Category Archives: Fans

What are Fan Laws and how do you use them in thermal management design?

During a product’s life cycle a redesign may be carried out which replaces older components with new, higher powered ones. Due to the resulting higher heat flux, increased thermal management is often needed to maintain adequate component junction temperatures and reduce temperature rise within the system.  Fan Laws are useful mathematical tools to understand, compare and contrast different fan approaches.  Using Fan Laws before choosing a fan can help engineers to make solid choices to reduce cost, experimentation and time to market.  ATS’s five-page presentation on Fan Laws for thermal management which includes examples on how to use them, is a good introduction to this important engineering tool:

[slideshare id=4205722&doc=atsslidecastfanlaws-100521141058-phpapp02]

How to Understand Fan Curves and Optimum Operating Points


Fans, or other air movers, are a critical part of any system level thermal management solution. There are cases where a fan is not preferred, such as in medical equipment (see our earlier post on that topic here), some military applications and in some consumer applications. And, fans do present the unwanted chance of mechanical failure being introduced into a system.

In a white paper written by ebmpapst, they note that:

Fans create a flow of air, which they can then force through equipment that needs cooling. The necessary output is determined from the flow rate and the required static pressure. If the airflow through the equipment is restricted to any great extent by built-in components or bends and junctions, then this will lead to a loss of pressure; the fan will try to compensate for this by an increase in the static pressure, though the fan will have to work harder than in free air operation. The characteristic curve of the fan gives precise information about the flow rate at specific static pressures.

Understanding these curves is critical and ebmpapst has a good, introductory white paper to help you understand them. You can get your copy of their quick and useful read by clicking:  Fan Curves and Optimum Operating Points.

How system airflow affects active heat sinks: ATS “how to” white paper

In our post, “Active heat sinks direct air on hot chips but are they always the right choice” we wrote about the benefits and drawbacks of using an active heat sink or fansink.  We also talked about system design approaches that should be considered by a thermal engineer.  If a system is designed well, be it a workstation or printer, active heat sinks with fans probably won’t be necessary.  But if you do decide to go the way of using an active heat sink you should be aware of how overall system air flow affects fan sink performance.

ATS has produced a white paper that can help you understand this important issue. Cooling fans consist of an aggregate of airfoils, i.e., blades positioned around a hub that is driven by an electric motor. Due to their airfoil nature, a pressure differential is required across the blades to create the required flow. Therefore if this pressure differential is disturbed, fans will suffer performance degredation. Our white paper addresses this important issue so you can implement fan sinks in the best way possible. You may download our white paper from our qats.com by visiting the link, “How system airflow affects active heat sinks”