Numerical Simulation Of The Mono-disperse Droplet Spray Drying Process:Effect Of Nozzle Movement And Optimization Of Probiotic Inactivation Process

With the increasing demand of uniform particles in the fields of medicine,health care products and functional food,the research on monodisperse droplet spray dryer(MDSD)becomes more and more important.Due to the characteristics of the monodisperse droplet generator itself,the drying efficiency of this dryer is not high,how to further improve the drying efficiency of the drying tower and shorten the height of the tower has become a subject worth studying.Inspired by the rotary atomizer,the DPM model of FLUENT is integrated with the reaction engineering approach(REA)based drying model to study the influence of different nozzle movement schemes(reciprocating linear motion,reciprocating sinusoidal motion and uniform circular nozzle motion)on the final drying performance taking the 20 wt%reconstituted skim milk as an example.It is found that the final moisture content of particles can be significantly reduced by accelerating the moving speed of the nozzle,and the movement of the nozzle leads to a wider distribution of the final moisture content of particles,but this effect becomes less significant with the increase of the velocity of nozzle motion.For all motion types under investigation,the circular motion is superior to the other motion types in terms of the average and standard deviation of final moisture content of particles.And under the current experimental situation,it is found that the change of droplets dispersion state is the main factor to improve the drying performance.At the same time,naturally much attention has been paid to probiotics powder,so it is necessary to model and optimize the deactivation process of probiotics during spray drying.In this work,one-dimensional calculation and three-dimensional CFD model of spray drying have been used to optimize the spray drying process containing probiotics cooperated with the inactivation model of probiotics.In order to improve the accuracy of prediction of probiotics deactivation process in spray drying process,other factors,such as heating rate of droplets,have been introduced by re-modeling the experimental data and the factors in the two scenarios are compared to complete the modeling.