How airflow works
Airflow is simply displacement; for air to come into case, air must be leaving case .. or .. for air to leave the case, air must be coming into case.
Think of the air around us as water and we are divers in it and a sunken van is a computer case.
- We can't move more water into the van (case) through an open window (vent) unless we have another open window (vent) somewhere else in the van (case) moving the same amount of water (air) out through a window on other side of van (case).
- We can't take any water out of van unless we have the same amount of water coming in at the same time.
- This means we have to have as many open windows flowing water into van as we have open windows flowing water out.
- This is exactly how airflow works. Intake fan pushing / flowing air into case is pushing / flowing the same amount of air out of case.
- Adding an exhaust fan can help case airflow, same as adding a back fan on some coolers.
- But with good case intake fans we don't need exhaust fans, same as good cooler / radiator fans don't need pull fans.
- This is why I used to always change stock intake fans. Now some cases are finally coming with intake fans that have high enough pressure ratings to not need 'helper' (exhaust) fans. :thumb:
Setting up a case for optimum cooling
Setting up the case for optimum cooling is often the hardest and most time consuming part of a build... And the most neglected by most builders.
- There is much more to cooling than good cases and good CPU / GPU coolers. Add the fact that many GPU's make more heat than CPU means getting that heat out of the case and keeping a cool airflow to components can be a challenge.
- Cases, especially those with filters, usually benefit from fans with higher static pressure ratings than stock fans... "cooler" fans instead of "case" fans.
Intakes are typically have more restricted than exhaust because of air filters, more restrictive grills, HDD cages, etc.
- I prefer more intake than exhaust. And don't confuse number of fans with amount of airflow... or airflow with airblow
- airflow is flowing cool air from intake to component and flowing hot air from component out of case without the hot air mixing with the cool air.
- airblow is lots of fans blowing air with some of hot air from components mixing with cool air making it warmer resulting in warm air not cooling components as well as the cool air will.
- Putting fans in case as intake and/or exhaust is only the first step. These fans only move air in and out of case.
- This does not mean heated air is not mixing with cool air.
- Nor does it mean cool air is going to where it is needed.
- Getting the air to flow inside of case properly is even more important. We still need to manage where the air flows inside the case. We can do this several ways; deflectors, more intake fans.. & exhaust fans, removing vent grills, removing HDD cage, using fans with higher pressure/airflow, building ducts to or from CPU/GPU cooler, etc.
- Using a remote temperature sensor to monitor what air temps are is the key to finding out where the cool air is flowing and knowing heated air is not mixing into it. By monitoring this we can than make changes to get airflow the way we want it.
- Keep in mind your case needs to flow more air than components do. It isn't so much how many fans but how well they flow air through the case. If component fans move more air than case fans move through case components are using their own heated exhaust to make up the difference and case heats up. Good rule of thumb is 25-50% more case cfm than component cfm but well tuned airflow can be almost equal equal.
- Traditional tower cooler exhausting toward back of case must have rear / rear & top back case exhaust fan that remove as much or more cfm than cooler fans exhaust.
- A duct from back of cooler to back of case (like Thermalright HR-22 uses) is also an option that works very well.
For example
- My Define R2 system has three TY-140 74cfm intake fans. (no exhaust fans) in case while CPU has TY-143 130cfm fan and GPU has two TY-100 44cfm fans
- Case = 222cfm
- Components = 218cfm
- Air temp inside of case is never more than 3c above room.
- 2 front TY-140 & CPU cooler TY-143 fans are PWM controlled by CPU
- Bottom TY-140 & GPU TY-100 fans are PWM controlled by GPU
It is amazing how much cooler a system runs (and quieter) once the case airflow is setup to keep heated exhaust from contaminating cool intake air. Once we start doing these things, the concept seems like a no-brainer, yet most users seem to think more fans and/or powerful fans are needed to get better cooling. The reality is it's not so much the power and amount of air the fans move. but the currents / pathways the air flows in on it's way through the case that is important. Fan power/airflow only needs to be a little more than the amount the components are using at any given time. Using too many, fan and having too much
airflow airblow can be as detrimental to case's flow pattern as not using fans with enough flow .. and if the flow isn't tuned to keep cool and heated air separate the system is not going run as cool as it can.
How to monitor air temperature different places inside of case:
- A cheap indoor/outdoor thermometer with a piece of insulated wire and a plastic clothespin works great (aquarium / terrarium / fridge remote sensor thermometers too)
- Made up with floral wire and tape. (or single strand insulated electrical wire) If sensor is metal, wrap it with tape too. We don't want anything to short out with metal.
- Clip and position sensor where we want to check the temp. Make it easy to see what the air temp going into components actually is relative to room temp.
- When system is working air temps going into coolers will be 2-3c warmer than room.. up to about 5c is okay.
Please feel free to make suggestions and/or ask questions.
