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태양광발전 전력변환장치용 GaN-FET의 방열효율 향상을 위한 PCB 방열구조 열해석
이천규(Lee Cheonkyu),정효재(Jeong Hyo Jae) 한국태양에너지학회 2022 한국태양에너지학회 논문집 Vol.42 No.6
In 2021, the solar power generation capacity of South Korea was 14.6 GW, accounting for 71% of the total renewable energy generation capacity. The market for photovoltaic power conversion devices with high efficiency and power density is expanding rapidly in the country. Gallium Nitride (GaN), a compound semiconductor with a wide band gap, can be used under high voltage and current compared to silicon materials, resulting in its wide use in photovoltaic power conversion devices. Excellent heat dissipation performance of GaN-based devices should be achieved due to their significantly high power and efficiency. In this study, the heat dissipation characteristics of a PCB with FR4 (Flame Retardant 4) material composed of various heat dissipation structures for the effective heat dissipation of GaN-FETs for power conversion systems applicable to a 3 kW solar power generation system were investigated using thermal analysis. Part of the heat generated from the GaN-FET was directly dissipated on its surfaces to the external air, and the other part was transferred to the PCB through conduction and then discharged to the external air through convection on the surfaces of the PCB package. Via holes were considered to improve the heat transfer rate of the PCB in the thickness direction, and a heat sink was applied to expand the heat transfer area. In this study, the heat dissipation characteristics were investigated based on four types of heat dissipation structures of the PCB using the ANSYS transient thermal analysis program. The effect of via holes exposed to external air were analyzed using two types of heat dissipation structures. In addition, two other types of heat dissipation structures were analyzed to compare the top and top/bottom cooling of the PCB package. It was observed that the efficiencies of heat dissipation of the via holes that were unexposed to external air and in both the top and bottom cooling cases were more advantageous than that of the exposed holes and the top cooling case, respectively.
초임계 영역에서 R1234ze(E)의 대류 열전달 및 압력 강하 특성에 대한 실험적 연구
이천규(Cheonkyu Lee),김선창(Seon-Chang Kim) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.3
초임계 유기 랭킨 사이클은 열원으로부터 열을 흡수하는 과정이 초임계 영역에서 일어나며, 초임계 영역에서 열원과 작동 유체의 열교환을 담당하는 초임계 열교환기는 초임계 유기 랭킨 사이클에서 매우 중요한 요소기기이다. 초임계 영역에서는 유사 임계 온도를 기준으로 작동 유체의 열역학적 물성치가 급변하는 특성이 있다. 따라서 초임계 열교환기의 설계을 위해서는 유사 임계 온도를 기준으로 전후의 온도 구간에 대한 대류 열전달 계수를 각각 구하여야 한다. 본 연구에서는 초임계 유기 랭킨 사이클의 작동 유체로 R1234ze(E)를 사용하였으며, 초임계 영역의 유사 임계 온도 이하 온도 구간에서의 대류 열전달 계수 및 압력 강하를 실험적으로 측정하였다. 또한 실험적 Nusselt 수 및 마찰 계수에 관한 상관식을 제안하였으며, 이 상관식들은 실험 결과와 각각 ±20% 및 ±10% 이내에서 잘 일치하였다. In the supercritical organic Rankine cycle, the process of absorbing heat from a heat source takes place in the supercritical region. The supercritical heat exchanger, which is responsible for heat exchange between the heat source and working fluid in the supercritical region, is an important component of this cycle. The thermodynamic properties of the working fluid change rapidly based on the pseudo-critical temperature in the supercritical region. Therefore, for the design of a supercritical heat exchanger, the convective heat transfer coefficients should be obtained differently based on the pseudo-critical temperature. In this study, R1234ze(E) was used as the working fluid of the supercritical organic Rankine cycle, and the convective heat transfer coefficient and pressure drop were measured experimentally in the temperature range below the pseudo-critical temperature. In addition, correlations of the Nusselt number and Darcy"s friction factor were proposed, and these correlations agree with the experimental results within ±20 % and ±10 %, respectively.