On enhancing the performance of elbow thermosyphon heat pipes

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Mersen Canada Inc., located in Mississauga, ON, is a global designer, manufacturer, and provider of thermal management solutions for high power electrical systems. These include proprietary long-finned heat sinks, liquid cooled systems and heat pipe systems. Mersen Canada is strongly committed to developing new two-phase heat pipe systems and, to that end, they recently enhanced and expanded their test facilities at Mississauga. This project focusses on improving the performance of elbow thermosyphon heat pipes that Mersen Canada currently manufactures for, and uses in a number of thermal management applications. In this system, heat generated by losses in electronic modules is transported from a heat spreader to large, near-horizontal extended fin surfaces that are cooled by ram air-flow or natural convection. Thermosyphons are passive two phase heat transport devices; evaporating a working fluid in heated regions and condensing it in cooled regions, to transfer the heat with a small thermal resistance. The elbow thermosyphons considered here differ from most thermosyphons in that they are bent to pass along the heated surface to provide longer evaporator sections to meet the heat flux requirements. Mersen Canada is forced to deal with bent thermosyphons due to the packaging constraints of the application. The working fluid is water to meet environmental constraints. There is a need to improve the performance of the elbow thermosyphons to be competitive in markets with warmer climates, and to compete with more expensive cooling system designs, such as liquid cooling. Experiments will be performed to determine methods of enhancement that will include: inclining the evaporator section, changing the interior surface to a wick structure, and doping the working fluid with nanoparticles. These have been shown to reduce the thermal resistance of straight thermosyphons. An improvement in the performance of elbow thermosyphons will lead to new opportunities and markets for Mersen, which a resultant increase in sales and larger manufacturing footprint in Ontario.