具凹槽或阻塊結構微混合器流場數值模擬

Abstract

微混合器混合的好壞決定了整個反應系統的優劣，由於微管道受限於 微米幾何尺寸的限制，進行流場的精密實驗量測十分不易，因此本論文利用計算流體力學的數值方法，模擬分析了單邊斜凹槽(SRM)、雙邊斜凹槽(Double SRM)、人字形凹槽(SHM)、傾斜阻塊人字形凹槽(OBSHM)與阻塊(Block)結構等微混合器，探討被動式微混合器的流場現象與混合效果。首先本文重新再探討了 2005 年謝[42]的論文，對於計算model的處理有所不同，從本文模擬的結果得到，較深或較寬的凹槽，對混合效果會越好，而對太大或太小的的凹槽傾角，其混合效果會越差，在上下雙邊斜凹槽(Double SRM)的設計當中，其混合效果也可提升，和謝[42]當中的結果是相同的。之後我們再對於人字形凹槽(SHM)、傾斜阻塊人字形凹槽(OBSHM)與阻塊(Block)結構加以比較探討，從我們的結果發現到，在Pe =2×105時，OBSHM的混合效率不及於SHM，而在Pe =2×103 時，OBSHM的混合效率勝於SHM，而對於只有阻塊(Block)結構的混合器當中，阻塊變成傾斜45° 時混合效率會比較好；在Pe =2×103 的條件下，阻塊結構的混合效率均 比SRM 、SHM 及 OBSHM好。

The performance of a micro-mixer is corresponding to the mixing efficiency of it. Due to the tiny scale of the geometry of interest, instead of doing the experiment. In this study the computational fluid dynamics approach is employed to simulate and analyze the passive micro-mixers under consideration include: striaight ridges micromixer (SRM)、Double SRM, staggered herringbone micromixer (SRM), staggered herringbone micromixer with oblique block(OBSHM), and only blocks structure , whose flow patterns and mixing efficiencies were studied. On the other hand, the restudy of Hsieh’s work [42] has been done with different handling on modeling of the flow field. The wider and the deeper grooves of SRM bring the better mixing efficiency while the too sharp and the too dull angles of inclination of grooves degenerate the mixing performance which are on the contrarily bettered by the Double SRM with grooves placed on the top and bottom of the channel, quite consistent with results reported by Hsieh’s [42]. SHM, OBSHM, and Block are further investigated in the present study. OBSHM performs more poorly than SHM does as Peclet number is about 2×105 . whereas the contrary happens as Peclet number is about 2×103 . Block performs better only when the angle of inclination is 45 degree. The Blocks micro-mixer has great mixing efficiency then SRM, SHM, OBSHM, when the Peclet number er is about 2×103.