Assessment of Moisture Distribution Through Rough Rice Kernel During a Combined Hot Air and Far Infrared Drying

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

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.

Assessment of the effects of drying temperatures on effective moisture diffusion and quality properties of purple carrot slices dried by hot air method

This study examined the influence of hot-air drying temperature on the moisture ratio (MR), drying rate (DR), effective moisture diffusivity (Deff), color characteristics (L, a, b, C, and ΔE), and hardness (N) of purple carrot slices. A clear temperature-dependent response was observed for both the drying behavior and the quality attributes of the samples. Increasing the drying-air temperature resulted in a shorter drying period. The mean DR values obtained under the different drying conditions ranged from 0.0062 to 0.0201 g moisture/g dry matter·min. The calculated Deff values were within the range of 9.66 × 10⁻⁹ to 3.37 × 10⁻⁸ m²/s. Temperature also altered the color characteristics of the fresh purple carrot slices; specifically, the L and b values differed significantly from those of the fresh samples (p < 0.05). The α color values of fresh samples were preserved at 55 ºC and 65 ºC, the C color value at 55 ºC, and the ΔE color value at 55 ºC (p>0.05). The N values of fresh purple carrot slices are preserved at 75 ºC (p<0.05). Based on the findings, a temperature of 75 °C is recommended for the MR, DR, Deff, and N parameters, while a temperature of 55 °C is recommended for color characteristics.

Effects of Infrared, Hot Air and Infrared‐Assisted Hot Air‐Drying on Drying Characteristics, Quality, and Energy Efficiency of Turmeric Slices

The market value of turmeric is influenced strongly by volatile compounds which indicate product quality. In this study, turmeric slices of 5 mm with bed thicknesses of 50 mm were dried using three techniques: infrared (IR‐D), hot air (HA‐D), and infrared‐assisted hot air‐drying (IR‐HA‐D) at temperatures of 50°, 60°, and 70°C. This study examined the effects of increased bed thickness on drying kinetics, energy requirements, CO 2 emissions, and quality attributes under settings that more closely resemble industrial‐scale drying operations, in contrast to earlier studies that used a 25 mm bed thickness. Among the evaluated drying methods, IR‐HA‐D at 70°C exhibited the highest process efficiency, whereas IR‐HA‐D at 60°C provided superior retention of quality attributes, including curcumin, oleoresin, starch, and color. Seven thin‐layer drying models using nonlinear regression analysis were evaluated, with the Page model showing the best fit across all experimental conditions. The IR‐HA‐D method provided the highest retention of curcumin, oleoresin, starch and color value at 60°C, compared to both IR‐D and HA‐D. Statistical analysis confirmed that both drying techniques and temperature significantly influenced the quality characteristics of the dried turmeric ( p  < 0.01). Effective moisture diffusivity ranged from 7.61 × 10 −11 to 2.53 × 10 −10  m 2  s −1 while the activation energy required for moisture diffusion was 31.88 kJ mol −1 for IR‐D, 45.13 kJ mol −1 for HA‐D, and 32.11 kJ mol −1 for IR‐HA‐D.

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

Accurate prediction of moisture transfer during drying processes remains challenging. In the present study, a progressive numerical framework was developed to investigate moisture diffusion in ethanol-pretreated beetroot by systematically incorporating increasing levels of physical complexity into Fick’s second law of diffusion. Four one-dimensional formulations were examined, including constant moisture diffusivity, shrinkage under constant diffusivity, moisture-dependent effective diffusivity, and a fully coupled model combining moisture-dependent diffusivity with shrinkage. The methodology was further extended to two dimensions to evaluate the spatial evolution of moisture. The governing equations were solved using an implicit Crank–Nicolson finite difference scheme, while shrinkage was introduced through a time-dependent computational domain and moisture-dependent diffusivity was implemented as a variable transport property. The predicted moisture distributions demonstrated that incorporating shrinkage reduced the diffusion path length, whereas moisture-dependent diffusivity provided a more realistic representation of the transport resistance. The coupled formulation produced the most physically consistent description of moisture migration by simultaneously accounting for both mechanisms. Furthermore, the two-dimensional simulations provided additional insight into the spatial redistribution of moisture. The proposed framework establishes a physically based interpretation of the enhanced drying behavior observed after ethanol pretreatment and provides a flexible computational methodology for analyzing moisture transfer.

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.