Defect and Diffusion Forum

Preface

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449

Numerical Simulation of Natural Convection in an Inclined Cavity Filled with Ionanofluid

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Mouna Benshab, Said Bouchta, M‘Barek Feddaoui
This work presents a numerical study of natural convection heat transfer in a cavity filled with an ionanofluid. The governing equations are solved using the finite volume method and the SIMPLEC algorithm. This study aims to analyze the effects of key parameters influencing the flow structure and heat transfer, including the Rayleigh number (Ra), the volume fraction (), the inclination angle, and the type of base fluid.The results indicate that increasing the volume fraction () enhances heat transfer and underscores the superiority of ionic fluids over water as a base fluid. Additionally, heat transfer reaches its maximum at a specific inclination angle.

Analytical and Numerical Study of Double Diffusion Natural Convection in a Shallow Enclosure with Nanofluids: Impact of the Lewis Number on Heat and Mass Transfers

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Bilal El Hadoui, Mourad Kaddiri
Throughout this study, the Lewis number influence on double-diffusive natural convection inside a rectangular cavity horizontally disposed, filled with Copper nanoparticles dispersed in water, heated and salted by constant thermal and solutal fluxes on the side walls while the horizontal ones are assumed thermally adiabatic and solutally impermeable, is studied analytically (parallel flow approximation) and numerically (finite difference method) for a large range of the aspect ratio, 1 ≤ A ≤ 16, the Lewis number, 10-3 ≤ Le ≤ 103, and the nanoparticles volume fractions, φ = 0 and 0.05. The results revealed that the numerical and analytical outcomes showed a good agreement. Both the aspect ratio and the Lewis number have a range responsible for variations in heat and mass transfer rates, A ≤ 12 and 10-2 ≤ Le ≤ 10 for Nusselt number and Le ≥ 10-2 for Sherwood number. The results obtained by examining the interest of using nanofluids in the considered configuration were against all expectations, that they led to a degradation of the rates of heat and mass transfers with the increase in the nanoparticle volume fraction.

Lattice Boltzmann Method Simulations of Laminar Mixed Convection in an Inclined Lid-Driven Cavity Discretely Heated and Filled with Nanofluid

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Abdelhak Daiz, Ahmed Bahlaoui, Ismail Arroub, Soufiane Belhouideg, Abdelghani Raji, Mohammed Hasnaoui
The mixed convection of fluid flow and heat transfer in a discretely heated square lid-driven cavity has been numerically investigated using the lattice Boltzmann method. The fluid inside the inclined cavity is a water-based nanofluid, enhanced with Al₂O₃ nanoparticles. The cavity is discretely heated from the left and bottom walls and cooled from the right wall, while the top wall is adiabatic and moves at a constant velocity. Simulations have been performed to analyze the effects of key controlling parameters, including the Richardson number (Ri), inclination angle (θ), and the solid volume fraction of nanoparticles (ϕ). The results indicate that increasing the inclination angle enhances heat transfer on the left wall but reduces it on the bottom wall. Furthermore, to achieve the lowest mean fluid temperature, an inclination angle of 90° is recommended, regardless of the Richardson number and nanoparticle volume fraction. Additionally, the introduction of nanoparticles into the base fluid improves the heat transfer rate and increases the average temperature within the cavity. Nomenclature

Numerical Study of Mixed Convection Flows around Large-Scale Heat Sinks: Application to Data Center Cooling

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Fatima Zahra Laktaoui Amine, Mustapha El Alami, Elalami Semma
In this work, we present a numerical study of mixed convection flows around large-scale heat sinks. It is based on the Cascade Lattice Boltzmann Method (LBM) for values of the Rayleigh number, in transitional regime, in the range 5×107≤Ra≤5×108 and for a Reynolds value fixed at Re=1000. The study is carried out in a rectangular cavity of dimension H subjected to periodic thermal and dynamic boundary conditions on its vertical walls. Two heat sources of (L', l', H/2) with a hot temperature Th, are placed on the bottom wall of the cavity to simulate heat sinks. Fresh air (for cooling these heat sinks) is injected at a temperature Tc< Th from the bottom of the cavity through two openings of length L''. The hot air is extracted through an opening (2L'' long) managed on the upper horizontal wall. The preliminary results, presented in this paper, are in the form of streamlines, isotherms and thermal profiles in the range of the Rayleigh number considered. Heat transfer is studied in terms of the average Nusselt number calculated over the entire surface of the two heat sources.

