Journal of Thermal Analysis and Calorimetry最新文献

Effective thermal management in compact heat exchangers is crucial for enhancing energy efficiency and operational reliability. While vortex generators and hybrid nanofluids are recognized as effective passive enhancement techniques, their combined application remains underexplored. This study proposes a new deformation-based vortex generator with adjustable curvature governed by a dimensionless parameter (N) and evaluates its effect on the hydrothermal and exergy performance of a double-pipe heat exchanger. The k–ε turbulence model was employed for numerical simulations at Reynolds numbers ranging from 12,000 to 48,000. The nanofluid flow was considered as a two-phase mixture, and the mixture model was adopted for its simulation. To address the pressure–velocity coupling problem, the SIMPLC algorithm was utilized. Four vortex generator curvatures (N = 0, 1.5, 2.5, and 3.5) and three nanoparticle volume fractions (0%, 1.5%, and 3.5%) of a hybrid nanofluid containing single-walled carbon nanotubes and copper oxide nanoparticles in Syltherm 800 were tested under turbulent conditions. The hybrid nanofluid in the inner tube was modeled using the two-phase mixture approach, while hot water in the outer tube was modeled as a single-phase fluid. Results show that greater vortex generator curvature, nanoparticle concentration, and Reynolds number enhance the Nusselt number, achieving up to 71.25% improvement over the base fluid without a vortex generator. For the Syltherm 800 base fluid with a VG of geometric case N = 3.5, (Nu) increases by 69.91% compared to the case without a VG. Although these modifications increase pressure drop, the performance evaluation criterion remains above unity, indicating an optimal trade-off between heat transfer and hydraulic loss. Exergy efficiency also improves with higher curvature and nanoparticle content.

Based on the findings of this study, the sensitivity analysis demonstrates how variations in weighting scenarios quantitatively influence the ranking of heat transfer fluids. Under equal weighting, Syltherm 800 achieves approximately 4–8% higher overall scores than the other fluids, emerging as the most balanced option. When operating temperature is prioritized, Therminol VP-1 outperforms Syltherm 800 by about 3–4%, confirming its suitability for high-temperature CSP applications. In cost-dominated scenarios, Syltherm 800 provides more than a 10% advantage over Dowtherm A, indicating its economic competitiveness in budget-constrained systems. When thermal efficiency is emphasized, Marlotherm LH exhibits a 2–3% performance advantage, supporting its relevance for efficiency-driven designs. Overall, these results indicate that no single fluid serves as a universally optimal solution; instead, the ideal choice depends on the specific priorities of the application. Therminol VP-1 is most appropriate for high-temperature and stability-critical large-scale CSP systems, Syltherm 800 is advantageous where cost constraints dominate, Marlotherm LH is preferable in efficiency-focused configurations, and Dowtherm A offers a balanced alternative where supply reliability, safety considerations, or infrastructure compatibility are project-specific constraints. Given that these conclusions rely on numerical modeling and a WSM-based multi-criteria evaluation framework, further investigations are warranted. Future work should include experimental validation using parabolic trough test facilities, long-term assessments of fluid thermal stability and degradation behavior, and integration of environmental metrics such as toxicity, leakage risk, and life-cycle impacts. Moreover, comparing WSM with AHP, TOPSIS, fuzzy logic, or hybrid MCDM methods would provide insights into methodological consistency and robustness, further strengthening the position of this approach within the literature.

The selective fractionation of palm oil into olein and stearin remains a cornerstone in edible oil refining, yet its industrial potential is often constrained by the limitations of conventional dry fractionation methods. These approaches, though environmentally benign, typically yield only 60–70% of the desired phase due to viscosity-related inefficiencies during crystallization. This study introduces solvent-aided crystallization (SAC) as a process intensification strategy to overcome these barriers, with a particular focus on solvent selection and crystallization temperature optimization. Three solvents which are acetone, hexane, and 1-butanol were evaluated for their effectiveness in enhancing phase separation. Among them, 1-butanol emerged as the most effective, producing the highest olein yield (75.18%) at 18 °C and the highest stearin yield (27.98%) at 10 °C. Comprehensive analyses including iodine value, thermal behavior (DSC), fatty acid composition (GC–MS), and triglyceride distribution (HPLC–MS) confirm that lower crystallization temperatures enrich stearin with saturated triglycerides (TAGs), while higher temperatures favor unsaturated TAG retention in olein. These findings offer actionable insights for advancing SAC as a viable and scalable method for high-purity palm oil fractionation.

