Category Archives: Active

Performance Differences between Fan Types Used for Electronics Cooling

Posted on June 6, 2012 by | 3 comments

Billions of fans are now in use for active cooling of PCBs and other hot electronic components. An article in Qpedia, the thermal e-magazine from Advanced Thermal Solutions, Inc., (ATS), explores the two most common types of fans used in electronics cooling: the radial (or centrifugal) fan and the axial fan.

The difference between the axial fan and radial fans can be divided into two parts, namely geometry and fluid dynamics.

An axial-flow fan has blades that force air to move in a parallel direction to the shaft around which the blades rotate. For a radial fan, the air flows in on a side of the fan housing, then turns 90 degrees and accelerates, due to centrifugal force as it exits the fan housing. These differences in air flow direction have design implications. For example, a radial fan can blow air across a PCB more efficiently, and use less space, than mounting an axial fan to blow air down onto a board.

The fluid flow rate through an electronics system, e.g., enclosure, is determined by the intercept between the fan and system curves that plot the air pressure drop over volumetric flow rate. A system’s air flow curve can be calculated using 1D fluid mechanics, or it may require the use of high performance CFD or experimental data. In general, for the same power and rotation speed, the radial fan can achieve a higher pressure head than an axial fan. However, an axial fan can achieve a higher maximum flow rate than a radial fan.

In theory, this same approach applies when using two fans in series or in parallel. When the fans are in series, the maximum flow rate should stay the same as for the single fan, but the maximum pressure head doubles. When using two fans in parallel, the maximum pressure head should remain the same as for the single fan, but the flow rate doubles. In real situations, though, the fans may interfere with each other, thus providing lower than expected results. Thus, actual experimentation is typically needed.

Download the Full ATS White Paper Performance Differences Between Fans and Blowers and Their Implementation

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Posted in Active, Fan, Fans, Qpedia Thermal eMagazine, thermal management

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Why use active heat sinks? Here are some pros and cons to make an informed decision

Posted on June 17, 2010 by | Leave a comment

ATS has published two articles from the past on the topic of, “Why use active heat sinks” that we thought were worth putting some focus on to help our thermal management practitioners.  The fall back to an active heat sink can be alluring (what’s easier than slapping a cpu cooler fan onto your heatsink?  More air should cure all thermal management ills, no?)

The first article, “Active heat sinks direct air on hot chips but are they always the right choice?”  we published around the thought process on if an active heat sink was even necessary for your design.  It’s a good read to help prime your personal thought process and to think through your system design first.

The second article, “How system airflow affects active heat sinks: ATS ‘how to’ white paper“, covers the topic of the affect of your overall system airflow on your active heat sink. 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.

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

Posted on April 13, 2010 by | Leave a comment

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”

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Posted in Active, Fan, Fans, Heat Sinks