Natural Air Convection Using LBM in a Cavity Heated Linearly

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Mohsine Qaffou, Youness Ighris, Zakaria Abbassi, Youssef Elguennouni, Mohamed Hssikou, Jamal Baliti
The numerical study of natural convection of confined air flow within a closed square cavity was conducted using the lattice Boltzmann Method (LBM) employing the BGK model. In this setup, the right side of the enclosure is maintained at a cooling temperature, while the left side exhibits a linear decreasing temperature profile from the heated bottom wall to the adiabatic top one. The effect of buoyancy, induced by gravitational acceleration and influencing the convection force, was assessed through the Rayleigh number, varied between (laminar regime). The analysis of heat transfer was conducted using the Nusselt number for different Rayleigh values. The results are represented by streamlines, isotherms, as well as velocity and temperature profiles. By analyzing these results, it can be concluded that an increase in the Rayleigh number leads to an increase in natural convection heat exchange inside the cavity.

Theoretical Analysis and Numerical Simulation of Thermosolutal Mixed Convection in a Vertically Oriented Rectangular Enclosure

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Mohamed Rahmoun, Taoufik Makayssi, Bilal El Hadoui, Mohamed Lamsaadi
This study presents an analytical and numerical approach to thermosolutal mixed convection in a vertical rectangular cavity containing a Newtonian fluid of Prandtl number, Pr = 7. The vertical walls are mobile and subject to constant heat and mass fluxes, while the horizontal walls are considered impermeable and adiabatic. The mathematical model is based on the Navier-Stokes equations, as well as the conservation of energy and concentration equations. An analytical solution, based on the parallel flow approximation, has been developed for elongated cavities (A >> 1). At the same time, the governing equations were solved numerically using the finite-difference method. The results show that the analytical solution is in good agreement with the numerical one for all the considered parameters. Rayleigh number and Peclet number growth play roles in enhancing mixed convection, thus influencing the overall flow and heat transfer characteristics.

Free Convective Thermal Transmission through Different Shapes of Enclosures: An Overview

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Abrar Al-Hadad
Abstract. The topic of free convection thermal transmission through different geometrical shapes of enclosures is an engaging subject. It has caught the attention of the researchers during the last decades according to its significance in lots of engineering applications. Nuclear reactors, solar collectors, cooling electronic equipment, Oil wells, cooling electric components (as in the copper electric wires that are surrounded by the housing), and many industrial systems. Many parameters are discussed and analyzed to see their effect on the process of transferring heat such as: the effect of the geometrical shape, Nusslet number, and Rayliegh number. The studies were divided into seven categories based on the geometrical shape of the enclosure ( square , triangular, circular, trapezoidal, polygonal, elliptical, and wavy). The governing equations of the free convective thermal transmission were stated. The objective of this study is to collect the data from a large number of previous studies and compare them to reach a conclusion about the best results.

Sustainable Aerodynamics Analysis of Heavy Vehicles: Solution for Drag Reduction

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Ammar Abdulkadhim, Fatimah AL-Daamee, Mohammed Abdulsada, Azher M. Abed
Aerodynamics contributed directly on the energy efficiency and fuel consumption reduction of heavy vehicles in addition to its stability. The present study examines numerically the aerodynamics of heavy vehicles considering different drag-reduction devices using SolidWorks programme. Four different drag-reduction devices such as Base flaps, filled boat tail, Deflector and Rear offset plate in order to compare them with the baseline model. the results showed that the reflector contribute in more drag formation while Rear offset plate leads to lower drag.

