Research On Numerical Simulation Of Spray Cooling Of The Hot Vertical Moving Strip

Spray cooling is widely applied in metallurgy,electronic components and other industries as a new cooling method with the advantages of high efficiency,high heat transfer coefficient and high utilization rate of working fluid.The current research on spray cooling mainly focus on the horizontal and static wall cooling,however,it often appears the cooling problem of vertical wall in moving,especially the cooling object in the cooling section of galvannealing furnace is the vertical moving strip,so it is necessary to study on spray cooling of the hot vertical moving strip.In this paper,first of all,established the physical model and the mathematical models of spray cooling of the hot vertical moving strip,the cooling characteristics of the strip under different cooling mediums were studied by the FLUENT with reasonable boundary conditions.The results showed that compared with air and water cooling medium,the spray cooling model of aerosol two-phase medium showed the largest cooling rate and smaller temperature uniformity of the strip.Secondly,the influences of nozzle inclination,and strip's vertical velocity on cooling characteristics of the spray cooling in the hot vertical moving strip were studied.The results showed that,at the same absolute value of nozzle inclination,the nozzle inclination which against the strip moving direction,had the faster cooling rate of the strip than the nozzle inclination which along the strip moving direction,and the cooling rate of the strip was the largest when the nozzle inclination was-30°.With strip's vertical velocity increasing,the instantaneous cooling rate of the strip decreased gradually,and the temperature distribution of the strip was more uniform.Thirdly,the influences of spacing of nozzles on cooling characteristics of the spray cooling with two nozzles in the hot vertical moving strip were studied.The results showed that,with the increase of the transverse spacing of two nozzles,the cooling rate of the strip decreased continuously,and the cooling rate was the largest when the longitudinal spacing of two nozzles was 20 mm.When the transverse spacing was equal to the longitudinal spacing,the cooling rate of the strip with two nozzles arranged in the longitudinal direction was larger than the transverse direction,but the uniformity of the temperature distribution was worse than that of the latter.Finally,the influences of the arrangement of nozzles on cooling characteristics of the spray cooling with multi-nozzle in the hot vertical moving strip were further studied.The results showed that when the four nozzles were arranged in parallel,the cooling rate of the strip was the largest,and the temperature distribution of the strip was the most uniform than the four nozzles completely staggered.And when the four nozzles were arranged in parallel,50 mm was an optimal longitudinal spacing,which made the largest cooling rate of the hot vertical moving strip in the spray cooling process.The spray cooling process of the hot vertical moving strip had been studied by numerical simulation,which provides a theoretical basis and practical guidance for the research of the spray cooling device in the cooling section of galvannealing furnace.