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심부지열 용 동축 열교환기 성능예측을 위한 열전달 실험 및 해석
정국진,정윤성,박준수,이동현,Jung, Kuk-Jin,Jeong, Yoon-Seong,Park, Jun Su,Lee, Dong Hyun 한국교통대학교 융복합기술연구소 2017 융ㆍ복합기술연구소 논문집 Vol.7 No.1
The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.
하이드로사이클론 내벽 헬리컬 패턴 최적 설계에 따른 미세 입자 집진 효율 향상 연구
정국진(Kuk Jin Jung),Rahmadio Catur Putra,김윤제(Youn-Jea Kim) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.5
하이드로사이클론은 서로 다른 밀도의 상을 중력과 원심력을 이용하여 분리하는 장치이다. 간단한 구동 원리와 손쉬운 유지 보수로 인해 많은 분야에서 활용되고 있다. 그러나 산업 현장에서 미세 먼지 등으로 인한 많은 문제가 발생하고 해당 장치는 미세 입자 분리에는 한계를 보인다. 따라서 본 연구에서는 미세 입자 분리 효율 향상을 위해 내벽에 헬리컬 패턴의 설계안을 제시하고 검증 후 분리 효율에 대한 최적 설계안을 도출하였다. 물과 구형으로 가정한 지름 1μm 아스팔트에 관하여 수치 해석적 연구를 진행하였으며, 실험계획법과 반응표면법을 통하여 최적 설계를 진행하였다. 내벽 특성에 대해 각각의 인자에 따른 영향도를 분석하고 효율 상승 원인을 고찰하였다. A hydrocyclone is a device that separates phases of different densities using gravity and centrifugal force. It is used in a wide range of applications owing to its simple driving principle and easy maintenance. However, the fine particle separation occurring in industrial sites is limited. To address this limitation, a helical-patterned design was applied to the inner wall of the hydrocyclone. In this study, numerical research and optimal design were conducted on water and 1-μm asphalt particles, which were assumed to be spherical, using a hydrocyclone with a modified configuration. The optimal design targeted the diameter, pitch, and roughness of the helical pattern, and utilized the response surface method using genetic algorithm and design of experiment. As a result, the helical pattern characteristics and roughness were derived for optimum fine particle collection efficiency, and the cause was determined.
블레이드 전방 베인 설치에 따른 블레이드 바닥면에서의 이차와류 및 열전달 특성 연구
정국진(Kuk Jin Jung),박성호(Seong Ho Park),피용희(Yong hui Pi),박준수(Jun Su Park) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
To reduce NOx emissions in gas turbines, there is a change in combustion method and combustor design. This change not only adds to the heat load in the endwall but also creates a step in assembling the blades and vanes. Depending on the shape and size of the steps, various heat transfer characteristics are exhibited in the endwall. Therefore, this paper investigated the characteristics of secondary vortex and heat transfer on the endwall according to the step size through experimental study. Experiments were performed using a seven-blade linear cascade with a rod simulating step. Experimental results show that the horseshoe vortex and passage vortex were most noticeable. The influence of the horseshoe vortex on the leading edge depends on the diameter of the rod. Also the passage vortex had different ranges of influence on the suction side and the pressure side. Therefore, the cooling method for each area of the endwall should be studied to meet the step size.