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Optimal Design Method for Plate Fin Heat Sinks Subject to Natural Convection
변찬 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10
In this study, an optimal design method for minimizing the size of plate fin heat sinks subjectto natural convection is proposed. An analytic model for predicting the thermal resistance of a finarray, as well as the heat sink substrate, is developed. In order to validate the analytic results,we performed numerical study and experimental studies. The results indicate that the proposedanalytic model predicts the numerical and the experimental results well, within a maximum errorof 5%. Based on the validated analytic results, we suggest an algorithm for minimizing the size ofa natural convective plate fin heat sink subject to a constant thermal resistance. As the substratesthickness increases, the substrates conduction thermal resistance decreases while the convectionthermal resistance decreases as the fin height increases. The minimum heat sink size is determinedby a balance between those two competing effects. The minimum heat sink size is shown to increaseas the heat source localization intensity increases.
비 균일적 마이크로 원기둥 배열을 이용한 고성능 냉각 표면
변찬(Chan Byon),김성진(Sung Jin Kim) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.12
본 논문은 비 균일적 마이크로 원기둥 배열을 이용한 고성능 냉각 표면에 대해 다루고 있다. 비균일적 원기둥 배열은 원기둥간의 거리 및 배열 규칙이 균일한 종전의 균일 배열과 달리, 두 개의 특성 공극 길이를 갖기 때문에 구조물의 모세관 능력을 획기적으로 향상시킬 수 있다. 본 연구에서는 비 균일적 마이크로 원기둥 배열을 제작하고, 모세관 상승률 실험을 통하여 모세관 능력을 측정하였다. 그리고 수치해석을 통하여 실험 결과를 검증하였고, 비 균일적 원기둥 배열의 모세관 능력 향상 원인에 대해 검토하였다. 실험 및 수치해석 결과, 마이크로 원기둥 배열의 모세관 능력은 배열의 고체 분율에 대한 일의적 함수로 주어지며, 고체 분율이 감소할수록 증가하는 것으로 나타났다. 하지만 고체 분율이 약 0.25 이하로 줄어들면 모세관 능력은 급격히 감소한다. In this article, an advanced cooling surface based on micro-post arrays with non-homogeneous configurations is investigated and compared with conventional micro-post arrays with homogeneous configuration. The capillary performance of micro-post arrays are characterized using the capillary rate of rise experiments and numerical simulations which take into account the meniscus curvature. The experimental and numerical results show that that the capillary performance of the micro-post wick can be significantly enhanced, compared with the homogeneous type wick, by employing non-homogeneous configurations. The capillary performance is shown to be primarily a function of the solid fraction and increases linearly with decreasing solid fraction, regardless of the wick configuration, when the solid fraction is larger than 0.25. However, the capillary performance is found to be significantly reduced when the solid fraction falls below approximately 0.25.
변찬(Chan Byon),김성진 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In this study, the thermal performance of bio-inspired wick is investigated. In the first chapter, the capillary limit of bio-inspired wick is considered. The capillary flows in the wicks are visualized using a high speed camera. From the experiments, it is shown that the capillary performances of bio-inspired wicks are significantly higher than those of conventional mono-porous wicks. In the bio-inspired wicks, three distinct capillary flow regimes are observed, depending on the ratio between particle and cluster sizes. A semi-analytic model for predicting the capillary performance of bio-inspired wicks is developed for each regime. The model prediction indicates that the cluster size should be 4-6 times larger than the particle size for an optimal capillary performance. In the second chapter, the boiling limit of bio-inspired wick is considered. In order to gain understanding of the boiling phenomena, the bubble movements in the wicks are visualized. Based on the visualization results, an analytic model for predicting the boiling limit of the bio-inspired wicks is developed. The model predicts the experimental data well, and indicates that the permeabilities of liquid and vapor are key parameters for determining the boiling limits of wicks. The bio-inspired wicks have much higher boiling limit than the mono-porous wicks, since they have much higher liquid/vapor permeabilities, by separating the flow paths of the phases. From the model, an optimal configuration of bio-inspired wick is found to be 4 < D/d < 6.
Experimental Study on the Performance of Superhydrophilic Cu Micropost Wicks
변찬(Chan Byon),김성진(Sung Jin Kim) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
Fabrication of superhydrophilic Cu microposts is demonstrated using electrochemical deposition through photoresist molds and controlled chemical oxidation. Modification of photoresist surfaces using oxygen plasma treatment and careful control of electrodeposition currents are found to be critical in creating dense arrays of uniform defect-free posts over large areas. The capillary performance of micropost arrays is characterized using the capillary rate of rise experiments and is found to be primarily a function of solid fraction. The shape of the liquid menisci on the micropost array is predicted through surface energy minimization and is shown to have significant effect on the permeability of micro-post arrays. The present work provides a useful starting point to achieve optimal balance between the capillary performance and the effective thermal conductivity of advanced wicks for micro heat pipes.