小尺度管壳式换热器流动和传热数值模拟

摘要

Through symmetry simplification,the heat transfer model of small shell-and-tube heat exchanger was established; and basing on the Simple algorithm,RNG k-ε equation,porous medium model,enhanced wall function,finite volume method and the structured grid,the discrete control equation was dispersed to solve three-dimensional N-S equations and energy equations so that the heat transfer process of the fluid flow in shell can be simulated; and in the case of keeping constant tube diameter and 1.2,1.4 and 2.0 pitch diameter ratio,the distribution pattern of both flow and temperature fields was analyzed,including the key factors that affecting heat transfer pedormance.The results show that,at the same boundary conditions,the smaller pitch diameter can result in eddy current around the tube wall,this can bring higher heat transfer performance,larger turbulence intensity and tube bundle erosion which can decrease the device service life.%通过对称性简化,建立了小尺度管壳式换热器的传热模型.基于Simple算法,采用RNG k-ε方程、多孔介质模型和增强壁面函数法,结合有限体积法及结构化网格对控制方程进行离散,求解三维N-S方程和能量方程模拟了流体在壳程流动的传热过程,在管径不变的情况下,针对节径比分别为1.2、1.4和2.0下的流场及温度场的总体分布规律进行分析,对影响其传热性能的关键因素进行了探讨.结果表明:在相同边界条件下,设计较小的节径比,易在管壁周边形成涡流,换热器的传热性能指标较高,但湍流强度过大,流体剧烈冲刷管束,将对设备的寿命产生影响.