在方箱炉、圆筒炉中区域法计算辐射传热的数学模型及其应用

本文叙述了以区域法计算辐射传热的数学模型。在区域法中,系统被分为表面区和气体区,区域数取决于所要求的结果精度和计算时间。炉子的温度分布可通过解每区的能量平衡而得。作为Hottel和Cohen的原始开发,直接交换面积限于立方体和正方形;本文给出了在方箱炉、圆筒炉中任何两区之间直接交换面积方程式的推导。这些方程式可适用于任何大小的矩形、共轴圆筒壁、炉底环形区和其他形状。 本文提供了一个关于烃类一段蒸汽转化炉和圆筒炉的设计方法。计及反应动力学、对流传热、管内压降,采用区域法计算这些炉子的温度分布,从而预言工艺气、烟气、管表面和耐火墙表面的温度分布。计算结果与工厂实测数据相吻合。

Mathematical Model of Zone Method in Calculating Radiating Heat Transfer and its Application in Box or Cylindrical Furnace

A mathematical model using zone method to calculate radiating heat transfer is described. In the zone method, the system is divided into surface zones and gas zones and the number of which depends on the accuracy of results desired and calculation time required. The temperature profiles in a furnace are obtained by solving simultaneously energy balances on each zone. As originally developed by Hottel and Cohen, the direct exchange areas are limited to cubes and squares. In this paper, the derivation of the direct exchange area equations is extended between any two zones in the box or cylindrical furnace.These equations are adaptable to any dimension of rectangles, coaxial cylinder walls, end rings and other shapes.A design method for the primary reformer of hydrogen production unit and cylindrical furnace is proposed. By considering the reaction kinetics,convective heat transfer and pressure drop inside the tubes, the zone method has been adopted to predict temperature profiles of process gas, furnace gas, tube surface and refractory surface in such furnaces. Results of calculation agree well with data obtained from commercial units.