Category Archives: Fan

Edge Computing Applications Use Device Level Cooling to Ensure Performance and Reliability

Edge computing devices are often installed environmentally severe and/or remote locations where reliable, long-term operation is essential. It is critical to thermally manage the CPUs, FPGAs, GPUs and other processing devices housed inside. Active cooling from ATS fanSINKs provides the cooling airflow continuously needed at the device level.

fanSINKs feature cross-cut, straight fins that maximize fan airflow for more efficient cooling. They are available for component packages from 27mm-84mm. Depending on their size, fanSINKs can be securely clipped onto a device with the ATS maxiGRIP attachment system, or with PEM screws or push pin hardware for direct attachment to the PCB. Smaller fanSINKs attach with maxiGRIP’s high performance plastic frame clip and 300 series stainless steel spring clip. The secure maxiGRIP attachment eliminates the need to drill holes in the PCB. Larger size fanSINKs fit tightly on components and attach firmly to the PCB with standoff and spring hardware.

Edge computing devices are often installed environmentally severe and/or remote locations where reliable, long-term operation is essential. It is critical to thermally manage the CPUs, FPGAs, GPUs and other processing devices housed inside. Active cooling from ATS fanSINKs provides the cooling airflow continuously needed at the device level. fanSINKs feature cross-cut, straight fins that maximize fan airflow for more efficient cooling. They are available for component packages from 27mm-84mm.

fanSINKs are pre-assembled with Chomerics T-412 thermal adhesive tape (smaller sizes), or with Chomerics T-766 phase change thermal interface material (larger sizes). These proven interface materials increase heat flow into the sinks to maximize cooling performance. Fans for use with fanSINKs are customer specified and provided.

fanSINKS can be purchased via ATS’s global distribution network, including Mouser and Digi-Key and Sager. Also, Sager provides customer specific value add of fans to meet customer application requirements.

==> Learn about our Edge Computing and Appliance fanSINKS at ATS’s website

fanSINK Line Expanded by ATS, Footprints Now 27mm x 84mm

Does your design need cooling for hot components not getting enough air or have components that simply need spot cooling?

The ATS fanSINK line is now available in sizes from 27mm to 84mm. Engineers can now easily add industry leading thermal management across a very wide set of component footprints.

Available from ATS distribution partners now or learn more at:
* Video (1:48)
* Website:

Utilizing Fans in Thermal Management of Electronics Systems

Fans in Thermal Management

There are different types of fans that are used in thermal management of electronics with tube axial fans being the most common. (Wikimedia Commons)

The ongoing trend in the electronics industry is for increasingly high-powered components to meet the ever-growing demands of consumers. Coupled with greater component-density in smaller packages, thermal management is more and more of a priority to ensure performance and reliability over the life of an electronics system.

As thermal needs have grown, engineers have sought out different cooling methods to supplement convection cooling. While options such as liquid cooling have grown in popularity in recent years, still one of the most common techniques is to add fans to a system.

Through the years, fan designs have improved. Fan blades have been streamlined to produce great flow rate with less noise and fans have become more power-efficient to meet the desires of customers trying to use less resources and save costs.

While much has changed in the presentation of fans, there are many basic concepts that engineers must consider when deciding how to implement fans in a project.

This is part one of a two-part series on how to select the best fan for a project. Part one will cover the types of fans that can be used. Part two, which can be found at, will cover fan laws and analyzing fan curves.


As described by Mike Turner of Comair Rotron in an article for Electronics Cooling Magazine, “All You Need to Know About Fans,” fans are essentially low pressure air pumps that take power from a motor to “output a volumetric flow of air at a given pressure.” He continued, “A propeller converts torque from the motor to increase static pressure across the fan rotor and to increase the kinetic energy of the air particles.”

In a white paper from Advanced Thermal Solutions, Inc. (ATS) entitled, “Performance Difference Between Fans and Blowers and Their Implementation,” it was added that fans are at their core, dynamic pumps. The article added, that in dynamic pumps “the fluid increases momentum while moving through open passages and then converts its high velocity to a pressure increase by exiting into a diffuser section.”

The biggest difference between a fan and a blower is the direction in which the air is delivered. Fans push air in a direction that is parallel to the fan blade axis, while blowers move air perpendicular to the blower axis. Turner noted that fans “can be designed to deliver a high flow rate, but tend to work against low pressure” and blowers move air at a “relatively low flow rate, but against high pressure.”

