Journal of Thermal Analysis and Calorimetry最新文献

One way to amend the heat transfer process in heat exchangers is to add substances with high thermal conductivity (TC) to the base fluid. The usage of nanofluids (NFs) in energy systems is rapidly growing. This study investigates the TC of graphene oxide (GO)–Al₂O₃/(50% ethylene glycol (EG) and 50% water) NF at temperatures T = 25–50 °C and the volume fraction of nanoparticles (φ = 0.1–1.6%). The two-step technique was applied to create the samples. The results show raising the φ from φ = 0.1 to 1.6%, the temperature from 25 to 50 °C, and the TC by 38%. The maximum increase in TC occurred at φ = 1.6%. Finally, the experimental equation is provided for estimating the TC of the generated NF over T and φ. The study reveals a MOD of 1.75%, indicating its accuracy. In addition, the proposed equation and experimental results were compared with the Li and Peterson model, which were in good agreement with the second equation presented by Li and Peterson.

This study explores the enhancement of phase change material (PCM) melting performance within a double-tube heat exchanger, a key factor in improving thermal energy storage and transfer efficiency. Optimizing PCM melting behavior is essential for efficient thermal management and sustainable energy applications. In this research, a novel double-tube energy storage system with twisted tape inserts is analyzed numerically, with findings validated through experimental data. The system utilizes twisted tapes with three pitch lengths (60 mm, 80 mm, and 100 mm) to investigate their impact on melting rates. The numerical results reveal significant improvements in charging time, with reductions of 34%, 46%, and 53% for twisted tapes with pitch lengths of 100 mm, 80 mm, and 60 mm, respectively, compared to a plain tube. The average PCM temperature shows a 13.7% increase with the 60-mm pitch length twisted tape. Furthermore, the system achieves a total energy storage of 260 kJ kg⁻¹ in just 120 min with the twisted tape insert (60 mm pitch length), in contrast to 250 kJ kg^-1 over 240 min in a plain tube setup. Temperature contours along the axial and radial directions indicate elevated temperatures near the twisted tape surface, promoting a higher melting fraction and accelerating the complete melting process. These findings underscore the potential of twisted tape inserts to significantly improve PCM-based thermal energy storage, offering promising applications in sustainable energy systems.

This study presents a computational investigation of various minichannel configurations to enhance heat transfer for battery surface cooling in electric and hybrid electric vehicles. Nanofluids and rib structures are incorporated to achieve improved thermal performance. Copper oxide (CuO)/water nanofluid is employed as the coolant, while ribs are introduced to disturb the boundary layer and generate eddies, thereby intensifying convective heat transfer. Magnetic fields are further applied to promote eddy formation and augment the overall heat transfer rate. To determine the optimal configuration, the Nusselt number (Nu), friction factor (f), Colburn j-factor, and thermal enhancement factor (TEF) are evaluated using empirical correlations. The upstream staggered ribbed configuration demonstrates a 136.036% increase in Nu and a 136.045% rise in the Colburn j-factor compared with a plain channel using water as the base fluid. The corresponding TEF value of 1.92 confirms its superior heat transfer performance. The findings establish that the integration of ribs, magnetic fields, and nanofluid coolants offers a promising approach for enhancing thermal management and extending battery life in electric vehicle applications.

Efficient recovery of high-grade waste heat from solid oxide fuel cells (SOFCs) is crucial for enhancing energy utilization and environmental performance. This study addresses this challenge by proposing an advanced SOFC-based cogeneration system that integrates a gas turbine (GT), a recuperated regenerative organic Rankine cycle (RRORC), and a water heater for simultaneous power and hot water production. A comprehensive thermodynamic, economic, and environmental assessment was conducted using a detailed computational model to evaluate system performance and feasibility. The results indicate that incorporating the RRORC with the SOFC-GT system enhances exergy efficiency by 9.56%, while the inclusion of a water heater further raises the improvement to 11.14%. The overall energy efficiency increased by 30.76% with only an 11.16% rise in total cost, and CO_₂ emissions were reduced by 23.49% compared to the conventional SOFC-GT system. These findings demonstrate that the proposed configuration effectively harnesses SOFC waste heat for improved energy recovery and sustainability. The novelty of this work lies in the integration of a RRORC and a water heating subsystem with the SOFC-GT cycle, extending the efficiency and environmental advantages beyond previously reported hybrid configurations.

Flaxseed gum (FSG) comprises neutral and acidic polysaccharides. Research shows that flaxseed gums with high arabinoxylan concentration have shear thinning and weak gel-like properties, whereas those with high acidic monosaccharides have decreased rheology. FT-IR and DSC tests described a bio-PCM composite made from flaxseed gum and fatty acid anhydrides. The study examined how fatty acid type affects bio-synthesized composite materials made from flaxseeds and various fatty acids with and without octadecane as phase transition materials. In the final composite structure, the fatty acid backbone lengthened, increasing the host material’s latent heat. As phase transition material, 20% octadecane yielded best results. Polymer-based materials (PCM) are used to make bio-synthesized composite materials from flaxseeds and stearic acid. Latent heat of host materials increases with PCM content, optimum at 20% octadecane. The treated cotton cloth regulates temperature better than the untreated. The study shows that PCM composite material treatment creates a homogenous thin coating on cotton fiber surfaces, improving thermal characteristics and heat retention.

