大型换热器分段模块式优化模拟方法分析

Analysis of Modular Optimization Simulation Method for Large Heat Exchanger

为解决计算流体力学(CFD)软件模拟大型换热设备的流体流动与传热特性时计算机内存不足的问题,提出用分段模块式有限元模拟方法计算管壳式换热器等大型设备的流动与传热。分段模块式模拟方法把整体模型分成几个独立的单元模块各自处理,而后综合各单元模块的数据得到总体结果。文章以一折流板管壳式换热器为例,将换热器划分为进口模块,周期性边界模块和出口模块依次计算。其中单元模块的截取位置是影响计算准确性的关键因素,所以首先计算换热器整体模型的流场和温度场,利用流体进入充分发展状态后压降、流速和无量纲温度达到稳定值的特性,判断进口模块的截面位置在第三块折流板处,周期性边界模块的截面在靠近折流板的流体区间,出口模块的截面在最后一块折流板处。根据模块截面位置建立换热器分段模块模型,用模块模型计算一系列湍流雷诺数(Re)下的热流场,并对比整体模型的计算结果和试验数据以验证其准确性。结果显示当Re小于10000时,模块模型的计算结果和整体模型相似,可以用模块模拟法替代整体模型法计算换热器的热流场。相较于试验数据,模块法得到的壳程压降较小,传热效率更高。与整体换热器模型对比,模块法的计算周期约为前者的36%,计算效率至少提高了5倍,大大节约了计算机硬件配置并缩短了计算周期。

In order to solve the problem of computer resource allocation when simulating large heat exchange equipment with CFD software,a modular model finite element simulation method is proposed to calculate large flow field equipment such as shell and tube heat exchanger.The module model calculation method divides the overall model into several independent unit modules,processes them respectively,and then synthesizes the data of each unit module to obtain the overall result.Taking a baffle shell and tube heat exchanger as an example,the heat exchanger is divided into inlet module,periodic boundary module and outlet module.The divided position of the unit module is the key factor affecting the calculation accuracy.Therefore,the flow field and temperature field of the overall model of the heat exchanger is calculated firstly,according to the characteristics that the pressure drop,velocity and dimensionless temperature reach a stable value after the fluid enters the fully developed state,the section position of the inlet module is judged to be at the third baffle,the section of the periodic boundary module is in the fluid section close to the baffle,and the section of the outlet module is at the last baffle.The module model of the heat exchanger is established according to the above section position.The heat flow field under a series of turbulent Reynolds numbers is calculated by the module model,and its accuracy is verified by the overall model and the experimental data.The results show that when Re is less than 10000,the calculation results of the module model are similar to the overall model,and the module simulation method can be used instead of the overall model method to calculate the heat flow field of the heat exchanger.Compared with the experimental data,the shell side pressure drop of the module method is smaller,and the heat transfer coefficient is larger.Compared to the overall heat exchanger model,the calculation duration of the modular method is about 36%of the former,and the calculation efficiency is improved by at least 5 times,greatly saving computer hardware configuration and shortening the calculation duration.