Journal of Thermal Analysis and Calorimetry最新文献

Fossil fuel depletion and its emissions lead to finding an alternative source to fulfill the world’s energy needs. Alternative fuels in particular biodiesel are the fusible alternative due to their availability and cost. The main drawback of biodiesel is its higher viscosity which can be effectively reduced by the transesterification process. The key objective of this research is to find biodiesel with higher performance, stable combustion, and lower emission characteristics. By keeping the above aim in consideration, this investigation has three phases as mentioned below. The first phase deals with finding the best waste cooking oil (WCO) blend in proportions tested. The second phase is used to find the best dosage level of titanium dioxide nanoparticle inclusion in biodiesel to improve combustion characteristics. For the intention to reduce oxides of nitrogen emission, the third phase comprises using exhaust gas recirculation (EGR) in nominal percentages. As a result, W20 (20% waste cooking oil and 80% diesel in volume) has a comparative brake thermal efficiency (BTE) of 26.9% with diesel and other blends in the first phase. In the second phase, the BTE is further increased by a maximum extent of 32.34% by the addition of 150 ppm of titanium dioxide nanoparticle, but it had the drawback of higher emission of (oxides of nitrogen) NO_x around 13.44 g kWh^–1. The third phase is aimed to minimize the emission of NOx by the inclusion of EGR which pulls down NOx by about a maximum of 25.3% for the W20 with 150 ppm of TiO₂ with 15% of EGR (W20T150EGR15%) blend, but it dips down the performance characteristics slightly. Overall, it can be concluded that W20 with 150 ppm of TiO₂ with 5% of EGR (W20T150EGR5%) has comparatively better performance and combustion with reduced NOx emissions.

Graphical Abstract

The reliance on fossil fuels has propelled technological growth but has led to pressing global challenges, including waste accumulation, resource depletion, and environmental degradation due to greenhouse gas emissions. With annual production of 464 million metric tons of biomass and 321.5 billion metric tons of plastic waste, innovative waste management strategies are essential. This study explores the co-pyrolysis of biomass and plastic waste as a promising approach to convert these materials into biofuels, particularly hydrogen. The paper emphasizes hydrogen’s role as an energy carrier and feedstock, assessing eleven pathways for hydrogen generation while analyzing their environmental impacts, energy efficiency, and risks to ecological and human health. Although acid gas production ranks as the least impactful method, biomass gasification exhibits a larger ecological footprint. Additionally, the review highlights hydrogen generation via gasification and pyrolysis, emphasizing the importance of operational conditions, including temperature management and gas-cleaning systems. While gasification, operating at higher temperatures (800–1200 °C), produces more hydrogen, pyrolysis offers greater feedstock versatility and simpler residue management. The findings underscore the potential of waste-to-hydrogen technologies in advancing sustainability and reducing waste, advocating for effective hydrogen storage and transportation solutions.

Shape memory alloys based on the Ni–Ti system derive their versatile properties from the non-stoichiometric intermetallic compound NiTi. The transformation temperature associated with its shape memory effect is dependent on composition, which can be controlled by minor additions of a third element like iron. This work considers the formation of various intermetallic compounds and the evolution of phases during the sintering of ternary Ni–Ti–Fe powder compacts. Elemental powder mixtures of nickel, titanium and iron were prepared by adding 0–20 at.% Fe to equiatomic Ni–Ti. The powders were compacted into discs and sintered by heating to 1200 °C in a differential scanning calorimeter. In separate experiments, heating was interrupted to identify the phases present in the partially sintered samples at various temperatures. The microstructures of the sintered samples were characterized using scanning electron microscopy. The distribution of nickel, titanium and iron in the samples was studied with EDS mapping and the phases present were identified using XRD. In the equiatomic Ni–Ti powder compact, NiTi₂, NiTi and Ni₃Ti were formed in the solid state (< 942 °C) through diffusion. At 942 °C a strong reaction between the remaining titanium and NiTi₂ takes place, leading to the formation of a liquid. At 1120 °C, NiTi and Ni₃Ti combine to form a liquid. These reactions are affected by the addition of iron to the powder mixture. The results show that at 20 at.% iron in the ternary compact, the first reaction occurred at 999 °C, instead of 942 °C for the binary composition and iron did not form any compound with nickel or titanium. Instead, the iron could replace nickel in NiTi₂ and in NiTi, forming (Fe, Ni)Ti₂ and (Fe,Ni)Ti. This leads to more Ni₃Ti formation and explains why the reaction at 1120 °C is more prominent at high iron contents. A linear dependence on the iron content in the sample was also observed for the onset temperatures for two split exothermic peaks in the DSC curves. The results also suggest that the temperatures associated with the β-Ti + (Fe, Ni)Ti₂ → L and (Fe, Ni)Ti₂ → (Fe,Ni)Ti + L reactions depend on the ratio of iron to nickel in (Fe, Ni)Ti₂.

