基于CFD数值模拟的外取热器管束爆裂原因分析

Cause analysis of tube bundle burst in external heat exchanger based on CFD numerical simulation

某厂催化裂化装置外取热器管束出气管根部与三通连接位置接连发生爆裂,此处发生爆裂尚属首次。为找出管束爆裂的主要原因,运用了计算流体力学软件Fluent中的DPM模型对该处气液两相流场、管壁的冲蚀情况及水蒸汽中水滴分率对管壁冲蚀的影响进行了数值模拟。结果表明,管束爆裂处混合流体速度最大,冷凝水滴浓度最高,致使冲刷最严重,且水滴的分率越大,冲刷越严重。腐蚀及冲刷的交替恶性循环是造成外取热器管束爆裂的主要原因。

The tube bundles burst has taken place firstly at the root of the external heat exchanger and the three way pipe bundle connection position. In order to find out the main reasons for the burst of tube bundles,numerical simulation for the movement of liquid-vapor two-phase flow in pipe bundle,erosion of pipe wall and the influence of water drop fraction in vapor on erosion of pipe wall is performed by using the DPM model in CFD Fluent. The results show that the velocity of the mixed fluid at the burst position is the largest and the concentration of condensed water droplets is highest,resulting in the most serious erosion of the pipe wall. More water drop fraction gives rise to more serious erosion. The vicious cycle of corrosion and erosion is the main cause of the burst of the external heat exchanger tubes.