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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>
( Sangkwon Lee ),( Chi-ok Oh ) 한국스포츠정책과학원(구 한국스포츠개발원) 2016 International Journal of Applied Sports Sciences Vol.28 No.1
The cost of attending professional sporting events has been increasing steadily but the median household income has been relatively stagnant over the last three decades. While sport fans have increasingly spent more of their income on experiencing professional sport games, little information is available on a relationship between the costs of attending professional sporting events and sport consumers’ ability to pay and how this relationship has changed over time. Similar to housing affordability, this study proposed the concept of sport affordability, measured with a ratio between per capita income and the income needed to attend a sporting event and examined the degree of changes in the sport affordability index over time. The study results showed that the sport affordability index has become polarized among major league baseball teams. For 21 teams, the study showed that their sport affordability indexes have been deteriorating steadily over time but the trend was different for the other eight franchises. Policy and management implications related to equitable accessibility to sport and recreation events and marketing strategies are discussed.
이상권(Sangkwon Lee),김병수(Byungsoo Kim),박동철(Dongchul Park),정승균(Seunggyoon Jung) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In our previous study, we have developed sound quality index for steady rumbling sound of passenger car. In this paper, we will study sound quality index for transient rumbling noise. The subjective evaluation of rumbling sound can be indicated to objective parameters by sound metrics of psychoacoustics and principal rumble component. And artificial neural network can be estimated complexity and nonlinear characteristics of relation between subjective evaluation and sound metrics. We applied to sound metrics and artificial neural network to development of sound quality index for transient rumbling sound of passenger car.
Investigation on Cryogenic Refrigerator and Cooling Schemes for Long Distance HTS Cable
Jisung Lee,Cheonkyu Lee,Sangkwon Jeong,Jiho Park,Si Dole Hwang,Hyung Suk Yang,Se Yong Jung,Ji Hyun Lim Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>High-temperature superconducting (HTS) cable is one of the most prospective superconducting technologies for its low electric power transmission loss and high power density. One difficulty of practicing this technology is maintaining the HTS cable at a cryogenic temperature approximately at 70 K. The types of cryogenic refrigerators are briefly reviewed to apply in long-distance HTS cables. Recuperative-type refrigerators, such as Brayton and Joule-Thomson (JT) refrigerators, are more appropriate to satisfy the required high cooling power. The theoretical reliability of the newly proposed dual mixed refrigerant (DMR) JT refrigerator is analyzed. The cycle configuration of the DMR JT refrigerator is more complex than that of a Brayton refrigerator; however, the degradation of reliability was not significant. Furthermore, a remote operation apart from the compressor is possible in the JT refrigerator without moving components inside the cold box. This is the most desirable characteristic for long-distance HTS cable cooling. Finally, the advantage of using an oxygen and nitrogen mixture as the circulating coolant is discussed. The number of cooling stations can be reduced in a long-distance HTS cable by lowering the coolant feeding temperature.</P>
Effects of environmental parameters for offshore wind turbine system with jacket support structure
이종선(Lee, Jong-Sun),박현철(Park, Hyun-Chul),김용환(Kim, Yong-Hwan),Shi, Wei,나상권(Na, Sangkwon),이종현(Lee, Jonghyun) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11
This study investigates the effects of Pierson-Moskowitz, Jonswap spectrum that are typical irregular wave spectrums for wind turbine system with jacket support structure. Also various offshore environmental parameters based on korean local condition were used in our study. The loads acting on the system was considered by referring to the Design Load Case from IEC guide line. And improved von Karman model was used as a turbulence model. As a result, various significant wave height and peak spectral period cause noticeable difference of extreme and fatigue loads prediction.
