Abstract:

A direct contact dynamic type of fluidization ice-making technique was proposed. Through building a two-way couple model of combined continuum and discrete model (CCDM) and using a unstructured grid search method, the flow and heat transfer characteristics of fluid-particle multiphase about the process of fluidization ice-making were calculated and discussed. The data calculated based on CCDM were in agreement with experimental data, and the model accuracy was validated. A definition of particle freezing degree was presented as a simplification criterion of choosing particles collision model and equivalent calculating particle surface heat transfer. The effect of particles collision and coalescence on particle size further changed the velocity, residence time and axial density distribution of particles, which could not be ignored in studying multiphase flow and heat transfer characteristics of fluidization ice-making process.

Key words: multiphase flow, fluidization, heat transfer, granular flow, CCDM, collision and coalescence, ice-making

摘要：

流态化制冰是一种新型的直接接触式动态制冰方式,通过建立联合连续和离散模型的CCDM(combined continuum and discrete model)全耦合模型,采用一种非结构网格颗粒搜索法,计算了流态化制冰过程所涉及的颗粒-流体多相系统的流动和传热特性。结果表明:基于CCDM模型计算出的结果与实验数据有较好的一致性,模型的准确度高;冻结程度关键值的提出,简化了颗粒间碰撞模型的判断和颗粒相表面传热量的等效计算;颗粒间的碰撞、聚并对颗粒粒径的作用,会进一步影响颗粒的运动速度、停留时间以及轴向浓度分布的变化,难以忽略其对于流态化制冰过程的多相流动与换热特性的影响。

关键词: 多相流, 流态化, 传热, 颗粒流, CCDM, 碰撞聚并, 制冰