This study presents the development and evaluation of a stand-alone solar dryer designed to improve the efficiency of bee bread dehydration. Unlike the electric prototype powered by conventional energy sources, the proposed system operates autonomously, utilizing solar energy as the primary drying agent. The drying chamber is equipped with solar collectors located in its lower section, which ensure convective heating of the product. Active convection is generated by a set of fans powered by photovoltaic panels, maintaining the drying agent’s temperature near 42 °C. The research methodology integrates both numerical simulation and experimental investigation. Simulations focus on the variations in temperature (288–315 K) and relative humidity (1–1.5%) within the honeycomb structure under convective airflow. Experimental trials examine the relationship between moisture content and variables such as bee bread mass, airflow rate, number of frames (5–11 units), and drying time (2–11 h). A statistically grounded analysis based on an experimental design method was conducted, revealing a reduction in moisture content from 16.2–18.26% to 14.1–15.1% under optimized conditions. Linear regression models were derived to describe these dependencies. A comparative assessment using enthalpy–humidity (I–d) diagrams demonstrated the enhanced drying performance of the solar dryer, which is attributed to its cyclic operation mode. The results confirm the potential of the developed system for sustainable and energy-efficient drying of bee bread in decentralized conditions.

This paper presents a simulation of the heat exchange process in a solar dryer designed for corn cobs placed in flexible bulk containers (Big-Bag type). The distinctive feature of this drying system is the use of soft load-bearing containers, which simplify loading, unloading, and transportation, while also reducing mechanical damage to the corn cobs. The bottom of each container is perforated to allow the free flow of heated drying agent into the chamber. The study aims to improve the efficiency of the solar drying process to reduce the moisture content of corn cobs below 15%, thereby ensuring the required quality during storage and transport. To validate the drying regimes and parameters, heat and mass transfer processes were simulated using numerical modeling and experimental design methods based on a laboratory-scale physical model of the drying chamber. Numerical simulations were performed using the Reynolds-averaged equations coupled with the heat conduction equation for three porosity coefficients: 0.35, 0.45, and 0.55. The models provided contours of temperature and humidity distribution within the confined boundaries of the drying chamber and individual corn cobs, positioned both vertically and horizontally within the airflow zone, for varying drying durations. The core novelty of this research is the development of an optimized framework for solar drying corn in flexible containers, which integrates numerical simulation with experimental validation to establish key efficient parameters. Specifically, the study provides the following: (1) a validated regression model linking moisture content to airflow rate, drying time, and layer thickness at 45 °C; and (2) a detailed analysis of thermo-hydraulic contours within both the chamber and individual cobs for different porosities, offering practical insights for system design and operation.

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.

This study presents the results of experimental and computational fluid dynamics (CFD) modeling of vacuum compaction of partially dried alfalfa haylage in a flexible hermetic container. The objective was to increase the density of vacuum-packed haylage by flattening the plant material before compaction and to establish rational process parameters that avoid excessive release of plant juice. Laboratory experiments were performed using haylage with a moisture content of 50%. The flexible container was placed in a liquid medium to enable measurement of changes in container volume and haylage compaction. The true density of alfalfa stems at 50% moisture content was determined using a pycnometric method with kerosene as the immersion liquid for subsequent porosity calculations. A mathematical model of haylage compaction in a flexible container was developed to represent the effect of pressure during air removal. Numerical simulations were performed using the Reynolds-averaged Navier–Stokes (RANS) equations, the k-ω SST turbulence model, and the SIMPLE algorithm. The Volume of Fluid (VOF) method was used to describe the interaction between the gas phase and the plant material. Two pressure-application configurations were considered: pressure applied to the upper boundary only and pressure applied simultaneously to four boundaries. The results showed that flattening the haylage by passing it between squeezing rollers increased the compacted density by approximately 15–20% compared with the non-flattened material over the 40–80 kPa pressure range. Based on the experimental results, a vacuum level of 70–75 kPa is recommended for compacting pre-flattened haylage, providing substantial densification while avoiding excessive release of plant juice.

This study presents an experimental and numerical investigation of the sealing performance of welded joints in flexible polyethylene containers subjected to external pressure during vacuum compaction of forage material. The objective was to improve the reliability of welded seams under vacuum gauge pressures of up to 75 kPa. A three-dimensional transient heat-conduction model was developed to investigate the thermal behavior of polyethylene film during heat sealing. The governing heat-conduction equation was solved using ANSYS Fluent based on the finite volume method, employing a pressure-based transient solver and first-order implicit time discretization. Temperature distributions and their temporal evolution, T(t), were determined at selected locations within the film. The strength of welded joints in thin polyethylene films subjected to pressure loading of up to 75 kPa was experimentally evaluated as a function of weld-seam width and clamping force at a selected heat-sealing temperature of 175 °C. High-density polyethylene film (PE-180) with a thickness of 200 μm was used to carry out research specimens measuring 100 × 100 mm. The experimental results were analyzed using a design-of-experiments approach, and a regression equation was developed to describe the dependence of welded-joint strength on seam width and clamping force. The combined numerical and experimental findings provide a basis for selecting appropriate heat-sealing parameters to enhance the reliability of welded seams at the neck of flexible polyethylene containers subjected to vacuum-induced loading.