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Thermo, Volume 5, Issue 3 (September 2025) – 11 articles

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12 pages, 1831 KB  
Article
Inverse Chemical Equilibrium Problem in Reacting Gaseous Mixtures: The Choice of Temperature to Maximise Product Yield
by Igor Donskoy and Oleg Khamisov
Thermo 2025, 5(3), 31; https://doi.org/10.3390/thermo5030031 - 21 Aug 2025
Viewed by 387
Abstract
A usual problem in chemical engineering and fuel processing is to achieve the highest possible efficiency concerning the target products. In this paper, we consider the inverse problem of chemical equilibrium and propose mathematical methods to obtain conditions under which the equilibrium state [...] Read more.
A usual problem in chemical engineering and fuel processing is to achieve the highest possible efficiency concerning the target products. In this paper, we consider the inverse problem of chemical equilibrium and propose mathematical methods to obtain conditions under which the equilibrium state of the reacting system achieves the required characteristics. For the case of maximising the aim component yield, a new two-step algorithm is developed based on the inverse problem solution. The methods are tested using the methane reforming example. Full article
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37 pages, 1588 KB  
Review
Enhancing Thermal Efficiency in Power Electronics: A Review of Advanced Materials and Cooling Methods
by Tahmid Orville, Monem Tajwar, Raghav Bihani, Parnab Saha and Mohammed Abdul Hannan
Thermo 2025, 5(3), 30; https://doi.org/10.3390/thermo5030030 - 20 Aug 2025
Viewed by 415
Abstract
Over the last several years, a significant advancement in high-voltage electronic packaging techniques has paved the way for next-generation power electronics. However, controlling the thermal properties of these new packaging solutions is still a major challenge. The utilization of wide bandgap semiconductors such [...] Read more.
Over the last several years, a significant advancement in high-voltage electronic packaging techniques has paved the way for next-generation power electronics. However, controlling the thermal properties of these new packaging solutions is still a major challenge. The utilization of wide bandgap semiconductors such as SiC and GaN offers effective methods to minimize thermal inefficiencies caused by conduction losses through high-frequency switching topologies. Nevertheless, the need for high voltage in electrical systems continues to pose significant barriers, as heat generation remains one of the most significant obstacles to widespread implementation. The trend of electronics design miniaturization has driven the development of high-performance cooling concepts to address the needs of high-power-density systems. As a result, the design of effective cooling systems has emerged as a crucial aspect for successful implementation, requiring seamless integration with electronic packaging to achieve optimal performance. This review article explores various thermal management approaches demonstrated in electronic systems. This paper aims to provide a comprehensive overview of heat transfer enhancement techniques employed in electronics thermal management, focusing on core concepts. The review categorizes these techniques into concepts based on fin design, microchannel cooling, jet impingement, phase change materials, nanofluids, and hybrid designs. Recent advancements in high-power density devices, alongside innovative cooling systems such as phase change materials and nanofluids, demonstrate potential for enhanced heat dissipation in power electronics. Improved designs in finned heat sinks, microchannel cooling, and jet impingement techniques have enabled more efficient thermal management in high-density power electronics. By fixing key insights into one reference, this review serves as a valuable resource for researchers and engineers navigating the complex landscape of high-performance cooling for modern electronic systems. Full article
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21 pages, 5001 KB  
Article
Optimization of Cogeneration Supercritical Steam Power Plant Design Based on Heat Consumer Requirements
by Victor-Eduard Cenușă and Ioana Opriș
Thermo 2025, 5(3), 29; https://doi.org/10.3390/thermo5030029 - 10 Aug 2025
Viewed by 350
Abstract
High-efficiency design solutions for cogeneration steam power plants are studied for different steam consumer requirements (steam pressures between 3.6 and 40 bar and heat flow rates between 10 and 40% of the fuel heat flow rate into the steam generators). Using a genetic [...] Read more.
