Title: Modeling the Effect of Thermal Treatment on Hardness of Small Cashew Nut Shells
Authors: Joseph Gberindyer Jimeshio, Tawakalitu Bola Onifade, David Oluwafemi Idewu
Volume: 9
Issue: 12
Pages: 6-12
Publication Date: 2025/12/28
Abstract:
The mechanical modification of agricultural by-products through thermal processing has become an important pathway for value addition and sustainable utilization. Cashew nut shell, an abundant lignocellulosic residue in Nigeria, possesses engineering properties that can be enhanced through controlled thermal treatment. This study investigates the effect of temperature and time interactions on the hardness of small cashew nut shell accessions and developed a predictive model using the Buckingham Pi theorem. Small cashew nut shells obtained from the Cocoa Research Institute of Nigeria (CRIN) were thermally treated at 200°C, 250°C, and 300°C for 30, 60, and 90 minutes. Hardness and compressive strength measurements were conducted using a universal testing machine (UTM), while accompanying physical and thermal properties including density, moisture content, shrinkage, thermal conductivity, and specific heat capacity were determined using standard engineering methods. Dimensional analysis generated three fundamental ? terms that formed the basis of a hardness prediction model expressed as: H=?(??K/T?). The generalized reduced gradient (GRG) nonlinear Excel solver was used to estimate the model constant (?) by minimizing the sum of squared errors. Model validation revealed strong agreement between measured and predicted hardness values, with low RMSE (0.6963) and a high residual prediction deviation (RPD) = 21.58, indicating excellent predictive performance. Findings demonstrated that thermal treatment significantly modifies the hardness of small cashew nut shells and that the developed model reliably captures these changes. This model provides a useful tool for optimizing thermal processes in cashew shell valorization and related agro-processing applications.