稠密气固两相流是工业过程中一种常见的物质：循环流化床锅炉中调控物料循环的返料阀内部，颗粒和流化风会形成鼓泡状态的气固两相流；流化床干法选煤的过程中，煤粉颗粒被流化也会形成稠密的气固两相流；等等。其与传质传热有关的基本物理性质，例如黏度，对于这些工业过程的调控十分重要。本文为估测鼓泡的稠密气固两相流的表观黏度建立了一个具有物理意义的半经验模型，并通过实验测量对该模型的可靠性进行了验证。论文总结归纳了过往研究中固体颗粒悬浮体的表观黏度理论预测模型，并分析了其推导时所作出的导致误差的各种假设。此外，还调研了两相流的组分气体与固体颗粒的密度、多分散性、速度等各种物性参数对气固两相流表观黏度产生的影响。在此基础之上，本文根据鼓泡的稠密气固两相流的乳化相与液体相似的物理性质，将包含气泡相与乳化相的气固两相流与气液两相流对比，利用适用于气液两相流的黏度混合模型推导并建立了新的适用于鼓泡状态稠密气固两相流的表观黏度理论预测模型，描述了气固两相流表观黏度随颗粒体积分数变化的关系式，以及关系式中系数受气固两相物性参数的影响。论文调研并总结了气固两相流表观黏度的实验测量方法和仪器，在此基础之上，选择了Brookfield旋转黏度计作为主要测量仪器，设计并搭建了验证新理论模型可靠性的小型流化床实验台，采用空气、氦气、氩气3种气体，和两种不同粒径的玻璃珠、一种氧化铝粉末和一种流化裂化催化剂粉末分别形成的12种气固悬浮体，通过改变气体的流速来改变颗粒体积分数，从而改变气固悬浮体的表观黏度，得到11组有效的测量数据。然后将每个工况点的表观黏度测量值与通过理论模型计算得到的预测值进行对比，验证模型的可靠性。此外，还比较了本文新建立的理论模型与文献调研中总结的较有代表性的几个理论模型在这些实验工况点的预测表现；还采用了Reiling对空气和流化裂化催化剂粉末组成的气固悬浮体的实验测量、Colafigli等人对氮气和超细二氧化硅粉末组成的气固悬浮体的实验测量数据与本文所得到的实验数据，在这共计108个工况点上进行了理论计算值与实验测量值的对比，其中88个工况点上新理论模型相对实验测量值的偏差小于±25%，准确率达到81.5%。据此，本文新建立的理论模型是一个具有物理意义的、可根据组分气体和固体颗粒的物性参数进行调整的、可靠的稠密气固两相流表观黏度预测模型。
Dense gas-solid two phase flow commonly appears in various industrial processes, e.g. the bubbly flow consisted of particles and fluidized air in the loop seal of circulating fluidized bed boiler, the suspension existing in dry coal cleaning process, etc. Its fundamental physical properties related to mass and heat transfer, namely, viscosity, is important in the regulation of these processes. Therefore, in this paper, a new semi-empirical model with physical meaning is established for the prediction of the apparent viscosity of dense, bubbly gas-solid two phase flow. The reliability of this model is then verified by a series of experiment.To begin with, the previous theoretical models of apparent viscosity of particle suspension are reviewed and the assumptions they based on which lead to deviations are analyzed. Next, the influence of parameters of gaseous and particulate compositions on the apparent viscosity is reviewed as well. After this preparation, an analogy between gas-solid two phase flow and vapor-liquid two phase flow is committed for reasonably applying the viscosity mixing model of the latter to the former, in consideration of their similar physical performances. On the basis of this analogy, a new apparent viscosity model for dense, bubbly gas-solid two phase flow is deduced, which gives the variation of apparent viscosity as a function of the particle volume fraction, as well as the influence of parameters of gaseous and particulate compositions on the factors in the expression.Last but not least, the measuring methods and instruments are reviewed, among which the Brookfield rotating viscometer is selected for the experiment to verify the model. Besides, three kinds of gases (air, helium and argon) and four kinds of particles (glass bead a & b, alumina powder and fluidized cracking catalyst powder) are selected to form 12 different kinds of gas-solid suspensions in a small fluidized bed bench. The apparent viscosity varies with the variation of particle volume fraction, on account of the variation of gas velocity. Comparison between eleven valid sets of measured values derived from the experiment and calculated values of apparent viscosity derived from the new model is conducted to verify the reliability of this model. In addition, the predicting performances of several typical models in the previous review are compared with that of the new model. Dataset of air - fluidized cracking catalyst (FCC) powder suspension derived by Reiling, as well as dataset of nitrogen – ultrafine silica powder suspension derived by Colafigli et al. are also used for verification. As a result, among the total 108 cases, there are 88 cases at which the deviation of calculated apparent viscosity values produced by the new model from the measured values is no more than ±25%. That is to say, the accuracy rate of this new model is 81.5 % within the testing range. Thus it is concluded in this paper that the new model is a valid, physically reasonable predicting model for apparent viscosity of dense, bubbly gas-solid two phase flow, whose semi-empirical factors can be regulated according to the properties of the gaseous and particulate compositions.
