Experimental design approach to evaluating factors for enhanced cork mass insulation

Abstract

This research examines the mechanical properties of cork, explicitly focusing on enhancing its mass insulation characteristics by calculating the apparent diffusion coefficient. This coefficient was obtained by combining conductimetric measurements with model calibration and further refined using an optimization model based on the Bat Algorithm. A series of eight experiments was conducted to examine the impact of operating parameters and their interactions on cork’s diffusion coefficient using the experimental design according to the response surface methodology. The factors considered included three potential growth areas spread over the North of Algeria, cutting directions, and material states (treated and native). Given the duration and expense of the experiments, a linear model incorporating interactions was employed to examine the effects of all parameters. The Minitab software allowed for estimating the model’s coefficients, including interactions, indicating that the diffusion coefficient remains unaffected by the planting area. However, the tangential cutting direction influences the mass insulation property. Additionally, the negative sign of the coefficient associated with thermal heat treatment indicates that this factor enhances cork’s insulation performance, reducing the diffusion coefficient from 3.40·10–12 m²/s to 4.57·10–13 m²/s. Moreover, treated cork exhibits a diffusion coefficient value four times lower than that resulting from the tangential cutting direction. As a result, the experimental findings enabled the development of a simplified predictive model for mass diffusivity, with a coefficient of determination of 0.90 and a significance level of 0.05.