The Tech Blog

Back to Basics: Heat Pipes

Posted under Uncategorized on May 7th, 2023 by Amaldev

Most circuit designers would have used heatsinks in their circuits to dissipate heat generated by Regulators, MOSFETs, Drivers, etc. Heatsinks are used to dissipate heat to the surroundings whereas heat pipes are designed to transfer heat from one region to the other where cooling can take place. It is used in spaces where there is not enough space to have a large area of heatsink right next to the heat source. You would probably have seen them as closed copper-coloured tubes on processor heatsinks or inside laptops.

At their most basic level, heat pipes are simply sealed tubes filled with a liquid that is designed to absorb and transport heat. When one end of the heat pipe is exposed to a heat source, the liquid inside the tube absorbs the heat and evaporates into a gas. This gas then travels down the length of the tube to a cooler area, where it condenses back into a liquid and releases the heat it has absorbed(Via a heat sink or fan or any cooling mechanism). The liquid then flows back to the hot end of the tube by a wick. What makes them extremely good is that they have a very large(at least 10x) thermal conductivity than that of a pure metal block like Copper or Aluminium because the liquid inside can change to vapor and carry heat faster. They rely on evaporation on one side and condensation on the other side. They can also operate over long distances, allowing heat to be transferred away from critical components to a remote location.

Heatpipes do come with a drawback, since it relies on fluid moving from a colder section to a hotter section in the liquid phase via wicking, their performance of heat transfer drops significantly if it’s made to work against gravity. If you see the charts you will find that how heat transfer properties fall as you change the orientation angles. So, when using heatpipes, it’s important to consider the orientation of the product to maximize heat transfer

For more Recommended Reading: Wakefield Thermal Design guide, ACT Cooling & Celsiainc website

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Back to Basics: Solid vs MultiStranded vs Litz Wires

Posted under Back to Basics, Educational, Technology on April 30th, 2023 by Amaldev

Let’s talk wires! When it comes to building systems, wiring between subsystems is often overlooked. The type of wire you use can significantly impact performance. Everyone knows what solid wires are. As the name suggests, it’s a wire made of a single-core material. It’s great for passing DC current with low resistance. However, it struggles with higher-frequency currents due to skin depth(Refer to Older Posts) limitations. Solid cable does not fully utilize its entire thickness to transmit current.

The multistranded wire is made up of multiple strands of smaller gauge wires that are twisted together. It is more flexible than a solid wire. Where multi-stranded wires differ from Litz wires is that Litz wires have a small insulator in between each of the wire strands. So each strand is not shorted each other as in a multistranded cable. From the basics of Skin depth, we know that current likes to travel on the outer surface for higher frequencies. Multistranded wires do perform better with more area utilization (compared to solid wires) but they can still act as an almost solid wire since everything internally is shorted. Litz wire on the other hand ensures there is individual insulation and because of that, Skin depth is large, and hence current passes through the entire cross-section of the tiny wires. This is usually why Litz wires are usually the preferred choice in high-frequency applications such as transformers, inductors, induction coils, and high-frequency power supplies. While Litz wires are more expensive and have enamel insulation that can be easily scrapped or sanded off, they are worth considering for high-frequency applications.

Experienced professionals in the industry who use Litz wires, feel free to share any other benefits you have noticed.

So, next time you’re choosing wires, consider the application carefully and choose the wire type that will give you the best performance.

Fun fact: Litz wire gets its name from the German word “litzendraht,” which means braided or stranded wire.

#BacktoBasics #Wire #Current #Electronics #Power #transmission #Skindepth

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