Journal of Thermal Energy Systems

Enhanced Thermal Performance of a Circular Heat Exchanger with Internal Blades through Bayesian Optimization and Experimentation

2026-01-02T11:03:40+00:00

This study presents an experimental investigation of convective heat transfer and hydrodynamic behavior in a circular water‑cooled heat exchanger equipped with internal blades under turbulent flow. A 1000 mm long, 30 mm inner‑diameter tube was tested in plain and internally bladed configurations with 2, 4, 6, and 8 blades over a Reynolds number range of 6000–14,000. Inlet and outlet temperatures and pressure drops were measured to determine the Nusselt number, friction factor, convective heat transfer coefficient, and thermal performance factor (TPF), enabling a detailed assessment of heat transfer enhancement relative to the associated hydraulic penalties. The results show that internal blades effectively disrupt the thermal boundary layer and generate secondary flow vortices, yielding a substantial increase in convective heat transfer accompanied by a rise in friction factor. To identify operating conditions that maximize thermal efficiency, Bayesian optimization was applied to the experimental database, predicting the optimal combination of blade count and Reynolds number that achieves the highest TPF. The optimized configuration delivered superior heat transfer with an acceptable pressure drop penalty, demonstrating the value of Bayesian optimization as a predictive design tool and supporting the development of compact, high‑efficiency water-cooled heat exchangers for industrial applications.

Integrated Evaluation of Energy Technologies across Economic, Environmental, and Social Dimensions

2026-03-12T11:49:25+00:00

The global transition toward sustainable energy systems requires integrated evaluation frameworks capable of simultaneously assessing economic, environmental, technical, and social performance. This study conducts a comprehensive comparative assessment of ten major electricity generation technologies: biogas, geothermal, hydropower, solar photovoltaic (PV), concentrated solar power (CSP), onshore wind, offshore wind, natural gas, coal, and oil, using the technique for order preference by similarity to ideal solution (TOPSIS) multi-criteria decision-making method. A structured decision matrix was developed, incorporating installation cost, levelized cost of electricity (LCOE), capacity factor, life-cycle CO₂ emissions, water consumption, land-use intensity, and employment generation indicators. Cost-type criteria were minimized, while technical and social criteria were maximized. After normalization and calculation of positive and negative ideal solutions, closeness coefficients (Cᵢ) were computed to determine overall sustainability ranking. The results reveal that renewable and low-carbon technologies dominate the top positions. Biogas achieved the highest TOPSIS score (Cᵢ = 0.681), closely followed by geothermal (0.680), onshore wind (0.662), offshore wind (0.638), and solar PV (0.634). In contrast, fossil-based technologies ranked lower, with natural gas (0.534), coal (0.477), and oil (0.344) occupying the bottom positions. The findings indicate that technologies combining relatively low emissions, moderate cost, stable operational performance, and employment benefits achieve superior integrated sustainability performance. The study demonstrates that single-metric evaluations, such as cost alone, may produce misleading conclusions, whereas multi-criteria frameworks provide balanced and transparent decision support. The results offer evidence-based guidance for policymakers and energy planners, supporting diversified renewable portfolios and gradual fossil fuel phase-down strategies aligned with long-term sustainability and decarbonization objectives.

Effective Maintenance Management Strategies for Air-conditioning Systems in Administrative Offices

