• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1270-1275
• /
• 2004

Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.

• 설비공학논문집
• /
• 제16권6호
• /
• pp.589-598
• /
• 2004

Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

• 설비공학논문집
• /
• 제17권7호
• /
• pp.649-658
• /
• 2005

Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2005년도 동계학술발표대회 논문집
• /
• pp.249-255
• /
• 2005

Flow condensation heat transfer coefficients(HTCs) of R22, R4IO, Propane(R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53 m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of 0.1 ${\sim}$ 0.9 at mass flux of $200{\sim}400$ $kg/m^2s$ and heat flux of $7.3{\sim}7.7$ $kW/m^2$ at the saturation temperature of $4^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within 25% deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than 20% for all data.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.96-103
• /
• 2000

In this study, evaporation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the following range of variables ; vapor quality $(0.1{\sim}0.9)$, mass flux$(100{\sim}600kg/m^2s)$ and heat flux$(5{\sim}15kW/m^2)$. The micro-tin tube showed higher heat transfer coefficients compared with those of the smooth tube. Results showed that, for the smooth tube, the effects of mass flux, quality and heat flux were not prominent, and existing correlations overpredicted the data. For the micro-fin tube at low quality, the heat transfer coefficient increased as heat flux increased. However, the trend was reversed at high quality Kandlikar's correlation predicted the low mass flux data, and Shah's correlation predicted the high mass flux data. The heat transfer coefficient of the micro fin tube was approximately two times larger than that of the plain tube. New correlation was developed based on present data.

• 설비공학논문집
• /
• 제14권7호
• /
• pp.575-583
• /
• 2002

In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-410A, and the results are compared with those of R-22. Two internal geometries were tested; one with a smooth inner surface and the other with micro-fins. Data are presented for the following range of variables; vapor quality (0.1~0.9), mass flux (200~600 kg/$m^2$s) and heat flux (5~15 ㎾/$m^2$). Results show that the effect of surface tension drainage on the fin surface is more pronounced for R-22 than R-410A. The smaller Weber number for R-22 may be responsible. For the smooth tube, the heat transfer coefficient of R-410A is slightly larger than that of R-22. For the micro-fin tube, however, the reverse is true. Possible reasoning is provided considering the physical properties of the refrigerants. For the smooth tube, a correlation of Akers et at. type predicts the data reasonably well. For the micro-fin tube, the Yang and Webb model was modified to correlate the present data.

• 한국인터넷방송통신학회논문지
• /
• 제18권2호
• /
• pp.11-17
• /
• 2018

본 연구는 국내에서 제작된 인기 있는 YouTube 채널들의 특징들을 탐구한다. 과학과 기술이 발달함에 따라, 일반인들도 동영상을 촬영한 뒤, 자신의 영상을 업로드를 할 수 있는 상황으로 변화였다. 전 세계적으로 인기 있는 동영상 제공 서비스 사이트 YouTube에서, 국내에서 인기 높은 YouTube 채널들의 특징들을 조사한다. 구체적으로, 1) 구독자 2) 시청 항목의 인기 채널 100개를 조사 한 뒤, 1) 가장 높은 구독자/시청 숫자 2) 비디오 개수 3) 시청/구독자 숫자 4) 장르 5) 제작자로 나누어 탐구한다. 이를 통해, 한국에서 인기 있는 YouTube 채널들의 다각적인 모습뿐만 아니라 한국 멀티채널네트워크(MCN) 시장을 전망한다.

• 대한기계학회논문집B
• /
• 제24권2호
• /
• pp.241-250
• /
• 2000

In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality($0.1{\sim}0.9$), mass flux($200{\sim}600kg/m^2s$) and heat flux($5{\sim}15kW/m^2$). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제11권3호
• /
• pp.114-124
• /
• 2003

In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-410A, and the results are compared with those of R-22. The flat tubes have two internal geometries; one with smooth inner surface and the other with micro-fins. Data are presented for the following range of variables; vapor Quality (0.1∼0.9), mass flux (200∼600 kg/$m^2$s) and heat flux (5∼15 kW/$m^2$). Results show that the effect of surface tension drainage on the fin surface is more pronounced for R-22 than R-410A. The smaller Weber number of R-22 may be responsible. For the smooth tube, the heat transfer coefficient of R-410A is slightly larger than that of R-22. For the micro-fin tube, however, the trend is reversed. Possible reason is provided considering physical properties of the refrigerants. For the smooth tube, Webb's correlation predicts the data reasonably well. For the micro-fin tube, the Yang and Webb model was modified to correlate the present data. The modified model adequately predicts the data.

• International Journal of Internet, Broadcasting and Communication
• /
• 제13권3호
• /
• pp.12-16
• /
• 2021

Soccer is one of the popular sports globally, and South Korea is no exception; the professional domestic soccer tournament has been held in South Korea since 1983. The national soccer team in South Korea has shown outstanding performances, hosting the 2002 World Cup and achieving a bronze medal at the London 2012 Olympic Games and second place at the 2019 U-20 World Cup. In addition, one of the South Korean soccer players, Heung-min Son, has played a remarkable role in the English Premier League. Like other global soccer clubs, South Korean domestic soccer clubs create and manage their own YouTube channel to interact with fans and keep them updated. In this study, we explore how and why Seoul E-Land Football Club (SEFC) utilizes its YouTube channel. SEFC is distinctive in that they are playing at the second division, their home ground is based in Seoul, and they are sponsored by a company run on Christian values. We analyze one of the soccer club's YouTube channels multi-dimensionally and discover the roles of YouTube.