Abstract
Due to the rapid increase of electric vehicles in the market, a corresponding significant increase in fast chargers will be needed. However, expanding the adoption of fast chargers such as direct current fast chargers is challenging with the current grid infrastructure. Medium-voltage (MV) electronics are an essential component in grid-tied applications. However, thermal management of such components presents a barrier to pushing the boundaries of high-power density, while maintaining high efficiency and reliability. Thermal management is further complicated by the need to maintain sufficient voltage isolation. Under a Small Business Innovative Research (SBIR) Phase I program funded by the U.S. Department of Energy (DOE), Advanced Cooling Technologies, Inc. (ACT), in collaboration with the University of Colorado, Boulder (UC Boulder) developed innovative ceramic Pulsating Heat Pipes (PHP)s, which significantly improved the thermal management and provided voltage isolation. Different flat ceramic PHPs were fabricated for the lab-scale testing. The thermal performance and voltage isolation were evaluated through both experimental testing and numerical modeling. The effect of different parameters, such as the fill ratio, gravity-aided and against-gravity orientations, and heat input, on the thermal performance of the ceramic PHP, was investigated. It was found that at the optimal fill ratio, a thermal resistance reduction of 41%–67% was achieved for different gravity-aided orientations (0–90°) when compared to the uncharged ceramic PHP (i.e., the ceramic PHP without fluid in it). The ceramic PHP was able to efficiently transport up to 6 W/in2 with a thermal resistance reduction of 58% at the horizontal position. The voltage isolation testing showed that the ceramic PHP can provide electrical insulation when exposed to a voltage of 28 kV. In addition, the effect of different working fluids and fill ratios, on the voltage isolation capability of the ceramic PHP, was investigated.
