Numerical investigation and optimization of a hot air-based rotary desoldering reactor for waste printed circuit boards treatment

Casting process optimization of stainless-steel pump impellers using finite element simulation

This study employed ProCAST numerical simulation to assess and enhance the casting design of a stainless-steel CF8M pump impeller by analyzing six gating and feeding configurations. The simulations were executed at a pouring temperature of 1650 °C, an initial mould temperature of 25 °C, and an estimated filling duration of 20 s. The examined configurations comprised a baseline horizontal design and modified designs featuring enhanced riser and gate arrangements, mould tilt angles ranging from 5° to 20°, and supplementary ventilation in the final design. The findings indicated that the original design resulted in detrimental temperature distribution and localized final solidification within the impeller body, especially around the hub and blade-hub connections, hence heightening the propensity for shrinkage porosity. The progressive alteration of the riser, sprue, gate configuration, mould angle, and ventilation system optimized the temperature gradient, augmented feeding efficiency, and relocated the final solidification zone towards the riser/feeder. Design 6, optimized with a 20° mould tilt and ventilators, had the most advantageous solidification characteristics and reduced anticipated shrinkage porosity within the functioning impeller body. The findings indicate that numerical simulation can significantly diminish dependence on conventional trial-and-error casting experiments by facilitating virtual evaluation of several design options before to production. This study presents a simulation-based approach for regulating solidification behavior, enhancing feeding efficiency, and reducing shrinkage porosity in the casting of stainless-steel pump impellers.

Numerical Analysis of Gravity Casting of a 34CrMo4 Steel Flywheel Rotor for Energy Storage Applications

Flywheel energy storage systems impose high demands on the mechanical properties and structural integrity of rotors, particularly in high-speed applications. This study focuses on the numerical analysis of gravity casting of a steel rotor manufactured from low alloy 34CrMo4 steel, with the aim of identifying critical regions related to molten metal flow, solidification behaviour and shrinkage defect formation. Numerical simulations were calculated using a MAGMASOFT® 5.5 software environment based on the finite volume method and included both mold filling and subsequent solidification and cooling stages. Flow stability, temperature field distribution and solidification characteristics were researched thoroughly. The results showed that optimization of the gating and feeding system lowered porosity under 2% within the casting and relocated shrinkage defects to the risers. At the same time, solidification directionality was improved and the Hot Spot value was reduced. From the perspective of casting quality, the proposed design represents the most suitable solution, despite a lower metal utilization rate. The analysed casting forms the structural body of a hybrid flywheel rotor intended for the subsequent integration of high-density tungsten segments.

Novel static analysis of a rotary sinter cooling process for determination of temperature distribution and waste heat recovery potential to generate power with ORC

Optimization of Hot Air Inlet Position in a Biomass-Fueled Rotary Drum Dryer Using CFD Simulation and Experimental Validation

This study evaluates the impact of hot air inlet positioning on heat transfer efficiency within a biomass-fueled rotary drum dryer system using Computational Fluid Dynamics (CFD) simulation combined with experimental validation. Three inlet configurations - at the drum head, at one-third of the drum length, and at the center of the drum - were compared based on velocity distribution, temperature fields, and energy loss characteristics. Simulation results using ANSYS Fluent indicate that the head-inlet configuration leads to non-uniform thermal distribution and high exhaust velocities $(\approx 3 mathrm{m} / \mathrm{s})$. Conversely, the internal-inlet configuration optimizes airflow circulation with lower velocities $(\approx \mathbf{1} \mathrm{m} / \mathrm{s})$, enhancing heat transfer efficiency to the material bed and minimizing energy loss to the environment. Experimental drying of agricultural products within a temperature range of 60-80°C confirmed the accuracy of the simulation model, with deviations in final temperature and moisture content below 5%. The results demonstrate that the internal-inlet configuration shortens drying time and improves product uniformity. This research confirms the critical role of CFD simulation in designing and optimizing renewable energy drying systems, particularly for decentralized small-scale production.

Failure Analysis and Thermo-Structural Design Simulation of a Cylindrical Dual-Chamber Solid Waste Incinerator

The generation of municipal solid waste (MSW) is rapidly increasing. This has worsened environmental pollution and public health hazards, especially in places with poor waste management policies. This research employs finite element simulation techniques to investigate the thermo-structural response and failure behaviour of a cylindrical dual-chamber MSW incinerator. The study's objectives were to assess the structural stability and operational reliability of the system under various service situations. A three-dimensional computer-aided model of the incinerator was developed using CATIA CAD modelling. Finite Element simulations were used to analysed various operational fault conditions like over-heating, refractory deterioration, chamber deformation, cracking, corrosion, chimney blockage, seal leakage and ash accumulation. The main structural material was mild steel, with refractory linings used mainly to improve insulation and also to prevent the combustion chambers from high temperatures. The numerical analysis was performed with tetrahedral meshing and appropriate thermal boundary conditions. The simulation results showed that the combustion chambers and connecting duct had the highest temperature distribution, and the major thermal stresses were concentrated around the welded joints and support regions. During normal operation, the secondary chamber temperatures ranged from 995°C to 1050°C, and the maximum Von Mises stress ranged from 145 MPa to 180 MPa. The results indicated that repetitive thermal cycling, corrosion, inadequate airflow circulation and excessive heat loading increased the likelihood of deformation and structural collapse. The study showed that the cylindrical dual-chamber design had better heat distribution, lower stress concentration and better combustion performance when compared to the conventional rectangular incinerator.

Design and Thermal Modeling of a Sealed Autoclave for Compatibility Testing of Mineral Oil–Rock Systems in Thermal Energy Storage Applications

This paper presents the design, numerical modeling, and experimental implementation of a sealed autoclave developed for compatibility testing of mineral thermal oil with natural rocks in packed-bed thermal energy storage (TES) systems. Delcoterm Solar E15 was selected as the heat transfer fluid (HTF) based on its potential thermo-physical properties, low vapor pressure (<0.3 bar at 300°C), high specific heat (2180-2900 J/kg. K), and economic viability compared to synthetic oils. The structural material of the autoclave was chosen as AISI 304 stainless steel due to its corrosion resistance and thermal conductivity (16.2 W/m. K). A finite element model was developed using COMSOL Multiphysics to simulate transient heating and cooling cycles between 100°C and 300°C. Results show uniform internal temperature distribution after 432 s during charging and a discharge time of approximately 1000 s. Based on simulation results, heating and cooling rates were optimized at 5°C/min and 1-2°C/min, respectively. The proposed system enables controlled isothermal and cyclic compatibility testing under inert atmosphere conditions up to 2 bars. The preliminary compatibility tests showed a good compatibility with the selected AISI304 and trondhjemite rock.