Computational Fluid Dynamics-Based Characterization of Heat Transfer and Airflow in an Indirect Solar Fish Dryer Under Tropical Conditions

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.

Integrated CFD simulation and thermal imaging for monitoring convective drying of tomato wedges

The overarching aim of this study was to develop and validate a computational fluid dynamics (CFD) model to predict heat and mass transfer processes during the convective drying of tomato wedges. Experimental drying trials were conducted at three air temperatures (60, 70, and 80 °C) to evaluate model performance by monitoring drying kinetics under controlled conditions. During the drying process, the moisture content of tomato wedges was reduced from an initial value of 15.67 kg water/kg dry matter to a final value of 0.17 kg water/kg dry matter, requiring 21, 13, and 11 h at 60, 70, and 80 °C, respectively. Spatiotemporal surface temperature distributions were continuously obtained from radiometric infrared thermography recorded by a highly sensitive thermal camera and was used for monitoring of temperature changes and for CFD model validation. The results revealed that a close correspondence was observed between experimental data and simulated results across all operating drying temperatures, with improved predictive accuracy observed at lower temperatures. The model also demonstrated good predictive performance for moisture content during drying, with root-mean-square error (RMSE), and chi-square (χ2) values of 0.812 and 0.313, respectively. Additionally, color change, lycopene content, antioxidant activity, and total phenols were determined to evaluate the impact of drying temperatures on tomato quality. Drying air temperature of 70 °C resulted in the highest lycopene retention and lower color change, while a higher temperature of 80 °C showed lower degradation of antioxidant activity and phenols, indicating that drying temperature not only affects drying rate but also influences the nutritional and quality values. Overall, the developed CFD model can serve as a robust tool for analyzing and predicting the drying behavior of tomato wedges, improving process optimization, quality preservation, and enhanced control of drying operations.

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

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.

Numerical Analysis of Outlet Number Effects on Temperature Distribution in a Briquette Oven Using CFD

The performance of briquette drying systems is strongly influenced by airflow distribution and thermal uniformity within the drying chamber, which are governed by outlet configuration and internal flow patterns. However, limited studies have systematically quantified the effect of exhaust outlet arrangements on the coupled heat transfer and fluid flow behavior in industrial-scale briquette ovens. This study aims to numerically investigate the influence of single-, double-, and four-outlet configurations on airflow characteristics, temperature distribution, and overall thermal performance of a briquette drying oven. A three-dimensional geometric model representing the combustion chamber, drying chamber, and briquette racks was developed and analyzed using Computational Fluid Dynamics (CFD). Steady-state simulations were performed in ANSYS Fluent employing the standard k–ε turbulence model, with air properties, inlet velocity (9.97 m/s), and thermal boundary conditions defined based on operational data. The results reveal that outlet configuration significantly affects flow recirculation intensity and temperature uniformity across the briquette racks. The four-outlet configuration produced the most homogeneous airflow distribution and reduced thermal gradients, thereby enhancing convective heat transfer effectiveness compared to single- and double-outlet designs. Conversely, the single-outlet case exhibited pronounced recirculation zones and localized temperature variations, potentially leading to uneven drying. These findings demonstrate that optimizing outlet arrangement is a critical design parameter for improving drying efficiency and energy utilization in briquette oven systems, providing a validated numerical framework for future thermal system optimization.

Computational fluid dynamics modelling of a sustainable evaporative cooling storage system for agricultural products

Evaporative cooling is a sustainable and energy-efficient technique for preserving perishable agricultural products, particularly in off-grid environments. However, existing studies are largely limited to small-scale systems and steady state analyzes, with limited understanding of transient heat and mass transfer behaviour in large storage configurations. This study develops and analyzes a large-scale evaporative cooling storage system using locally available porous materials such as clay, sand, and bricks. A transient three-dimensional Computational Fluid Dynamics model was implemented in ANSYS Fluent, incorporating porous media flow, species transport, and buoyancy-driven natural convection to simulate coupled heat and mass transfer within the chamber. Results indicate a temperature reduction from 310 K to 302.8 K, corresponding to a cooling effect of 7.2 °C within 8.3 h. The airflow stabilizes at approximately 0.85 m/s, promoting uniform cooling. The system demonstrates sustained evaporation-driven heat removal and an approximately 1.6-fold potential increase in shelf life based on temperature-dependent estimation. The findings highlight the coupled role of porous media evaporation and natural convection in governing thermal regulation and provide a scalable, low-cost framework for improving post-harvest storage in resource-constrained environments. Large-scale evaporative cooling storage system developed using clay–sand porous media. Transient 3D CFD model captures coupled heat and mass transfer with natural convection. Temperature reduction of 7.2 °C achieved under passive, energy-free cooling conditions. Porous media evaporation and airflow interaction enhance thermal uniformity inside chamber. Approximately 1.6× potential shelf-life improvement estimated using temperature-dependent model.