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首页> 外文会议>PID-vol.9; ASME International Mechanical Engineering Congress and Exposition; 20041113-19; Anaheim,CA(US) >ESTIMATION OF MASS TRANSFER DURING DROP FORMATION: NEW FLOW EXPANSION MODEL
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ESTIMATION OF MASS TRANSFER DURING DROP FORMATION: NEW FLOW EXPANSION MODEL

机译：液滴形成过程中的传质估计：新的流量扩展模型

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摘要

Although there is extensive experimental, theoretical and numerical research on dynamics of drop formation in liquid-liquid systems, the evaluation of mass transfer during drop formation is rather complex and there has been little research on that. The various mathematical models developed for this problem are generally based on a solution of the diffusion equation without any allowance for circulation within the drop. This is the main reason for the poor prediction of these models in many cases for which internal convection has an important effect on mass transfer rate. In this paper an attempt was made to define a parameter related to the extent of the convective mixing within the growing drop. For this purpose it is assumed that the entrance of the dispersed flow into the growing drop from the nozzle is analogous to the entrance of the flow from a smaller channel to a larger one (the expanding drops). This transfer mechanism presented in this paper has been dubbed "flow expansion". A global time-dependent Reynolds number was defined based on the equivalent diameter of growing drop as a length scale and also on a velocity scale, which is obtained using this flow expansion assumption. This time dependent Reynolds number of growing drop (Re_(gd)) has an important role on the mass transfer coefficient. The results of the model where predicting the effects of the nozzle diameter and dispersed phase flow rate on the mass transfer behavior showed good agreement with experimental data. This comparison demonstrates an improvement on famous models such as surface stretch and fresh surface elements for evaluation of mass transfer during drop formation.
机译：尽管对液-液系统中液滴形成的动力学进行了广泛的实验，理论和数值研究，但是在液滴形成过程中传质的评估相当复杂，对此的研究很少。针对该问题开发的各种数学模型通常基于扩散方程的解，而不考虑液滴内的循环。这是在许多情况下内部对流对传质速率有重要影响的情况下对这些模型的预测不佳的主要原因。在本文中，试图定义一个与生长液滴内对流混合程度有关的参数。为此目的，假设分散的流从喷嘴进入生长的液滴的入口类似于从较小的通道到较大的通道（膨胀的液滴）的入口。本文介绍的这种传输机制被称为“流扩展”。全局时间相关的雷诺数是基于生长液滴的等效直径（作为长度尺度）和速度尺度（使用此流动扩展假设获得）定义的。时间相关的雷诺数增长滴（Re_（gd））对传质系数具有重要作用。预测喷嘴直径和分散相流速对传质行为影响的模型结果与实验数据吻合良好。该比较证明了对著名模型（例如表面拉伸和新鲜表面元素）的改进，以评估液滴形成过程中的传质。

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