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Case Airflow, Cooling the right way.
While venturing on the internet looking for some tips on airflow and to see if cooling is done by air, for the most part, has changed I was disappointed. The lack of good material or even bad material was stunning so I decided to contribute with a fellow overclocker showing good cooling practices. Nothing has changed it remains pretty much the same while fans have greatly improved and so does the fan assortment. For this article, there will be 2 examples of a Ryzen based system and an Intel-based system with different cases.
1. When placing fans in your case or even other hardware ensure that airflow is in the right direction. In any case, this means cold air goes in and hot air goes out, a common mistake what will result in higher temperatures or even hot air blowing in your face. Even if it is extremely hot outside the air will still have a lower temperature than inside your case, this also goes for liquid cooling solutions. Intake Fans: the front and the bottom of your case, Exhaust Fans: the back and the top of your case.
Very important to note is that hot air rises and the rear of your case is confined especially on enthusiast builds with a big CPU cooler. And the overall trick for the best cooling solution is that cool air is not mixed with the hot air but that air on the intakes has enough pressure to reach the centre so that the hardware fans on your GPU and CPU will be able to scoop up the cold air to cool the components and then push hot air towards the exhaust fans. Below is a looped video of my new Phanteks Enthoo Luxe case that depicts the flow of air, stage 1 intake, stage 2 hardware picks up the air, stage 3 hot air exhaust.
2. Always have negative pressure inside your case by having more exhaust fans than intake fans or by calculating your CFM and high static pressure. You can opt for overpressure if your system does not generate excessive amounts of heat but this is only with budget setups without overclocking. Also important to note that especially with negative pressure to use dust filters on your fans where you can, either pre-installed or aftermarket filters. The general rule for fan placement is that high static fans are used as intake fans while high CFM fans are used for exhaust. For those who are new CFM stands for cubic feet per minute and high static pressure the ability to overcome obstacles and travel distance.
To aid in finding the right cooling solution use this excel sheet Case Cooling CFM, Static Pressure, and Watt Calculator located on Google Drive. To use the Excel sheet download and open an excel sheet or move a copy to your own Google Drive. Simply enter the numbers of your fans located in your case, above the column is a note that this part is either intake or exhaust. With the exclusion of hardware and internal fans who are calculated with hardware CFM/mmH20 for a different calculation. Now you can see there are different results, CFM Rating(+ or - airflow), Case vs Hardware actual CFM, Case vs Hardware optimal CFM. Also included are watts and decibels, PWM hubs and Fan controllers have ratings if want to buy one check if you are buying the right one. Noise generating can be indicated, not taking into account acoustic deformation of the room or any noise-reducing padding your case might have.
CFM Rating(+ or - airflow): take the intake CFM and deducts it with the Exhaust CFM this will either give a positive or negative result, this will indicate whether your fans will generate a negative or positive pressure inside the case and you can adjust accordingly, removing/adding fans.
Case vs Hardware actual CFM: Weighs the CFM by deducting Hardware Total CFM from Case Total CFM to give indicate surplus CFM. Useful to indicate if you installed too much or too little fans, too many fans could create too much turbulence making it harder for hardware fans to scoop up the air, and that could great stall pockets of hot air increasing the temperature overall.
Case vs Hardware optimal CFM: This will calculate the CFM of your Hardware CFM vs your Case CFM if the amount of airflow is too much or too little, the throughput of your hardware CFM is an indicator when cool air is pushed in and then hot air pushed out if the airflow can be used efficiently by your installed hardware. Normally 25% ~ 50% on top of your Hardware CFM is optimal, here I used 25% so anything above it should be sufficient.
3. When shopping for fans ensure they are of good quality even if that means paying a bit extra, cheaper fans means less performance. When cooling your system you want the best CFM and static pressure at the lowest noise levels to fully enjoy your build. High-end fans are money well spend and will offer the best airflow scenario for your build optimal cooling temperatures. As mentioned above you want to generate negative pressure by generating more exhaust CFM then intake CFM.
The difference between static pressure is merely air that travels at higher speeds than the actual volume that translates in CFM. Therefore by ensuring you the cubic feet per minute(CFM) is higher with the exhaust fans then the intake fans you will generate negative pressure. High static pressure fans are always fitted with less but bigger blades generating a lower CFM and higher CFM fans always have more but smaller blades.
4. PWM, PWM Hubs, and Fan Controllers are vital for regulating your fans speed and the noise they generate. However you can only use one even if there are several PWM connectors with most motherboards, check your manual to ensure you can use multiple PWM signals. You will either use your PWM signal that can ideally have enough signal strength to support 6 to 9 fans at a time through PWM hub. Or use a fan controller that controls the fans speed through its PWM signal setting the RPM, or using them in or decrease of watts. Motherboard PWM signals are more accurate and will react better to heat fluctuations over a fan controller since the heat sensors will interact with the motherboard. A fan controller will detect temperatures through a series of sensors you have to place around your case, closer to a heat source the better. But a fan controller allows you to tweak your RPM better with smaller steps over a motherboard PWM signal + motherboard software. Also important to note that fans have steps some have more like others that are usually more costly with more steps but offer more control.
5. To make a fully informed decision regarding what type of cooling flow you want to use here are some of the basics. While it remains true that negative pressure will result in the best cooling when setup correctly there are other options you could try out. Positive Pressure: More combined CFM on intake fans and/or more intake fans, this will result in far less dust attracted to your cooling loop. Negative Pressure: More combined CFM on exhaust fans and/or more exhaust fans, will attract more dust to your cooling loop there for filters are a must. Neutral Pressure: Roughly the same combined CFM on your intake and exhaust fans with a balanced fan setup. To give you a more accurate picture below is a video painting an accurate picture of what the above setups will do in terms of airflow with pros and cons.
6. Dust is your enemy, where dust accumulates it well hamper cooling performance, less cooling when dust sits on your filters or heatsinks. Cable management is also very important, dust will stick to most surfaces so having wires in the airflow path beside hampering the airflow altogether. Investing in a good case that has cable management features will have a better look, better airflow and less surface for dust to settle. Besides dust filters and a solid tight-fitting case placing your rig on your desk will reduce dust intake by 80%, never place it on the floor or carpet. And make sure your PSU is modular try to use the least possible amount of cables for a clean look and fewer places for dust to accumulate.
This concludes an introduction to the best cooling practices, covering the basics of setting up a proper airflow with some guidelines to get you going. The first step towards setting up your cooling showing that air cooling and getting the right airflow is a skill, as much as water cooling. Make sure to test out your setup and move some fans around to gain experience and the perfect solution for your case, each case is different. Stay tuned to this article and website since 2 more articles will follow soon with 2 case by case examples of setting up an airflow.
- Paul "HisEvilness" Ripmeester