Category Archives: Active

How Chillers Are Used in the Liquid Loop and How to Choose the Right Fluid

Chillers can be a key component in the liquid loop. They serve the function of conditioning the coolant before it heads back into the cold plate in a liquid loop. The standard refrigeration cycle of recirculating chillers is displayed below in Fig. 1.

Heat Exchanger
An example of a standard liquid cooling loop using a heat exchanger to transfer heat from the liquid to the ambient. (Advanced Thermal Solutions, Inc.)

The choice of the chiller and the fluid are an important part of the creation of the liquid loop. ATS has some resources to help engineers in this work.

First, engineers can get some help identifying the right fluid to use in their liquid loop with our article “Engineering How-To: Choosing the Right Fluid to Use with Cold Plates“. While water is the most common fluid, our article helps engineers with a specification grid on which fluid to use given different applications.

Another helpful resource for engineers is our article, “Cold Plates and Recirculating Chillers for Liquid Cooling Systems“. This article helps engineers understand the use of both cold plates and chillers deployed in the liquid loop. We also include a comparison of ATS and other industry chillers for quick reference for engineers.

But what if your new to how the liquid cooling loop works? Our 2 min. video walks engineers through. The video “What is a Cold Plate and How Does it Work” is a 2 minute video on the ATS YouTube Channel showing how the liquid loop works.

The Liquid Cooling Loop for thermal management of electronics
The liquid cooling loop and some key features of

Finally, ATS has a line or recirculating, immersion and TEC based chillers that engineers can deploy in their liquid loop to efficiently cool high power electronics. You can learn about them on our web sit here: “ATS Family of
recirculating, immersion and TEC based chillers

ATS Family of Recirculating, TEC Based and Immersion Chillers
ATS Family of Recirculating, TEC Based and Immersion Chillers

dualFLOW Coolers – Airflow Video Show Airflow Pathway for Server CPU Cooling

dualFLOW coolers are used in dense systems with high-powered processors, e.g., CPUs, FPGAs and GPUs. They feature a straight fin heat sink base with a high-performance blower that pulls air across the device from two directions for enhanced cooling. ATS dualFLOW coolers provide at least 20% improvement in thermal performance compared to other CPU coolers on the market.

Click the image for a 10 second video on ATS’s YouTube channel showing how the
dualFLOW blower works

They fit standard Intel™ LGA2011 square or LGA2066 sockets, also known as Socket R. A PCB backing-plate is available for applications other socket types.

ATS PCB backing-plate is available for applications other than socket LGA Socket 2011 and LGA Socket 2066 (FPGA, GPU, etc.). Part number ATS-HK379-R0.

dualFLOW models include aluminum or copper fins, and a vapor chamber base to match with needed thermal performance or weight restrictions.

==> Learn more about dualFLOW on

==> Wondering if dualFLOW is right for your application? Email our engineering team to ask:

Increased Performance from High Aspect Ratio Heat Sinks

High Aspect Ratio Heat Sinks from ATSA heat sink’s aspect ratio is basically the comparison of its fin height to the distance between its fins. In typical heat sinks the aspect ratio is between 3:1 and 5:1. A high aspect ratio heat sink has taller fins with a smaller distance between them for a ratio that can be 8:1 to 16:1 or greater.

Thus, a high aspect ratio heat sink provides greater density of fins in a given footprint than a more common sink, and/or stands taller than its conventional counterpart. The great benefit from a high aspect ratio heat sink is the increased amount of heat dissipating surfaces it provides due to its additional fins. Further, these heat sinks do not occupy any more length or width. The result is a more efficient heat sink with higher performance per gram in the same footprint.

Many common heat sinks are unable to serve the needs of high volume applications, due to the fact that their cooling capacity – measured in part by the aspect ratio – is simply not great enough. By nearly doubling a heat sink’s aspect ratio the cooling performance is optimized and heat issues resolved without the need for more complex solutions.

Because high aspect ratio heat sinks are manufactured in similar fashion as conventional heat sinks, their cost is not significantly higher. They can be extruded or bonded. Fins can be straight or folded. For omnidirectional purposes a high density of pins can be used as heat spreaders in place of fins.

High aspect ratio heat sinks are often ideal thermal solutions for workstation CPUs, high performance power supplies and converters, and high-end amplifiers.

Of critical importance when using high aspect ratio heat sinks is providing sufficient airflow to carry away the radiating heat. Passive cooling, e.g. conduction and radiation may be inadequate. Convective heat transfer removes essentially all of the energy from a heat sink under forced air cooling. Particularly with dense fin fields, an improperly directed fan may create stagnation points and high pressure loss. Thermal modeling is recommended when determining the needed active cooling resources.

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

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

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.