The increasing demand for electric vehicles (EVs) has brought new challenges in managing battery thermal conditions, particularly under high-power operations. This paper provides a comprehensive review of battery thermal management systems (BTMSs) for lithium-ion batteries, focusing on conventional and advanced cooling strategies. The primary objective of this study is to assess and compare the effectiveness of various cooling approaches, including air-based, liquid-based, phase change material (PCM)-based, and hybrid systems. This review paper reveals that while traditional air- and liquid-based systems offer certain benefits such as simplicity and cooling efficiency, they are constrained by limitations in thermal conductivity and energy consumption. In contrast, PCM-based systems, despite their poor thermal conductivity, provide stable temperature regulation without requiring additional energy input. To overcome these limitations, the integration of thermal conductivity enhancers (TCEs) like carbon fibers, expanded graphite, and metal foams into PCMs significantly improves their performance. For instance, composite PCM (CPCM) enhanced with expanded graphite shows a marked improvement in thermal conductivity, increasing from 0.2 Wm⁻¹ K⁻¹ to 16.6 Wm⁻¹ K⁻¹, resulting in battery temperature reductions by up to 28%. Additionally, hybrid systems that combine active cooling with CPCMs, particularly when using nanoenhanced PCM with additives like graphene and metallic nanoparticles, demonstrate superior cooling efficiency, with temperature reductions of up to 50% compared to traditional systems. The uniqueness of this paper lies in its detailed comparison of the various BTMS strategies, including a thorough evaluation of hybrid systems that merge passive and active cooling techniques. We also explore the potential of nanoenhanced PCMs and hybrid CPCM systems, which offer significant advantages for high-power battery applications by providing both efficient heat dissipation and improved battery longevity. By synthesizing recent advancements in this field, this review highlights the most promising thermal management strategies, paving the way for future innovation in BTMS design for electric vehicles.

This paper explores diverse techniques aimed at enhancing the heat transfer performance of solar air heaters, with a primary emphasis on impinging jet arrays. The discussion includes an examination of available standards governing the manufacturing, evaluation, and certification of solar air heaters. Traditional approaches, such as the use of turbulators (ribs, baffles, and dimples), improve thermo-hydraulic performance but often lead to thermal stress due to nonuniform cooling. In contrast, jet impingement heat transfer has gained attention for its ability to provide enhanced and consistent cooling even in confined spaces. The study examines key geometric and operational parameters that influence jet impingement heat transfer, such as nozzle-to-target plate spacing, jet diameters, jet arrangement, and jet angle. Among these, the nozzle-to-target spacing and jet diameters are identified as critical factors in optimizing heat transfer. The paper also highlights the superior performance of pipe jets over orifice jets, as pipe jets generate higher fluid velocity on the target plate, resulting in enhanced heat transfer and more uniform cooling. This research underscores the growing importance of jet impingement technology in improving the efficiency of SAH and opens avenues for its application in other thermal management systems, including concentrated solar power and electric vehicle cooling systems.

In this study, CuAlMn alloys, a popular Cu-based shape memory alloy, were chosen because they exhibit superior shape memory properties and improved ductility compared to other Cu-based SMAs. The rare earth element Nd (neodymium) was added to CuAlMn alloy at the specified atomic percentages in the composition Cu_70-xAl₂₄Mn₆Nd_x(x = 0,2,4,8) and their thermal behavior, crystal structure, surface morphology and magnetic properties were investigated after fabrication. As a result of the thermal analysis measurements, it was observed that for low Nd ratios, the austenite phase transformation initial temperature of the CuAlMn alloy was increased, while at high Nd ratios, a decrease in the shape memory property was detected. Martensitic phase and precipitate phase α phase were observed in the crystal structure properties of CuAlMn alloys without and with Nd doping. These results were also detected in surface morphology observations. In addition, the crystal size decreased from 135 to 105 nm with Nd doping. As a result of magnetic measurements, CuAlMn ternary shape memory alloy was found to be paramagnetic at room temperature. Magnetic susceptibility values of the alloys showing paramagnetic magnetic properties were calculated as 11.5 × 10^–6, 12.5 × 10^–6, 9.15 × 10^–6 and 6.15 × 10^–6 emu.Oe⁻¹.g⁻¹, respectively. According to these results, the magnetic susceptibility value decreased with increasing Nd ratio.

