Research Of Flow And Heat Transfer Of Liquid Film In Spray Cooling Of Vertical Moving Wall

Spray cooling is widely applied in metallurgy,electronic components and other industries as a new cooling way with the advantages of high cooling efficiency,heat transfer coefficient and utilization rate of working fluid.As the current domestic and international research on spray cooling mainly focused on the cooling of the horizontal and stationary wall,but in real production,it often appears the cooling problem of vertical wall in moving,so it is necessary to explore the spray cooling of vertical moving heat source.Because film is one of the main heat transfer methods in spray cooling,it is very important to analyze the flow and heat transfer mechanism of liquid film.In this paper,taking the structural characteristics of the wall into account,the fan nozzle is used for spray cooling in vertical moving wall.Firstly,the physical model of spray was built.The first order linear non-homogeneous differential equation of the velocity distribution function of spray fluid was obtained on basis of three conservation laws of fluid dynamics and was solved with variation of constant.The velocity distribution function of spray fluid was simulated by MATLAB software combined with spray characteristic parameters such as spray angle,spray distance and mass flow rate of the sector of fan nozzle and the distribution curve of fluid velocity was obtained.The results showed that the closer to the edge of the spray,the smaller and more uniform the velocity of fluid.Secondly,the mass and momentum conservation model of liquid film flow was built.The flow velocity and thickness of the liquid film was theoretically deduced,and the distribution function of the flow velocity and thickness of liquid film with respect to the spray distance and equivalent spray radius was obtained.The structure parameters of the spray system were set and the flow velocity and thickness distribution of the liquid film with equivalent spray radius under different spray distance were simulated.The results showed that the film flow velocity in the edge region of spray is faster than that in the center region and the distribution of film thickness is more uniform.The obvious bulge phenomenon appeared in the center and the phenomenon of accumulation and retraction of film outside the spray area appeared as the film flow velocity reduced.Based on the analysis of the liquid film flow characteristics,the energy conservation model of thesystem is established in this paper.The function of the heat flux of liquid film with the spray distance and equivalent spray radius was derived and the distribution curves of heat flux of liquid film heat transfer with respect to equivalent spray radius under different spray distance were obtained by MATLAB.It showed that the heat flux of the liquid film in the spray edge region was higher than that of the center region,and the distribution was more uniform,so the heat transfer effect was better.In summary,the study was done from three aspects with the spray fluid velocity distribution characteristics,the flow velocity and thickness distribution and the heat transfer characteristics of liquid film in the paper.The relevant conclusions obtained in this paper provides a theoretical reference and technical guidance for the practical application and the experimental study of the heat transfer mechanism in spray cooling.