cyrixMII300

Ok I am not sure whether this has been done before but considering all the questions related to this topic lately I had decided to write this.

First thing to remember is that you are talking about air cooling. Air by itself has a very very low heat transfer coefficient meaning it is almost useless as a heat transfer medium unless it has lots of moisture content or is constantly removed or replaced hence air cooling.

Secondly you have to remember that your casing is a sort of heater box which produces lots of heat which must be removed in order to allow the components inside to operate at lower temperatures.

Thirdly, there are two types of air present inside your system. One is cold air and the other is hot air. These exist in groups commonly called air pockets.

Now, let’s try to understand a little bit about hot air pockets and cold air pockets. Air is heated up when there is heat lost from a hot surface to the ambient air and on the other hand air is cooled when it loses heat to a cold surface.

Just a bit of thermodynamics here for general knowledge. A very important thing to remember is energy cannot be created nor can it be destroyed. It can only be converted to an equivalent amount of energy in a different form. This simply means that 100kW of electricity cannot be destroyed but can be converted to equivalent amount of kinetic or other types of energy. Hence heat being a form of energy cannot be destroyed but it can be converted and removed.

When your computer components consume electricity they convert them to kinetic and thermal energy. The kinetic energy is consumed to move electrons and spin motors inside your system. Since the efficiency of this circuits and motors aren’t 100% efficient, they will lose energy in the form of thermal energy. This is when your cpu, ram and such stuff runs hot. When electrical components run hot they tend to first malfunction due to heat flux which distorts the electron flow which basically carry instructions and information whereby you will encounter for example boot failures. If too much heat is produced then the component will fail due to thermal failure.

Now that you have a basic understanding of how is heat produced and why they must be removed let’s move on. As mentioned earlier there are hot air pockets and cold air pockets inside your casing. Hot air pockets (HAP) exist in areas around critical heat equipment such as PWM, PSU, CPU, GPU and RAM. These components produce heat which is consequently lost to the surrounding air and thereby produce HAP which has a limited amount of capacity to accept heat from the component. Cold air pockets (CAP) exist in almost all other parts of your system especially where there are no components and are close to the casing body. Since there are no heat producing components near CAP they are cooler and can accept more heat.

Also hot air will rise to the top of your casing due to lower density while cold air will settle to the bottom due to higher density. The difference in density is primarily due to distance between air molecules and % of moisture. HAP has lower density due to higher kinetic energy of the molecules while the opposite is true for CAP. Another contributing factor is the presence of H2O. HAP has less H20 than CAP due to evaporation.

Considering all the above information, you know now that you must remove the heat from your PWM, PSU, CPU, GPU and RAM as fast as possible. You also know that air at the bottom of your casing is cooler than the air at the top. So now what do we do?

We must;
1. Make sure air flow is from the front to the back of the casing since the biggest heat producer is the PSU. Never suck air in from the PSU into your casing because you will only be sucking in hot air.
2. Make sure that you have two powerful fans of equivalent sizes at the suction and exhaust points of your casing. The best will be to install 120mm fans with at least 90-100 CFM of air flow. I propose this fan due to the higher area coverage at the front bottom and the back top of the casing. If you are not able to install a fan of this size then opt for a smaller fan but with the same amount of flow. There are a number of fans in the market that are able to produce equivalent flows with smaller fan size.
3. Sleeve as much as possible all cables to prevent pressure drop and restriction to air flow. Loose cables will block air flow and thereby introduce pressure drop.
4. Make sure that all suction flow comes in from one direction. Meaning if it’s coming from the front of the casing all other inlet fans must also be installed there. (Do not install suction fans all over the casing unless you are using a tube which will direct all flow directly into the intended area without affecting the general flow pattern inside the casing).
5. Contrary to popular believe, side fans are more destructive for heat removal than helpful unless the side fan is the main suction fan and the fans at the front and the back of the casing serve as the exhaust fans. This is because if you install a side suction fan and a main suction fan at the front, it will only cancel each other out and at the end of the day you will have lots of turbulence and no results since you will only be circulating hot air inside the casing (consider that this is only true if your side fan is at the same epicenter of the main fan).
6. In the case that you still want to install a side suction fan without it being the main suction fan do the following. Make sure that there is a direction tube for the fan to direct flow into the intended area. These should be either the PWM & CPU (even if you are using water cooling), GPU and RAM. This is to make sure that you do not disrupt the main flow direction inside your casing.
7. Make sure that the exhaust fans are installed only at the back of the casing at the top (just below the PSU because it will suck any stray heat loss from PSU) or at the top of the casing itself.
8. Make sure that there is at least 1 feet (30cm) of clearance from the back of your casing to the wall to allow free flow of exhaust air. If the exhaust air is blocked then the exhaust fan will have to work harder to get the hot air out which will result in higher residence time of the hot air inside the casing.
9. Make sure that the suction port of your casing has at least 1/2 feet (15cm) clearance from any restriction or wall to make sure your fan can suck in enough amount of air without working too hard.
10. Check your PSU fan exhaust direction and make sure that its exiting the casing and not the other way around. If not mod the fan so its sucking air out of the PSU and casing.
11. Make sure you get fans which are able to produce at least 90 CFM of air flow for effective air flow for a mid tower casing.
12. Make sure you don’t butcher your fan casing (they are there for a reason namely to guide flow thru the fan and avoid unnecessary damage to ones finger). A fan without a casing will result in a ineffective fan since the air flow will be all over place and there will not be enough pressure produced.
13. Always try to use a fan shroud especially with the main fans. The shroud for main inlet fan should be between the fan and casing while for main exhaust fan should touch the casing directly with the shroud behind it. The shrouds will assist in directing the flow of air thru the fan blades to increase the efficiency.

Remember that the flow of air should be from the front (or rear) bottom of your casing to the upper rear (or front) portion of your casing. This is again simply because hot air rises and cold air drops down so you want to do this installation to remove all the hot air from the bottom of your casing produced by your drives and your VGA card. Then the air should pass thru the exhaust fan before reaching the vicinity of your cpu cooling fan. This way your cpu cooling fan will continue to receive clean cold air from the front of your casing. I would also strongly advise installing couple of exhaust at the top of your casing since this will allow the trapped hot air to exit faster. Using this method I was able to reduce the temperatures of my last system overall by about 5°C.

cyrixMII300

I am just wondering. I have seen that lots of people have looked at this FAQ but not a single person commented. What gives? I mean if there is something lacking I can improve it but I need input to do that. So can someone comment?

thank you

ColdTriton

Ty :)

3xtr3m3

Good one!
But what about the fans at the bottom ?

cyrixMII300

that would really work especially if you have also fans at the top of the casing and that the casing is elevated by again at least 15cm from the floor. but u must be prepared for dust collection :D

thanks for pointing that out anyway

Bindusar

Great FAQ...not completely convinced about the cancelling effect mentioned about multiple intakes...but great FAQ nonetheless.

GigaHertz

I wouldnt say they cancel eachother, but it does make sense that If you have intake at the front and the side they will disturb the current of air as it travels from front to back. My Aspire X-Plorer case has a funnel which directs the current from the side intake directly to the CPU, but I still plan on using that as an exhaust.
Good FAQ!, it's a good read!
Thanks for the Info,

Octapus

no pics :(

cyrixMII300

sorry mate. i m in rome living in a hotel. since i dont have my system here its a bit difficult to take pictures and so on. i will update this FAQ as soon as possible with pictures though. :D

Thumper

Would be good to add in something on positive and negitive balance/flow inside the case. For instance is it better to have more air going in than coming out? Or is it better to have more air coming out than going in?