Journal of Thermal Analysis and Calorimetry最新文献

According to irreversible Diesel cycle (DC) model considering finite piston speed (FPS) established in previous literature, expression for cycle efficient power is obtained firstly by using theories of finite-time thermodynamics (FTT) and FPS thermodynamics (FPST) herein. Impacts of piston speed ratio and piston speed on characteristics of efficient power vs. compression ratio and efficient power vs. efficiency are analyzed, and secondly, taking compression ratio, piston speed and piston speed ratio as design variables, taking dimensionless power, thermal efficiency, dimensionless efficient power and dimensionless ecological function as optimization objectives (OOBs) and applying NSGA-II to perform multi-objective optimization (MOO) for DC performances. Deviation indices (DIs) of different OOB combinations under three decision-making methods of TOPSIS, LINMAP and Shannon entropy are compared, and combination with the smallest DI and the most ideal design scheme are obtained. The study’s findings indicate that when piston speed ratio and piston speed are constants, efficient power first enlarges and then diminishes with enlargement of compression ratio, and there is an optimal compression ratio to maximize efficient power. When four-objective optimization is performed, compression ratio is mainly distributed between 20 and 50, piston speed is mainly distributed between 15 and 44 m s^–1, and piston speed ratio is mainly distributed between 0.1 and 0.3. The most important contribution herein is to introduce NSGA-II algorithm, to select three optimization variables and four OOBs, and to realize performance optimizations with 15 OOB combinations for FPS and FTT irreversible DC.

This research focuses on the fabrication and characterization of vinyl ester-based composites reinforced with basalt fiber and chemically activated, surface-treated Cucumis melo fruit peel-derived biocarbon using the hand lay-up process. To assess their mechanical strength, durability, flame resistance, and electromagnetic shielding capability, the tensile, flexural, impact, hardness, flammability, electromagnetic interference (EMI) shielding, and dielectric tests were performed in accordance with American Society for Testing and Materials (ASTM) standards. Among the fabricated composites, the sample containing 3 vol% biocarbon (MFB2) exhibited superior mechanical performance, with tensile strength and modulus of 132 MPa and 4.1 GPa, flexural strength and modulus of 174 MPa and 5.3 GPa, and an impact strength of 4 J. The tensile fracture surface was analyzed using scanning electron microscopy (SEM) to investigate the failure mechanisms. Meanwhile, the composite with higher filler content (MFB3) demonstrated enhanced EMI shielding effectiveness and dielectric properties in the 8–20 GHz frequency range. Additionally, the composite displayed a maximum Shore D hardness of 81 and a minimum flame propagation rate of 17 mm min^-1, confirming its improved multifunctional performance.

Shale ash waste could be used as a solid heat carrier and potentially serve as a low-cost catalyst. Dachengzi oil shale samples were retorted in a self-made reactor over shale ashes with three different particle sizes to evaluate the catalytic performance of shale ashes in upgrading shale oil. The results indicated that adding shale ashes improved kerogen reactivity and secondary reactions of pyrolysis products, which slightly affected the shale oil yield but significantly influenced product composition and quality. The shale ashes contributed to cracking heteroatomic compounds, and generating more light oil, short-chain aliphatics and aromatics. The total n-paraffins content was about twice as high as the total 1-olefins content in the derived shale oils which mainly contained bicyclic and tricyclic polycyclic aromatic compounds. Among three shale ashes, 0.20 mm shale ash generated the most shale oil with the lowest atomic H/C and O/C ratios, and O content, the lowest average boiling point, the maximum asphaltenes, C₇-C₁₂ n-paraffins and 1-olefins, the minimum heavy fractions and aromatics. Both the non-hydrocarbon content and the total content of N, S and O in the obtained shale oil were decreased over 0.20 mm shale ash compared to the non-catalytic pyrolysis. 0.20 mm shale ash was referred as the optimal solid heat carrier among three shale ashes in simultaneously improving the shale oil yield and quality.