High-efficiency design solutions for cogeneration steam power plants are studied for different steam consumer requirements (steam pressures between 3.6 and 40 bar and heat flow rates between 10 and 40% of the fuel heat flow rate into the steam generators). Using a genetic algorithm, optimum designs for schemes with extraction-condensing steam turbines, reheat, and supercritical parameters were found considering four objective functions (high global efficiency, low specific investment in equipment, high exergetic efficiency, and high power-to-heat ratio in full cogeneration mode). A second Pareto front was computed from the prior solutions, considering the first two objective functions, resulting in the high-efficiency cogeneration schemes with a primary energy savings (PES) ratio higher than 10%. The results showed that the PES ratio depends strongly on the steam consumer requirements, rising from values under 10% for low heat flow rates and few preheaters to over 25% for a higher number of preheaters, high heat flow rates, and low steam pressures to the consumer. At the same heat flow rate to the consumer, the power-to-heat ratio in full cogeneration mode increases with the decrease in the required steam pressure to the consumer. Full article
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19 pages, 3198 KB  
Article
Thermodynamic Analysis of Oxygenation Methods for Stationary Water: Mathematical Modeling and Experimental Investigation
by Mihaela Constantin, Cătălina Dobre and Mugurel Oprea
Thermo 2025, 5(3), 28; https://doi.org/10.3390/thermo5030028 - 8 Aug 2025
Viewed by 307
Abstract
This paper presents a detailed thermodynamic and mathematical modeling study of the oxygenation processes in stationary water bodies, focusing on improving oxygen transfer efficiency, an essential factor in sustaining aquatic ecosystem health. The study employed mathematical models implemented in MATLAB R2024a to simulate [...] Read more.
This paper presents a detailed thermodynamic and mathematical modeling study of the oxygenation processes in stationary water bodies, focusing on improving oxygen transfer efficiency, an essential factor in sustaining aquatic ecosystem health. The study employed mathematical models implemented in MATLAB R2024a to simulate the influence of temperature, bubble size, and mass transfer parameters. Key parameters, such as dissolved oxygen concentration, volumetric mass transfer coefficient (akL), and water temperature, were evaluated under different operational scenarios. The oxygenation system was powered by solar energy and included rotating fine-bubble generators mounted on a floating platform. Mathematical modeling carried out in MATLAB validated the theoretical models, showing how environmental factors such as temperature and bubble size influence oxygen dissolution. Initial experimental data, including dissolved oxygen levels (C0 = 3.12 mg/dm3), saturation concentrations at various temperatures (Cs = 8.3 mg/dm3 at 24 °C; Cs = 7.3 mg/dm3 at 30 °C), and a mass transfer coefficient of akL = 0.09 s−1, were used to support the model accuracy. The results highlight the potential of digitally controlled energy-efficient aeration technologies for applications in lake restoration, aquaculture, and sustainable water management. This paper introduces a coupled approach to oxygen transfer and temperature evolution validated experimentally, which has rarely been detailed in the literature. The novelty of this study lies in the combined thermodynamic modeling and exergy–entropy analysis along with real-time tracking, showing the relevance of energy-optimized, digitally monitored oxygenation platforms powered by solar energy. Full article
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36 pages, 16047 KB  
Article
Insights into Sea Spray Ice Adhesion from Laboratory Testing
by Paul Rübsamen-v. Döhren, Sönke Maus, Zhiliang Zhang and Jianying He
Thermo 2025, 5(3), 27; https://doi.org/10.3390/thermo5030027 - 30 Jul 2025
Viewed by 341
Abstract
Ice accretion from marine icing events accumulating on structures poses a significant hazard to ship and offshore operations in cold regions, being relevant for offshore activities like oil explorations, offshore wind, and shipping in arctic regions. The adhesion strength of such ice is [...] Read more.
