Entropy production during the drying process of milk droplets in an industrial spray dryer

Development of high energy efficiency spray dryers is of great importance for the future of the dairy powder industry. The present research studied energy efficiency in an industrial scale spray dryer with the second law of thermodynamics. The entropy production rate is computed from the CFD modeling results of the transient multi-phase flow in the spray dryer. Influences of particle size, inlet air flowrate and inlet air temperature on the entropy production rate are analyzed. The results show that large particles produce more entropy per unit mass on dry basis. To decrease the moisture content of product powders, it will produce more entropy by increasing inlet mass flowrate than by increasing the air temperature. The study shows that the second law of thermodynamics is a potential tool for optimizing dryer operation and design.