Advanced Engineering Forum Vol. 58

Abstract: Electromechanical impedance (EMI) sensing with bonded piezoelectric patches is a compact option for structural health monitoring at high frequencies. This study evaluates the detectability of submillimeter microcracks in an Inconel 718 plate using a surface-bonded lead zirconate titanate (PZT) transducer through a finite element-based harmonic analysis. A two-dimensional coupled-field model represents a 20 × 20 × 5 mm³ plate and a PIC255 patch with an in-plane size of 10 × 10 × 0.5 mm³. The model performs a 10–100 kHz voltage sweep at 0.5 V to compute electrical resistance. Damage is introduced as circular notch-like defects with diameters of 0.25, 0.50, and 0.75 mm at nine locations that vary the sensor-to-defect distance. A mesh convergence study ensures numerical stability. Damage sensitivity is quantified using Root Mean Square Deviation (RMSD) of impedance signatures relative to the healthy baseline. Results show that frequency bands around local resonances provide the strongest separation between healthy and damaged states, with the most discriminative band observed near 54–57 kHz. RMSD increases monotonically with defect diameter and decreases with distance from the sensor, demonstrating an anisotropic positional sensitivity that is stronger along the patch axis.

Abstract: The LEAPET model is a cross-layer design for Wireless Sensor Networks (WSNs) that combines the functionalities of already existing Low-Energy Adaptive Clustering Hierarchy (LEACH), Power-Efficient Gathering in Sensor Information Systems (PEGASIS), and Adaptive Time Division Multiple Access (TDMA) protocols to improve energy efficiency and data transmission. Since rapid energy depletion of the sensor nodes is a major concern of WSNs, LEAPET overcomes this limitation by leveraging hierarchical clustering, chain-based data aggregation, and adaptive time-division scheduling to optimise both energy usage and communication efficiency. In this study, the LEACH forms clusters and chooses Cluster Heads (CHs). All other members within the cluster will send data to the CH instead of an individual data transmission to the base station (BS). The PEGASIS introduces chain-based data routing, which reduces energy consumption by limiting long-distance transmissions. In the PEGASIS chain formation, each node aggregates data sent to it and then transmits it to the neighbouring node in the chain until the aggregated data reaches the chain leader, which forwards it to the BS. To reduce the data collision from the chain leaders of the PEGASIS chain, an adaptive TDMA technique was used to allocate time slots for data transmission. The performance of the LEAPET protocol was compared to the existing LEACH and PEGASIS protocols using the number of alive nodes after rounds of data transmission, energy consumption and network lifetime metrics. The results of the simulations show that LEAPET outperforms existing LEACH and PEGASIS in terms of prolonged network lifetime, energy consumption and throughput. All simulations were carried out using the MATLAB programming language.

Abstract: Considering the dearth and limited supply of potable water for daily consumption globally, developing a desalination technique to produce water sufficient for the need has become imperative. This study examines the improvement of freshwater productivity in a single-slope solar still by incorporating a solar preheating system. The proposed design utilizes solar still distillation to preheat the feed water before it enters the distillation basin. This approach aims to increase the temperature gradient between the water surface and the glass cover, thereby accelerating the evaporation and condensation process. Experimental evaluations were conducted under varying climatic conditions and flow rates, with and without the preheater. We note that the productivity has improved at each flow rate as follows: at a flow rate of 1 L/min, the improvement percentage reached 96% (CLISS:130 g/hr and CLIPSS:170 g/hr), at a flow rate of 2 L/min, the improvement percentage reached 73% (CLISS:180 g/hr and CLIPSS: 220 g/hr), while the improvement percentage at 3 L/min became 61% (CLISS:240 g/hr and CLIPSS:290 g/hr.), and at a flow rate of 4 L/min, it reached 64% (CLISS:280 g/hr. and CLIPSS: 320 g/hr.), and up to a flow rate of 8 liters/minute, the productivity improvement percentage between the two systems reached 31% (CLISS:310 g/hr. and CLIPSS:340 g/hr.). The results showed that the preheated system significantly improved solar thermal performance and daily production, especially during the early morning and late afternoon hours. Compared to a conventional design, the preheated system achieved an overall productivity increase of 25% to 35%.

