Theoretical and experimental research on heat and mass transfer in a turbine thin layer dryer

Abstract

The research is based on an engineering project to develop an efficient and energy-saving sludge drying apparatus. A heat and mass transfer model was developed to understand the drying mechanism in a turbine thin-layer dryer. Numerical simulation was performed to investigate the changes in sludge content, temperature, and moisture content under different paddle angles. The results showed that the paddle angle of 45° provided the optimal effect of water evaporation and sludge conveying. Subsequently, a turbine thin-layer drying system was established and drying experiments were conducted to explore the influence of different operating parameters on the drying efficiency. The experimental drying results were compared with the simulation results, which showed that the developed model could predict the experimental results. The residence time experiment showed that the developed dryer was efficient in treating highly viscous sludge. The results of the orthogonal experiments showed that the heat source temperature and the rotating speed were the main influencing factors of the moisture content and energy consumption, respectively. A sensitivity analysis determined the optimal operating parameters for the experimental apparatus.