The three types of fans are centrifugal, propeller, tube axial, and vane axial:

• In centrifugal fans, the air flows into the housing and turns 90 degrees while accelerating due to centrifugal forces before being flowing out of the fan blades and exiting the housing.
• Propeller fans are the simplest form of a fan with only a motor and propellers and no housing.
• Tube axial fans, according to Turner, are similar to a propeller fan but “also has a venture around the propeller to reduce the vortices.”
• Vane axial fans have vanes trailing behind the propeller to straighten the swirling air as it is accelerated.

The most common fans used in electronics cooling are tube axial fans and there are a number of manufacturers creating options for engineers. A quick search of Digi-Key Electronics, offered options such as Sunon, Orion Fans, Sanyo Denki, NMB Technologies, Delta Electronics, Jameco Electronics, and several more.

Fans in Thermal Management

A fan is added to a heat sink on a PCB in order to increase the air flow and heat dissipation from the board component. (Advanced Thermal Solutions, Inc.)


When selecting a fan, engineers must consider the specific requirements of the system in which they are working, including factors such as the necessary airflow and the size restrictions of the board or the chassis. These basic factors will allow engineers to search through the many available options to find a fan that fits his or her needs.

In addition, engineers may look towards combining multiple fans in parallel or in a series to increase the flow rate across the components without increasing the size of the package or the diameter of the fan.

Parallel operation means having two or more fans side-by-side. When two fans are working in parallel, then the volume flow rate will be increased, even doubled when the fans are operating at maximum. Turner added. “The best results for parallel fans are achieved in systems with low resistance.”

In a series, the fans are stacked on top of each other and results in increased static pressure. Unlike parallel operations, fans in a series work best in a system with high resistance.

The ATS white paper noted, “In real situations, the fans may interfere with each other. The end results is a lower than expected performance.” Turner warns that in either parallel or series configurations there is a point in the combined performance curve that should be avoided because it creates unstable and unpredictable performance, but analyzing fan performance and fan curves will be covered in more detail in part two of the blog.

Efficiency is a major factor when selecting a fan. As noted in an article from Qpedia Thermal eMagazine, “A large data center contains about 400,000 servers and consumes 250 MW of power. It has been estimated that about 20% of the total power supplied to a high end server is consumed by fans.”

Clearly, finding a fan that can work efficiently with lower power will save a considerable about of resources. The article details several methods for creating efficiency in designing a system that includes fans:

“Fan power consumption is traditionally reduced by controlling the motor speed to produce only the airflow required for adequate cooling, rather than operating continuously at full speed. Significant energy savings can be achieved beyond this technique through fan efficiency increase. Optimizing the motor and electronic driver, increasing fan aerodynamic efficiency through careful redesign, and optimizing fan-system integration are three ways of achieving this.”

Read more about the techniques for achieving efficiency at


To learn more about Advanced Thermal Solutions, Inc. consulting services, visit or contact ATS at 781.769.2800 or

How to Use Fan Curves and Laws in Thermal Design

In today’s electronics industry, there is a constant and well documented push to higher powered components, tighter grouping of devices, and overall increased system thermal dissipation. The higher dissipation must be managed effectively to ensure long term reliability of the system.

With forced convection being the dominant mode of electronics cooling, more efficient heat sinks are often used for cooling these increased thermal loads. But, they are only half the solution. Due to volumetric constraints, it may not be possible to design an adequate heat sink for a given component. A large amount of air preheating may occur if multiple components lie in the flow path. The increased ambient temperature resulting from this preheated air often brings the need for a larger heat sink, but the space may not be available.

The solution to higher power levels and decreasing heat sink space is to increase the system’s air flow rate. A boost in flow rate has a twofold benefit: first, it lowers the thermal resistance of the heat sink, which reduces the temperature difference from junction to ambient. Secondly, it reduces the overall temperature rise in the chassis. The reduced temperature rise allows downstream components to suffer less preheating and operate at lower ambient temperatures.

This direct relationship between air velocity and component temperature indicates the importance of understanding how fans behave in electronics cooling.

System Curve

Prior to selecting any fan it is important to characterize the overall system with respect to air flow and pressure drop. For example, a tightly packed 1U chassis will require a much different fan configuration than a larger desktop one, even if both systems use the same CPU. In the 1U chassis, components are spaced very tightly and exhibit a large resistance to flow. This requires a fan with a high pressure head. A benefit of the 1U chassis design is less bypass flow, reducing the need for larger volumetric flow rate. In an ATX style desktop chassis the requirements are very much the opposite. There is typically much more open space in the ATX chassis, which lowers the chassis pressure drop. The widely spaced components create a less efficient flow path, and thus a larger volumetric flow is needed to ensure adequate cooling of all components.

