取热区蜂窝陶瓷几何特性对换热器取热率的影响

摘要

The influence of geometry characteristics of honeycomb ceramic in vertical packed bed heat extraction zone on heat extraction rate was numerically studied using three-dimensional mathematical model on the basis of model validity by experimental validation.Existence of heat extraction zone honeycomb ceramic resulted into different resistance in different positions of heat extraction zone,so gas would redistribute,so one part of the gas entered space where heat exchanger was embedded and there existed directly convective heat transfer between the part of the gas and heat exchanger exterior,while the other part of the gas entered honeycomb ceramic packed in heat extraction zone,heated the honeycomb ceramic through mode of convective heat transfer and then heat was transferred to heat exchanger exterior though thermal radiation.The characteristic sizes of the packed honeycomb ceramic in heat extraction zone had influence on heat extraction zone resistance and gas redistribution,and finally influenced heat extraction rate of heat exchanger.The calculated results show heat extraction rate of heat exchanger decreases with the increasing the characteristic size in the direction of gas flow of heat extraction zone honeycomb ceramic,but when the other two characteristic sizes increase,the heat extraction rate shows a trend of first increase and then decrease.%在实验验证数学模型有效性的基础上,数值研究了立式蜂窝陶瓷填充床内取热区蜂窝陶瓷几何特性对填充床内置换热器取热率的影响。热风从取热区下侧的蜂窝陶瓷流出后进入的取热区阻力不匹配,热风会重新分配,一部分进入换热器内置空间,与换热管外壁进行直接的对流换热,另一部分进入取热区蜂窝陶瓷将其加热后与换热管外壁进行辐射换热,取热区蜂窝陶瓷的几何结构影响取热区热风阻力不匹配程度与热风分配,最终影响到换热器取热率。计算结果表明：沿热风流动方向上取热区蜂窝陶瓷几何特性尺寸增大时,换热器取热率减小;垂直热风流动方向上取热区蜂窝陶瓷的两个几何特性尺寸增大时,内置换热器取热率呈现先增大后减小趋势。