Tech Corner

By Rutronik

Thermal management: Everything you need to know about fans

Figure 1.

For the proper functioning and longevity of electronic systems, the maximum operating temperature of any component must not be permanently and/or significantly exceeded. To ensure this, thermal management is often necessary, for example with a fan. The decisive factor here is the selection of the optimum model for the application in question. A fan uses a motor to generate a rotation of the fan blades and thus a pressure difference, which in turn causes a continuous airflow. The fan consists of a rotating part, the impeller, and a fixed part, the package.

The different types of fans

There are numerous types of fans. If it is a question of using them to cool an electronic device, the most important criterion is the direction of the airflow. Accordingly, a distinction is made between:

• Axial fans (the airflow is parallel to the axis)

• Radial fans (the airflow is perpendicular to the axis)

• Tangential fans or cross-flow fans (their long package produces a wide, flat airflow perpendicular to the axis and tangential to the package)

• Spiral radial fans (the blades in the impeller are not straight as in radial fans, but have a spiral or helical structure; this allows them to produce an airflow that is somewhere between that of an axial fan and a radial fan, as seen in Figure 1.

In addition, fans are classified by their supply voltage as DC voltage or AC voltage fans. Current AC models are primarily electronically commutated fans. They achieve higher energy efficiency due to their brushless DC motor and electronic control.

The most important selection criteria

Airflow volume is also an important indicator for selecting a fan. It is characterized by the amount of air that is discharged from or introduced into an electronic system within a given period. Fans impart the necessary pressure to an air mass to create a pressure differential and thus airflow. Three types of pressure are involved in this process:

• Static pressure (PE) is the force exerted by the stationary air on the system walls perpendicular to it.

• Dynamic pressure (PD) is the force per unit area and is used to overcome the resistance of the airflow in a system. It therefore ensures that the air moves and is generated by the rotational speed of the fan. It is always positive and has the same direction as the airflow.

• Total pressure is the sum of PE and PD at a given point in the system. This is the pressure exerted by the air on a body resisting its motion at that point. It is important to note that the total pressure at different points in a system can vary due to the velocity and flow conditions of the air.

Factors influencing life expectancy

The most important factors influencing a fan’s service life are its temperature profile and its type of bearing. In the case of a plain bearing, it again depends heavily on the lubricants used. A two-ball bearing consists of small metal balls in a raceway, allowing for lower friction and higher efficiency. More detailed information on the fan’s operating temperature profile can typically be found in its data sheet.

Main markets

Fans are used in numerous industries to remove heat and maintain optimal temperatures. Major markets include:

• Electronics: For cooling internal components and preventing overheating.

• HVAC (heating, ventilation, and air conditioning): For air circulation, indoor temperature regulation and for generally improving air quality in buildings, homes, offices and industrial facilities.

• Motor vehicles: For regulating the engine temperature and preventing overheating. • Renewable energy: For use mainly in wind turbines and solar inverter cabinets.

• Industry: For keeping machines and equipment, e.g. in manufacturing, power generation, or petrochemical industries, at their optimal operating temperatures.

• Data centers: For ensuring cooling to remove heat generated by servers and other IT infrastructure. Fans are an important component of data center cooling systems.

• Consumer electronics: For refrigerators, air cleaners or game consoles.

• Aerospace: For cooling systems and components.

Innovations — Where do we start?

Further development of fans focuses on the following aspects:

Energy efficiency. Fan suppliers are working to improve the aerodynamic design of fan blades, reduce friction losses and optimize motor efficiency to achieve higher overall energy efficiency. This includes the use of advanced materials and manufacturing techniques to reduce weight and increase performance.

Improved ball bearings. Suppliers are using newly developed bearing technologies to increase the reliability and service life of their fans. For example, fluid dynamic bearings (FDBs) and magnetic levitation bearings (MLBs) offer a longer service life and lower noise compared to conventional plain or ball bearings.

Noise reduction. An important issue in fan applications, especially in environments where low noise levels are required. Technical development focuses on improved blade designs, optimized motor controls and the use of noise-absorbing materials. Computational fluid dynamic simulations and other modeling techniques are used to study and minimize noise.

Fan control systems. These play a major role in optimizing fan performance and overall system efficiency. Intelligent control algorithms that dynamically adjust the fan speed based on temperature, humidity and other environmental factors ensure that fans operate at maximum efficiency while creating optimal cooling conditions.

Integration with cooling systems. Aiming to maximize the heat dissipation of the entire cooling system, fans are integrated with other cooling technologies such as heat sinks, radiators and liquid cooling systems.

Smart and IoT-enabled fans. The Internet of Things (IoT) has enabled the development of smart fans with advanced features and connectivity. They can be monitored and controlled remotely and enable real-time adjustments based on environmental conditions and user preferences. In addition, IoT-enabled fans can provide valuable data on performance, energy consumption, and maintenance needs for their optimization and predictive maintenance.

All of these advances aim to further improve the cooling performance of fans, further reduce their energy consumption, and provide more reliable and efficient cooling systems for a wide range of industries.