Direct cooling of a planar magnetic converter using dielectric liquid forced convection enabled by additive manufacturing

Abstract

Power densification of magnetic converters has encountered a fundamental challenge due to the inability to effectively remove heat produced by power losses. State-of-the-art thermal management technologies for planar printed circuit board (PCB) transformers are limited by the inability to substantially improve the overall thermal conductance from the transformer to the cold plate. Furthermore, a lack of thermal management technologies capable of reducing temperature gradients in these devices exists. Direct liquid cooling reduces the number of thermal resistances from hot spot to coolant, resulting in lower maximum temperatures and reduced thermal gradients. Here, we study the thermal-hydraulic performance of a PCB planar transformer cooled using a polymer additively manufactured (AM) housing and single-phase internal flow with Novec 7300 and pure ethylene glycol. Computational fluid dynamics simulations were used to identify hot spots, quantify temperature gradients, and characterize pressure drop. Experiments in a custom-made setup quantified the maximum temperature and pressure drop with different flow rates (0.4–4 LPM) of Novec 7300 and ethylene glycol. Both working fluids showed better thermal-hydraulic performance when compared to results found in literature which implements cold-plates. Analysis reveals that selection between both fluids is guided by flow rate, pressure drop and pumping power, such that if low pressure drop is a priority, Novec 7300 is a better choice, and if low pumping power and flow rate are a priority, ethylene glycol is better. Our results show that direct liquid cooling can reduce thermal resistance by up to 80% using an 80% lower pressure drop when compared to a cold-plate benchmark. As a result, the developed AM-enabled thermal management technology can potentially improve the reliability of the converter, provide an alternative for high temperature heat recovery, and facilitate further converter power densification.