Ice accretion from marine icing events accumulating on structures poses a significant hazard to ship and offshore operations in cold regions, being relevant for offshore activities like oil explorations, offshore wind, and shipping in arctic regions. The adhesion strength of such ice is a critical factor in predicting the build-up of ice loads on structures. While the adhesion strength of freshwater ice has been extensively studied, knowledge about sea spray ice adhesion remains limited. This study intends to bridge this gap by investigating the adhesion strength of sea spray icing under controlled laboratory conditions. In this study, we built a new in situ ice adhesion test setup and grew ice at −7 °C to −15 °C on quadratic aluminium samples of 3 cm to 12 cm edge length. The results reveal that sea spray ice adhesion strength is in a significantly lower range—5 kPa to 100 kPa—compared to fresh water ice adhesion and shows a low dependency on the temperature during the spray event, but a notable size effect and influence of the brine layer thickness on the adhesion strength. These findings provide critical insights into sea spray icing, enhancing the ability to predict and manage ice loads in marine environments. Full article
(This article belongs to the Special Issue Frosting and Icing)
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16 pages, 3079 KB  
Article
Optimized Solar-Powered Evaporative-Cooled UFAD System for Sustainable Thermal Comfort: A Case Study in Riyadh, KSA
by Mohamad Kanaan, Semaan Amine and Mohamed Hmadi
Thermo 2025, 5(3), 26; https://doi.org/10.3390/thermo5030026 - 30 Jul 2025
Cited by 1 | Viewed by 449
Abstract
Evaporative cooling (EC) offers an energy-efficient alternative to direct expansion (DX) cooling but suffers from high water consumption. This limitation can be mitigated by pre-cooling incoming fresh air using cooler exhaust air via energy recovery. This study presents and optimizes a solar-driven EC [...] Read more.
Evaporative cooling (EC) offers an energy-efficient alternative to direct expansion (DX) cooling but suffers from high water consumption. This limitation can be mitigated by pre-cooling incoming fresh air using cooler exhaust air via energy recovery. This study presents and optimizes a solar-driven EC system integrated with underfloor air distribution (UFAD) to enhance thermal comfort and minimize water use in a temporary office in Riyadh’s arid climate. A 3D CFD model was developed and validated against published data to simulate indoor airflow, providing data for thermal comfort evaluation using the predicted mean vote model in cases with and without energy recovery. A year-round hourly energy analysis revealed that the solar-driven EC-UFAD system reduces grid power consumption by 93.5% compared to DX-based UFAD under identical conditions. Energy recovery further cuts annual EC water usage by up to 31.3%. Operational costs decreased by 84% without recovery and 87% with recovery versus DX-UFAD. Full article
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32 pages, 3675 KB  
Article
Gibbs Quantum Fields Computed by Action Mechanics Recycle Emissions Absorbed by Greenhouse Gases, Optimising the Elevation of the Troposphere and Surface Temperature Using the Virial Theorem
by Ivan R. Kennedy, Migdat Hodzic and Angus N. Crossan
Thermo 2025, 5(3), 25; https://doi.org/10.3390/thermo5030025 - 22 Jul 2025
Viewed by 388
Abstract
Atmospheric climate science lacks the capacity to integrate thermodynamics with the gravitational potential of air in a classical quantum theory. To what extent can we identify Carnot’s ideal heat engine cycle in reversible isothermal and isentropic phases between dual temperatures partitioning heat flow [...] Read more.
