Simulation Analysis On Swirl Nozzle For Liquid Distributor In Horizontal-tube Falling Film Device

In a horizontal tube falling-film evaporation device, the uniform distribution ability of the liquid distributor has a very important impact on device total heat transfer coefficient. Nozzle type liquid distributor has the advantages of not easy to jam, simple structure. Therefore, analysis and grasp the law of internal flow field and external liquid spray uniformity is the key in the study of liquid distributor nozzle. In this paper, three types of top structure swirl nozzles are numerically investigated.Three kinds of nozzle inner cavity as well as the external cylindrical area physical model and mathematical model are set up. The inner and external flow fields of the three nozzles are numerically investigated by using the VOF model and the realizable k-ε turbulent flow model. The velocity and pressure characteristics of water and air inside the nozzle are analyzed, especially near the spiral structure. Based on the total mass flow distribution in equally divided districts along the circumferential direction and centroids distribution of the water mass flow on different horizontal planes below the nozzle exit, analyses about the nozzle spray uniformity are conducted.Geometric structure and size parameters of the nozzles are important factors influencing flow characteristics and spray uniformity. Detailed analysis to the geometry structure change is carried on in this paper. How the column height and radius of the cap structure at the top, the height, starting angle of the spiral structure at the top, the height above and below the swirl chamber influence nozzle performance is analyzed.It was obtained that the structure of the flow field consists of eccentric and screwy air core inside the nozzle. The spray outside the nozzle is circumferential non-uniform, to decrease this phenomenon, changing the top structure inside the nozzle with the cap structure or spiral structure is feasible. The higher the height of the cap structure, the spray is more uniform, and there exists an optimal value of the cap structure radius, so is the height of the spiral structure. When the starting position of spiral structure is0°, spray uniformity is the best. The height of the swirl chamber above the entrance is greater, the height below is smaller, spray is more uniform.