The purpose of this study is to develop an integrated analytical-machine learning framework for optimizing heat transfer in unsteady squeezing nanofluid flow between parallel plates. The research employs a higher-order Akbari–Ganji method (AGM) coupled with random forest regression to quantify the effects of squeeze number (S) ((S<0): squeezing; (S>0): expansion), Eckert squeeze number (S), Eckert number (Ec), and nanoparticle volume fraction (ϕ) on thermal performance. Four nanoparticles (TiO₂, Al₂O₃, Ag, Cu) dispersed in water were analyzed. The key findings demonstrate that: (1) The higher-order AGM achieved exceptional accuracy with maximum deviations of 3 × 10⁻⁷ for temperature and 5 × 10⁻⁸ for velocity profiles compared to numerical solutions; (2) machine learning analysis revealed Eckert number as the dominant parameter with 75.7% influence on Nusselt number, followed by volume fraction (12.3%) and squeeze number (12.0%); (3) increasing Ec from 0.5 to 2.0 resulted in 300% enhancement in Nusselt number; (4) silver nanoparticles provided 35% higher heat transfer rate compared to Al₂O₃ at ϕ = 0.05, though with 28% increase in friction factor; (5) optimal operating conditions were identified as Ec = 1.5–2.0, ϕ = 0.05–0.06, and S = − 1.0 to − 0.3, achieving maximum Nusselt number of 15.13. The integrated framework offers practical design guidelines for thermal management systems in microelectronics cooling, photovoltaic systems, and microfluidic heat exchangers, with potential for 40–50% improvement in heat transfer efficiency compared to conventional approaches.

Drawing on biomimetic principles, this study designs a bionic dragonfly-inspired liquid cooling plate by incorporating dragonfly wing vein patterns into the flow-channel layout to reduce the pump power of the battery thermal management system (BTMS). First, the influence of the cooling plate’s installation positions on the thermal performance of the battery module is analyzed, and the dual-sided counter-flow liquid cooling system developed in this work delivers superior heat dissipation. Subsequently, single-factor experiments, orthogonal experiments, and comparative experiments are conducted for the bionic flow-channel structure. The single-factor experiments determine the effects of structural and operating parameters—including flow-channel width (W, 3, 4, 5, 6, and 7 mm) and height (H, 3, 4, 5, 6, and 7 mm), coolant flow rate (v, 0.1, 0.15, 0.2, 0.25, and 0.3 ms⁻¹), and coolant temperature (T, 19, 21, 23, 25, and 27 °C)—on the maximum temperature, maximum temperature difference, and pressure drop. Orthogonal experiments are then employed to identify the optimal parameter combination under multi-factor working conditions. Finally, comparative experiments evaluate the performance of the bionic flow-channel design relative to a conventional serpentine channel. The results show that, under comparable heat dissipation performance, the bionic design achieves 88%, 92%, and 91% pressure drop reductions for the v3W3H3T1 (v = 0.3, W = 7, H = 7, T = 19), v3W3H1T1 (v = 0.3, W = 7, H = 3, T = 19), and v1W3H3T1 (v = 0.1, W = 7, H = 3, T = 19) configurations (units consistent with the above parameter definitions), respectively. The proposed biomimetic design approach helps reduce BTMS energy consumption and thereby enhances the driving range of electric vehicles.