Atmospheric climate science lacks the capacity to integrate thermodynamics with the gravitational potential of air in a classical quantum theory. To what extent can we identify Carnot’s ideal heat engine cycle in reversible isothermal and isentropic phases between dual temperatures partitioning heat flow with coupled work processes in the atmosphere? Using statistical action mechanics to describe Carnot’s cycle, the maximum rate of work possible can be integrated for the working gases as equal to variations in the absolute Gibbs energy, estimated as sustaining field quanta consistent with Carnot’s definition of heat as caloric. His treatise of 1824 even gave equations expressing work potential as a function of differences in temperature and the logarithm of the change in density and volume. Second, Carnot’s mechanical principle of cooling caused by gas dilation or warming by compression can be applied to tropospheric heat–work cycles in anticyclones and cyclones. Third, the virial theorem of Lagrange and Clausius based on least action predicts a more accurate temperature gradient with altitude near 6.5–6.9 °C per km, requiring that the Gibbs rotational quantum energies of gas molecules exchange reversibly with gravitational potential. This predicts a diminished role for the radiative transfer of energy from the atmosphere to the surface, in contrast to the Trenberth global radiative budget of ≈330 watts per square metre as downwelling radiation. The spectral absorptivity of greenhouse gas for surface radiation into the troposphere enables thermal recycling, sustaining air masses in Lagrangian action. This obviates the current paradigm of cooling with altitude by adiabatic expansion. The virial-action theorem must also control non-reversible heat–work Carnot cycles, with turbulent friction raising the surface temperature. Dissipative surface warming raises the surface pressure by heating, sustaining the weight of the atmosphere to varying altitudes according to latitude and seasonal angles of insolation. New predictions for experimental testing are now emerging from this virial-action hypothesis for climate, linking vortical energy potential with convective and turbulent exchanges of work and heat, proposed as the efficient cause setting the thermal temperature of surface materials. Full article
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22 pages, 2359 KB  
Article
Investigation of the Charging and Discharging Cycle of Packed-Bed Storage Tanks for Energy Storage Systems: A Numerical Study
by Ayah Marwan Rabi’, Jovana Radulovic and James M. Buick
Thermo 2025, 5(3), 24; https://doi.org/10.3390/thermo5030024 - 18 Jul 2025
Viewed by 306
Abstract
In recent years, packed-bed systems have emerged as an attractive design for thermal energy storage systems due to their high thermal efficiency and economic feasibility. As integral components of numerous large-scale applications systems, packed-bed thermal energy stores can be successfully paired with renewable [...] Read more.
In recent years, packed-bed systems have emerged as an attractive design for thermal energy storage systems due to their high thermal efficiency and economic feasibility. As integral components of numerous large-scale applications systems, packed-bed thermal energy stores can be successfully paired with renewable energy and waste heat to improve energy efficiency. An analysis of the thermal performances of two packed beds (hot and cold) during six-hour charging and discharging cycles has been conducted in this paper using COMSOL Multiphysics software, utilizing the optimal design parameters that have been determined in previous studies, including porosity (0.2), particle diameters (4 mm) for porous media, air as a heat transfer fluid, magnesia as a storage medium, mass flow rate (13.7 kg/s), and aspect ratio (1). The performance has been evaluated during both the charging and discharging cycles, in terms of the system’s capacity factor, the energy stored, and the thermal power, in order to understand the system’s performance and draw operational recommendations. Based on the results, operating the hot/cold storage in the range of 20–80% of the full charge was found to be a suitable range for the packed-bed system, ensuring that the charging/discharging power remains within 80% of the maximum. Full article
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22 pages, 1906 KB  
Article
Explainable and Optuna-Optimized Machine Learning for Battery Thermal Runaway Prediction Under Class Imbalance Conditions
by Abir El Abed, Ghalia Nassreddine, Obada Al-Khatib, Mohamad Nassereddine and Ali Hellany
Thermo 2025, 5(3), 23; https://doi.org/10.3390/thermo5030023 - 15 Jul 2025
Viewed by 612
Abstract
Modern energy storage systems for both power and transportation are highly related to lithium-ion batteries (LIBs). However, their safety depends on a potentially hazardous failure mode known as thermal runaway (TR). Predicting and classifying TR causes can widely enhance the safety of power [...] Read more.
