Thermo

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

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

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

Based on the First and the Second laws of Thermodynamics the energy dissipated in engineering materials and structures is calculated in a multidimensional mechanics framework. The existing practice of computing the dissipated energy by the area of the stress-strain (or force-displacement) curve is objected to. The conditions under which the area of a stress-strain diagram correctly measures the dissipated energy are derived and clearly presented. A general mathematical form for the dissipated energy when those conditions are not satisfied is provided. An internal variables formulation is employed in this work. Erroneous results from the literature calculating the dissipated energy are given. Erroneous calculations are abundant in publications, Theses and Dissertations, books, and even engineering codes. The terms hysteresis and hysteretic loss are technically explained and their wrong use in cases other than in viscoelasticity is explicated. Full article

This study investigates the effects of varying hydrogen percentages in fuel blends on combustion dynamics, engine performance, and emissions. Experimental data and analytical equations were used to evaluate combustion parameters such as equivalent lambda, in-cylinder pressure, heat release rate, and ignition timing. The findings demonstrate that hydrogen blending enhances combustion stability, shortens ignition delay, and shifts peak heat release to be closer to the top dead center (TDC). These changes improve thermal efficiency and reduce cycle-to-cycle variation. Hydrogen blending also significantly lowers carbon dioxide (CO₂) and hydrocarbon (HC) emissions, particularly at higher blend levels (H0–H5), while lower blends increase nitrogen oxides (NO_x) emissions and risk pre-ignition due to advanced start of combustion (SOC). Engine performance improved with an average hydrogen energy contribution of 12% under a constant load. However, the optimal hydrogen blending range is crucial to balancing efficiency gains and emission reductions. These results underline the potential of hydrogen as a cleaner additive fuel and the importance of optimizing blend ratios to harness its benefits effectively. Full article

A crucial stage in the post-harvest processing of cocoa beans, drying, has a direct effect on the finished product’s quality and market value. This study investigates the efficiency, quality outcomes, and environmental implications of a mixed forced convection solar dryer designed for drying cocoa beans in Ntui, Cameroon, compared to traditional open-air drying methods. The solar dryer’s design, incorporating a solar collector, forced ventilation, and thermal storage, leverages local materials and renewable energy, offering an environmentally sustainable alternative by reducing fossil fuel reliance and post-harvest losses. Experimental trials were conducted to assess key drying parameters, including the temperature, relative humidity, water removal rate, pH, and free fatty acid (FFA) content, under the equatorial climate conditions of high solar irradiation and humidity. Results demonstrate that the solar dryer significantly reduces drying time from an average of 4.83 days in open-air drying to 2.5 days, a 50% improvement, while maintaining optimal conditions for bean quality preservation. The solar-dried beans exhibited a stable pH (5.7–5.9), a low FFA content (0.282% oleic acid equivalent, well below the EU standard of 1.75%), and superior uniformity in texture and color, meeting international quality standards. In contrast, open-air drying showed greater variability in quality due to weather dependencies and contamination risks. The study highlights the dryer’s adaptability to equatorial climates and its potential to enhance cocoa yields and quality for small-scale producers. These findings underscore the viability of solar drying as a high-performance, eco-friendly solution, paving the way for its optimization and broader adoption in cocoa-producing regions. This research contributes to the growing body of knowledge on sustainable drying technologies, addressing both economic and environmental challenges in tropical agriculture. Full article

In the age of widespread renewable energy integration, coal-fired power plants are transitioning from a primary baseload role to a more flexible peak-shaving capacity. Under frequent load changes, the thermal efficiency will significantly decrease. In order to achieve efficient dynamic operation, this study proposes a comprehensive mechanical model of a 300 MW drum-type boiler. Based on the Modelica/DYMOLA platform, the multi-domain equations describing energy and mass balance are programmed and solved. A comprehensive evaluation of the energy transformation within the boiler’s heat exchange components was performed. Utilizing the principles of exergy analysis, this study investigates how fluctuating operational conditions impact the energy dynamics and exergy losses in the drum and heating surfaces. Steady-state simulation reveals that the evaporator and superheater units account for 81.3% of total exergy destruction. Dynamic process analysis shows that the thermal inertia induced by the drum wall results in a significant delay in heat transfer quantity, with a dynamic period of up to 5000 s. The water wall exhibits the highest total dynamic exergy destruction at 9.5 GJ, with a destruction rate of 7.9–8.5 times higher than other components. Full article

