چكيده به لاتين
Nowadays, due to the increasing progress of the food, pharmaceutical and advanced materials industries, the importance of producing raw materials or dry powder products with good quality and in accordance with the needs of the market is felt more than ever. Meanwhile, the spray drying process is very important. The Spray is used for proper distribution of liquids in various applications; Extinguishing fire, delivering medicine, delivering fuel to combustion chambers, producing powder of various materials, spreading food and pesticides to plants, and air cooling are examples of the many uses of spray. This method has many applications in food, pharmaceutical and chemical industries. In these applications, the spray mainly consists of a gas stream containing liquid droplets. This method is widely used for drying solutions, suspensions, emulsions and pastes in food, chemical, pharmaceutical, ceramic, etc. industries. A special device called atomizer turns the liquid into fine droplets and simultaneously disperses it inside the chamber along with the hot air. In this research, the droplet evaporation process has been investigated, analyzed and simulated in four steps using CFD in Fluent software: the first step includes simulating the single-phase evaporation of water vapor and air, the second step is simulating evaporation of single drop and hot air with Eulerian-Lagrangian approach, the third step of simulation of drops with two diameters of 10 and 100 micrometers under the same conditions in the discrete phase model (DPM) in order to check the model and in the fourth step of simulation of drops under the same conditions Different diameters, speed and initial location of droplet entry into the chamber with a specially designed nozzle were investigated using Fluent software and the effect of changing these parameters on droplet evaporation was investigated and evaluated quantitatively and qualitatively, the important effect of location The entrance of the drop in the continuation of the drop movement, as well as the effect of the drop diameter and its speed in determining the process and approach of evaporation are important results of this research. It was observed that the greatest effect of changing the mentioned parameters on the droplet evaporation rate is observed in the diameters of 100 and 10 microns, and in the diameter of 50 microns, changing the values of these parameters has an insignificant effect on the evaporation process and the droplet diameter reduction. Also, the higher the droplet speed is, the greater the reduction in droplet diameter will be in the condition of fixed inlet location, and with the increase of the droplet speed to values greater than 1m/s, no noticeable change in the process of evaporation and droplet diameter reduction is observed. If the initial location of the drop is too close to the hot air inlet, due to the location of the drop in the high-pressure area, it will leave the chamber and it is not possible to observe the evaporation process and conditions.
