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R448A를 적용한 가스인젝션 냉동사이클의 성능특성에 대한 해석적 연구
강유비(Yubi Kang),양원석(Wonseok Yang),조원희(Wonhee Cho),정종호(Jongho Jung),김용찬(Yongchan Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The objective of this study is to analyze and compare the performance of R448A, an alternative refrigerant of R404A used in cold storage, in the FTVI (Flash Tank Vapor Injection) cycle using EES (Engineering Equation Solver). Analysis is carried out in the 1st stage compression cycle and FTVI cycle. The COP and compressor discharge temperature are compared with the variation of the evaporation temperature and the condensation temperature. the R448A shows low COP at the 0℃ and the same COP at -40℃ e and the compressor discharge temperature is higher than that of R448A in all temperature conditions. Performance according to the injection pressure ratio was analyzed in the FTVI cycle and the optimum injection ratio was found to be 0.3.
R449A를 사용한 플래시탱크 가스인젝션 냉동시스템의 성능특성에 대한 실험적 연구
강유비(Yubi Kang),이상헌(Sang Hun Lee),김용찬(Yongchan Kim) 대한설비공학회 2020 설비공학 논문집 Vol.32 No.4
R449A has been adopted as an alternative refrigerant of R404A, because it has lower global warming potential (GWP) than R404A. However, a refrigeration system using R449A shows slightly lower cooling capacity and higher compressor discharge temperature compared with that using R404A. The high compressor discharge temperature can degrade system reliability. A flash tank vapor injection (FTVI) technique can overcome the problem of the lower cooling capacity and higher discharge temperature in the refrigeration system with R449A under severe operating conditions. In this study, the performance characteristics of a FTVI refrigeration system and a conventional refrigeration system were compared in the AHRI 1251 condition. The annual walk-in energy factor (AWEF) of the R449A FTVI refrigeration system was similar to that of the R449A conventional refrigeration system. However, the cooling capacity and compressor reliability of the R449A FTVI refrigeration system were higher than those of the R449A conventional refrigeration system.
김지혁,강유비,강혜진,김승현,송정은,이상일,이섭 한국지역사회건강관리협회 대한건강과학학회 2017 대한건강과학학회지 Vol.14 No.2
PURPOSE : The purpose of this study is how the difference in leg lengths affects the initial body changes. After making an artificial leg length difference for normal people, we will measure the tilt of the spine and the torsion of the pelvis in the body. Based on this, we tried to provide the basic data of correction prescription(shoe lift or heel lift) for the difference of leg length. METHOD : This study was conducted to investigate the effects of leg length differences on the body. After measuring the leg length of the subjects, the leg length difference was given using 1cm, 2cm, 3cm, 4cm, 5cm insole. For adaptation to an artificial leg length difference, each height was stepped for 10 minutes, and measurements were made during the last minute of adaptive gait. We used Formetric as a Measuring tools. RESULT : The subjects who participated in this study were 16 male and 15 female adults in the age group of 20, who were in the K age group. The increase in the insole height resulted in a difference in leg length, And the extent to which it is concerned. CONCLUSION: This study used a spinal structure analyzer (Formetric 4D, Diers Inc, Germany) to investigate the effect of general characteristics, BMI, VAS, leg length, and gender insole height on body changes. According to statistical results, the higher the difference of anthropomorphic leg length, the more influence on pelvic torsion and tilt angle, but it did not affect kyphotic angle and lordotic angle.
R448A를 사용하는 냉동시스템의 내부열교환기 용량 최적화에 대한 해석적 연구
윤일주(Iljoo Yoon),강유비(Yubi Kang),김용찬(Yongchan Kim) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.11
Recently, the role of the refrigeration and air-conditioning industry has become critical as environmental issues become more important. GHG emission and global warming can be prevented by using low GWP refrigerants. In this study, the performance of the cooling system with the internal heat exchanger(IHX) is analyzed using R448A, an alternative refrigerant to R404A, and the capacity of the IHX is optimized. Due to the limit of the discharge temperature, R448A and R404A can have maximum IHX ratio of 12% and 28%, respectively. As a result, the cooling capacity and COP of the refrigeration system using R448A with 12% IHX ratio is shown to increase by 32% and 20%, respectively, compared to the system without IHX.