Mechanistic Interpretation of Ethanol-Pretreatment-Enhanced Drying of Beetroot Through Coupled Diffusion–Shrinkage Modeling

Experimental investigation of convective drying behavior of in-shell hazelnuts: moisture diffusivity, transport phenomena, and pressure drop

This study investigates the convective hot-air drying behavior of in-shell hazelnuts under controlled operating conditions, with emphasis on drying kinetics, thin-layer modelling, heat and mass transfer characteristics, and pressure drop behavior within the hazelnut bed. The experiment was performed in a laboratory dryer set to 50–60 °C and 1.5–2.1 m s⁻¹ airflow. The temporal evolution of moisture content, drying rate, and moisture ratio was experimentally determined, and the effective moisture diffusivity was evaluated using Fick’s second law of diffusion. The results showed that internal moisture diffusion governed the drying process. Higher drying air temperature and air velocity reduced the drying time and enhanced the drying rate. Effective moisture diffusivity increased with temperature. The two-term model provided the best agreement with the experimental data, efficient R² values between 0.9770 and 0.9953, RMSE values between 0.0178 and 0.0384, and X² values between 5.26 × 10− 4 and 2.90 × 10− 3. The coefficient of heat transfer was between 131 and 180 W m⁻² K⁻¹, governed by air velocity rather than temperature. The pressure drop values predicted by the Ergun equation showed good agreement with the experimental measurements, with deviations generally remaining below approximately 8% under the investigated airflow conditions.

Numerical Solution for Chloride Transport at the Corners of Square Piles Subjected to Wetting–Drying Cycles

The durability of marine concrete square piles is critically governed by chloride transport at the corners of piles, regions subject to multi-directional erosion and pronounced accumulation under cyclic wetting–drying conditions. In this study, we developed a two-dimensional coupled moisture–chloride convection–diffusion model for a quarter section of the corner of a square pile, incorporating the time-dependent surface chloride concentration and a nonlinear moisture diffusion coefficient. The governing equations were numerically solved using the unconditionally stable alternating direction implicit (ADI) finite-difference method, which effectively overcomes the instability issues inherent in long-term simulations of strongly coupled systems. Model predictions were validated against experimental data from the literature, showing good agreement. Parametric investigations revealed that (1) the effect of moisture–chloride coupling is significant, with a low initial degree of saturation intensifying capillary-driven convection and accelerating early-stage chloride ingress; (2) a higher water-to-cement ratio markedly increases pore connectivity, exacerbating chloride accumulation under bidirectional erosion; and (3) increasing the drying-to-wetting time ratio effectively reduces net chloride buildup by curtailing the total duration of immersion. These findings provide a theoretical foundation for durability design and service-life assessment regarding square pile foundations in marine tidal and splash zones.

Modeling Environmentally Driven Seasonal Moisture Migration and Ground Movements in Expansive Clays

This paper describes the formulation of a numerical model for simulating environmentally driven one-dimensional (1D) ground movements of expansive clay. The formulation is based on a finite-element model that simulates the redistribution of matric suction through a diffusion-type equation, explicitly accounting for volume changes due to wetting and drying of the clay. We synthesize and modify highly nonlinear constitutive relationships for (1) hysteretic soil water retention; (2) reversible soil shrinkage and expansion of clay; and (3) hydraulic conductivity, explicitly incorporating desiccation cracks through a multidomain framework and assuming a critical surface crack depth. These models are well-calibrated to published laboratory tests on a reference expansive clay, Denver bentonite. We demonstrate capabilities of the proposed formulation to simulate the response of a homogeneous expansive clay to periods of drying and wetting, considering the initial matric suction, saturated hydraulic conductivity of the intact clay, and critical crack depth as three primary sources of uncertainty. We compare ensemble model simulations with measured ground movements from an instrumented expansive clay test site in Texas over a 3-year period using detailed records of potential evapotranspiration and precipitation. By assigning weights to the ensemble simulations based on their performance, we constrain the ranges of the three key uncertain parameters. The results showed very reasonable first-order agreement with the measured data and highlight the potential of the proposed formulation. We anticipate that more reliable predictions can be achieved through direct measurements of actual in situ evaporation rates and local soil properties.

Effect of the Mass Transfer Biot Number on Moisture Desorption and Hygrothermal Stress in QFN Packages

Package-level hygrothermal simulations commonly represent drying at epoxy molding compound (EMC) surfaces using idealized boundary conditions, which may not fully capture the coupled effects of bulk moisture diffusion and surface evaporation during reflow soldering and thermal cycling. This study developed a diffusion- and evaporation-based hygrothermal mechanical model for quad-flat no-lead (QFN) packages by incorporating an evaporation boundary formulation with moisture transport parameters obtained from independent moisture absorption and desorption experiments. The mass transfer Biot number S was introduced to quantify the relative roles of bulk moisture diffusion and surface evaporation in package desorption. Comparative simulations demonstrated that S influenced surface moisture removal kinetics and moisture retention during thermal loading, resulting in variations in predicted hygrothermal stress evolution. The proposed approach provides an experimentally calibrated and physically representative treatment of desorption boundaries for reliability analysis of plastic encapsulated packages.

Numerical investigation of coupled heat and mass transfer in deformable granular beds during humid-air and superheated-steam drying

Grout Splitting and Diffusion of a Non-Newtonian Fluid with Time-Varying Viscosity