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Branching of two-phase flow from a vertical header to horizontal parallel channels
이준경 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6
The objective of the present experimental work is to investigate the two-phase flow distribution from a vertical main to parallel horizontal branches. Both the main and the branches have rectangular cross-sections simulating the header and the channels of the compact heat exchangers for air-conditioning systems. The cross section of the main is 8 mm × 8 mm while that of the parallel branches is 8 mm × 1 mm. Here, the second (downstream) junction was taken as the reference. The effect of the distance between the branches was mainly examined by changing it from 9 mm to 49 mm for the given flow conditions at the inlet of the downstream junction. Air and water were used as the test fluids. The superficial velocity ranges of air and water at the test section inlet were 13.2 – 21.4 m/s and 0.08 – 0.28 m/s, respectively. When the branch spacing becomes smaller, the fraction of liquid separation through the downstream branch decreases. The trend remains the same over the entire range of the present experiment, i.e., for different values of quality and the mass flow rate at the inlet of the downstream junction. Based on the correlation for single T-junctions, a modified correlation was proposed to take into account the effect of the branch distance in predicting the fraction of liquid separation. The correlation represents the experimental results within the accuracy of ±15 %.
소방보호복 소재의 공기간극이 열보호 성능에 미치는 영향
이준경,권정숙 한국화재소방학회 2014 한국화재소방학회논문지 Vol.28 No.4
To ensure adequate protection from the risk of burns, fire fighter’s turnout has a composite of more than three componentsand air gaps between layers of materials. During the flame exposure, radiation and convection heat transfer occursin the air gap, thus the air gap acts as a thermal resistance with non-linear characteristics. Therefore, in this study, theexperiments were performed to identify the effect of various air gap width (0~7 mm) on the thermal protective performanceof fire fighter’s clothing. The temperatures on each layer and RPP (Radiant Protective Performance, the mosteffective index representing the thermal protective performance) were measured with various incident radiant heat fluxes. The temperature at the rear surface of the garment decreased and RPP increased with increasing air gap width because thethermal resistance increased. Especially, it could be found that RPP value and air gap width has almost linear relation forthe constant incident heat flux conditions. Thus relatively simple RPP predictive equation was suggested for various incidentheat flux and air gap conditions. 소방보호복은 고열유속에 의한 화상방지를 위해 3층 이상의 복합소재로 구성되어 있으며, 각 소재 사이는 공기 간극이존재한다. 화재에 의한 고열유속 노출 시 공기 간극 내에서의 열전달은 대류와 복사에 의해 주로 발생하며, 그로 인해간극의 크기에 따라서 비선형 특징의 열 저항 크기를 갖게 된다. 그러므로 본 연구에서는 보호복 소재 사이의 여러 가지 공기 간극(0~7 mm)에 대한 보호복의 열 보호성능을 자세히 파악하기 위한 실험을 수행하였다. 복사 열 유속 입사시에 시간에 따른 각 소재의 온도 변화뿐만 아니라, 열 보호성능을 가장 효과적으로 나타낼 수 있는 지표(RadiantProtective Performance, RPP) 값의 공기간극에 대한 변화 특성을 파악하였다. 공기간극이 증가할수록 단열효과가 커짐으로 인해 후면의 온도는 낮아지고, RPP는 커짐을 확인할 수 있었다. 특히 일정 열유속 조건에서 공기간극에 대한RPP 값은 선형적인 특성을 나타내었고, 그러한 결과를 바탕으로 다양한 입사 열유속 및 공기 간극 조건에 대해 비교적간단한 형태의 RPP 지표 예측 식을 제안하였고, 좋은 예측 결과를 얻을 수 있었다.
Study on Pressure drop characteristics in HTS cable core with two flow passages
이준경,김석호,김해준,조전욱 한국초전도.저온공학회 2008 한국초전도저온공학회논문지 Vol.10 No.4
The main objective of this study is to identify the pressure drop characteristics of coolant flow passages of 154kV/1GVA High Temperature Superconducting (HTS) power cable, experimentally. The passages were consisted of two parts, the one is the circular path with spiral ribs in the core to cool the cable conductor layer and the other is annular path with spirally corrugated outer wall to cool the shield layer. Thus the experiments to acquire the pressure drop data were performed with two types of circular spiral tubes and eight types of the concentric annuli in various range of Reynolds number. The pressure drops in the core tubes and the annuli were much higher than those in the tubes with smooth surface. Therefore, modified correlations to present the experimental results in each flow passage were suggested.
이준경,김정구 Academy of Asian Business (AAB) 2023 Academy of Asian Business Review Vol.9 No.1
Performing arts satisfaction plays a crucial role in influencing advocacy and life satisfaction among individuals. This study examines the influence of artistic products, theater facilities, and social enjoyment on performing arts satisfaction and the relationship between performing arts satisfaction, performing arts advocacy, and life satisfaction among Asian performing arts attendees. The findings reveal that performing arts satisfaction is significantly influenced by artistic product and social enjoyment, and it, in turn, significantly impacts performing arts advocacy and life satisfaction. Consistent with previous research, artistic product is the most influential factor in shaping performing arts satisfaction. Specifically, aspects such as music, actor performance, and storyline demonstrate high average ratings, underscoring their importance. Additionally, the study uncovers an interesting gender difference in the significance of social enjoyment, with men attending performances for romantic dates and women attending with friends. However, theater facility enjoyment does not exhibit a significant effect, supporting previous research emphasizing the relative insignificance of facility factors compared to performance factors. Furthermore, this study reveals that performing arts satisfaction positively influences both performing arts advocacy and life satisfaction, highlighting the broader significance of performing arts as an experience that enhances individuals' overall satisfaction and happiness beyond monetary gains. In conclusion, the study emphasizes the importance of performing arts satisfaction in influencing performing arts advocacy and individuals' life satisfaction. It highlights the significance of artistic product and social factors, with recommendations for performing arts organizations to prioritize audience satisfaction, strives for artistic excellence, and foster social engagement among attendees. These findings provide valuable insights for enhancing audience satisfaction, fostering long-term advocacy, and promoting the transformative power of performing arts.
연료전지 자동차용 R-134a 전동식 히트펌프 시스템 개발에 관한 연구
이준경,이동혁,원종필,Lee, Jun-Kyoung,Lee, Dong-Hyuk,Won, Jong-Phil 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.3
The main objective of this work is to investigate the characteristics of a heat pump system for fuel cell electric vehicle (FCEV). The present heat pump system adopts an electrically driven compressor running with R134a and uses the heat from the fuel cell stack as the heat source for the exterior heat exchanger. The experimental work has been done with various operating conditions such as different compressor speeds, fuel cell stack coolant temperatures and flow rates. The heating capacity was measured to be from 4 to 10 kW at $-20^{\circ}C$ ambient temperature, and the outlet temperature of interior heat exchanger was up to $70^{\circ}C$. After 30 seconds from start-up, the system reached a steady state and the heating capacity of 6.8 kW was acquired, and after 90 seconds, the air outlet temperature of interior heat exchanger became $35^{\circ}C$.