Study On Heat Transfer Law Of Submerged Jet Impingement On High-temperature Steel Plate

Ultra-fast cooling technology plays an important role in the cooling process of hot rolled steel.The performance of the hot rolled product was directly affected by the cooling capacity and cooling homogeneity of the steel after hot rolling.The jet impingement was applied in the cooling system of the high-temperature steel to achieve high-strength and homogeneous cooling of the rolled products.In this paper,mainly research into the heat transfer process of hot rolled steel after submerged jet impingement.The main factors influencing the heat transfer ability of submerged jet impingement were analyzed.The heat transfer law of high temperature steel and the flow characteristics of the plate surface were analyzed when the submerged jet impingement,and the influence of the pressure and nozzle spacing variation on the cooling capacity and cooling homogeneity of different thickness positions were explained.The difference in heat transfer performance between the submerged jet and free jet in the thickness direction of the steel plate was verified.The main research contents and results are as follows:(1)The flow characteristics of the plate surface and the heat transfer law of the plate were simulated when the single nozzle submerged jet impacted on the high-temperature steel plate.The main factors affecting the heat transfer performance of the submerged jet impingement were determined by orthogonal test.The influence of inlet pressure and nozzle cone angle on the flow characteristics of the plate surface and the heat transfer process in the thickness direction of the plate were studied.The research results showed that the heat transfer ability of the jet impingement was significantly affected by the inlet pressure of the nozzle.Increasing the nozzle inlet pressure was beneficial to improving the heat transfer capacity of the submerged jet impingement.(2)The flow characteristics of the plate surface and the heat transfer law of the plate at the intersection of nozzles were simulated when four nozzles submerged jet impacted on the high-temperature steel plate.The effects of inlet pressure and nozzle spacing on the cooling rate and temperature gradient of the jet intersection at different positions in the thickness direction of the plate were studied.The relationship between cooling rate,temperature gradient and temperature was analyzed.The results showed that increasing the nozzle inlet pressure and reducing the nozzle distance were beneficial to improve the heat transfer capacity of the jet impingement.(3)The heat transfer process when submerged jet and free jet impacted on the high temperature steel plate were simulated and compared.The impact pressure,turbulence intensity,shear force and flow velocity on the plate surface under the jet impingement process of the single nozzle and four nozzles were compared.The temperature drop curves and cooling curves in different positions of the plate thickness direction were obtained and the cooling effect of the two kinds of jets was compared.By comparison with the free jet impingement,better cooling performance and cooling homogeneity was obtained in the submerged jet impingement(4)Based on the numerical simulation and experimental results,the temperature drop curves and cooling curves of the different thickness positions during the jet impingement process of free jet and submerged jet were obtained.Furthermore,the relative error between the numerical simulation results and the experimental results was less than 10%and the numerical simulation results were consistent with the experimental results.