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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.
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.