Figure 1. Typical Overlay of a System Curve and Fan Curve

Fan Curve

A fan curve example is shown in Figure 1. Point A is the no flow point of the fan curve, where the fan is producing the highest pressure possible. Next on the curve is the stall region of the fan, Point B, which is an unstable operating region and should be avoided. From point C to point D is the low pressure region of the fan curve. This is a stable area of fan operation and should be the design goal. It is best to select a fan that operates to the higher flow point of this region to improve fan efficiency and compensate for filter clogging.

The system pressure curve can then be compared to a specific fan curve to determine if the fan is adequate. To compare fan curves from different manufacturers, it is important to follow a testing standard. For electronics applications, the relevant standard is the AMCA 210-99/ ASHRAE 51-1999 test guidelines.

Figure 2a. AMCA Fan Testing Chamber

The AMCA fan testing chamber, shown in Figure 2a, consists of a supply fan, a variable blast gate, two test chambers, flow nozzles and an opening to place the test fan. A commercialized testing module from Advanced Thermal Solutions, Inc. is shown in 2b.

During a typical fan test, a dozen or more operating points are plotted for pressure and flow rate, and from this data a fan curve is constructed. To obtain the highest pressure rating of the fan, the blast gate shown in Figure 2a, is closed to ensure zero flow while the fan is running. The chamber pressure is then read from the static pressure manometer to obtain the maximum pressure rating of the fan. The blast gate is then slightly opened in successive steps to obtain additional operating points. Finally, the maximum flow capability of the fan is found by opening the blast gate completely and running the supply fan. The supply fan ensures the secondary chamber is operating at atmospheric pressure, which removes the flow losses in the system.

Figure 2b. FCM-100 Fan Characterization Module from Advanced Thermal Solutions, Inc.

The operating pressure of the fan curve is found by taking measurements from a static manometer. The volumetric flow rate, Q, is found by measuring the pressure drop across an AMCA nozzle (Figure 3) using a differential manometer. The flow rate through an AMCA nozzle is a function of its size and differential pressure as shown in the following equation.

In contrast, the FCM-100 is void of any nozzles and works based on volumetric flow rate measurement using the ATVS technology flow sensing system. It is compact, portable and capable of characterizing single fans or fan trays.

Figure 3. Various AMCA Nozzles (CTS, Inc.)

Air Flow

Fan Laws

Fan laws are a set of equations applied to geometrically identical fans for scaling and performance calculations.

Published fan laws apply to applications where a fan’s air flow rate and pressure are independent of the Reynolds number. In some applications, however, fan performance is not independent and thus the change in Reynolds number should be incorporated into the equation. To determine if the Reynolds number needs to be considered, it must first be calculated.

According to AMCA specifications, an axial fan’s minimum Reynolds number is 2.0×106 When the calculated Reynolds number is above this value, its effects can be ignored.

Fan Law Application

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 cooling is often needed to maintain adequate junction temperatures and reduce temperature rise within the system.

Consider for example a telecom chassis using a single 120 mm fan for cooling. The maximum acceptable temperature rise in the box is 15°C. The chassis dissipates 800 W, but a board redesign will increase the power to 1200 W. The current 120 mm fan produces a 3³/min flow rate at 3000 RPM using 8 W of power. How do we calculate the requirements of a substitute fan for the higher powered system?

Next, calculate the change in RPM needed:

Thus, to meet this example’s cooling requirement for 1200 W, a fan is needed with a 4³/min flow rate, 4,000 RPM speed and 18.9 W of power. Note that the system power, flow rate and fan RPM all increased in a linear fashion from those in the original system. However, the fan power increased by nearly a factor of three.


Bulk testing of electronics chassis provides the relationship between air flow and pressure drop and determines the fan performance needed to cool a given power load. The fan rating is often a misunderstood issue and published ratings can be somewhat misleading. Knowledge of fan performance curves, and how they are obtained, allows for a more informed decision when selecting a fan. Continued and ever shortening product design cycles demand a “get it right the first time” approach. The upfront use of system curves, fan curves and fan laws can help meet this goal.

1. Ellison, G., Fan Cooled Enclosure Analysis Using a First Order Method, Electronics Cooling, October 1995.
2. Daly, W., Practical Guide to Fan Engineering, Woods of Colchester, Ltd, 1992.
3. Turner, M., All You Need to Know About Fans, Electronics Cooling, May 1996.
4. Certified Ratings Program – Product Rating Manual for Fan Air Performance, AMCA 211-05 (Rev. 9/07).

This article was first published in Qpedia. To buy the complete Qpedia book set, please visit:

To learn more about Fan Characterization and the FCM-100, please visit:

Performance Differences between Fan Types Used for Electronics Cooling

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