Heat and mass transfer characteristics and drying process optimization of Camellia oleifera seeds after hot air drying and shelling of the fruits

To elucidate the intricate dynamics of moisture and temperature alterations in Camellia oleifera seeds throughout hot air drying and subsequent bursting, this investigation embarked on an exhaustive quest for a superior drying technology parameter system, characterized by exceptional energy efficiency and minimized energy expenditure. The cornerstone of this study involved systematic measurement of pivotal physical attributes of Camellia oleifera seeds, encompassing thermal conductivity and density, to furnish a comprehensive understanding of their inherent properties. A meticulous exploration of the thermodynamic behavior of Camellia oleifera seeds during drying was undertaken at distinct temperature intervals 52 ℃, 62 ℃, and 72 ℃. Leveraging Fick's Second Law, we precisely ascertained the effective moisture diffusivities corresponding to each temperature regime. A reverse engineering methodology was then employed to construct an Arrhenius equation model, grounded in the empirically derived data on effective moisture diffusivity. This model elucidated the complex interplay between effective moisture diffusivity, drying temperature, and activation energy, unveiling profound insights into their intrinsic correlations. Parallel to this, a mathematical simulation framework was devised, synthesizing principles of heat and mass transfer, to model the drying process of Camellia oleifera seeds. The model's predictions exhibited a striking congruence with experimental findings, maintaining a maximum discrepancy of merely 8.5%. This underscored the model's remarkable precision and reliability. Our findings illuminated that the hot air drying dynamics of Camellia oleifera seeds are fundamentally steered by internal mass transfer phenomena. The establishment and endurance of moisture gradients vastly outlast those of temperature gradients. Intriguingly, the drying rate's fluctuation trend manifests a uniform pattern across varying drying temperatures. Spanning the temperature spectrum from 52 ℃ to 72 ℃, the effective moisture diffusivity of Camellia oleifera seeds escalates significantly, ranging from 3.299 4×10⁻¹⁰～5.582 6×10⁻¹⁰ m²/s, with a computed activation energy of 25.025 kJ/mol. This quantitative revelation delineates the energetic transformations intrinsic to the drying process. Expanding upon the theoretical edifice established thus far, this study ventured into the realm of variable temperature drying strategies for Camellia oleifera seeds. A meticulous dissection of the impact laws governing three pivotal parameters—the initial wind temperature, the moisture conversion threshold, and the concluding wind temperature on specific energy consumption and drying velocity was executed. Through the application of Response Surface Optimization techniques, the ideal amalgamation of drying parameters was crystallized: an initial wind temperature of 64 ℃, a moisture conversion point of 38.5%, and a terminal wind temperature of 75 ℃. Under these optimized conditions, a commendable performance was achieved, marked by a specific energy consumption plummeting to 5.040 kJ/g and a drying rate peaking at 0.048 36 g/(g·h). Relative discrepancies compared to the model projections for specific energy consumption and drying rate were 7.4% and 12.1% respectively, affirming the pragmatic applicability and accuracy of the optimized parameters. In summation, this scholarly endeavor not only lays a robust theoretical groundwork for the refinement of Camellia oleifera fruit hot air drying and bursting methodologies but also delineates practical drying process parameters, paving the way for industrial implementation and dissemination of Camellia oleifera fruit drying technologies. It thus bears considerable academic significance and promising avenues for practical application.