煤矿乏风瓦斯流入特性对填充床内置换热器取热的影响

Influence of coal mine ventilation air methane inflow characteristic on heat extraction of heat exchanger embedded in packed bed

在实验验证数学模型有效基础上,研究了气体流入特性对煤矿乏风氧化床内置换热器取热的影响,结果表明:填充床内置换热器取热率随床层入口气体质量流速均匀性指数的下降而减小,蜂窝陶瓷的存在导致气体流动单向导通、增大床层物理流速及辐射面积,使床层入口气体质量流速均匀性指数减幅相同时填充床内置换热器取热率减小幅度要比空床换热器大;床层入口气体平均质量流速不变时,内置热器取热率随床层入口气体温度均匀性变差而减小,温度分布不均同时引起流速分布不均,温度分布不均引起的取热率下降幅度要明显大于相同平均质量流速、温度下床层入口气体流速不均引起的取热率下降幅度;对于立式氧化床,各部分气体由于温度不同导致的浮力大小不同以及气体所受浮力由于进风方式不同导致的对流动影响差异,换热器取热率也随之发生变化,随着床层入口气体平均温度逐步升高,进风方式对取热率影响越来越明显。

On the basis of the mathematical model which was validated by experiment,the influence of coal mine ventilation air methane inflow characteristics on the heat extraction of the bed was studied by the numerical method.Numerical results show that the heat extraction rate of embedded heat exchanger in the packed bed decreases with the decrease of the gas inlet mass velocity uniformity index,the gas unidirectional flow and increasing physical flow rate in bed and radiation heat transfer area resulted from packed honeycomb ceramic make that the decreasing scope of heat extraction rate of the packed bed embedded heat exchanger is larger than that of the empty bed heat exchanger when the gas inlet mass velocity uniformity index decreases same value;when gas inlet average mass velocity is constant,the heat extraction rate of the embedded heat exchanger decreases with the decrease of inlet gas temperature uniformity index,and uneven temperature distribution results in uneven flow velocity distribution,so the decreasing scope of the embedded heat exchanger heat extraction rate caused by the uneven temperature distribution of inlet gas is bigger than that caused by the uneven flow velocity distribution when gas inlet average temperature and mass velocity are constant.For vertical oxidation bed,different buoyancy resulted from uneven temperature and the influence difference of buoyancy on flow caused by different gas inflow mode make the gas to be redistributed in gas collecting box,and make theheat extraction rate of the heat exchanger changed,the influence of gas inflow mode on the heat extraction rate is more and more obvious with the inlet gas average temperature increase.