This study experimentally demonstrates that enhancing solar absorptance and heat transfer in a single-pass solar air collector can be achieved through a coating of reduced graphene oxide-doped black paint. The introduction of carbon-based nanoparticles results in an augmented thermal conductivity in a turpentine-oil nanofluid. Subsequently, a homogeneous blend of the thermally modified turpentine oil with the black paint is coated onto the absorber plate, resulting in a consequent increase in absorptance across the incident solar spectrum. In this regard, two different solar air collectors were fabricated, namely (i) a single-pass flat plate SAC with BP coating and (ii) a single-pass flat plate SAC with rGO-doped BP coating as surface coating. The thermal performance of both solar air collectors was evaluated across a range of airflow rates. Data obtained during the experiments demonstrated that the collector with the surface coating exhibited superior thermal response: specifically, higher absorber temperatures, increased exit air temperatures, and an improved temperature difference between the exit and inlet air streams. However, the increase in the flow rate of air through the rectangular channel decreases the absorber, exit air temperature, and temperature difference between the exit and inlet of the rectangular channel. Furthermore, the results also showed that at the higher flow rate of air through the channel, the Nusselt number and the heat transfer coefficient increase from coated and uncoated absorber plates. From the experimental results, the average daily efficiency of the single-pass SAC with BP coating ranged from 30.12 to 67.2% for a flow rate of 0.01 to 0.03 kg s⁻¹. However, with surface coating and improved surface roughness, the daily efficiency increased to 34.6 to 79.5%. Furthermore, in this study, a response surface methodology is employed to optimize the exit, absorber temperature, and the change in temperature between exit and inlet, considering the impact of solar radiation, ambient temperature, and concentration of nanoparticles. Moreover, the correlations are expressed in the form of a quadratic function.

In response to the increasing demand for energy efficiency and sustainability in marine applications, this study presents the design and thermodynamic analysis of a combined-cogeneration power plant integrated with an LM2500 gas turbine-powered naval ship. The proposed system aims to enhance operational efficiency, minimize fuel consumption, and reduce carbon emissions by leveraging waste heat recovery from the gas turbine exhaust. A comprehensive energy analysis is conducted to evaluate system performance under varying compressor pressure ratios (11.4–18.1) and steam extraction ratios. The results indicate that as the compressor pressure ratio increases, both net power output and overall system efficiency improve significantly, reaching a maximum of 23,233 kW and 60.28%, respectively. In addition, exergy analysis was conducted, revealing that the overall exergy efficiency of the proposed system is up to 0.419 with rising compressor pressure ratios, indicating reduced irreversibility and improved utilization of the fuel’s available energy potential. However, fuel savings and emission reductions exhibit a decreasing trend at higher pressure ratios, highlighting the diminishing returns in energy conservation. The system achieves a maximum fuel savings of 552.009 kg h^–1, a cost reduction of 684.492 USD h^–1, and a CO₂ emission reduction of 1749.871 kg h^–1 at an optimal pressure ratio of 11.4. Furthermore, the obtained results are compared with data taken from naval surface ships, demonstrating strong agreement and validating the effectiveness of the proposed system. These findings underscore the effectiveness of combined-cogeneration cycles in naval propulsion systems, offering a promising pathway for enhancing sustainability, fuel economy, and mission endurance in marine operations.

In this article, both local non-similarity and global non-similarity solutions of the governing equations for momentum and thermal transport of Williamson nanofluid over a curved surface are reported. Effects of magnetic field, Joule heating, Brownian motion, and thermophoresis are taken into account. The problem is model using conservation laws of mass, momentum, energy, and nanoparticle concentration. The boundary layer approach, along with suitable dimensionless variables, simplifies the governing partial differential equations. The resulting equations for local non-similar and non-similar solutions are solved numerically. The flow features are presented and discussed for both curved and flat surfaces. The obtained velocity, temperature profiles, skin friction, local Nusselt number, and Sherwood number for different values of parameter are presented and discussed. Numerical values of skin friction, the Nusselt number, and Sherwood number are presented in tabular form. The results are validated with existing literature. A comparative analysis between local non-similarity solutions and global non-similarity solutions shows that flow and heat transfer features are strongly influenced with streamwise coordinate.

Pool boiling is a fundamental heat transfer process with wide-ranging applications in electronics cooling, energy conversion, and power systems. However, its performance is often constrained by the inherent limitations of the heat transfer coefficient (HTC) and critical heat flux (CHF). To address these challenges, extensive research has focused on tailoring surface characteristics through advanced microstructural modifications. This review consolidates and critically evaluates recent progress in chemical treatments, mechanical patterning, nanostructuring, and laser-based fabrication methods designed to improve pool boiling efficiency. The discussion encompasses surface modifications across macro-, micro-, and nanoscales, highlighting structural configurations such as cavities, grooves, channels, fins, and hybrid architectures that integrate multiple geometries. By comparing modified surfaces with conventional smooth counterparts, the review identifies key mechanisms responsible for performance enhancement, including increased density of nucleation sites, capillary-assisted liquid replenishment, vapor bubble departure control, and improved wettability. Notably, laser surface texturing and hybrid micro/nanostructured surfaces consistently demonstrate superior outcomes, with reported HTC enhancements of up to threefold and CHF improvements exceeding 100% under optimized conditions. Beyond summarizing experimental findings, the review emphasizes critical considerations for practical deployment. Scalability of fabrication methods, compatibility with diverse materials such as metals and ceramics, and long-term durability under repeated thermal cycling are assessed as essential factors for industrial integration. Furthermore, attention is given to the potential trade-offs between fabrication complexity, cost, and achievable thermal gains. Overall, this review highlights the transformative potential of microstructural surface engineering in advancing pool boiling performance. Bridging fundamental mechanisms with technological applications provides a comprehensive framework to guide future research and innovation. The findings suggest that next-generation boiling heat exchangers, enabled by tailored surface designs, could deliver compact, energy-efficient, and high-reliability thermal management solutions for emerging fields ranging from microelectronics to renewable energy systems.