Modeling and evaluation in transient analysis of industrialized counter-flow tea drying system

The main purpose of this work is to develop a transient analytical model of an industrial tea dryer based on the theory of heat and mass balance, and provide the variation characteristics in tea moisture content and drying air temperature throughout the whole drying process in the drying chamber. A numerical simulation focusing on the established transient analytical model was conducted, and the simulation results show that the moisture content of tea in the drying chamber performs a descend trend along the flow direction over drying time, while the temperature of the dry air performs an ascend trend along the flow direction of tea. The variations coefficient for the tea moisture content and the dry air temperature in the whole drying chamber were determined to be 0.009-0.09 and 0.065-0.126, respectively, indicating that the overall drying process is relatively stable. An actual production drying test was conducted to validate the analytical model, the test results showed that under dynamic drying conditions, the dynamic changes in tea moisture content and dry air temperature in the drying warehouse are consistent with the corresponding trends predicted by the model. Besides, the determination coefficient of tea moisture content is greater than 0.99, the determination coefficient of dry air in the initial drying period is 0.8027, while it is determined to be 0.9872 in the redrying period. The predicted results of the model are in good agreement with the experimental results, which confirms the effectiveness and reliability of the model. The developed transient analytical model can provide a certain reference for the anaphase development of energy optimization, dynamic state monitoring, and parameter matching systems for tea dryer.