循环流化床辐射传热模型

循环流化床中，炉膛壁面与床中的传热源自辐射，颗粒相对流和气相对流3部分，有关固体颗粒相传热系数的计算，研究人员主要提出了单颗颗粒模型，颗粒团更新模型和连续膜模型，但关于辐射传热系数的计算则比较简单，在这些模型中，有关辐射传热部分均采用经验或半经验公式，在辐射传热机理上探索尚欠不足，文中根据循环流化床密相区和稀相区的特性，分析其中的传热特点，特别是对循环流化床稀相区部分的颗粒团和对壁面的传热系数计算采用辐射双通量模型进行分析，从传热机理上建立了完整的循环流化床辐射传热模型，有助于了解循环流化床锅炉中的辐射传热机理和规律，模型计算结果与某电厂165MWe循环流化床锅炉相应工况条件下的实际运行数据相比，符合较好。

RADIATION HEAT TRANSFER MODEL OF A CIRCULATING FLUIDIZED BED

Heat transfer coefficient of bed to wall is a combination of the convective heat transfer coefficients due to the cluster and dispersed phase, and the radiative contributions of the cluster and dispersed phase in a circulating fluidized bed. Researchers developed a few heat transfer models to compute the convective heat transfer coefficient. However the calculation of radiative heat transfer coefficients mainly based on empirical and semi empirical equations. Computation on the radiative heat transfer coefficient is relatively poor.A radiation heat transfer model is presented based on mechanism analysis of dense region and dilute region in a circulating fluidized bed. A radiative two channel model is used to compute the radiative heat transfer coefficient between clusters and a wall in a dilute region. Influences of different parameters on the radiative heat transfer coefficient were analyzed, including solids particle diameter, solids annual thickness, operation velocity and temperature. The model helps to understand the radiative heat transfer mechanism in a circulating fluidized bed.Model predictions agree well with those heat transfer data of a 165 MWe circulating fluidized bed boiler.