The lumped approach in drying modeling of roofing tiles – variable effective diffusivity determination

Abstract

In this paper, the drying modeling of roofing tiles was done using a "lumped" approach. In other words, several forces that are influencing internal moisture transport are combined to create effective moisture diffusivity. For this reason, the effective diffusivity coefficient was added to Cranck's diffusion equation. In their earlier works, the authors published the solution to the diffusion equation, which assumes that effective diffusivity is constant. It was demonstrated that, particularly if shrinkage is not taken into account during the computation stage, the simulated drying curves differ from the experimental results. The next step was to ascertain the time-dependent effective diffusivity and to more precisely anticipate the drying kinetic. The general functional relationship between effective moisture diffusivity and Fourier number was first determined to fulfill this assignment. Experimental proof of the proposed model was provided. Less than 3% of the outcomes from the simulation and the experiment deviated from each other. This was a resounding affirmation that effective diffusivity is not constant during drying and that all internal transport mechanisms are observable in their timedependent relation.