The development of power electronics continuously increases their power density and therefore creates challenges for their cooling. Conventional cooling methods, such as heatsinks, are no longer able to cope with the cooling of high heat densities, and therefore, new cooling methods are needed. Two-phase compact thermosyphon (COTHEX) cooling allows the cooling of higher heat densities without having to resort to using pumps. The standard COTHEX technology, however, cannot replace heatsinks due to their structure because it does not match with the cuboid shape of a heatsink. This thesis focuses on designing a thermosyphon concept for power electronics cooling that can replace a heatsink without the need to redesign the products in which they are installed. In this thesis, three thermosyphon based cooling elements were designed, and their structures were optimized to provide as effective cooling as possible with thermal simulation. The thermal performances of the optimized elements and a conventional heatsink of same size were then compared to determine the solution which most effectively transfers heat. The best thermosyphon cooling method was selected, and its features were studied in more detail. The most suitable thermosyphon cooling element substantially improved the cooling of the power electronic device, semiconductor, compared to a conventional heatsink of the same size.The selected thermosyphon construction was able to cool more effectively than the conventional heatsink at higher heat loads, higher surrounding temperatures and with lower air flows. The construction generates lower pressure drop and therefore allows higher air flow rates pass the finned structure of the cooling element. The coolant circulation enables stable heat distribution to the whole area of the baseplate in which the semiconductor is attached. Thus, thermosyphon technology provides heat transfer at the baseplate at a constant temperature, which offers many benefits. For example, even temperature distribution has a positive effect on the aging of semiconductor chips.This thesis developed a new thermosyphon type and analysed its thermal performance. The new thermosyphon gave such positive results that it is highly recommended to replace conventional heatsinks with thermosyphon technology in power electronics cooling.
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