a recent article from electronic design gave engineers five easy steps for choosing the right fan to fit into their thermal design, including calculating the size fan that is required, the heat that needs to be dissipated, and even how much noise is acceptable in a particular system.

the article gives tips for picking the right fan. (wikimedia commons)

the article, written by jeff smoot, vice-president of application engineering and motion control at cui, inc., explained, “in many instances, heat can be conducted away from critical components, through the circuit board and case, and dissipated to the surrounding air. for larger systems, especially computers, servers and similar rack-mount equipment, where the combination of conduction and natural convection cooling isn’t sufficient, fans are often needed to provide forced-air cooling.”

the first step is to determine which components are creating the heat and how much heat is being added to the system. next, determine how much airflow is needed to keep the temperature of the system at a manageable level.

smoot wrote, “component performance and reliability can be dramatically impaired when operating at higher temperatures. even though a device will normally have a specified operating temperature range, it’s often desirable to keep the actual operating temperature well below the upper limit of that range.”

in order to choose the fan that will give the right amount of airflow, smoot said that it is critical to understand and calculate airflow impedance, which refers to the drop in air pressure from inlet to outlet. using a graph that plots impedance with airflow at static pressure allows engineers to find the optimal operating point.

the last steps are choosing the type of fan and finding a fan that meets noise and power requirements, such as fans with speed controllers that automatically change airflow depending on the temperature within the system.

smoot concluded, “like it or not, unwanted heat will always be a challenge to most electronic designs.  however, the effective implementation of a cooling fan can allow an electrical system to operate optimally while also improving the design’s longevity.”

read the full article at http://www.electronicdesign.com/analog/how-choose-cooling-fan-five-easy-steps.