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Heat Transfer Augmentation in a Divergent Duct with Angled Ribs
안수환,이명성 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.1
Heat transfer characteristics in the rectangular divergent duct with parallel angled ribs are experimentally compared with the straight smooth circular duct. The ribs with four different parallel angles ( ¼ 30, 45, 60, and 90) are glued on the duct's two opposite walls as well as on the duct's one sided wall only, respectively. The 0.72-inclined walls are installed at the two opposite walls of the rectangular divergent duct. The test section of 1000mm long has the cross section of 100 『 75mm2 at inlet and 100 『 100mm2 at exit. The ribbed walls are manufactured with a rib height ðeÞ ¼ 10mm and the ratio of rib spacing (p) to height(e) ¼ 10. The main ¯ndings are summarized that the increase in the dimensionless Nusselt number for the flow attack angles can be seen in the order of 90, 30, 60, and 45 at the two opposite ribbed divergent wall ducts, in addition, the average Nusselt number in the divergent rectangular duct with two opposite ribbed walls is somewhat greater than in the ribbed straight cross-sectional rectangular duct.
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안수환,이병걸 한국방재학회 2025 한국방재학회논문집 Vol.25 No.4
본 연구는 해수면상승에 따른 연안지역 재해취약지역의 공간적 특성을 살펴보고, 이를 토대로 관리상 시사점을 도출하여 지역 맞춤형 방재정책 수립 시 기초자료를 제공하는 데 목적이 있다. 이를 위해 선행연구를 바탕으로 물리적, 환경적, 사회적 지표를 수집하여, 재해취약성 평가를 통해 재해취약지역을 식별하였다. 분석 결과, 저지대 및 해안가에 위치한 행정동에서 상대적으로 높은 재해취약성이 나타났으며, 특히 인구 밀도, 노약자 비율, 방재시설 접근성 등의 인문사회적 요인이 물리적 요인과 결합하여 취약성을 증폭시키는 것으로 확인되었다. 본 연구는 정량적 접근을 통해 해수면상승에 따른 공간적 취약성의 구조적 특성을 파악하였으며, 향후 우선 관리지역 설정 및 재해위험도 차등화 대응 전략 수립에 실증적 근거를 제공할 수 있을 것으로 기대된다. This study aims to examine the spatial characteristics of disaster-vulnerable coastal areas affected by sea level rise and derive policy implications for developing region-specific disaster prevention strategies. Based on previous research, physical, environmental, and social indicators were collected to identify vulnerable areas through a disaster vulnerability assessment. The analysis revealed that administrative districts located in low-lying and coastal zones exhibited relatively high levels of vulnerability. In particular, socio-demographic factors such as population density, the proportion of the elderly, and accessibility to disaster prevention facilities were found to exacerbate vulnerability when combined with physical risks. By adopting a quantitative approach, this study clarifies the structural characteristics of spatial vulnerability to sea-level rise and is expected to provide empirical evidence for prioritizing management areas and formulating differentiated disaster risk response strategies.
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Characteristics of Heat Transfer in the Channel with Twisted Tape
안수환,Ho Keun Kang 대한설비공학회 2007 International Journal Of Air-Conditioning and Refr Vol.15 No.3
Heat transfer distributions and friction factors in square channels (3.0×3.0cm) with twisted tape inserts and with twisted tape inserts plus interrupted ribs are respectively investigated. The rib height-to-channel hydraulic diameter ratio, e/Dh, is kept at 0.067 and test section length-to-hydraulic diameter ratio, L/Dh is 30. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. The twisted tape is 0.1mm thick carbon steel sheet with diameter of 2.8cm, length of 90cm, and 2.5 turns. Two heating conditions are investigated for test channels with twisted tape inserts and rib turbulators:(1) electric heat uniformly applied to four side walls of the square duct, and (2) electric heat uniformly applied to two opposite ribbed walls of the square channel. Results show that the twisted tape with interrupted ribs provides a higher overall heat transfer performance over the twisted tape with no ribs.Nomenclature†Corresponding authorTel.: +82-55-640-3125; fax: +82-55-640-3128E-mail address: swahn@gaechuk.gsnu.ac.kr: heat transfer area [2]: hydraulic diameter []: rib []: friction factor: Mass flux []: heat transfer coefficient []: thermal conductivity []: mass flow rate []: Nusselt number, : rib pitch []: heat transfer rate []: Reynolds number, x: distance from entrance []
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유리입자에 의한 순환유동층 수평 관에서의 압력강하와 마찰계수
안수환 경상대학교 농업생명과학연구원 2008 농업생명과학연구 Vol.42 No.1
Generally, the economic concept of optimized design and operating conditions in fluidized bed heat exchangers can hardly be realized. Because the lack of fundamental knowledge about the particle flows, the optimum design of the fluidized bed heat exchanger is rather limited. In the present work, measurements are made on pressure drops and friction factors in the horizontal circular tube with solid particles in the circulating water. Two different solid particles of diameters of 3mm and 4mm are covered. The Reynolds numbers are ranged from 10,000 to 45,000. It is concluded that the friction factors for the particles of 4mm diameter are much higher than those for the particles of 3mm diameter. And at the lower particle concentration, the friction factors are strongly influenced by the fluid velocity rather than the particle concentration; However, the effect of the particle concentration on friction factors is also significantly higher at a higher particle concentration operating condition. 일반적으로 순환유동층 열교환기에서 최적의 운전과 설계에 대한 지식은 아직 잘 알려져 있지 않다. 입자 유동에 관한 기초적 지식이 부족하기 순환유동층 열교환기를 최적 설계하는 데에는 아직 제한적이다. 그러므로 본 연구에서는 순환하는 물속에 고체입자(유리)가 유동하는 수평 원형관에서 압력강하와 마찰계수에 대해 실험적으로 측정한다. 고체입자의 직경은 3 mm와 4 mm를 각각 취급하였고 레이놀즈수의 범위는 10,000에서 45,000이었다. 연구 결과 4 mm 직경의 입자가 3 mm의 입자보다 마찰계수가 더 컸다. 그리고 고체입자의 농도가 낮은 경우에서는 마찰계수는 고체입자의 농도보다 유체속도에 의해서 더 영향이 컸다. 그러나 입자의 농도가 큰 운전조건에서는 고체입자의 농도도 마찰계수에 큰 영향을 주었다.
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