多线圈薄板电磁加热的均匀性及可控性

以矩阵式多线圈结构电磁加热方式为研究对象,采用数值模拟仿真和对比研究的方法对薄板温度均匀性和可控性进行了分析,设计并优化多线圈电磁加热模型。首先,对加热薄板进行有限元分析与数值模拟,并在涡流损耗与模型尺寸相同条件下,对矩阵式线圈结构与蜂窝式线圈结构进行仿真结果比较;其次,分析电流强度以及线圈间距离对薄板温度均匀性影响;获得气隙尺寸与频率对温度的影响关系。结果表明:等温度区间,矩阵式多线圈结构在薄板温度均匀性以及可控性方面优于蜂窝结构;在电流密度一定条件下,薄板加热的径向温度梯度与电流呈正相关;适当调整相邻线圈的间距,薄板表面温度的均匀性得到改善;薄板表面温度,与气隙长度呈负相关,与频率呈正相关。

滚筒烘丝机内壁加热薄板温度直接测定方法

目前滚筒烘丝机筒壁温度理论计算误差较大且存在一定的滞后,为此提出一种滚筒烘丝机内壁加热薄板温度直接测定方法。通过应用热电阻接触式测温和数据无线传输技术,实现滚筒烘丝机内壁加热薄板温度的在线实时测定。测试结果表明,该方法能实时准确测定加热薄板温度,测量精度达0.1℃,且可实时监测其温度变化和分布状况,从而为提高滚筒烘丝机控制精度、监测滚筒烘丝机工作状态、设计分段式滚筒烘丝机提供可靠的数据支撑。

Free Convention Heat Transfer from an Isothermal Horizontal Thin Strip:the Influence of the Prandtl Number

Simultaneous free convection above and below a uniformly heated horizontal plate has been widely investigated,both in the case of an isothermal surface,and of a uniformly heated surface,but always assuming only air as fluid(Pr=0.7).Nevertheless,there are works dealing with horizontal plates whose results show that the Nu dependence on Pr may not be simply expressed by a power law with the same exponent of the Gr one.So it was considered useful to study the Prandtl number influence in the case of the isothermal horizontal strip.Results show that,while for the lower surface of the strip the Nu dependence in Gr can be expressed by a power law with an exponent close to the Gr one,for the upper surface the exponent is sensibly different.Correlating equations related to the investigated situations are proposed.