連續蜿蜒管道微混合器流場分析

Abstract

在微尺度下的管道中，流體受到尺寸的限制只能以層流的形式流動，流體間的混合通常只藉由分子擴散機制來進行混合，必需利用其他機制來提升混合效果，減少管道長度。本文探討在S型波狀、方形波狀及三維蜿蜒三種不同幾何結構的管道中流場性質及混合分析，利用管道簡單彎曲的變化，產生二次流場，使介面快速扭曲、拉長，增加接觸面積及減少管道的長度。並且改變雷諾數，觀察流場二次流場及混合效果。由數值模擬結果發現，在低雷諾數(Re<6)下，S型波狀及方形波狀管道中，二次流相當微小，混合由擴散機制主導，混合效果較差，須提升雷諾數增加混合效果。而流場在三維蜿蜒管道中變化大，混合效果最佳。提高雷諾數，相對增加管道中的橫向速度，有助於增加擴散面積，提升混合效果。

Due to micro-scale channel, the internal fluid is constrained to flow laminar and the mixing mechanism is mostly dominated by molecular diffusion as well. the mixing efficiency is still needed to be improved by utilizing more other mechanisms, due to which the required length of channel is surely shortened. In thesis, the simulation focused on predicting the properties of fluid field and mixing efficiency in the different geometries of channels. We selected three different kinds of geometry of channel: S wave channel, square wave, and 3D serpentine channel. By changing of the channel simple geometries, in order to the interface quickly twists, stretches, and increase the area of contacting and reduce the length of the channel.Furthermore, the changed Reynolds number, to observe the property of secondary flow and mixing efficiency. As the Reynolds number < 6 , however, the mixing process is dominated by molecular diffusion instead of effects of the secondary flow being too small in both S wave and Square wave channels. On the other hand, the best mixing process can be seen in 3D channel of which the geometries is more complicated and causing the interfacial deformation and elongation to enlarge diffusion area.The higher Reynolds number relatively magnifies the intensity of secondary flow and speeds up the velocity as well.The mixing efficiency is undoubtedly improved.