Thermal modelling of additive manufacturing is a key method for furthering the quality of the components produced, as it allows for analysis that is not possible via experimental methods due to the difficulties involved with in situ monitoring. The thermal gradients present during the additive manufacturing process have a large impact on the formation of defects, such as porosity, residual stress, and cracking. The thermal gradients also have a large impact on material properties by controlling the microstructure formed. Thermal modelling methods are often based on numerical solutions of the heat conduction equation. Whilst numerical methods can be more accurate, they are often very slow because of the fine mesh requirements to capture high thermal gradients and iterative solvers to approximate the real-world solution to the required thermal field equations. An analytical model was developed to provide a fast solution to the problem. The analytical model used in this research was based on the Rosenthal equation and was analysed under a range of process parameters. A temperature-dependent Rosenthal model was also created with the aim of improving the results. The analytical model was then compared with a finite element numerical model to act as verification for the results. The analytical model accurately predicted the meltpool width over a range of process conditions. The analytical model underestimated the meltpool length compared to the numerical model, especially at high velocities. When using the standard Rosenthal model, the use of room-temperature or high-temperature thermal conductivities underestimated or overestimated the cooling rates from the meltpool, respectively. A temperature-dependent Rosenthal model was shown to produce more accurate cooling rates compared to the original Rosenthal equation. Full article

Passive solar desalination with no discharge promises great potential for sustainable desalination. Herein, we provide a comprehensive modelling scheme for the investigation of coupled heat and mass transport in passive desalination devices. Our modelling approach integrates mass, momentum, species, and energy transport models to study the coupled phenomena of wicking, solar-driven evaporation, and salt precipitation. Our numerical model can predict the impact of spatiotemporal variation in temperature, salt concentration, and wicking velocity on the evaporation flux and thermal efficiency of solar evaporators. The impact of the evaporator’s shape, solar flux, salt concentration, and light reflection by salt crystals has been studied on the evaporator’s performance. We observed a two-fold increase in evaporation flux when solar irradiance increases from 1000 W/m² to 2500 W/m². A reduction in the thermal efficiency of the evaporators is predicted at higher solar fluxes. The modelled evaporator can achieve an evaporation flux of over 0.5 kg/m²h under 1000 W/m² for 3.5 wt.% saline water. The salt concentration along the z-position of the evaporator exhibited a double arch-shaped profile, which influences its evaporation performance. These findings provide vital guidelines for the design of high-throughput solar desalination systems. Full article

Energy transition is a challenge for remote northern communities mainly relying on diesel for electricity generation and space heating. Solar-assisted ground-coupled heat pump (SAGCHP) systems represent an alternative that was investigated in this study for the Kuujjuaq Forum, a multi-activity facility in Nunavik, Canada. The energy requirements of community buildings facing a subarctic climate are poorly known. Based on energy bills, technical documents, and site visits, this study provided an opportunity to better document the energy consumption of such building, especially considering the recent solar photovoltaic (PV) system installed on part of the roof. A comprehensive model was developed to analyze the building’s heating demand and simulate the performance of a ground-source heat pump (GSHP) coupled with PV panels. The air preheating load, accounting for 268,200 kWh and 47% of the total heating demand, was identified as an interesting and realistic load that could be met by SAGCHP. The GSHP system would require a total length of at least 8000 m, with boreholes at depths between 170 and 200 m to meet this demand. Additional PV panels covering the entire roof could supply 30% of the heat pump’s annual energy demand on average, with seasonal variations from 22% in winter to 53% in spring. Economic and environmental analysis suggest potential annual savings of CAD 164,960 and 176.7 tCO₂eq emissions reduction, including benefits from exporting solar energy surplus to the local grid. This study provides valuable insights on non-residential building energy consumption in subarctic conditions and demonstrates the technical viability of SAGCHP systems for large-scale applications in remote communities. Full article

