均匀受热垂直上升管内的流动压降特性及界限质量流速

Pressure drop and critical mass flux of water flowing upward in a uniformly heated vertical tube

界限质量流速G0是垂直管圈水冷壁直流锅炉的重要设计参数之一。当水冷壁管中的质量流速小于G时，水冷壁呈现正流量响应特性。目前普遍认为G的范围在1000-1200kg／（m^2·s）。在公开文献中，关于G0的影响因素的系统研究还相对较少。该文基于经验关联式和经典的流动压降计算方法，分析了超临界／亚临界压力条件下，均匀受热垂直上升管内水的流动压降随热流密度的变化情况，系统研究了热流密度、管长、管径等因素对G0的影响规律。计算结果表明：热流密度减小，G0增大；管长变短，G0增大；管内径增加，G0增加。

The critical mass flux, G0, is a key parameter in the design of vertical water wall in once-through boilers. A vertical water wall has positive flow characteristic only when the mass flux inside the parallel tubes is less than Go. While Go has been reported to be 1 000-1 200 kg/（m^2·s）, there are few studies on the factors influencing Go in the literature. This paper presents a hydrodynamic model based on the classical pressure loss computation method and empirical correlations. The model predicts the pressure drop variation for water flowing upward inside a uniformly heated tube at supereritical/subcritical pressures for various heat fluxes, tube lengths and tube inner diameters. The results show that Go increases with decreasing heat flux and tube length and decreases with increasing inner diameter.