With the acceleration of urbanization, the safety of urban underground utility tunnels, as an important component of urban lifeline engineering, has received increasing attention. In this study, commonly used cables (VVR cables) in urban utility tunnels were selected as the research object, and a cone calorimeter and thermogravimetric analyzer were used to detect the combustion characteristics of the cables. The results show that the combustion process can be roughly divided into six different stages, namely ignition, sheath fire, slow spread, rapid spread, full development, and decay. Additionally, an L-shaped utility tunnel numerical model was established using FDS software to study the fire spread law under the coupling effect of different blockage rates and ventilation. The dynamic spread changes of cable fires, heat release rate, temperature distribution, and other internal fire parameter variation laws in the utility tunnel under different blockage and ventilation conditions were analyzed. This study provides valuable insights for understanding the combustion behavior of power cables and effectively offers reliable support for the safe construction of fire prevention and control in urban underground utility tunnels.

Micropolar and nanofluids have garnered significant attention due to their superior thermal and mass transfer properties, as well as their extensive applications in the industrial and engineering sectors. This article takes into account the micropolar nanofluids under parallel plates' rotation and investigates the impact of thermal radiation, which remarkably boosts and analyses the thermal efficiency of copper (Cu) nanoparticles. Additionally, it examines how nanoparticle volume fraction, magnetic field strength, and other parameters affect the hydromagnetic flow using the bvp4c methodology, with a focus on velocity, microrotation, thermal, and concentration profiles. The reliability is proved by the validation of the results against the exact solutions and precision of the adopted method, demonstrate its possible implementation with regard to complicated engineering systems, including porous media and sophisticated methods of heat transfer. The study emphasizes the nanofluid’s improved heat and mass transfer capabilities over non-nanoparticle fluids and computes the Skin friction, Nusselt, and Sherwood numbers.

The existing thermal analysis techniques to study reactions were based on the overall information from detection signals. The overall information represents the integrated behavior of all substances and reactions in terms of quantity and species. As a scalar, it cannot mathematically and physically resolve the high-dimensional information of reactions. In this paper, a linear spatial system for substances and reactions is constructed, based on absolute quantity mole, to achieve dual identification of substances and reactions, analyze the coupling relationships among complex multiple reactions, and utilize vectorization methods to clarify the nonlinear mapping relationship between substance space and reaction space. Thus, the theory and implementation of vector thermal analysis (({upnu }) TA) exactly align with the physical essence of reactions. Through experimental examples of typical gas–solid phase reactions and coexistence of multiple reactions, the accuracy and reliability of the ({upnu }) TA from substance to reaction are verified.

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The present research focuses on preparation and characterization of nano-coated heat transfer medium. It also focuses on its utilization and subsequent performance evaluation in half-cylindrical solar greenhouse dryer. The carbon nano tube and nano silicon carbide (CNT- nano SiC) coated heat transfer medium was successfully prepared by spray coating method. The ratio of CNT- nano SiC was optimized to be in 70:30 mass ratios and it provided the maximum coating efficiency of 83.9%. The structural, morphological and optical characteristics were found to be favorable for getting the desirable thermal characteristics of the greenhouse solar dryer. The maximum achievable temperatures in stagnation and operative conditions of the scaled-up greenhouse solar dryer were found to be 59.7 °C and 55.9 °C with the thermal and drying efficiencies of 77.8 and 74.8% respectively. As the effects of CNT- nano SiC coating were substantial in outdoor, stagnation and operative conditions, it could be concluded that CNT- nano SiC coating would be preferred for reaping enhanced thermal characteristics in different heat transfer media and greenhouses.

In the worldwide scenario, solar air heating system (SAHS) is mainly used for various applications. Renewable energy plays very important role in air heating system for industrial and domestic applications. Basically solar air heating system using Copper U-Tube Evacuated Solar Collector is useful for agricultural applications. In our experimentation, author primarily focuses on improving the thermal performance of solar air heating system. Experimental result shows that maximum output temperature of air achieved is 130–140 °C. This solution will be easily adoptable in agricultural as well as selected industrial applications.