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손성균(Sung Gyun Son),김용찬(Yongchan Kim),이대영(Dae-Young Lee) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.8
A simplified rotary heat-exchanger model was developed with an assumption of a linear temperature distribution along the flow direction. Based on the model, the exact fluid solution and solid temperature variations were obtained and verified from a comparison with previous numerical studies. The heat transfer in the rotary heat exchanger was investigated using the theoretical solutions. The heat exchanger’s effectiveness was shown to be saturated, with a rotational-speed increase that is higher than a critical value that is solely dependent on the thermal capacity of the solid matrix but independent of the fluid flow rate; the saturated value of the effectiveness was determined only by the NTU of the heat exchanger. Where the thermal diffusivity of the solid matrix is so slight that the thermal penetration depth becomes smaller than the matrix thickness, the effective thermal capacity of the solid matrix decreased according to the penetration depth.
워터젯을 이용한 블라스팅 유리 마이크로 채널의 표면거칠기 개선
손성균(Sung-Gyun Son),한솔이(Sol-Yi Han),성인하(In-Ha Sung),김욱배(Wook-Bae Kim) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.12
파우더 블라스팅은 미세 유리가공법으로서 가공속도가 빠르고 저비용의 장점이 있지만 유리를 취성파괴 시키기 때문에 표면거칠기가 좋지않다. 블라스팅된 표면에 저압의 워터젯을 분사하여 표면에서의 연마 슬러리의 흐름을 통해 표면거칠기를 저감할 수 있다. 본 연구에서는 소다라임 유리에 블라스팅으로 마이크로 채널을 가공한 후 워터젯을 연속 적용하고, 마이크로 채널의 표면거칠기 및 단면 형상의 변화의 과정을 관찰하였다. 워터젯의 적용결과, 초기단계에서는 블라스팅에 의한 미세 요철이 제거되었고, 이후 표면하부의 크랙이 제거되어 평균 표면거칠기 50 nm 근방의 매끈한 표면을 얻을 수 있었다. 표면거칠기 저감에 동반하여 채널단면의 확장 과정도 함께 관측하였다. 마지막으로 제안한 방법에 의해 미세유체칩의 가공 결과를 제시하였다. Powder blasting, which is an efficient micromachining method for glass, silicon, and ceramics, has a critical disadvantage in that the surface finish is poor owing to the brittle fracture of materials. Low-pressure waterjet machining can be applied to smoothen the rough surface inside the blasted structure. In this study, the surface roughness and sectional dimension of micro-channels are observed during the repetitive application of a waterjet to blasted micro-channels. The asperities and subsurface cracks created by blasting are removed by waterjet machining. Along with the surface roughness, it is found that the sectional dimension increases and the edges of the finished microchannel become slightly round. Finally, a microfluidic chip is machined by the blasting-waterjet process and a transparent microfluidic channel is obtained efficiently.
서장원(Jang-Won Seo),손성균(Sung Gyun Son),이대영(Dae-Young Lee) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.6
In this study, a theoretical analysis of the effectiveness of a rotary enthalpy exchanger was conducted. Relevant variables were converted to dimensionless forms and used in governing equations to obtain theoretical solutions, with the various physical variables that exist in heat and mass transfer having been simplified as much as possible. Based on these simplified theoretical assumptions, the uniform temperature distribution was determined to be a sine wave, with the working fluid assumed to be an incompressible, fully-developed laminar flow. Through this analysis, the appropriate assumptions and dimensionless forms, the internal physical conditions of a rotary enthalpy exchanger were considered.