Study On Temperature Field Of Hot Galvanized Steel Sheet In Cooling Tower

Strip temperature at the outlet of cooling tower is too high to make coating come off on top roll in the production of hot galvanized sheet steel,resulting in the surface quality defect and wrinkle of the coating,and the adhesion of zinc slag fall from top roll lead to security risk.In order to solve the problem,this paper uses ANSYS CFX software to simulate and analyze the cooling process,and verifies the correctness of calculation model and numerical simulation with experimental test.To reduce energy consumption and optimize operating parameters of unit,by adjusting strip transmission speed and injection velocity of cooling tower to meet the heat treatment process curve.It has a certain help and significance for safety production and improving the quality of hot galvanized sheet steel.The specific research contents are as follows:(1)Taking galvannealing furnace of a cold rolling mill plant as the research object,proper simplification and reasonable assumption are made,physical models for strip transmission,heat exchange and cooled by air blowing in galvannealing furnace are established by using ICEM CFD,combining basic control equations of fluid mechanics and turbulence model,a mathematical model for numerical simulation is determined.(2)Because soaking zone of galvannealing furnace is closed and cooling tower is open only on both sides,the test position is limited by the floor height of the production site,and the test instrument can not contact strip directly.Therefore,the thermocouple is used to test temperature field around strip,and strip temperature measured by the thermal infrared imager in cooling tower.Comparing numerical simulation results with experimental results,the relative error of simulation results of temperature field is less than 10%,and the relative error of simulation results of strip temperature is less than 5%.Strip temperature curve of measured in accord with simulation result,which proves the correctness of calculation model and numerical simulation.(3)On the basis of the model,by adjusting strip transmission speed and injection velocity of cooling tower to meet the heat treatment process curve,the results show that:when strip transmission speed u=1.5m/s,increasing injection velocity can aggravate convective heat transfer of cooling tower,but it causes the phenomenon of forced convection heat transfer,the relationship between strip cooling rate v and injectionvelocity V is a exponential function,and the critical minimum injection velocity is24.4m/s;when injection velocity V=25m/s,decreasing strip transmission speed appropriately is conducive to strip cooling,the relationship between strip cooling rate v and strip transmission speed u is a power function,and the critical maximum strip transmission speed is 1.6m/s.The matching relationship between strip transmission speed u and injection velocity V is V=14.02u+2.28.