| Continuous annealing and cooling technology is the key link of the production process of advanced high-strength steel.The modern continuous annealing process raises extremely high requirements on the annealing cooling technology in order to ensure the quality of strip.Modern popular annealing and cooling technology has many disadvantages in strip surface quality,cooling rate and production specifications and models.These disadvantages of process have not been solved effectively due to the lack of technological innovation on continuous annealing cooling technology.In this paper,pentane is regarded as the cooling medium(the chemical formula of pentane is C5H;2),C5H12 aerosol spray annealing cooling process is developed.The process mainly uses aerosol nozzle,with high-pressure nitrogen to spray pentane onto the strip surface in the form of thin droplets to cool the strip.The process has the advantages of high cooling rate,good strip surface quality and less demand for working fluid.For this new continuous annealing process,software simulation analysis on cooling rate of pentane aerosol spray cooling process was carried out.Also,the experimental platform of pentane aerosol spray was built and the pentane spray cooling experiment of strip cooling rate was finished to compare with the software simulation.This paper also carried out the study of the heat transfer mechanism of the experimental process.The advantages of the pentane aerosol spray technology were carried out through the comparison with the gas-water spray experiment and pressure spray experiment of pentane.The main contents of the research in this paper are as follows:(1)Get the cooling rate of different thickness strips under different parameters simulated through software simulation.The cooling rate of strip increased with the increasing of pentane pressure.The cooling rate of 0.5 mm strip steel increased with the increasing of nitrogen pressure,but the change of nitrogen pressure has little effect on the cooling rate of 1.0 mm,1.5 mm and 2.0 mm strip steel.(2)Pentane aerosol spray experimental device was built,the pentane aerosol spray experiment was carried out and the simulation results were verified.Get the variation of the cooling rate with different parameters through experiment.The comparison between simulation and experiment shows that:for the 0.5 mm strip,there is a certain deviation in the simulation results.For 1.0 mm,1.5 mm and 2.0 mm strip steel,the simulation results are accurate and the error is small.The simulation results provide foundation for establishing C5H12 aerosol jet cooling control model.(3)During the pentane aerosol spray cooling process,heat exchange reach the Leidenfrost point of the minimum heat flux density while the surface temperature is 130?,and the maximum heat flux density and heat transfer coefficient CHF point is reached at a surface temperature of 100?.When the surface temperature is higher than Leidenfrost point,the heat exchange mode is mainly film boiling heat transfer;when the surface temperature is lower than Leidenfrost point,the heat transfer mode is mainly nucleate boiling and transition state boiling.(4)The cooling rate of pentane aerosol spray is lower compared with gas-water spray cooling,but the cooling rate is significantly higher than high-speed hydrogen spray cooling which meets the production requirements of high quality strip.The strip surface is also smooth without oxide scale.Compared with pentane pressure jet cooling,the requirement of pentane for aerosol spray cooling at the same cooling rate is only one quarter of the pressure jet cooling.C5H12 aerosol spray annealing cooling process has the advantages of less demand for working fluid. |
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