超声场作用下污泥对流干燥过程的数值模拟

为了有效预测超声场作用下污泥对流干燥过程中内部湿分迁移规律,基于非平衡态热力学理论,建立了超声场与热风联合作用下污泥对流干燥热质传递过程的数学模型.模型中考虑了超声作用对污泥孔隙率、渗透率及湿扩散速率的影响,以及污泥内部声压梯度引起的物料液相湿分渗流.对不同超声声能密度及对流温度作用下污泥内部湿度场分布进行数值模拟.模拟结果表明,超声作用有效加速了污泥干燥的湿分迁移速率,且当超声作用密度与热风温度、风速等外部传质条件相匹配时,才能发挥超声作用的最佳强化能力,达到最优的干燥效率.

Numerical Simulation on Convection Drying Process of Sludge Under the Effect of Ultrasonic Field

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.