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Design of mixed refrigerant Joule-Thomson refrigeration system for semiconductor etching process
Cheonkyu Lee(이천규),Seon-Chang Kim(김선창) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
A mixed refrigerant(MR) Joule-Thomson(J-T) refrigeration system for –100℃ temperature was designed to be applied to the semiconductor etching process. 2-stage cascade type MR J-T refrigerator and 3-stage cascade refrigeration system are analyzed to figure out the coefficient of performance (COP). Working fluids of the MR J-T refrigerator are mixture of argon(Ar), tetrafluoromethane(R14), trifluoromethane(R23) and Octafluoropropane(R218). The design of experiment for mixture is conducted to optimize the mixture composition of the refrigeration system. The working fluid of the precooling system of entire refrigeration systems (2-stage cascade type and 3-stage cascade) is utilized low global warming potential (Low GWP) refrigerant. Maximum COP of the refrigeration system is obtained as 0.3013. The detailed COP variations according to the mixture composition and optimal composition of the MR J-T refrigeration system are described in this study.
Investigation of ejector-equipped Joule–Thomson refrigerator operating below 77 K
Lee, Jisung,Lee, Cheonkyu,Baek, Seungwhan,Jeong, Sangkwon Elsevier 2017 International Journal of Refrigeration Vol.78 No.-
<P><B>Abstract</B></P> <P>The lowest attainable refrigeration temperature of a nitrogen based Joule–Thomson refrigerator is generally limited to 77 K since the compressor suction pressure is usually higher than atmospheric pressure. The Joule–Thomson process with an ejector is proposed to achieve a refrigeration temperature as low as 68 K by adjusting the evaporation pressure down to 28 kPa and boosting the return stream pressure up to 147 kPa. A one-dimensional numerical model is developed to predict the performance of the ejector at cryogenic temperature, and its accuracy is compared with experimental data. The analysis results show that the addition of the ejector in the Joule–Thomson refrigeration cycle increases up to 5 times the overall efficiency, where the maximum achievable COP and exergy efficiency are 0.0195 and 6.65%, respectively. Other featured advantages of the proposed Joule–Thomson refrigeration cycle with ejector are the simplicity of cycle, minimization of mechanical moving components, cost effectiveness, and high reliability compared to other cryogenic refrigeration methods using pumps or cold compressors in Joule–Thomson cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cryogenic Joule–Thomson refrigerator with an ejector is proposed. </LI> <LI> The ejector JT refrigerator is proposed to achieve 68 K at 28 kPa. </LI> <LI> A numerical model is developed to predict performance of ejector. </LI> <LI> Analysis shows that the COP and efficiency are increased in the proposed process. </LI> </UL> </P>
Cheonkyu Lee,고지운,Hyung Yong Ji,Seon-Chang Kim 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
In the supercritical organic Rankine cycle, the process of absorbing heat from a heat source occurs 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 a crucial component of this cycle. In this study, the correlation of the Nusselt number and Darcy’s friction factor was proposed, according to the experimental result of the heat transfer and pressure drop of the supercritical R1234ze(E) for the temperature ranges below and above the pseudo-critical temperature. Correlations of the Nusselt number and Darcy's friction factor agree with the experimental results within ±20 %. Supercritical heat exchangers were designed and tested using the proposed correlations. The developed supercritical heat exchanger satisfied the condition within a -0.5 % margin of error, based on the heat exchange rate between the design and experimental results.
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.