In this study, a thin film of silicon carbide (SiC) was deposited on a porous silicon (P-Si) substrate using pulsed laser deposition (PLD). The photo–electrochemical etching method with an Nd: YAG laser at 1064 nm wavelength and 900 mJ pulse energy and at a vacuum of 10⁻² mbar P-Si was utilized to create a sufficiently high amount of surface area for SiC film deposition to achieve efficient SiC film growth on the P-Si substrate. X-ray diffraction (XRD) analysis was performed on the crystalline structure of SiC and showed high-intensity peaks at the (111) and (220) planes, indicating that the substrate–film interaction is substantial. Surface roughness particle topography was examined via atomic force microscopy (AFM), and a mean diameter equal to 72.83 nm was found. Field emission scanning electron microscopy (FESEM) was used to analyze surface morphology, and the pictures show spherical nanoparticles and a mud-sponge-like shape demonstrating significant nanoscale features. Photoluminescence and UV-Vis spectroscopy were utilized to investigate the optical properties, and two emission peaks were observed for the SiC and P-Si substrates, at 590 nm and 780 nm. The SiC/P-Si heterojunction photodetector exhibited rectification behavior in its dark I–V characteristics, indicating high junction quality. The spectral responsivity of the SiC/P-Si observed a peak responsivity of 0.0096 A/W at 365 nm with detectivity of 24.5 A/W Jones, and external quantum efficiency reached 340%. The response time indicates a rise time of 0.48 s and a fall time of 0.26 s. Repeatability was assured by the tight clustering of the data points, indicating the good reproducibility and stability of the SiC/P-Si deposition process. Linearity at low light levels verifies efficient photocarrier generation and separation, whereas a reverse saturation current at high intensities points to the maximum carrier generation capability of the device. Moreover, Raman spectroscopy and energy dispersive spectroscopy (EDS) analysis confirmed the structural quality and elemental composition of the SiC/P-Si film, further attesting to the uniformity and quality of the material produced. This hybrid material’s improved optoelectronic properties, achieved by combining the stability of SiC with the quantum confinement effects of P-Si, make it useful in advanced optoelectronic applications such as UV-Vis photodetectors. Full article

The thermochemical properties of three sulfur-containing furan derivatives, 2-furanmethanethiol, furfuryl methyl sulfide, and methyl 2-methyl-3-furyl disulfide, were investigated using experimental and theoretical methods. Standard molar enthalpies of combustion were determined by combustion calorimetry, while enthalpies of vaporization were obtained through Calvet microcalorimetry. These experimental results allowed for the calculation of standard molar enthalpies of formation in the gas phase at 298.15 K. Theoretical calculations using high-level quantum chemical methods (G3) were performed to complement the experimental data. A comparison between experimental and theoretical values revealed good agreement, validating the computational approach. This study enhances the understanding of the energetic properties of sulfur furan derivatives, contributing reliable thermochemical data to existing databases and aiding in the development of predictive models for related molecular systems. Full article

The growing volume of end-of-life photovoltaic (PV) panels, projected to reach 60–78 million tons by 2050, poses significant environmental challenges. With landfilling being the most cost-effective but unsustainable disposal method, developing eco-friendly processes to recover valuable materials is essential. One potential solution for recovering raw materials from PV panels is thermal treatment. Therefore, in this study, PV modules were heat-treated at a low heating rate, and their components were manually separated with an average efficiency of 90%. The recovered silicon wafers and tempered glass sheets were utilized to fabricate new PV panels using lamination technology. The applied heating parameters enabled the cells to be removed from the PV panels without structural damage. However, the results of electroluminescence tests showed that thermal treatment significantly damages the p-n junctions, rendering direct reuse in new panels unfeasible. The thermal separation methods outlined in this study offer valuable opportunities for industries employing various PV-panel-recycling technologies. These methods lay the groundwork for environmentally responsible management and recovery of materials from end-of-life solar panels, advancing sustainable recycling practices. Full article

This study addresses the critical challenge of performing a detailed calculation of energy savings in buildings by implementing suitable actions aiming at reducing greenhouse gas emissions. Given the high energy consumption of buildings’ space heating systems, optimizing their performance is crucial for reducing their overall primary energy demand. Unfortunately, the calculations of such savings are often based on extremely simplified methods, neglecting the dynamics of the emitters installed inside the buildings. These approximations may lead to relevant errors in the estimation of the possible energy savings. In this framework, the present study presents a novel 0-dimensional capacitive model of a radiator, the most common emitter used in residential buildings. The final scope of this paper is to integrate such a novel model within the TRNSYS 18simulation environment, performing a 1-year simulation of the overall building-space heating system. The radiator model is developed in MATLAB 2024b and it carefully considers the impact of surface area, inlet temperature, and flow rate on the radiator performance. Moreover, the dynamic heat transfer rate of the capacitive radiator is compared with the one returned by the built-in non-capacitive model available in TRNSYS, showing that neglecting the capacitive effect of radiators leads to an incorrect estimation of the heating consumption. During the winter season, with a heating system turned on from 8 a.m. to 4 p.m. and from 6 p.m. to 8 p.m., the thermal energy is underestimated by roughly 20% with the commonly used non-capacitive model. Full article

