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Hojin Kang,Yongjae Kim,Junhyun Kim,Heeyeop Chae 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
High selective etching process precision control is required in semiconductor devices. Perfluorocarbon compounds have intrinsic global warming issue. In this work, reactive ion etching process was conducted for SiO<sub>2</sub> and a-C in a dual frequency superimposed capacitively coupled plasmas (DFS-CCPs) reactor with C<sub>4</sub>H<sub>3</sub>F<sub>7</sub>O ether and alcohol plasmas. The etch rate and radical density showed that ether was higher than alcohol. Selectivity was superior when the low frequency power ratio was higher than high frequency power ratio.
Atomic layer etching of SiO₂ with low-global warming potential C₄H₃F₇O isomers
Yongjae Kim,Yebin Lee,Seonghyeon Lee,Heeyeop Chae 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
Atomic layer control of semiconductor processing is essential as critical dimensions are reduced below the 10nm scale. [1,2,3] In this work, cyclic plasma atomic layer etching process was conducted for SiO<sub>2</sub> with surface modification in an inductively coupled plasma (ICP) reactor with fluoroether plasmas. Etch rate were compared at various conditions of precursor, reactive gases, and ion energy. High etching selectivity of SiO<sub>2</sub>/Si was obtained with fluoroether precursor having low Fls/Cls ratio and the higher carbon on surface is attributed to the lower Si etch rate.
김준성,김도엽,김유택 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7
The combined use of generation and propulsion gas turbines and steam turbines is efficient and can meet the environmental regulations. In this study, the thermodynamic performance of waste heat recovery systems of a marine gas turbine was analyzed. These systems combine the steam Rankine cycle and the organic Rankine cycle to form a dual-loop cycle. Working fluids R32, R134a, R152a and R1234yf, that are low-global warming potential, were selected for the organic Rankine cycle. All of the working fluids exhibited better performance than for the single-loop cycle, and R134a exhibited the greatest efficiency with energy and exergy efficiencies of 29.50 % and 45.58 %, respectively. The most important components contributing to the exergy destruction of the cycle were the heat exchangers. Therefore, it is essential to select the optimum heat exchanger as well as the working fluid in the waste heat recovery system for marine gas turbines.
Gang Li 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.11
To quicken the process for high global warming potential (GWP) working fluid replacement for organic Rankine cycle (ORC) systems, a thermo-economic evaluation of low GWP fluid R1233zd(E) as an R245fa alternative has been performed in comparison with other natural fluids n-Pentane, Isopentane, and Isobutane for geothermal applications. The heat source water mass flow rate remains constant and 5K pinch point is set for both evaporator side and condenser side. All working fluids have a close net thermal efficiency within 2%. Increasing the heat source from 120 oC to 160 oC gives a more than 20% efficiency rise. The low critical temperature of Isobutane limits its application for 160 oC heat source. R1233zd(E) displays a close mass flow rate (within 2%) from R245fa and others exhibit more than 40% flow rate reduction. The component level performance has also been investigated in this study. All alternatives exhibit a lower evaporator side (evaporator and preheater) heat transfer area than baseline R245fa, and a slightly higher condenser side (condenser and desuperheater) heat transfer area. For turbine performance, R245fa displays the highest volume flow ratio, indicating a significant change of the rotor blade height should be made between the inlet and outlet point for the expansion process. R1233zd(E) displays ~10% increase for turbine size parameter from baseline, n-Pentane shows ~22% rise, Isopentane exhibits ~11% rise, while Isobutane presents 32% decrease, respectively. In general, R1233zd(E) only exhibits ~2.3% higher specific investment cost than R245fa, while n-Pentane and Isopentane exhibit more than 15% cost rise. Thus, from the thermo-economic scale with an extended application range, R1233zd(E) exhibits a better overall performance index when compared with other R245fa alternatives and can be serviced as promising candidate to replace R245fa.
소형 냉각시스템에서의 R-436b 냉매 적용에 관한 연구
진병주(Byoung Ju Jin),고정수(Jung Su Koh),오주철(Ju Chul Oh),이재호(Jae Ho Lee) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6
This study analyzes the performance and feasibility of alterative refrigerant R-436b using on the small sized cooling system. Environmental friendly refrigerant R-436b was used current cooling system for test. And systems were operating under actual using conditions by costumers. Until the systems were recovered, they were operating cooling system and any changes of their parts. We are analyzed refrigerant component ratio, cooling performance and inspected the compressor parts. After the system was installed, cooling performance appears to be almost equivalent level to the initial system and its parts still remained in good condition. Considering these results, it is deemed possible to apply environmental friendly refrigerant R-436b to the current small sized cooling system. The results of these studies are used as the basic performance data for the development of environmental friendly refrigerants.