循环流化床传热系数的计算模型

A Model of Heat Transfer in Circulating Fluidized Bed Combustor

本文在循环流化床流动模型的基础上建立了传热模型。流动模型根据实际运行情况考虑了颗粒的宽筛分，并把床层在轴向上分为密相床和稀相床两部分。在密相床内，传热按照鼓泡床传热模型进行计算；在稀相床内，传热模型建立在颗粒团更新的假设基础上。根据假设，床层由颗粒浓度很低的上升稀相和相对颗粒浓度较大的颗粒团两部分组成，两部分交替地与床壁面接触，床层和受热面间局部换热系数和颗粒浓度及两部分接触壁面的份额有关。

Aiming at getting a better understanding of the heat transfer in circulating fluidized bed boiler,a heat transfer model has been developed based on a hydrodynamic model.According to the wide particle size distribution,the model divided the furnace into two parts:a dense one at bottom part and a dilute one at upper part.In the dense bed,the heat transfer coefficient is determined by a bubble fluidized bed heat transfer model.In the dilute bed,a particle cluster renew model is adopted to describe the heat transfer.According to the assumptions,a fraction of the wall is covered by particle clusters while others is exposed to the emulsion phase.The local heat transfer coefficient consists of two parts:the particle cluster to the wall and the emulsion phase to the wall.The given model can predict the heat transfer in CFB boiler accurately.