Analysis of entropy generation and classification performance of turbo air classifier

The entropy production theory in the second law of thermodynamics was used to analyze the entropy generation caused by the irreversible factors in turbo air classifier. The classification performance of the turbo air classifier was evaluated by powder classification experiments. The entropy generation caused by gas viscosity, turbulent and wall fraction were obtained. Meanwhile, the effects of operational parameters on entropy generation and classification performance were investigated. The results showed that the ratios of turbulent entropy generation and wall entropy generation to total entropy generation were 56.41% and 43.11%, respectively. The turbulent entropy generation mainly occurred in the blade clearance and the inner rotor cage, while the wall entropy was mainly caused by walls of the air inlet and outlet. The rotor cage speed and inlet air velocity dominated the gas entropy generation in the regions of the rotor cage and air inlet, respectively. The variation of the entropy generation/total energy in the classifier was insignificant and the stability of the flow field was high when the classifier worked on the conditions of 8.6m/s-800r/min and 18m/s-1200r/min, respectively. In this case, the flow field distribution was helpful for particle separation and the classifier had higher classification efficiency. Therefore, the entropy generation analysis can be used for the prediction of the flow characteristics and operational optimization of the air classifier. © 2020, Chemical Industry Press Co., Ltd. All right reserved.