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김동억,박노복,홍순중,강동현,우영회,이종원,안율균,한신희,Dong Eok, Kim,Nou Bog, Park,Sun Jung, Hong,Dong Hyeon, Kang,Young Hoe, Woo,Jong Won, Lee,Yul Kyun, Ahn,Shin Hee, Han 국립한국농수산대학교 교육개발센터 2022 현장농업연구지 = Journal of practical agricultural resear Vol.24 No.4
Growing agricultural products in greenhouses controlled by creating suitable climatic conditions and root zone of crop has been an important research and application subject. Appropriate environmental conditions in greenhouse are necessary for optimum plant growth improved crop yields. This study aimed to establish web-based remote monitoring system which monitors crops growth environment and status of crop on a real-time basis by applying to greenhouses IT technology connecting greenhouse equipment such as temperature sensors, soil sensors, crop sensors and camera. The measuring items were air temperature, relative humidity, solar radiation, CO<sub>2</sub> concentration, EC and pH of nutrient solution, medium temperature, EC of medium, water content of medium, leaf temperature, sap flow, stem diameter, fruit diameter, etc. The developed greenhouse monitoring system was composed of the network system, the data collecting device with sensors, and cameras. Remote monitoring system was implemented in a server/client environment. Information on greenhouse environment and crops is stored in a database. Items on growth and environment is extracted from stored information, could be compared and analyzed. So, A integrated monitoring system for smart greenhouse would be use in application practice and understanding the environment and crop growth for smart greenhouse management. sap flow, stem diameter and pant-water relations
초임계 이산화탄소의 수직 상향 유동에서의 관내 열전달에 관한 실험적 연구
김동억(Dong Eok Kim) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.7
초임계 CO₂의 수직상향유동에서의 난류열전달에 관한 실험적연구가 내경 4.5 mm 의 원형관에서 수행되었다. 실험범위는 유체평균온도 29 - 115 ℃, 압력 74.6 - 102.6 bar, 국부 벽면 열유속 38 - 234 kW/m² 그리고 질량유속 208 - 874 kg/m²였다. 중간정도의 벽면 열유속 및 낮은 질량유속에서 벽면온도는 확연한 최대점을 나타냈다. 열전달에 대한 부력 및 유동가속의 영향을 살펴보기 위하여 실험 및 참조상관식(Kranoshchekov and Protopopov<SUP>(12)</SUP>)에서 획득된 Nusselt 수의 비를 부력 및 유동가속을 나타내는 변수인 Bo<SUP>*</SUP> 및 q<SUP>+</SUP>를 이용하여 분석하였다. 이 분석을 통해 유동가속 변수인 q<SUP>+</SUP>는 실험에서의 열전달 현상을 적절히 표현할 수 있는 변수라는 것을 확인할 수 있었다. 마지막으로 초임계 유체의 수직상향 유동에서의 새로운 열전달 상관식이 개발되었으며, 이 상관식은 ±30 %의 오차범위에서 실험데이터를 잘 예측하였다. An experimental investigation of turbulent heat transfer during the vertical upward flow of supercritical CO₂ was conducted in a circular tube with inner diameter of 4.5 mm. The experiments were conducted at bulk fluid temperatures ranging from 29 to 115 °C, pressures from 74.6 to 102.6 bar, local wall heat fluxes from 38 to 234 kW/m², and mass fluxes from 208 to 874 kg/m²s. At moderate wall heat and low mass fluxes, the wall temperature had a noticeable peak value. For observing the buoyancy and flow acceleration effects on heat transfer, the ratios of Nusselt numbers from the experimental data and a reference correlation were compared with the Bo<SUP>*</SUP> and q<SUP>+</SUP> distributions. The flow acceleration parameter q<SUP>+</SUP> appropriately represented the heat transfer phenomena in the experiments. A new heat transfer correlation for the vertical upward flow of the supercritical pressure fluid was developed, and was found to agree with the experimental data with an error margin of ±30 %.
논문 : 노외기계시스템공학 ; 소립종자용 평면배열 진공노즐식 반자동 파종기 개발에 관한 연구
김동억 ( Dong Eok Kim ),이공인 ( Gong In Lee ),강동현 ( Dong Hyeon Kang ),김유호 ( You Ho Kim ),이혜진 ( Hye Jin Lee ),김현환 ( Hyeon Hwan Kim ),김종구 ( Jong Ku Kim ),김용현 ( Yong Hyeon Kim ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.6
A large scale seeding system was stable in terms of techniques but a convenient seeding system of small size was unsettled. This study was performed to develop a semi-automatic seeder for small and medium sized scale farm. To investigate optimum needle diameter and vacuum pressure was used vacuum suction needle seeder. Although the needle diameter according to the kinds of seed was different, the needle diameter for salvia and lettuce seed was suitable for 0.34 mm needle nozzle and 0.4 mm taper nozzle. The prototype consisted a seeding frame attached with needle nozzle, seed hopper, vibrating device, seeding part, vacuum ejector, seed tube etc.. As the result with the experiments, the seeding rate of the seeder was 92% and more at 0.34 mm diameter needle nozzle and 0.4 mm taper nozzle. Eccentric weight for seed hopper vibration was suitable that weight is 11 g and eccentric distance is 0.5 mm. Vibration acceleration of upward direction was 0.363 m/s2. Working capacity of the seeder was possible 160 trays per hour. It was possible for sowing small seeds but it was required to make compact and simple model.
나노 구조가 형성된 열전달 표면에서의 임계 열유속 증진 메커니즘
김동억(Dong Eok Kim) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.7
나노 구조가 형성된 열전달 표면에서 유체의 비등 시 임계 열유속 값이 나노 구조가 없는 표면보다 현저히 증가한다는 것은 잘 알려진 사실이다. 다수의 물리적 메커니즘들이 이러한 나노 구조에서의 임계 열유속 증진 현상을 설명하기 위해 제안되어 왔다. 하지만 지금까지 대부분의 연구들은 정성적인 결과를 제시해 왔으며, 이러한 현상을 일반적으로 설명할 수 있는 이론은 아직 확립되지 않았다. 본 연구에서는 나노 구조가 형성된 표면에서의 임계 열유속 증진에 관한 정량적인 메커니즘을 증기 반동력 및 표면 접착력에 기초하여 제안하고자 한다. 특히, 본 연구에서는 임계 열유속 증진 현상을 표면에 형성된 나노 구조로 인한 액체, 증기, 고체의 삼중선 길이의 증가 및 나노 구조와 액체 사이의 접착력에 근거하여 설명하였다. The critical heat flux (CHF) on a heat transfer surface with nanostructures is known to be significantly better than that on flat surfaces. Several physical mechanisms have been proposed to explain this phenomenon. However, almost all studies conducted so far have been qualitative, and a generalized theory has not yet been established. In this study, we developed a quantitative mechanism for CHF enhancement on a surface with nanostructures, based on vapor recoil and surface adhesion forces. We focused on the increase in the length of the triple contact line owing to the formation of nanostructures and the adhesion force between them and the liquid.