A Study On Corrosion Behavior Of Tube And Tube Sheet In Multi-factor Coupling Heat Exchanger Transfer Process

The heat exchanger is a kind of equipment to realize heat exchange.It has been widely used in many industrial fields.In the production process,the heat exchanger often leaks because of the corrosive contact medium.Crevice corrosion is an important cause of heat exchanger leakage.The crevice corrosion of heat exchanger tube and tube sheet is the most serious.Heat exchanger tubes,tube sheets,and welds have different fluid temperatures and different materials.It is multi-factor.Therefore,it is necessary to study the flow process of circulating water in the crevice and the corrosion behavior of the heat exchanger tube and tube sheet crevice under multi-factor coupling.First,the numerical simulation was used to study the flow process of circulating water in the crevice and the corrosion behavior of the crevice between the tubes and tube sheets of the heat exchanger under multi-factor coupling.Fluent software was used to study the flow process of circulating water into the crevice and the velocity distribution and temperature distribution were obtained;Using COMSOL Multiphysics software to numerically study the crevice corrosion of heat exchanger tube sheet Q345 R in circulating water.Selecting the secondary current and dilute substance transfer modules in the corrosion module and establish a two-dimensional simplified model for the crevice between tube and plate of heat exchanger,selecting the appropriate boundary conditions and calculating the distribution of Clconcentration and potential under different crevice depths,crevice widths,temperatures and concentrations.Then,Q345 R composite board is taken as the research object.Using the method of polarization curve and AC impedance test in the electrochemical test to study the corrosion process of circulating water at different temperatures and different concentrations.Numerical simulation and electrochemical experiments were conducted to study the flow of circulating water in the crevice and the corrosion behavior of heat exchanger tubes and tube sheet crevice in circulating water.with the decrease of width,the increase of depth,the increase of chloride ion concentration and the increase of temperature,the chloride concentration and potential increased in the crevice.When the crevice depth is 9mm and the crevice width is greater than 0.65 mm,the crevice corrosion is not serious;When the temperature is below 50?,the Cl-concentration is not sensitive to crack corrosion.Crevicedepth and crevice width have the greatest influence on the crevice corrosion of heat exchanger tube and tube sheet,followed by temperature,followed by temperature.The difference between tube side and tube plate side in the crevice is significant.Therefore,it is necessary to consider the galvanic corrosion caused by different materials when studying the crevice corrosion of heat exchange tube and tube plate.The research can provide reference for the corrosion problem of different material structure combinations and the revision of heat exchanger standards.