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고열유속에 놓인 수냉식 냉각장치 표면의 냉각 성능 개선
정욱진(Woog Jin Jeong),이근식(Geun Sik Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In order to reduce the thermal stress of the water-cooling wall in high heat flux, it is necessary to reduce the wall temperature and its gradient. In this study, characteristics of inner flow and temperature field and the wall temperature distribution were numerically examined with variations of the water channel geometries (such as the length of inner wall separating between in and out water-flow, the rounding size of the comer, and swirl angle) and the external heat flux. As a result, the wall temperature was mainly reduced by extending the inner wall length compared with other channel geometries. However, in a point of view of the wall temperature gradient, only variations of the water channel geometries had difficulty in the reduction but decrease in external heat flux could be a desirable solution of the temperature gradient reduction.
주기적 기둥 패턴의 나노 구조물 위에서 힘을 받는 수액적의 거동 특성
정욱진(Woog-Jin Jeong),하만영(Man-Young Ha),윤현식(Hyun-Sik Yoon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Using molecular dynamics simulations of an atomistic water model, we study the behavior characteristics of the water droplet under a constant horizontal force on graphite surfaces with periodic nano-sized pillars. We first select two heights of pillars that Cassie-Baxter state and Wenzel state are been in static equilibrium state when a water droplet is put on the pillar surfaces. Then, we apply a constant horizontal force to the water droplet that is in static equilibrium state and observe the behavior characteristics of it. The simulation results show that there is a interesting moving mechanism. In both cases, moving velocity of water droplet is similar or slightly low compared with a case of the flat surface in spite of the high static contact angle: this shows an enhancement of static hydrophobicity by existence of pillars does not leads to the increase of mobility of water droplet.