Investigation of Temperature Influence on Mass Transfer during Sustainable Biodiesel Production from Castor Oil

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Shahad M. Alagha, Salih Rushdi, Noor K. Hasan
Biodiesel represents a renewable alternative fuel that reduces dependence on petroleum and lowers greenhouse gas emissions. In this study, biodiesel was produced from castor oil via alkaline transesterification to investigate the influence of temperature on mass transfer between the immiscible oil and alcohol phases. A series of transesterification experiments were carried out using methanol and a homogeneous alkaline catalyst (1.12 wt% KOH). The temperature was varied at 35 °C, 50°C, and 65°C to evaluate its influence on the mass transfer rate between the oil and alcohol phases. The molar ratio of methanol to oil was maintained at 14.12:1, and each experiment was conducted for a reaction time of 60 minutes. Increasing temperature significantly enhanced interfacial diffusion, reduced viscosity, and increased miscibility between the two phases. The intersection of TG and FAME curves occurred earlier at higher temperatures, at 65 °C, triglyceride (TG) conversion reached 92% within 10 min and approximately 99% after 60 min, while slower conversions were observed at 35 °C and 50 °C. Product composition and FAME yield were evaluated by GC-MS examination at the Ministry of Industry and Minerals' Industrial Research and Development Authority. Overall, the study highlights that optimized temperature conditions minimize mass transfer limitations, improves phase interaction and conversion efficiency also shortens the total reaction time supporting the creation of an effective and sustainable method of producing biodiesel process from renewable castor oil feedstock.

A Study on the Effect of Wire-Net Stainless Steel Porosity on Heat Transfer Enhancement in a Solar Air Heater

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Sophon Sinsang, Ponthep Vengsungnle, Ratinun Luampon
Wire-net stainless steel (WS) is an alternative material used to enhance heat transfer in solar air heater (SAH) by inducing swirling or rotating airflow as air passes through its pores. In this study, WS with varying porosity—corresponding to pore per inch (PPI) of 16, 20, and 25—and a constant pitch distance (P) of 0.06 m was installed within the flow channel of the SAH, and air was used as the working fluid under turbulent flow. The results showed that WS significantly improved heat transfer performance, though accompanied by increased pressure drop. An increase in PPI resulted in a maximum of Nusselt number and friction factor by factors of 13.81 and 238.61, respectively, compared to SAH without WS. The highest thermal enhancement factor of 2.48 was observed at PPI=20.

Simulation and Optimization of Heating Networks

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Daniyar Bossinov, Gaukhar Ramazanova
Heating networks are a crucial part of modern urban infrastructure, delivering heat to residential, commercial, and industrial consumers efficiently and reliably. Ensuring their safe and continuous operation is essential for maintaining comfort and supporting daily urban life. The integration of digital twins has become increasingly important, as they allow operators to monitor network behavior in real time, predict potential failures, and implement corrective actions promptly. By reducing response times and minimizing the frequency of accidents, digital twins help ensure a stable and uninterrupted heat supply. For a digital twin to be effective, it must be based on accurate numerical models that capture fluid flow, heat transfer, and pressure distribution throughout the network. Proper design and modeling enable efficient use of resources, including pumping power and pipe sizing, while reducing energy waste and operational costs. This study presents a comprehensive approach to optimizing heating networks. Control variables such as pipe diameters, pump pressure, and the settings of bypass and radiator valves for each consumer are defined. A constraint aggregation function ensures that no consumer experiences freezing, while the objective is to minimize both the initial installation costs and long-term operational expenses. Advanced numerical solvers were used to perform the calculations, enabling efficient optimization of large and nonlinear networks. This approach demonstrates how careful modeling and control can improve the efficiency, reliability, and cost-effectiveness of heating networks.

