Mathematical Modeling And Experimental Study Of Laminar Cooling Process On Plate Temperature Field

The critical of laminar cooling is temperature field.The purpose of laminar cooling is to refine the grain to improve performance.The establishment of an accurate temperature field model is the premise of improving the control cooling effect,and the heat transfer coefficient is the key parameter of the model boundary conditions,and its accuracy is the basis to ensure the accuracy of the model.Based on the established model of the temperature field,the heat transfer coefficient has been solved by experiment.The heat transfer coefficient formula has been obtained,and applied on controlled cooling after rolling to testify accuracy of the temperature model.The main contents of this thesis are as follows:(1)Establishment of plate process model.For the upper surface and lower surface of the cooling differences,the cooling heat transfer model was put forward based on the overall thickness direction,according to the different boundary conditions of air-cooling and water-cooling,different heat transfer coefficient models were adopted,then models were combined with the initial conditions and numerically solved by finite difference method,the final matrix was obtained,the simulation of temperature field was completed in the thickness direction according to the time sequence.(2)Solving heat transfer coefficient based on Improved Particle Swarm Optimization(PSO)algorithm.The heat transfer coefficient was obtained by inverse calculation of the experimental data based on the temperature field model,the improved particle swarm optimization was adopted in this thesis to identify various parameters in the heat transfer coefficient model;The error of improved particle swarm optimization is better than the conjugate gradient method and GA algorithm.(3)Designing and conducting laminar cooling experiments.The experiment platform was constructed,the COMSOL software was used to simulate the temperature field in order to determine the location of temperature measurement points and the preliminary experiment was carried out.The original temperature field error is less than 0.1%.The billet processing sample was improved according to problems existing in the preliminary experiment,thermal and water retaining measures were added,temperature data under different operating conditions are acquired by changing experimental conditions,the inertia and measuring error 1.1? of thermocouple are analyzed.(4)Temperature field model accuracy verification and parameter optimization.For three stages of air-cooling,water-cooling,and self-tempering of controlled cooling process after rolling,the upper surface and lower surface heat transfer coefficient models were solved separately,then they were substituted in temperature field model to compare errors between test point calculation results and measured results to verify the accuracy of the model.The deviation of the three stages have been respectively 2.4?,7.7?,8.5?.According to the calculation results of static temperature field,the dynamic temperature drop process of billet was simulated,and the optimum water ratio was put forward according to the inconsistent heat transfer intensity between the upper and lower surfaces.The analysis and numerical computation of temperature field and transfer coefficient have a great conclusion.More than 91.7%of the value of test point within 8.0?.The temperature field is stabilization and high efficiency.