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A novel phase-change microencapsules (MEPCMs) with paraffin wax as the core material and chitosan (CS) as the shell material were prepared. The microstructure, chemical composition, thermal properties and thermal conductivity of the CS/MEPCMs were measured by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and hot-disk thermal constant analyzer, respectively. The results showed that the ratio of core–shell, the type and amount of emulsifier had great effects on the properties of the CS/MEPCM. For 5% of emulsifier, when the hydrophilic–lipophilic balance (HLB) value of the emulsifier was 12.2 and the core–shell ratio was 2:1, the prepared CS/MEPCM had regular spherical morphology and smooth surface. The phase-change latent heat of the prepared CS/MEPCM was 47.44 J g⁻¹, and the coefficient of thermal conductivity was 0.159 W m⁻¹ K⁻¹. The prepared CS/MEPCM was suitable for the thermal storage systems.

High temperature can lead to windows breakage, significantly altering ventilation condition within the compartment and critically influencing fire development. In this study, several subway carriage fire scenarios were conducted to examine window breakage time and temperature profiles under different heat release rates (HRR) and fire locations with multiple lateral openings through numerical modeling. Results show that higher HRR leads to more and earlier windows breakage, while different fire locations significantly affect the sequence and quantity of window breakage. For fires with low HRR in the center of the carriage, temperature distribution beneath the ceiling shows a transformation from “parallelogram” to “X-shaped” pattern due to windows breakage. For fires with high HRR or deviate the carriage center, temperature distribution sustains an “X-shaped” pattern throughout the process. The influence of window breakage on the temperature of lateral openings near the fire source is clear, but on the maximum temperature rise and longitudinal temperature decay are not sensitive. Considering fire locations, a prediction model for maximum ceiling temperature rise within subway carriage is established, with a proportionality coefficient ranging between 17.2 and 19.9, and validation contrast to existing studies confirms the formula’s accuracy. Further, Experimental data were compared with established models for dimensionless maximum temperature rise in strong plume zones, indicating that this study’s predicted temperature rise in strong plume zones substantially exceeds earlier predictions. The findings of this study contribute to a deeper understanding of the thermal hazards of subway carriage fires impacted by window breakage.

Hybrid nanofluids represent a novel class of nanofluids, created by dispersing various types of nanoparticles within a base fluid. This study presents an experimental analysis of how the temperature and nanoparticle concentration influence the thermal conductivity of graphene–multiwalled carbon tubes/distilled water, ethylene glycol, and distilled water/ethylene glycol (70:30) hybrid nanofluids. Graphene–multiwalled carbon tubes nanoparticles were characterized using field emission scanning electron microscopy and X-ray diffractometry techniques. The experiments were carried out to investigate the variation of thermal conductivity with temperature and volume fraction of nanoparticles. The temperature was varied from 30 to 60 °C, while the volume fractions of nanoparticles at 0.001%, 0.01%, and 0.1% were observed. The improvement in the value of thermal conductivity with the increase in both the temperature and the volume fraction of nanoparticles was observed. It was observed that a higher volume fraction of nanoparticles and the elevated temperatures have a favorable effect on the thermal conductivity. Based on the experimental data, an empirical correlation was established for the prediction of thermal conductivity ratio of graphene–multiwalled carbon nanotubes/distilled water/ethylene glycol hybrid nanofluids using python code taking into consideration the hybrid nanofluids concentration, temperature, hybrid nanofluids, and base fluids thermal conductivity. The proposed correlation showed a good agreement between the experimental data and correlation within a margin of deviation of less than 10%.

Cement-based materials, as fundamental construction materials, significantly influence the advancement and quality standards of engineering projects. Traditional early-strength technologies often face challenges such as decreased durability, increased carbon emissions, and unbalanced material properties. The addition of nano-C–S–H accelerates the growth of cement hydration products, thereby markedly improving the early strength of cementitious composites. Magnesium is a ubiquitous element in cement-based materials, but its potential role in nano-C–S–H remains not fully investigated. This study innovatively introduces an external Mg²⁺ modification strategy for the preparation of nano-C–S–H and systematically studies the effects of nano-C–(M)–S–H on the early hydration kinetics and strength performance of cement. C–(M)–S–H nanocomposites with various Mg/Si ratios were synthesized via the co-precipitation method and were added into cement paste. The early hydration characteristics of cement paste were characterized using isothermal calorimetry, Q-XRD, and TG-DTG. Moreover, the compressive strength, pore structure, and micromorphology of the cement paste were tested and observed through setting time test, mechanical property test, BET, and SEM. The results indicate that nano-C–(M)–S–H can greatly speed up the early hydration of cement when the Mg/Si ratio is 0.05. Compared with nano-C–S–H, the S-0.05 showed a much shorter setting time and a larger specific surface area. At 16 h, the compressive strength increased by 77.46% compared with the Ref. The formation of early C–S–H gel and CH is promoted, and the strength at 28d keeps increasing steadily. The external addition of Mg²⁺ in nano-C–(M)–S–H is found to be highly advantageous in enhancing the early-age performance of cement-based materials. It provides a novel idea, offering innovative perspectives for the development and application of C–(M)–S–H nano-nucleating agents.