Abstract: This work offerings a numerical study of natural convection heat transfer within a triangular enclosure having a centrally positioned cylindrical heating source. The effect of the heat source size is investigated by varying its non-dimensional diameter from 0.1 to 0.5. The eating source cylinder and enclosure are maintained at constant temperatures. The buoyancy-driven flow field is analyzed using streamline distributions, non-dimensional velocity magnitudes, and isotherm contours. Results reveal that the size of the internal heating source significantly affects the thermal performance of the combined structure. For small values of , the flow remains weak and localized, with limited convective motion. As increases to moderate values ≈0.3, recirculation regions intensify, velocity fields expand, and thermal plumes rise symmetrically, which indicates enhanced convective transport. However, additional increasing of values leads to flow constriction, reduced circulation strength, and causes less effective heat transfer. It is found that the average Nusselt number decreases with increasing due to diminished temperature gradients and restricted fluid motion despite the larger surface area provided by bigger cylinders. The results are applicable for the design of passive electronic cooling systems, solar thermal collectors, and other natural heat convection-based enclosures.

Abstract: Diffusion Absorption Refrigeration (DAR) systems offer a sustainable alternative to vapor compression refrigeration by utilizing thermal energy instead of mechanical work, making them well-suited for renewable energy applications and waste heat recovery. This review presents a comprehensive analysis of DAR systems, incorporating a statistical evaluation of various research aspects. It focuses on energy sources, alternative working fluids, system configurations, and their impact on the coefficient of performance (COP) and operating temperature. The evolution of DAR technology is traced from early theoretical models to recent experimental developments, supported by a bibliometric study that highlights key research trends, contributing countries, and periods of increased academic activity. The review assesses DAR performance in terms of efficiency improvements, integration of renewable energy, and the use of alternative working fluids. Bibliometric data indicate a growing research interest since 1990, with a notable peak in 2019, and significant contributions from China, India, Germany, and the United States. The study concludes by emphasizing the need for further research into advanced working fluids, the integration of thermal energy storage to enhance stability, and the development of computational models for optimized design and performance. Addressing these challenges will help advance DAR technology as a viable, sustainable cooling solution, supporting innovation and contributing to global energy sustainability.

Abstract: Natural convective in enclosures are very important topics in thermal engineering because they find versatile industrial applications. An internal circular cylinder's vertical position and heat source on fluid flow and heat transfer in a triangular cavity are investigated. Numerical simulations were carried out to analyze variations in the average Nusselt number, streamline topology, temperature distribution, and velocity fields by using ANSYS Fluent. The results show that the Nusselt number rises from approximately 0.91–0.94 at lower positions (Y = 0.1–0.3) to a maximum of about 0.97 near Y = 0.4 driven by intensified thermal gradients and buoyancy-induced circulation. Within the upper-to-mid region (Y = 0.2–0.4) the formation of large adjacent vortices enhances macro-scale mixing, resulting in nearly a 4% improvement in heat transfer relative to the reference case. At mid-level positions (Y = 0.4–0.6) quasi-steady symmetric circulations are sustained, maintaining effective convection with Nu values of 0.95–0.97. In contrast, at higher locations (Y = 0.7–0.9), the weakening of vortex strength leads to flow stagnation and localized deterioration in heat transfer, reducing Nu to about 0.90–0.92. Overall, the findings underscore the critical importance of internal component placement in improving natural cooling performance, and further suggest that the most efficient thermal behavior is achieved when the cylinder and heat source are positioned within 0.2 < Y < 0.4, offering practical guidance for optimizing the thermal design of triangular enclosures.

Abstract: This study examines the thermodynamic performance of a ternary refrigerant mixture composed of R32, R1234ze (E), and R152a (20/20/60 % by mass fraction) as a low-global warming potential (GWP) alternative to R410A in vapour compression refrigeration systems. The simulation was performed using REFPROP under standard operating conditions linked with an engineering equation solver, including 5 K of superheating and 5 K of subcooling. Under different operating conditions of constant evaporation temperature (T_e = 5 °C) with varying condensation temperatures (T_C) (40 to 55 °C by step 2.5°C). Key parameters, including cooling capacity (Qₑ), compressor work (W_c), pressure ratio (P_r), discharge temperature (T_D), mass flow rate (ṁ), and volumetric efficiency (ηᵥ), were evaluated to assess performance. The mixture’s discharge temperature was slightly lower than that of R410A; this will reduce compressor thermal stress and increase compressor life span. Charts illustrating the effect of Tc on all performance indicators were created. In addition to thermodynamic analysis, safety considerations were reviewed. Despite its mild flammability (A2L), the adopted mixture demonstrated stable operation across various conditions and offers potential for applications where safety measures can be effectively implemented. The results indicate that the new mixture presents an energy-efficient and environmentally sustainable replacement for R410A. Further experimental validation is recommended to confirm these findings in real-world scenarios.