소규모 행정구역의 일단위 농업가뭄 평가를 위한 농업용수 수급 가뭄지수 개발
이상권(Lee, Sangkwon),오국열(Oh, Kukryul),정상만(Jeong, Sangman),정태성(Cheong, Tae Sung) 한국방재학회 2021 한국방재학회논문집 Vol.21 No.2
가뭄은 장기간의 강수량 부족과 수자원 부족으로 인해 발생하는 것으로써 인간과 동물 모두의 생명과 생태계에 큰 영향을 미친다. 특히 농업분야는 식량안보와도 밀접한 연관성이 있어 그 중요성이 크다고 할 수 있다. 전 지구적으로 지구온난화, 도시화 및 산업화로 인해 농업용수 수요는 꾸준히 증가하고 있으며, 한국 또한 기후변화로 인해 증가추세에 있는 농업분야 피해경감을 위해 농업용수 공급원을 꾸준히 개발해오고 있다. 가뭄은 기상학적, 농업, 수문학적, 사회경제학적 가뭄지수를 이용하여 그 심각정도를 평가하는데, 농업가뭄지수는 토양수분과 농작물 마름 정도를 이용하여 가뭄을 평가하고 수문학적 가뭄지수는 저수지, 댐, 하천, 지하수 등 공급 가능한 수자원과 수요를 비교하여 용수 부족량으로 가뭄을 평가하는 방법이다. 그러나 이들 방법들은 생활, 공업, 농업 전체용수의 부족량을 평가함에 따라 상대적으로 민감도가 낮은 농업용수를 과대 혹은 과소평가하는 것으로 나타났다. 따라서 본 연구에서는 농업용저수지, 관개 및 배수, 지하수 시스템과 같은 용수 공급 시스템과 농업용수 수요량을 분석하여 농업가뭄을 평가하는 농업용수 수급 가뭄지수(Agricultural Water Demand and Supply Drought Index, AWDSDI)를 개발하였다. 개발된 가뭄지수의 적용성을 검토하기 위하여 과거 기록을 토대로 가뭄피해가 컸던 2017년 6~8월에 대해 진천군, 창녕군, 장성군 등 3개 군의 32개 읍⋅면에 AWDSDI를 적용하고 농업가뭄을 평가하였다. 적용성 검토결과 AWDSDI는 읍⋅면과 같은 소규모 행정구역의 일단위 농업가뭄을 잘 재현하는 것으로 나타났다. 더불어 개발된 가뭄지수를 검증하기 위하여 AWDSDI와 기존에 개발된 농업가뭄지수 그리고 수문학적 가뭄지수의 평가결과를 함께 비교하였다. 비교 결과 AWDSDI는 기존에 개발된 가뭄지수들보다 3개군 32개 읍⋅면의 가뭄기간 및 가뭄심도를 잘 재현하는 것으로 나타났다. Drought is caused by a long period of lack of rainfall and water resources, and has a great impact on the life and ecosystem of both humans and animals. It is particularly important for the agricultural sector, which is closely related to food security. Global warming, urbanization, and industrialization have led to a gradually increasing demand for agricultural water. In response, Korea has steadily developed its agricultural water sources to reduce rising damage to the agricultural sector due to climate change. The severity of drought is evaluated by using meteorological, agricultural, hydrological, and socioeconomic drought indexes. The agricultural drought index is evaluated using soil moisture and crop dryness, and the hydrological drought index is evaluated based on water shortage by comparing demands with water resources available for supply, such as rivers and groundwater, reservoirs and dams. However, these methods were found to over- or under-estimate the relatively low sensitivity of agricultural water as they assess the shortage of water for life, industry, and agriculture. Therefore, in this study, we developed the Agricultural Water Demand and Supply Drought Index (AWDSDI), which evaluates agricultural drought by analyzing water supply systems such as agricultural reservoirs, pumping stations and drainage, groundwater systems, and demands for agricultural water. In order to review the applicability of the developed drought index, AWDSDI was applied to 32 Eps and Myuns in three cities, including Jincheongun, Changnyeonggun, and Jangseonggun in the period June-August 2017, when drought damage was significant. It was found that AWDSDI reproduced the daily agricultural drought well in small administrative districts such as Eps and Myuns. In addition, in order to verify the developed drought index, the evaluation results of AWDSDI, the previously developed agricultural drought index and the hydrological drought index were compared together. The comparison found that the AWDSDI reproduced the drought period and drought depth in 32 Eps and Myuns in three cities better than previously developed drought indices.