Three Dimensional Numerical Simulation On Air-Blast Spray Drying

Air-spray drying device structure is simple, and its atomization performance isrelatively high, which makes it widely used in the food, chemical, pharmaceutical andother industries. Due to the complexity of motion state in the spray-drying tower andheat and mass transfer process between droplet and drying medium, detailed analysisof heat and mass transfer and gas-particle two phases movement in the drying tower isvery important. The experimental methods to obtain the detailed data of the drying gasin the spray-drying tower and the trajectories of the particles not only require a lot oftime, but also need expensive test equipment and laboratory fees, while somemicroscopic amount under the conditions of this technology is still difficult to measure.With the development of computer technology, computational fluid dynamics (CFD)method is an effective way to solve this problem.By studying the theory of numerical analysis, heat and numerical mass transferand CFD, this paper creates a3D numerical simulation of air-spray drying process withcomputational fluid dynamics software FLUENT.The paper uses GAMBIT software to build and mesh physical model of PC-015experimental air-spray drying tower, and creates the mathematical model of a vaporcontrol equation describing the air-spray drying process, the particle trajectory model,two-phase gas-particle heat and mass transfer model and the discrete phase and thecontinuous phase coupled equations. The finite volume method is used for equationsdiscretization, SIMPLE algorithm is used for solving the equations of gas control andPSI-Cell algorithm is used to couple the interaction between vapor and discrete phase.Considering the interaction between the gas-liquid two-phase flow and heat and theimpact to particle size distribution, particle trajectory caused by mass transfer, thepaper gives boundary conditions and simulates the spray drying tower with numericalmethods.By changing material, quality, flow rate and the gas-liquid relative velocity, thispaper studies the trajectories of the particles in the drying tower, drying conditions andduration. The most suitable conditions are found: the speed of the hot air0.05kg/s,nozzle diameter of1mm, the relative velocity of150m/s and material mass flow0.0034kg/s. By simulation of the spray drying process and study of the gas phase temperature field, humidity, velocity and trajectory of the particles, particle residencetime, particle diameter, it creates a an exact reproduction of droplet trajectory, particlesize distribution and hot air temperature field in tower, and provides a theoretical basisfor the future air-spray drying tower design and optimization.