Spray drying is one of the significant processes of various manufacturing sectors, especially for food processing industries which commonly use the process for drying milk, fruit juice, and vegetable juice. Prediction of the air flow, temperature, and humidity patterns in the co-current spray drying chamber with a pressure nozzle fitted at top of the drying chamber can help the design of the spray drying process. This thesis presents thermal fluid simulations of a spray drying chamber. The demonstrations were performed with two-dimensional and three-dimensional models using a Computational Fluid Dynamics package (CFD) ‘Fluent 14.5’. The gas phase was exhibited as a continuum using the Euler approach and the droplet phase was exhibited by the Lagrange approaches. We investigated the drying process considering the effects of air flow interacted with atomizing water droplets. The two-dimensional simulation generally predicted the fast downward flowing core and slow recirculation zones around it which successfully verify the simulation model. After that we performed the three-dimensional simulations, considering the application to the milk drying process. Most of the previous investigations have shown that the moisture content of the milk-air mixture is better to be around 4-6% (entering hot air up to 200℃) when the milk powders leave the chamber. This criterion was adopted to test our simulation parameters. The three-dimensional simulations correctly predicted the patterns of air flow, humidity, and temperature as well as particle tracks and distributions. The CFD simulation predicted the relationships between the inlet and outlet properties of the drying chamber. Variations of the inlet air temperature and water flow rate affect the outlet humidity of the exhaust air as well as the droplet sizes.
