Minimising microbubble size through oscillation frequency control
Minimising microbubble size through oscillation frequency control
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DOI：
10.1016/j.cherd.2015.08.002
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发表时间：
2015-12-01
影响因子：
3.9
通讯作者：
Zimmerman, William B.
中科院分区：
文献类型：
--
作者：
Brittle, Stuart;Desai, Pratik;Zimmerman, William B.
微气泡是尺寸小于1 mm的气泡，并且已经广泛地部署在工业环境中以改善气相和液相之间的气体交换。微泡提供的高表面积与体积比使其能够增强传输现象，因此可用于减少许多应用中的能量需求，包括废水曝气、泡沫浮选、油乳液分离和蒸发动力学。微气泡可以通过使气流通过放置在气液界面处的微孔扩散器来产生。以前的工作表明，振荡这种气体蒸汽可以减少气泡的大小，从而增加节能。在这项工作中，我们表明，它是可能的，以进一步减少微气泡的大小（并因此最大限度地增加气泡的数量），通过改变振荡气体供应的频率。已经研究了三种不同的微泡产生系统;声振荡系统和网状膜、耦合到单孔膜的流体振荡器和耦合到市售陶瓷扩散器的流体振荡器。在所有三种气泡产生方法中，存在最佳振荡频率，在该最佳振荡频率下，气泡尺寸最小化并且微气泡的数量最大化。在某些情况下，与非最佳操作频率相比，实现了高达73%的气泡尺寸减小。出现这种最佳情况的频率取决于气泡产生系统;更具体地说，取决于系统的几何形状、微孔扩散器的类型和气体流速。这项工作证明，通过调整工业微泡发生器的最佳振荡频率将导致微泡的尺寸减小，并增加其数量密度。这将进一步提高气体交换速率，并因此提高工业过程的效率，其中它们被用于产生气泡，从而导致相关的能量成本的降低和这些过程的总体经济和能量可行性的增加。(C)2015作者由爱思唯尔公司出版
Microbubbles are bubbles below 1 mm in size and have been extensively deployed in industrial settings to improve gaseous exchange between gas and liquid phases. The high surface to volume ratio offered by microbubbles enables them to enhance transport phenomena and therefore can be used to reduce energy demands in many applications including, waste water aeration, froth flotation, oil emulsion separations and evaporation dynamics. Microbubbles can be produced by passing a gas stream through a micro-porous diffuser placed at the gas-liquid interface. Previous work has shown that oscillating this gas steam can reduce the bubble size and therefore increase energy savings. In this work we show that it is possible to further reduce microbubble size (and consequently maximise the number of bubbles) by varying the frequency of the oscillating gas supply. Three different microbubble generation systems have been investigated; an acoustic oscillation system and a mesh membrane, a fluidic oscillator coupled to a single orifice membrane and a fluidic oscillator coupled to a commercially available ceramic diffuser. In all three bubble generation methods there is an optimum oscillation frequency at which the bubble size is minimised and the number of microbubbles maximised. In some cases a reduction in bubble size of up to 73% was achieved compared with non-optimal operating frequencies. The frequency at which this optimum occurs is dependent on the bubble generation system; more specifically the geometry of the system, the type micro-porous diffuser and the gas flow rate. This work proves that by tuning industrial microbubble generators to their optimal oscillation frequency will result in a reduction of microbubble size and increase their number density. This will further improve gaseous exchange rates and therefore improve the efficiency of the industrial processes where they are being employed to produce bubbles, leading to a reduction in associated energy costs and an increase in the overall economic and energetic feasibility of these processes. (C) 2015 The Authors. Published by Elsevier B.V.