Model of nonequilibrium drying hollow cylindrical porous media

A three-field gradient drive model with temperature, humidity, and pressure as physical quantities was established for the drying process of hollow cylindrical porous media. The nonlinear coupled heat and mass transfer equations were solved by an iterative method, and excellent agreement was observed with experimental data. The numerical results show that the drying time decreases as the nonequilibrium coefficient Ke increases, while at around 1.0 s-1, the drying time approaches a constant, showing no further effect of Ke on calculation results. There is excellent agreement in both figures in terms of average saturation or average temperature and experimental data when Ke = 0.03 s-1 whenever the valve is half or fully opened. Thus, 0.03 s-1 is the standard value of Ke for the residual ammonia recovery process. The calculation results based on this standard value revealed that no matter how fast the pressure dropped, only 22.5% of the residual ammonia can be dried. Therefore, the drying process with microwave was analyzed in the present study, showing that microwave heating can accelerate the drying process, and that the overheating effect caused by pressure drop is dominant when τ < 1200 s, but when over this critical time microwave heating is the only driving force mechanism of phase change in the porous media. © 2020 by Begell House, Inc. www.begellhouse.com