Modern energy storage systems for both power and transportation are highly related to lithium-ion batteries (LIBs). However, their safety depends on a potentially hazardous failure mode known as thermal runaway (TR). Predicting and classifying TR causes can widely enhance the safety of power and transportation systems. This paper presents an advanced machine learning method for forecasting and classifying the causes of TR. A generative model for synthetic data generation was used to handle class imbalance in the dataset. Hyperparameter optimization was conducted using Optuna for four classifiers: Support Vector Machine (SVM), Multi-Layer Perceptron (MLP), tabular network (TabNet), and Extreme Gradient Boosting (XGBoost). A three-fold cross-validation approach was used to guarantee a robust evaluation. An open-source database of LIB failure events is used for model training and testing. The XGBoost model outperforms the other models across all TR categories by achieving 100% accuracy and a high recall (1.00). Model results were interpreted using SHapley Additive exPlanations analysis to investigate the most significant factors in TR predictors. The findings show that important TR indicators include energy adjusted for heat and weight loss, heater power, average cell temperature upon activation, and heater duration. These findings guide the design of safer battery systems and preventive monitoring systems for real applications. They can help experts develop more efficient battery management systems, thereby improving the performance and longevity of battery-operated devices. By enhancing the predictive knowledge of temperature-driven failure mechanisms in LIBs, the study directly advances thermal analysis and energy storage safety domains. Full article
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21 pages, 3397 KB  
Article
Numerical Optimization of Multi-Stage Thermoelectric Cooling Systems Using Bi2Te3 for Enhanced Cryosurgical Applications
by Akram Kharmouch, Md. Kamrul Hasan, El Yatim Sabik, Hicham Bouali, Hayati Mamur and Mohammad Ruhul Amin Bhuiyan
Thermo 2025, 5(3), 22; https://doi.org/10.3390/thermo5030022 - 11 Jul 2025
Viewed by 555
Abstract
Cryosurgery employs extremely low temperatures to destroy abnormal or cancerous tissue. Conventional systems use cryogenic fluids like liquid nitrogen or argon, which pose challenges in handling, cost, and precise temperature control. This study explores thermoelectric (TE) cooling using the Peltier effect as an [...] Read more.
Cryosurgery employs extremely low temperatures to destroy abnormal or cancerous tissue. Conventional systems use cryogenic fluids like liquid nitrogen or argon, which pose challenges in handling, cost, and precise temperature control. This study explores thermoelectric (TE) cooling using the Peltier effect as an efficient alternative. A numerical optimization of multi-stage TE coolers using bismuth telluride (Bi2Te3) is performed through finite element analysis in COMSOL Multiphysics. Results show that the optimized multi-stage TE system achieves a minimum temperature of −70 °C, a 90 K temperature difference, and 4.0 W cooling power—outperforming single-stage (SS) systems with a maximum ΔT of 73.27 K. The study also investigates the effects of material properties, current density, and geometry on performance. An optimized multi-stage (MS) configuration improves cooling efficiency by 22.8%, demonstrating the potential of TE devices as compact, energy-efficient, and precise solutions for cryosurgical applications. Future work will explore advanced nanomaterials and hybrid systems to further improve performance in biomedical cooling. Full article
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12 pages, 1004 KB  
Review
Causes and Demonstration of Thermal Stress in Castings Made from Gray Iron
by Peter Futas, Alena Pribulova, Jozef Petrik, Peter Blasko, Marek Solc and Marcin Brzezinski
Thermo 2025, 5(3), 21; https://doi.org/10.3390/thermo5030021 - 27 Jun 2025
Viewed by 433
Abstract
Cast iron is a longtime reliable material for the production of heat-treated stressed castings, i.e., those that are long, are cyclically heated, and heat-stressed. The durability of thermally stressed castings used in practice is dependent on the choice of the optimum chemical composition, [...] Read more.
Cast iron is a longtime reliable material for the production of heat-treated stressed castings, i.e., those that are long, are cyclically heated, and heat-stressed. The durability of thermally stressed castings used in practice is dependent on the choice of the optimum chemical composition, metallurgy of production, macro- and microstructures, construction, and the way of exploitation. Today, the successful solution of this problem is dominated by simulation programs. The comprehensive analysis of heat stress is very important, i.e., the impacts of various physical quantities on its rise, progress, and size. This paper provides a comprehensive analysis of thermal stress mechanisms in gray iron castings, with a particular emphasis on the relationships between the material properties, microstructural characteristics, and component performance under thermal loading conditions. The theoretical foundations are complemented by experimental data, establishing practical guidelines for optimizing cast iron compositions and processing parameters for thermal applications. Full article
(This article belongs to the Special Issue Thermal Science and Metallurgy)
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