Potential‑Resolved In Situ Atomic Force Microscopy of Surface Film Formation on Graphite in Ethylene Carbonate with Lithium Perchlorate

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Soon Ki Jeong
Ethylene carbonate (EC) is essential for forming a passivating film on graphite, whereas practical electrolytes dilute EC with linear carbonates that modify that film. Here, we isolate an EC-only medium and track film formation by in situ electrochemical atomic force microscopy during slow-scan cyclic voltammetry on the basal plane of highly oriented pyrolytic graphite in EC with lithium perchlorate. A two-stage pathway is resolved: during the cathodic sweep a subsurface pre-insertion regime develops and transitions near 0.8 V vs Li/Li+; the subsequent anodic sweep produces a particulate precipitate layer. After the first cycle, the effective precipitate-layer thickness is approximately 20 nm; a second cycle increases it to approximately 30 nm with marked lateral heterogeneity and edge-proximal coarsening. These observations delineate the potential-dependent switch and provide quantitative benchmarks for the early growth of the EC-derived film. Minimizing the dwell time near the transition may suppress overgrowth and improve interfacial stability, thereby establishing an EC-only baseline for interpreting mixed-carbonate electrolytes.

Direct Regeneration of LFP Cathode Material from Spent Li-Ion Batteries via Aqueous Relithiation

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Charles Flores, Debabrata Mohanty, I Ming Hung, Rinlee Butch Cervera
Lithium iron phosphate (LFP) is a commonly used cathode material in lithium-ion batteries, particularly for electric vehicle (EV) battery energy storage systems. To support sustainability and the principles of a circular economy, recycling spent LFP batteries is essential. This study focuses on the direct regeneration of spent LFP cathode material using an aqueous relithiation method conducted at low temperature, followed by post-annealing. The waste precursors and regenerated LFP were fully characterized for its structural, morphological, and compositional properties. Fourier-transform infrared (FTIR) analysis confirmed the presence of additive carbon and electrolyte residues in the spent LFP. XRD analysis revealed that certain components of the LFP structure in the as received spent cathode material decomposed, as evidenced by the presence of impurity peaks due to FePO4 and P2O5, which disappeared after relithiation. The lattice parameter values (a=4.6897 Å and c=10.3211 Å) of the regenerated LFP were also found to be close to the theoretical (a=4.6925 Å and c=10.3253 Å), suggesting successful structure repair after regeneration. SEM indicated that regenerated LFP particles appeared to be more well-dispersed and finer than spent LFP particles. EDS mapping revealed a relatively homogeneous elemental distrbution of the major identified elements. ICP analysis further confirmed the successful restoration of Li content. The composition of the spent cathode, initially Li0.85FePO4, transformed to Li1.03FePO4 after regeneration, corresponding to an increase in Li content from the as-received 3.75 to 4.53 wt% Li after relithiation.

Monolith Multilayer Catalytic Membrane for Direct Conversion of CO2- Rich Natural Gas into Syngas and Energy

Thu, 5 Mar 2026 00:00:00 +0100

Publication date: 5 March 2026
Source: Defect and Diffusion Forum Vol. 449
Author(s): Norwahyu Jusoh, Amir Hafizi Md Nor, Alia Syuhada Abd Rahman, Yin Fong Yeong
The increasing demand for energy and the environmental challenges posed by CO₂ emissions necessitate the development of innovative solutions for utilizing natural gas reservoirs with high CO₂ content. In Southeast Asia, over 13 trillion cubic feet of natural gas remain undeveloped due to their high CO₂ content, reaching up to 87%. Current CO2 separation technologies, though effective in removing CO₂, are energy-intensive and economically unfeasible. In the present work, monolith multilayer catalytic membrane is utilized to directly converting CO₂-rich natural gas permeate streams into syngas and co-generated energy. The membrane consists of a gas conversion, ion-selective and ion-conducting layers to optimize syngas production and improve energy efficiency. Experimental results show that increasing the operating temperature from 600°C to 800°C significantly enhances the conversion of methane (CH₄) and CO₂, yielding higher amounts of CO and H₂, with improved CO selectivity. Additionally, electrochemical performance evaluations demonstrate relatively higher current densities and power outputs at elevated temperatures. These findings underscore the multilayer catalytic membrane's potential to provide an economically viable and environmentally sustainable solution for converting CO₂-rich natural gas into valuable products, while also reducing CO₂ emissions. The membrane offers a promising route for syngas and energy production, contributing to the development of more efficient, low-emission energy technologies.