23 Aug 2015

Airflow 101

Be it an entry level or a high end rig, keeping it cool is of top priority and the first step towards it is designing a good airflow.

The term ‘temperature’ is often associated with processor and GPU in a rig. There are many utilities to monitor and optimize settings of components to keep the temperature below a certain line. But the fact that the ambient temperature can also affect the components is being neglected. While enthusiasts go for cooling systems, a properly designed airflow can get half the job done for you. The following are the basic concepts in designing an airflow system for your rig. Before we start do keep in mind that airflow works best if intake and outflow is in the same line of sight.

RULE #1 COLD AIR IN, HOT AIR OUT

The basic rule is to keep the air inside the case moving. If the air is static, the ambient temperature will rise and affect the performance of the rig, which is often a result of significantly imbalanced airflow design. The rate of intake and outflow can spread out to a lot of factors like size, CFM, RPM of fans to even the size of perforations for ventilation. To avoid such a situation, start with the fan and always check the direction of airflow before fixing it. If they are behind any grill, make sure the perforation are large enough to provide good airflow. To reduce noise and increase airflow, remove the grill leaving the fan open. Bigger the opening, better the cooling.

RULE #2 HEAT RISES

Hot air is less dense and hence rises upward. This phenomenon makes the flow of air inside the case to be in a lazy ‘Z’ manner. The cold intake is from the front lower side of the case and the hot exhaust is from the rear top. The setup is ideal, unless extra fans come into the picture for hotspot cooling. Especially, the side fans create a whirlpool effect and interfere with the ‘Z’ pattern, leaving dead spots in the case. If there is a need for spot cooling, like for the core or the GPU, use air ducts that focuses the side fan to the target.

RULE #3 CHOOSE THE RIGHT FAN FOR YOUR RIG

There are three kinds of fans – Airflow optimized, Static pressure optimized and like always – the hybrid. An airflow optimized fan has more gap between its leaves to facilitate more air movement. This is useful when the fan does not suffer resistance from any component like the grills or a radiator. If the fan is over a radiator, the air will take the least resistant path and flow around the radiator. This is why you need a static pressure optimized fan, which leaves almost no room between its blades to form a suction and force more air to flow through it. It also has a wide exhaust angle, hence pressure optimized. The hybrid one has balanced gap and sometimes may also come with different kinds of blade shape in a single fan.

AirflowOptimized

Airflow optimized fan

StaticPressureOptimized

Airflow optimized fan

 

RULE #4 LOOK FOR RATINGS WHEN YOU BUY A FAN

Look for fans that have high CFM (Cubic Feet per Minute) ratings – which tells you the volume of air the fan can move in one minute. More the CFM, less the number of fans you need. If it is for a radiator or a ventilation, buy a fan with high static pressure rating, which is measured in mm/H2O.

RULE #5 KNOW YOUR AIRFLOW SYSTEM

More fans do not mean more cooling. Inconsiderate positions and running parameters of fans can result in no cooling at all. There are three types of airflow system that you can consider.

NEGATIVE LESS IN, MORE OUT

Since there is less intake, the system relies more on ventilation for air inflow. This is why negative systems are optimal when the exhaust is slow, so that there will always be enough air in the case to carry the heat. Negative systems are quieter as a result of low RPM. While implementing this system, make sure that there is enough ventilation at the right positions for intake. Radiators might need targeted intake, otherwise the air will go around the radiator through the ventilations to suffer least resistance.

Negative

 

POSITIVE MORE IN, LESS OUT

More inflow of air means better cooling. Positive systems are recommended only if you can keep a check on the dust inside the case periodically. Cooling is slightly better than Negative systems. Also, since there is a lot of intake the internal pressure builds up to aid in outflow.

Positive

NEUTRAL BALANCED IN AND OUT

A Neutral system is almost equivalent to a system running with the side panels open, which is otherwise very difficult to implement. The open panel setup is hazardous for many reasons starting with air being static.

RULE #6 ADJUST YOUR SETTINGS

Adjust the fan speed for normal use as well as heavy use. The noise is due to the air turbulence generated between the blades and the grill and can be reduced by lowering the RPM.

A good airflow system keeps the machine from high temperatures in medium load. But if overclocking or heavy applications are involved, always go for a cooling system. Hope this will get you started.