2026-02-04T10:25:30+00:00

The persistent failure of air conditioning systems in institutional settings, particularly in the exams and records office of the Mechanical Engineering Department at Rivers State University, has revealed not only technical inefficiencies but also critical lapses in management and maintenance planning. In Port Harcourt’s humid, high-temperature climate, these failures result in inadequate cooling, elevated energy expenditures, and risks to the preservation of sensitive academic documents, issues that demand both technical and administrative intervention. This study investigates the management and maintenance strategies required to ensure the reliable operation of air conditioning systems in such settings. A case-based approach was adopted, involving the repair and rehabilitation of a split-unit air conditioner, with the dual aim of restoring cooling efficiency and developing a sustainable facility management framework. The methodology included systematic diagnostic testing (pressure, temperature, and energy usage analysis), targeted component replacement (compressor, R410A refrigerant, capillary tube, thermostatic expansion valve, and filter drier), and routine maintenance procedures such as coil cleaning. Thermodynamic performance was assessed using pressure-enthalpy diagrams and heat transfer modeling to validate results. Performance outcomes showed a significant improvement: the coefficient of performance (COP) increased from 4.5 to 6 after repairs, discharge air temperature reduced from 28 to 22°C, and energy consumption dropped from 1.8 to 1.2 kW. Pressure readings normalized to 65 psi (suction) and 280 psi (discharge), confirming restored operational efficiency. Crucially, a structured preventive maintenance plan and resource management schedule were developed and implemented, leading to a 46% reduction in projected annual maintenance and energy costs. By integrating both engineering and management principles, this study presents a replicable, cost-effective framework for managing and maintaining split-unit air conditioning systems in institutional environments. It highlights the importance of proactive maintenance planning, resource optimization, and environmental sustainability in ensuring long-term operational reliability and cost control in facilities management, particularly within the context of academic institutions in tropical regions.

Structural Integrity and Thermal Management Assessment of Lithium-Ion Batteries under Crash Test for Different Cell Form Factors

2026-04-06T06:21:40+00:00

The safety of lithium-ion batteries (LIBs) in electric vehicles critically depends on their structural integrity and thermal stability under crash scenarios. This study presents a comprehensive assessment of cylindrical, prismatic, and pouch cell form factors through both experimental crash testing and finite element simulations using LS-DYNA and coupled thermal models. Structural responses, including stress distribution, deformation modes, and energy absorption, were analysed alongside thermal effects such as heat generation, dissipation, and risk of thermal runaway. Experimental observations were used to validate numerical results, ensuring accuracy in predicting coupled mechanical–thermal interactions. Comparative analysis revealed that cylindrical cells exhibit superior load-bearing capacity and delayed onset of thermal instability, prismatic cells are prone to localised stress concentrations, and pouch cells demonstrate higher vulnerability to deformation-induced heating. The novelty of this work lies in integrating structural crashworthiness with thermal management evaluation across different cell geometries, bridging a critical research gap in battery safety assessment. The findings provide actionable insights for optimised cell and pack design, development of crashworthiness standards, and formulation of advanced thermal management strategies, ultimately enhancing the safety and durability of next-generation EV battery systems.

Modelling and Analysis of the Heat Transfer Processes in a Diesel-CNG Dual-Fuel Compression Ignition Engine

2026-02-11T04:44:08+00:00

This study presents a comprehensive numerical investigation of heat transfer processes in a compression ignition (CI) engine operating under diesel-CNG dual‑fuel mode. Using a three‑dimensional finite volume computational fluid dynamics (CFD) framework, the work models transient in‑cylinder temperature fields, wall heat flux distribution, and combustion behaviour across varying substitution ratios, speeds, and loads. The model incorporates energy conservation equations, simplified combustion chemistry, temperature‑dependent thermo-physical properties, and validated turbulence formulations. Results reveal that moderate CNG substitution (25–50%) reduces peak cylinder temperature by 2–4%, decreases wall heat flux by up to 6%, and produces more uniform thermal gradients, thereby reducing component thermal stress. Combustion duration increases by 10–20% due to methane’s slower ignition characteristics. At high speeds and loads, wall temperatures rise significantly, demonstrating strong operational sensitivity. Model validation against benchmark data shows deviations below 9%, confirming predictive reliability. The findings demonstrate that controlled dual‑fuel operation can improve thermal management, enhance component longevity, and reduce cooling demands in marine CI engines. This study contributes a validated thermal modelling framework suitable for optimizing cleaner dual‑fuel marine propulsion systems.