Pin Fin Heat Sink Optimization Demonstrates the Value of Thermal Simulation

1 June, 2020

Engineers designing modern electronic products face a number of challenges. 

Consumer demands are constantly rising: consumers expect more powerful devices with increased functionality in ever-smaller packages. And this all must be carried out within tight budgets and rapid turnaround times. 

Thermal management is an essential element when ensuring products remain functional and safe to use. But as component-density and miniaturization become more important to satisfy end-user demands, engineers require cooling solutions that are small enough to fit the design, all while providing the optimal level of heat transfer for today’s modern processors. 

"Pin fin" heat sinks are a very popular solution to this problem, and are used in many systems that contain modern electronics. 

Pin Fin Testing

Thales Group — a multinational company that designs and builds electrical systems for the aerospace, defense, transportation and security markets — wanted to investigate how they could further optimize thermal management using pin fin heat sinks.

The group embarked on a study that focused on the optimization of a pin fin heat sink specifically for applications in which the heat sink is "hanging" in the air and natural-convection cooling is the primary heat transfer mechanism of choice. 

This is typically the case for luminaires (i.e. spot and down lights) and IoT devices, in which the volume below the electronic device is used for illumination and sensing, respectively.

A commercially available pin fin heat sink, containing 87 round pins distributed along 5 rings, was analyzed within 6SigmaET

The heat sink was modelled suspended in mid-air in a large computational domain with open boundaries to allow natural convection currents to develop. For meshing, an unstructured Cartesian grid was used with a fine mesh of 892,000 cells, while radiative heat transfer to the ambient environment was also accounted for.

At the center of the baseplate, on the bottom, a uniform dissipating heat source was modelled. 

Removing the Third Ring

The outer ring was found to have the largest contribution to the cooling performance, due to a combination of natural convection and radiation. In total, it was found that 94% of the total heat transfer is governed by the baseplate and the first two outer rings of pin fins.

As the inner rings do not contribute significantly to the total heat transfer, a second numerical study was conducted with the third ring of pin fins removed. 

In this case, the contribution of ring 1 to the total heat transfer increased to 62%, due to slightly better natural convection. Similarly, the contribution of ring 2 increased to 17%. 

Interestingly, without ring 3, 97% of the total heat transfer was governed by the baseplate and the first two outer rings of pin fins.

The result? An adapted heat sink with a lower maximum temperature and better thermal resistance. In fact, by removing the 18 pin fins of ring 3, the performance of the heat sink was improved by 10%. 

Less is More

The results have proven that, when it comes to heat sink designs, less can be more. 

By removing internal pin fins from a pin fin heat sink, the performance
is actually improved for natural-convection cooling. In this case — with a fully optimized design — a 16% gain could be realized compared to a commercially available pin fin heat sink. Removing pins also has the additional benefit of decreasing weight.

Thales Group’s investigations are a perfect demonstration of the value of thermal simulation software, such as 6SigmaET.

By optimizing through thermal simulation, companies like Thales can reduce the weight of their designs — ultimately reducing the cost. At the same time, the use of simulation also helps to limit the number of physical prototypes, allowing complex electronics to be virtually tested in a whole host of rugged environments. This makes it perfect for the aerospace industry, further streaming design projects in terms of both time and costs.

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Blog written by: Matt Evans, Product Engineer

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