For effectively estimating the moisture migration patterns in convection drying process of sludge under ultrasonic irradiation,based on the theory of non-equilibrium thermodynamics,a mathematical model for the coupled heat and moisture transfer process in convection drying of sludge under the effect of ultrasonic field was established.In the model,the ultrasonic effects on porosity,permeability and effective moisture diffusion rate of sludge were considered,and the permeable flow driven by acoustic pressure gradient in sludge was also taken into account.The effects of ultrasonic energy density and temperature of hot air on the moisture content distribution in sludge drying process were numerically studied.The simulation results show that,the ultrasonic irradiation effectively accelerates the moisture migration rate of sludge,and when the ultrasonic density matches with the external mass transfer conditions such as air temperature and velocity,the ultrasonic effect can best enhance the convection drying process of sludge,and the optimal efficiency of drying can be achieved.