Numerical Study of a Non-Linear Porous Sublimation Problem with Temperature-Dependent Thermal Conductivity and Concentration-Dependent Mass Diffusivity

Sublimation heat transfer occurs in a wide range of engineering processes such as Accelerated Freeze Drying, energy storage and food technology. Particularly, in microwave AFD process, preservation of material with least possible energy consumption is desirable. In connection with this, it is of interest to analyze the effect of temperature/concentration dependent heat/mass transfer properties. Given the limited literature available on sublimation, there is a general lack of physical understanding of this particular problem. The present work analyses non-linear sublimation process driven by convective heat/mass transfer and evaporation of water vapor using the Legendre wavelet-collocation method. Results from the present work are shown to be in excellent agreement with the exact solution of special case of a linear problem. Further, present numerical technique shows strong acceptance with finite-difference method in case of full non-linear model. The model is used for a comprehensive investigation of the impact of problem parameters appearing in this study on the rate of sublimation. It is found that sublimation rate increases with increasing values of ß1 and decreasing values of ß2. The impact of other dimensionless problem parameters such as Peclet numbers Pe1 and Pem, convection due to moisture flow of water vapor ß, latent heat of sublimation l0 and Luikov number Lu on sublimation process is also discussed in detail. These observations offer a comprehensive theoretical and mathematical understanding of sublimation heat/mass transfer under practical conditions for improving the performance and efficiency of freeze-drying related engineering processes.