In most application, single fan configuration is not powerful enough because the cooling effect will be limited by the fan size and the fan's ability. Worst of all, when facing the system level cooling, the range of the single fan is too restricted to take care of all the components. Therefore, a multiple fan cooling system is common, and it is the topic every PC player have to know.

There're basic two type of the multiple fan system: one is fans in series and another one is fans in parallel. The effect of each type is quite different and can be deployed and combined freely by tasks. The difference can be seen in below sections.

Fan in series

Fig 1. Fan in series arrangement properties

When the fans are arranged in series, the air pressure of the cooling system will be the sum of the total pressure generated by each fan. This result can be easy to understand in this way:

Imagine there're a pitcher and a hitter. The hitter stands in front of the pitcher and both players face the same direction to the home base. They play as usual: the pitcher will pitch the ball and the hitter will hit the ball. When the ball leaves the pitcher's hand, it gets an initial speed and fly to the hitter. When it passed the hitter, the hitter hits the ball and the ball is accelerated again and fly fast into the catcher's glove.

If we take the ball as the air, then the hitter and the pitcher will be the fans stand in series. During the process, the ball is firstly pitched by the pitcher and hit by the hitter just as the air is propelled twice by the fans and hit the device with more power. That's why the fans in series will generate more air pressure.

However, there's one thing we need to notice for series fan configuration. Just as what happened in the baseball case, a pitcher can only pitch a ball. The total air flow will be determined by the first fan. Considering the properties, we can apply the series fan in two different strategies:

  1. When the system requires more air pressure, we can directly increase the fan amount to achieve it. This is the most straightforward strategy and we'll get the sum total pressure of each fan to fulfill the requirement.
  2. If the system's air pressure requirement is easy to achieve but need larger air flow, we can replace the original fan with the one which meets the airflow requirement. The need of the air pressure can be satisfied by linking more fan in series.

Fan in parallel

Fig 2. Fan in series arrangement properties

The fan in parallel arrangement is the most common type you can find in general application. It has the widest cover range and the biggest air flow to cool the components inside the system. The idea is straightforward and easy to understand, so it is almost the first thing people will do when they encounter the cooling issues.

By arranging the fan in parallel, you can get the sum of the air flow each fan provides. The coverage area can be adjusted by changing the direction of the fan or their position. However, there's one thing need to notice. The fans you choose should have similar air pressure performance, or the cooling air will oscillate inside the system, causing turbulence and affecting the cooling effect.

Combination of series and parallel cooling systems

After understanding the properties of the series and the parallel systems, we can do a more advance cooling system design by joining the both systems together, according to the tasks in each heat zone.

For example, for processor area, we can set a multiple series fan cooling system to strengthen the cooling ability of the air to pass the complicated heatsinks. In the parameter area, we can set parallel fan system to increase the supply of the cooling air and the heat expelling effect. The cooling effect of the cooling system will be multiplied by taking the advantage of different fan systems.

To build the joint fan cooling system, keep in mind the following principles:

  1. The collocation of the air flow and the air pressure-
    The space inside the system is continuous. We always need to think cooling behavior in system level rather than taking it individually. For instance, you shouldn't place a parallel fan system with low air flow ability before the series fan system with higher ability. The cooling ability will be reduced due to the insufficient air supply under this circumstance.
  2. Simple is the best-
    Don't solve the cooling issues in a complicated way. If the issues can be solved by just changing the original fan to a more powerful fan, then we should change the fan rather than using the parallel or series system. Also, if we can't define the path well and the air flow and the air pressure of each system, we should try to make partition for each area to reduce the interference between each cooling system. By this way, the cooling issue can be solved just as the connection of the inlet and outlet of each system.
  3. Think before you act-
    Sometimes, it is not your cooling kit is not powerful enough, but it is you apply it in the wrong way or in the wrong place. For example, you shouldn't buy a small case but want to install the high-end CPU or graphic card inside the case. The cooling effect of the cooling kit will be restricted, even you have chosen the powerful one. In the meanwhile, the cost will be also expensive to choose the appropriate cooling system for the small case. The cooling issue can be simply solved by just buying a bigger case for the high-performance components. Plan the configuration preliminary can effectively save your time and money.
  4. Noise issue-
    As we know in the previous article, each fan will generate its noise. More fans mean more noise. When you widely adopt the multiple fan cooling system, you create the big noise source also. Therefore, be careful to use the multiple fan solution if you don't want your machine screaming all day.
  5. Capability of the System-
    When you use the multiple fan system, please check your power supply can withstand the additional load. Though the power consumption of only one fan is small, but it still be worth noting when the fans aggregate. It is unwitty to sacrifice the stability of the system to have better cooling effect.

With these principles, the multiple fan system you create definitely can run well and satisfy your anticipation.