Influence of climatic conditions on moisture storage in bio-based multilayer walls: a coupled heat and moisture transfer study

Modeling and experimental validation of an indirect active hybrid solar dryer for mint leaves: Coupled thermal and moisture-transfer analysis

A mathematical model was developed and experimentally validated to predict the thermal performance and drying behavior of an indirect active solar dryer (IAHSD) for mint leaves. The distinctive contribution of the proposed approach is its integration of solar-energy input, auxiliary gas heating, controlled fresh–recirculated air mixing, ambient-humidity effects, chamber heat losses, and mint-leaf moisture removal within a computationally accessible model suitable for operational assessment and control-oriented applications. The model describes coupled heat and mass transfer processes while considering key operating parameters, including drying air temperature (50–60°C), air recirculation ratio (70–90%), and ambient relative humidity (20–80%). Simulation results showed that increasing drying air temperature and recirculation ratio enhanced the drying chamber temperature, whereas higher ambient humidity reduced the thermal level and slowed moisture removal. Predicted chamber temperatures ranged from 37.83°C to 67.31°C depending on the inlet air temperature, while experimental values followed similar trends but were slightly lower due to environmental variations. Maximum temperatures occurred near midday, highlighting the influence of solar radiation on system performance. The model also captured moisture removal dynamics, indicating that higher drying temperatures accelerated drying rates, while elevated humidity reduced evaporation efficiency. Under low temperature and high humidity conditions, temporary moisture absorption was observed due to reversed vapor pressure gradients. Model validation showed strong agreement between predicted and measured data, with coefficients of determination (R 2 ) ranging from 0.85 to 0.96, confirming the reliability of the proposed model.

Influence of Yarn Micro-Architecture on Coupled Heat and Moisture Transport: Modeling and Validation

Heat and moisture are simultaneously generated during human activity, and evaporative heat loss becomes essential for comfort in warm environments; therefore, transport through voids of textiles must be understood at the structural level. This study uses parallel PET yarns as a controlled system to isolate yarn-scale effects and aims to quantify how packing factor, yarn density, filament number, filament denier, and twist govern moisture resistance under ISO 11092 skin-model conditions. Moisture resistance (Ret), water–vapor permeability (Wd), and heat flux were measured with a sweating guarded hotplate, and a fiber-level two-dimensional representative cross-section of the yarn–air array was built in COMSOL from measured yarn width, thickness, and packing factor, coupling solid heat transfer with diluted water–vapor transport using test-consistent boundary conditions and validated by experimental results. The results show that higher packing factor or higher yarn density reduces the connectivity of inter-filament voids, weakens the vapor-related convective component, and increases Ret; changes in filament-scale geometry mainly shift the balance between conduction and vapor-related transport when packing factor is similar; and twist further tightens the inter-filament void structure and strengthens these trends. Overall, the combined experimental–numerical approach links standard Ret measurements to fiber-level structure and offers practical guidance for designing PET yarn systems with targeted moisture management.

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

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.

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.

Experimental Investigation and CFD Modeling of Heat and Mass Transfer During Drying of Alfalfa Leaf Fraction in a Rotary Drum Dryer

The convective drying of agricultural materials is an energy-intensive process, and optimizing dryer design is critical for improving efficiency and product quality. This study presents a comprehensive heat and mass transfer model for the convective drying of alfalfa leaves in a rotary drum dryer. Freshly harvested leaves with an initial moisture content of approximately 70% (w.b.) were used as the test material. The proposed system features a simplified drum design aimed at enhancing process efficiency while reducing equipment complexity. The primary objective was to reduce the moisture content of alfalfa leaves to below 50% to ensure their quality during subsequent storage and transportation. To determine the optimal operating conditions, the kinematics of leaf motion inside the rotating drum and the associated heat and mass transfer phenomena were investigated through analytical modeling, numerical simulation, and experimental studies on a laboratory-scale physical model. An analytical model was developed to establish relationships between transverse kinematic characteristics (detachment condition, Froude number, drum inclination angle), average longitudinal velocity, and residence time. Numerical simulations based on the Navier–Stokes equations (continuity, momentum, and energy) provided detailed moisture content distributions within individual leaves under varying airflow orientations and drying durations. The novelty of this work lies in the integrated determination of optimized operating parameters through combined analytical, numerical, and experimental approaches. A regression model relating final moisture content to key process variables (air velocity, temperature of 60 °C, drum rotation frequency and mass of loaded material) was developed from experimental data, yielding practical recommendations for the design and operation of rotary drum dryers for alfalfa and similar agricultural materials.