非均匀气固两相系统中多尺度传质模型

MULTI-SCALE MASS TRANSFER MODEL FOR HETEROGENEOUS GAS-SOLID TWO-PHASE FLOW

建立了适用于气固循环流化床的多尺度传质模型 .从过程与尺度的角度出发 ,将非均匀气固两相流中的传质过程分解为静态与动态的过程 ,并将前者分解为稀相内、密相内以及稀密相间 3个尺度下的传质 ;在用多尺度能量最小 (EMMS)模型求解已知物系性质和操作条件的非均匀气固两相流体动力学参数的基础上 ,借助于前人的研究结果 ,利用相对滑移速度、空隙率等参数求解传质系数 ,求得轴向的浓度场分布 ,并讨论非均匀两相流动结构对传质效率的影响 .

By means of structure and process decomposition, this work is devoted to elucidating mass transfer process in heterogeneous flow theoretically. Mass transfer process in heterogeneous flow of gas-solid circulating fluidized bed is considered to consist of two subprocesses: static and dynamic. At the mean time, the static subprocess is decomposed to three scales: mass transfer in dilute phase; dense phase; and inter phase. Then, by virtue of EMMS model, local hydrodynamics of heterogeneous two-phase parameters are calculated from the condition of operation parameters (solids mass flux, gas velocity) and species characteristics. Mass transfer coefficient is obtained by slip velocity, voidage, etc. Based on above, axial distribution of concentration is studied. At last, effective mass transfer coefficient of circulating fluidized bed is discussed.