Carbon capture and sequestration have been recently presented as a viable option to reduce atmospheric carbon dioxide emissions and mitigate global climate change. The concept entails the capture, compression, transportation, and injection of the gas into a medium suitable for storage. This paper examines the thermodynamic and transport properties of carbon dioxide that are pertinent to its sequestration and storage, describes the various methods that have been recommended for its separation from the mixture of the flue gases, and determines the mechanical power and heat rate required for the capture of the gas. The power required for the compression and transportation of the gas by a pipeline is also determined, as well as the effect of the ambient temperature on the transportation power. Calculations for the total power required are performed for two cases, one a cement production unit and the second a coal power plant. The mechanical power needed for the sequestration of CO₂ is substantial in both cases, with the cement unit needing less power because of the availability of high-temperature waste heat. In both cases, the equivalent mechanical work needed for the sequestration and storage of this gas is on the order of 1 MJ per kg CO₂ sequestered. Full article

This study explored the relationship between the Nusselt number and the friction factor in the laminar boundary slip flow of a Newtonian liquid between parallel plates. In addition, simplified equations were developed to estimate two key parameters—slip velocity and temperature jump—both of which are typically difficult to measure in experimental settings. The primary objectives of investigating the relationship between the Nusselt number and the friction factor were twofold: (1) to uncover the previously unknown mathematical connection (or analogy) between momentum transfer and heat transfer in the presence of boundary slip and (2) to enable predictions of either the pressure drop or the heat transfer coefficient by measuring just one of these quantities, thus simplifying experimental procedures. Considering the difficulty of conducting experiments of this type of flow (as described in the published literature), a finite element-based numerical model built in COMSOL Multiphysics software was used to validate the theoretically developed relationship over a wide range of Reynolds numbers and boundary slip values. While surface modifications like dimples, bumps, and ribs typically modify both the Nusselt number and pressure drop, leading to their increase for a given fluid and constant inlet Reynolds number, their behavior changes when boundary slip is present, particularly in cases where there is a low temperature jump at the wall. The analysis identified a specific threshold for the dimensionless temperature jump below which the Nusselt number with boundary slip will exceed 8.235. Furthermore, the analysis showed that for the Nusselt number to rise above 8.235, the non-dimensional velocity slip must be at least 3.19 times larger than the non-dimensional temperature jump. This means that the velocity slip has to be significantly larger than the temperature jump to achieve enhanced heat transfer in boundary slip flows. Full article

When chips perform numerous computational tasks or process complex instructions, they generate substantial heat, potentially affecting their long-term reliability and performance. Thus, accurate and effective temperature measurement and management are crucial to ensuring chip performance and lifespan. This paper presents a multi-channel temperature measurement system based on a diode temperature-sensitive array thermal test chip (TTC). The thermal test chip accurately emulates the heat power and thermal distribution of the target chip, providing signal output through row and column address selection. The multi-channel temperature measurement system centers around a microcontroller and includes voltage signal acquisition circuits and host computer software. It enables temperature acquisition, storage, and real-time monitoring of 16 channels in a 4 × 4 array thermal test chip. During experiments, the system uses a constant current source to drive temperature-sensitive diodes, collects diode output voltage through multiplexers and high-precision amplification circuits, and converts analog signals to digital signals via a high-speed ADC. Data transmission occurs via the USB 2.0 protocol, with the host computer software handling data processing and real-time display. The test results indicate that the system accurately monitors chip temperature changes in both steady-state and transient thermal response tests, closely matching measurements from a semiconductor device analyzer, with an error of about 0.67%. Therefore, this multi-channel temperature measurement system demonstrates excellent accuracy and real-time monitoring capability, providing an effective solution for the thermal design and evaluation of high power density integrated circuits. Full article

Gas turbines are widely used in power generation due to their efficiency, flexibility, and low environmental impact. Modeling, especially in thermodynamics, is crucial for the designer and operator of a gas turbine. An advanced and rigorous thermodynamic model is essential to accurately predict the performance of a gas turbine under on-design operating conditions, off-design or failure. Such models not only improve understanding of internal processes but also optimize performance and reliability in a wide variety of operational scenarios. This article presents the development of a thermodynamic model simulating the off-design performance of a gas turbine. The mathematical relationships established in this model allow for quick calculations while requiring a limited amount of data. Only nominal data are required, and some additional data are needed to calibrate the model on the turbine under study. A key feature of this model is the development of an innovative relationship that allows direct calculation of the mass flow of air entering the turbine and, thus, the performances of the turbine according to atmospheric conditions (such as pressure, temperature, and relative humidity) and the position of the compressor inlet guide vanes (IGV). The results of the simulations, obtained using code implemented in MATLAB (R2014a), demonstrate the efficiency of the model compared to experimental data. Indeed, the model relationships exhibit high determination coefficients (R² > 0.95) and low root mean square errors (RMSE). Specifically, the simulation results for the air mass flow rate demonstrate a very high determination coefficient (R² = 0.9796) and a low root mean square error (RMSE = 0.0213). Full article