This study numerically investigates mixed convection heat transfer in a ventilated square cavity filled with an MWCNT–Fe₃O₄/water hybrid nanofluid and partitioned by dual porous layers with distinct properties. Unlike previous works that considered uniform porous media or single-phase nanofluids, the present study focuses on the combined influence of hybrid nanoparticles and multi-layered porous structures under varying Reynolds (50–1000) and Grashof numbers (10³–10⁶). Parametric analyses were performed for Darcy number (0.01–100), porosity (0.5–1.8), thermal conductivity ratio (0.2–5.0), and porous thickness (0.1–0.5). The results show that increasing Reynolds number strengthens vortices and enhances thermal dispersion, while higher Grashof numbers shift the system to buoyancy-dominated convection with significantly improved heat transfer. Porous layer thickness has little effect at low Gr but suppresses convection when enlarged (a = 0.5), reducing the average Nusselt number due to flow resistance. This suppression is alleviated by higher Darcy numbers or thermal conductivity ratios, which improve permeability and heat diffusion. At high Gr, increasing the conductivity ratio leads to conduction-dominated transfer. The hybrid nanofluid consistently augments thermal performance across regimes. Overall, the study highlights the synergistic role of hybrid nanofluids and dual porous layers in enhancing mixed convection. The findings provide practical guidance for optimizing porous media and nanofluid design in advanced thermal management applications.

Absorption cooling systems provide sustainable solutions to make renewable potential energy sources, such as solar energy or biomass energy, usable. These systems operate with eco-friendly working fluids and offer a significant reduction in electricity consumption compared to vapor compression cooling technologies. Absorption cooling systems are classified into single-effect, double-effect, and triple-effect types, with triple-effect systems achieving the highest efficiency. Furthermore, in addition to these three groups, half-effect and quadruple-effect systems, which have been relatively less explored in the literature, have also been designed. However, the increased thermodynamic complexity and the larger number of components in triple-effect systems pose significant technical and economic challenges. This review systematically categorizes research on triple-effect absorption cooling systems into five key areas: studies on specific configurations, comparative analyses, investigations of different configurations, hybrid systems integrating other thermodynamic cycles, and experimental/commercial developments. The analysis highlights emerging trends, such as the integration of triple-effect systems with hybrid cycles (e.g., organic Rankine and Kalina cycles) to enhance energy efficiency, and identifies gaps in experimental validation and commercial deployment. By addressing these challenges and opportunities, this paper underscores the potential of triple-effect absorption systems to expand their role in high-efficiency cooling applications, particularly when combined with renewable and waste heat energy sources. Future research directions are suggested to promote broader adoption and commercialization of these systems.

The thermal management of vehicle-mounted power batteries has emerged as a critical research focus, propelled by the rapid growth of the electric vehicle industry. During operation, batteries generate substantial heat, which may result in overheating, performance deterioration, shortened life span, and even thermal safety hazards, if not effectively dissipated. This paper presents a comprehensive review of thermal management technologies for vehicle-mounted batteries, covering key aspects such as internal temperature estimation, conventional cooling methods (e.g., air cooling, liquid cooling, and phase change materials), and emerging thermoelectric data integrated solutions. While traditional thermal management approaches offer distinct advantages in practical applications, they are also subject to inherent limitations. Emerging technologies, which integrate multi-source data and optimization algorithms, demonstrate significant improvements in thermal management efficiency and reliability. Furthermore, innovations such as cloud-based digital twins and sparse sampling data processing introduce novel methodologies through big data analytics and efficient data utilization, paving the way for more intelligent and stable long-term battery thermal management systems.