膜式水冷壁换热系数的有限元分析

将有限元用于水冷壁的换热分析,计算了鳍片结构对换热的影响,探讨了用测量壁面温差法求取炉内向水冷壁换热的可能性。计算发现,有限元计算与目前中国采用的标准吻合得非常好,但是标准给出的鳍片中间点温度偏大。增大管节距时,鳍片吸热份额和最高温度升高;较大的厚度可以降低鳍片最高温度,提高吸热份额。壁面上两点温差可以表征水冷壁受热状况,炉膛向受热面的换热系数与温差呈较好的线性关系。对几台商业运行的循环流化床锅炉的水冷壁进行了有限元测量,将有限元结果与热平衡结果进行了比较,表明有限元测量方法比较真实地反映了实际情况。有限元方法测量结果呈现偏大的趋势,主要与鳍片和母材的根部焊接出现附加热阻有关。

Finite element analysis of the heat transfer coefficient of a membrane wall

The finite element was used to predict the effect of the membrane water wall structure in circulating fluidized bed(CFB) reactors on the heat transfer and the feasibility of heat transfer measurements from measured temperature differences.The results indicate that most of the predicted temperatures agree well with the Chinese Standard with the maximum temperatures being somewhat less than the standard.The fraction of heat absorbed in the fin as well as the maximum temperature increase with increasing pitch,while with increasing fin thickness,the fraction of heat adsorbed increases while the maximum temperature decreases.The temperature difference in the water wall was found to be linearly related to the heat transfer from the CFB to the membrane water wall.Measurements using this method in commercial CFB boilers compare reasonably well with heat balance results with the measurements somewhat higher because of the additional heat resistance in the welds.