近年來，隨著電子元件微小化與功率提高，其單位面積產生的熱能也急遽上升，如何提高散熱效率來保持產品壽命成為一個重要問題。傳統散熱方法如鰭片與風扇已經無法滿足現今電子元件的散熱需求，利用矽等高分子材料製成水冷式微流道熱沉(MCHS)，是現在大量興起的散熱技術。本研究利用晶格波茲曼法(LBM)探討Al2O3/water奈米流粒子濃度(ϕ)與脈動流對微流道之層流強制對流熱傳的影響。為進一步提升擾流效果，微流道中排佈二到八個百葉窗型微結構，其對應的間距比(PR)為0.25到1.75。基於流道水力直徑與平均速度的雷諾數(Re)範圍為100到400，脈動流為三角波形，其史卓赫數(St)範圍為0到2.8，ϕ變化範圍為0到4%。數值方面，採用雙分佈函數LBM模擬通道內流場與溫度場。模擬結果發現穩態流場下百葉窗型微結構能擾亂主流且將冷卻流體導引至壁面，其平均紐塞數(Nu)在PR=0.25時相比於全展平滑管道提升4.94倍。而在流道中加入奈米流體後發現熱傳可進一步提升至7.06倍，且壓損(f ̅/f_0)幾乎不受影響。最後將穩態流入口改為脈動流入口後發現在特定St下脈動流場能在百葉窗型微結構後方產生多個膨脹收縮之渦流，並沖散結構後方的迴流死區，促進壁面高溫流體與中心冷卻流體混合。在百葉窗微結構、脈動以及奈米流體的共同效應下，本研究MCHS最大平均Nu較全展平滑直管道提升至8.79倍，而相應f ̅/f_0則達到29.1倍。與前人數據比較，當前流道設計在f ̅/f_0<30的區間內有最高的熱傳增益，從而填補這一區段內微流道設計的空白。

With increasing power and miniaturization of electronic components in recent years, their heat generation per unit area has grown rapidly, which makes effective cooling techniques necessary to maintain an acceptable electronic life. The traditional cooling techniques such as pin fin and fan cooling can no longer meet the heat load requirements of electronic components nowadays. Instead, the water-cooled silicon microchannel heat sink (MCHS) has emerged as the most promising technology of heat transfer enhancement. Hence, the present study reports the effects of Al2O3/water nanoparticle concentration (ϕ) and flow pulsation on laminar forced convective heat transfer in a microchannel heat sink with lattice Boltzmann method (LBM). For better flow mixing, two to eight louver-like microstructures are arranged in tandem within the channel, corresponding to a pitch ratio (PR) of 0.25 to 1.75. The Reynolds number based on channel hydraulic diameter and bulk mean velocity ranges from 100 to 400, the pulsating inlet velocity is a triangular wave with Strouhal number (St) ranging from 0 to 2.8, and the value of ϕ varies from 0 to 4%. In terms of numerical models, a double distribution function LBM approach is adopted for modeling both fluid flow and heat transfer. Simulation results show that the louver structure can disturb the core flow and guide coolant towards the heated walls effectively in steady-state flows, resulting in an average Nusselt number (Nu) enhancement around 4.94 relative to that of the fully developed smooth channel at PR=0.25. By adding nanoparticles into the working fluids, it is further found that the average Nu ratio is raised to a higher value of 7.06 without inducing extra pressure loss(f ̅/f_0). As the flow inlet is switched to pulsation, there exist several contracting-expanding vortices behind the louver structure at some certain values of St. These vortices elimate the recirculation zone in that region, thus leading to better mixing of near-wall and core flows. Considering both the louver microstructure, pulsating flow, and nanofluids, a maximum overall Nu ratio of 8.79 is found whereas the relative f ̅/f_0 increases to 29.1. The present MCHS fills the blank at moderate (f ̅/f_0 < 30) by providing the best heat transfer performance at that region.

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