Recently, film cooling has been continuously studied to increase the efficiency of gas turbines. A turbine inlet temperature increase occurs as a way to improve the efficiency. However, it is essential to improve the cooling performance of the blade surface because of the melting point of the part. In this paper, a side hole shape wherein a general cylinder hole and two auxiliary holes are combined, is proposed to improve the film cooling efficiency, and the blowing ratio was set to 0.4, 0.8, 1.2, and 2.0. When side hole was applied, the vortex interference at the hole entrance occurred less than that of the cylinder hole. That is, the flow rate of the coolant adsorbed to the surface increased to improve the cooling performance. In conclusion, compared to the cylinder hole, the cooling efficiency of the shape to which the side hole was applied was excellent, and in particular, the average area cooling efficiency with spanwisely designed side holes improved by 83%.

Power electronic systems have been widely applied in both industrial and domestic applications in the modern society for controlling and converting electrical energy. Due to their characteristics, such as excellent performance, low cost, high reliability, and low weight and size, power semiconductors, including insulated-gate bipolar transistors (IGBTs) dominate the market of power converters. The technical progress and development trend of IGBT for industrial applications are primarily driven by five aspects influenced by each other to an extent, including operating temperature, efficiency, dimension, reliability, and cost. Liquid cooling systems surpass the air cooling systems by supplying heat transfer coefficient, which is several orders of magnitude higher. Thus, using liquid cooling system enables much higher power densities of power modules and more compact converter solutions.

The high voltage direct current (HVDC) device has been used to transmit electrical power with an advanced technology of semiconductors. The sustainable energy generation technologies of solar power and windmills are demanding that the HVDCs have high performance and reliability. In this regard, the cooling performance of the HVDC becomes a significant research topic because the temperature increase affects the operation of the device. The evaluation system to assess the cooling performance has been developed and is proposed in this paper. The experimental apparatus is presented in detail. Our experiments have shown the accuracy of flow rates, pressure drops, and the temperatures in the desired measurement points. We have successfully developed an evaluation system of the cooling performance of the HVDC device which has 2.48 kW of heat dissipation.