

(If it's summer, hang you're clothes there, they will be dry in no time ).

For the cables in the pc, if you can use SATA (which is in all new pc's), please use them, they are smaller and enhance the air flow.

And to add...
The pathetic stock Intel CPU coolers, there rubbish at keeping the system cool, best to have one witch directs the airflow out of the case.

I think the stock coolers do quite well, considering they are stock. I overclocked this PC by 22% (2.66GHz to 3.4GHz) and its still using stock cooling, and idles at 36*c, and tops out at 60*c under full load... Not bad if you ask me.

However, if you can get a cooler to direct air straight outside the case and not into the case, then go for it. It'll greatly help to keep the system cool.

my computer originally had 2 8cm fans (one at the front and one at the back) but i noticed when i lanned at a mates place it would get very hot and even beeped. So i got 2 12cm ones and that made A LOT of difference (not to mention quieter). Along with the fans i cable tied the cables up and made a nice new vent in the front (filter foam in it to keep out dust), i'm not sure about the temp but it doesn't beep any more .

If you buy a new case for the PC, on one side there is a (sort of) ''sleeve'' that fits on top and let the CPU cooler blows the hot air away and the cooler draws fresh air in from the bottom.

Or if you do not have such case you can buy some cheap plastic thing that fits over the CPU and leads out of the back of the PC in the same manner.

Put the fan on the right way?

I did that with the case fan in our P4. whoops

I remember a load of Dell fans were put in the wrong way ..

Btw, I've noticed a small error:

Typo fixed. You didn't have to be that pedantic you know

Even more important is... cleanliness! Dust out your computer and power supply every few months or your fans will be worthless.

For me, my processors are running way too hot, so I have an antec P182 case sitting next to me for my desktop to go into. I still need to order a new heatsink for the processor (which isn't cutting it) and some replacement high power fans, but once it's all done it should run colder than my fridge and quieter than my flatulence.

When it comes to the stock coolers (or any coolers for that matter), be sure to remove the low quality cooling paste on them and apply some high quality paste. That alone can lower the CPU temp quite a lot. Be sure to get a good quality paste (Arctic Silver etc) and apply it as thin as you can. You shouldn't be able to see through it, but if it's too thick it will act in direct opposite as supposed to, it will HEAT up your CPU, efficiently insulate it from the cooler. I suggest you use some old credit card or something to apply a thin layer.

And before you apply any paste be sure to clean the CPU heat spreader and cooler thoroughly.

If you do this on a video card then you need to be extra careful, some stock coolers are glued on, if you force it too much you'll crack the GPU and you will end up with a very high tech paper weight.

And remember, because the cooler is big doesn't mean it's good. You need one with good airflow, and preferrably one that works with the case. If the air is blocked it will only produce a lot of noise and remove very little heat.

As for quality when it comes to stock coolers, I always found the ones supplied with Intel CPU:s quite good. They are silent and efficient. Most find them bad mostly because of the bad cooling paste applied on them.

And how about these slot coolers (like the ones you see in the second slot of dual-slot video cards)? Can they make the cooling better?

*I'm looking more at Macs than BetaArchive*

Only for video cards. Those are designed to pull out the air directly from the hot video cards to the outside of the computer. As a general solution cooler they are not so good because the internal hot air of the computer would be pulled towards the slots (where you already got at least one hot video card) and the fans would be too small and inefficient (and too loud because they are small) to do any good. So use the larger fan exhaust ports usually available on most ATX cases. The bigger fan you got the slower it can spin, thus reducing noise while still pulling a good deal of air.

Plus remember hot air rises, so all the hot air is at the top of the case anyway, not the bottom where those slot coolers will be.