Abstract: Phase Change Materials (PCMs) have become popular for thermal energy storage (TES) uses due to their large latent heat capacity and almost isothermal performance. However, melting rates and the overall effectiveness of the system are constrained by their intrinsically poor heat conductivity. Considering latest studies investigating innovative shapes and combinations to optimize heat transfer achievement, fin insertion has become an effective and affordable upgrade technique. The most recent computational and experimental studies on fin-enhanced latent heat thermal energy storage (LHTES) systems are covered in this review, with a concentrate on how fin materials, forms, and configurations enhance PCM melting performance. Fin shapes such as longitudinal, radial, tree-like, spiral, T-shaped, V-shaped, fractal, and hybrid fins have been studied with respect to temperature uniformity, natural convection impacts, and melting time decrease. The outcomes demonstrate that improving fin shape could decrease melting times by as much as 70%, with geometric and tree-like fins performing better due to increased conduction–convection coupling. Furthermore, included in the research are design trade-offs involving fin volume against surface area as well as the impact of computational optimization in the design of fin shape. subsequently, research gaps and future initiatives are noted, with a focus on the possibility of hybrid improvement techniques that combine heat transfer fluid optimization or high-conductivity additives with advanced fin design.

Abstract: As electric vehicles (EVs) gain traction in low- and middle-income countries, their role in grid modernization and energy resilience has become increasingly relevant. This paper explores the transformative potential of bidirectional charging, Vehicle-to-Grid (V2G) and Grid-to-Vehicle (G2V), in two emerging clean mobility landscapes: Pakistan and Sub-Saharan Africa (SSA). While both regions grapple with fragile power infrastructure and nascent EV markets, they also share promising conditions for decentralized energy solutions, including rising urbanization, policy interest, and renewable energy capacity.We present a comparative analysis of the clean mobility ecosystem, policy readiness, and energy mix dynamics in Pakistan and SSA, contextualizing the promise and pitfalls of V2G/G2V adoption. To complement the policy and systems-level insights, we simulate the grid impact of varying EV penetration scenarios (baseline, low-density, and high-density) under both unidirectional (G2V) and bidirectional (V2G) frameworks. Using realistic adoption figures and residential 7–11 kW charger profiles, we model hourly load interactions to assess how EVs can either burden or stabilize local grids. Our findings reveal that while G2V adoption under high-density scenarios introduces significant early-evening grid stress, V2G strategies during peak demand periods can offset this load, effectively transforming EVs into distributed energy assets. The results underscore the need for region-specific charging policies, infrastructure investment, and digital control systems to harness the co-benefits of clean mobility and grid flexibility. Ultimately, we argue that V2G and G2V systems, if strategically implemented, can accelerate both electrified transport and energy transition pathways in Pakistan and SSA.

Abstract: Africa’s transition to sustainable transport systems is critical for achieving climate goals, reducing energy poverty, and fostering inclusive economic growth. This paper examines the transformative potential of electric mobility (e-mobility) in addressing the continent’s dual challenges of rapid urbanization and carbon-intensive transport. Drawing on case studies from Nigeria, Kenya, and Uganda, we analyze the socio-economic, technological, and policy dimensions of e-mobility adoption. A mixed-methods approach combines quantitative data on emission reductions and cost savings with qualitative insights from stakeholders, including policymakers, industry leaders, and communities. Key findings reveal that Africa’s e-mobility landscape is poised for exponential growth by 2025, driven by declining battery costs, renewable energy integration, and innovative business models such as battery-swapping and pay-as-you-go systems. However, infrastructure gaps—particularly in charging networks and grid stability—remain significant barriers. Policy interventions, including tax incentives, localized manufacturing, and public-private partnerships, emerge as catalysts for scaling adoption. The study also highlights the role of electric two-and three-wheelers, which account for over 60% of passenger transport in urban areas, in democratizing access to clean mobility. The paper underscores the co-benefits of e-mobility, including a 30–45% reduction in transport-sector emissions, job creation in green manufacturing, and improved air quality. We propose a roadmap for African governments to align e-mobility strategies with renewable energy deployment and circular economy principles, emphasizing the need for continent-specific standards and cross-border collaboration. By leveraging its mineral resources and youthful population, Africa can position itself as a global leader in sustainable transport innovation while addressing systemic inequities in energy access. This research contributes to the discourse on just energy transitions by framing e-mobility as both a climate imperative and a vehicle for equitable development in low-income regions.