3D printing technology, as a landmark technology for significant changes in modern manufacturing industry, has become an important means to lead the future of construction to achieve convenient, personalised, functional integration. In this study, alpha hemihydrate gypsum (α-HH) was used as the 3D printing matrix material, and the accelerators were introduced to match the slurry-based 3D printing process. The hydration heat and thermogravimetric changes were characterised to analyse the effect of accelerators on the thermal properties via thermogravimetry–differential scanning calorimetry (TG-DSC) analysis. Further, X-ray diffraction analysis (XRD) and morphological observations of the hardened gypsum were conducted to assess the impact of accelerators on the hydration process of α-HH. The results showed that all accelerators considerably reduced the hydration reaction time of α-HH, with the maximum exothermic peak observed in the order lithium sulphate (LS, 6.78 min) > sodium sulphate (NS, 11.33 min) > potassium sulphate (KS, 15.64 min) > control sample (26.43 min). Under the influence of KS, the proportion of dihydrate gypsum crystals reached 50.5% within 5 min of α-HH hydration. The addition of accelerators was shown to be effective for slurry-based 3D printing gypsum process.

As part of the ongoing quest to optimize the application and operational performance of biodegradable polymer materials, mathematical models have been developed to predict the chemical stability and thermal properties of PLA/HKUST-1 mixed matrix biopolymer composites, utilizing machine learning deep neural networks and regression modelling. These models were constructed by integrating a single-entry input that encompasses the percentage mass composition of PLA and HKUST-1, immersion time, casting thickness, and immersion temperature into a test function designed to predict behavior characterized by the chemical stability and thermal properties of these materials. Leveraging experimental datasets available in the literature, the models were trained to derive arbitrary constants and empirical constants that are instrumental in forecasting the chemical stability and thermal properties of the materials. With error estimates ranging from 0.01 to 2.16%, the formulated models accurately represented most output signals, including thermal stability at 5.0 and 50.0% mass loss, glass transition temperature, crystallization temperature, and melting point temperature of mixed matrix biopolymer materials. The application of this methodology may prove beneficial for the design and fabrication of novel polymer/composite materials with diverse engineering applications.

Graphical abstract

Plots of experimental and (a) DNN predictive values of reduced Chemical stability at 5 °C against reduced values of X and (b) linear and quadratic regression model predictive values of chemical stability at 5% [^oC] against X = (x₃*x₄*x₅)/(x_a-x_b).

Phase-change materials (PCMs) with three-dimensional thermally conductive skeletons show promise for thermal energy storage, but they have poor stability. Therefore, based on hydrogen bonding between graphene oxide and polyvinyl alcohol, a shape-stable thermally conductive graphene oxide/graphene nanoplates/polyvinyl alcohol (GO/GNP/PVAs) 3D porous skeleton was prepared by a simple vacuum freeze–drying method in this paper. To further improve the thermal conductivity of the GO/GNP/PVAs 3D porous skeleton, so carbonization is applied on it. After encapsulating polyethylene glycol (PEG) in the skeleton, a thermally conductive phase-change composite with good shape stability was obtained, even at a PEG loading as high as 96.1%. The carbonized C-GO/GNP/PVAs/PEG phase-change composites exhibited higher thermal conductivity (1.57 W m⁻¹ K⁻¹) than uncarbonized GO/GNP/PVAs/PEG phase-change composites (0.52 W m⁻¹ K⁻¹). This was mainly due to the low thermal conductivity GO annealing into high thermal conductivity reduced graphene oxide (rGO), which formed a conductive three-dimensional network. Meanwhile, the formation of a carbon skeleton by PVA chains after annealing also improved the thermal conductivity of the composites. The C-GO/GNP/PVAs/PEG phase-change composites also showed excellent solar-to-heat conversion properties.

Thermal comfort is crucial for indoor environmental quality, impacting occupant well-being and intellectual productivity. Despite the widespread use of HVAC technologies in residential and commercial buildings, there is growing awareness of thermal comfort, leading to more studies on this issue. According to international publication indexes nearly 60% of publications belongs to the categories of construction building technology, energy fuels, and civil engineering. It should also be noted that 40% of world energy consumption pertains to construction sector. In this context, radiant cooling and heating systems come forward with their low exergy destruction rates pointing out the potential to be energy-efficient due to their higher and lower operation temperatures. Displacement ventilation, with its low heating and cooling capacity, has not gained widespread preference. However, the increasing consciousness of global warming and energy efficiency, along with the fear of airborne virus contamination, views stand-alone or hybrid applications of radiant heating/cooling and displacement ventilation as potential future solutions. This review study investigates the impact of radiant heating/cooling and ventilation types, mixing, and displacement on thermal comfort performance, focusing on factors affecting thermal comfort in trending radiant cooling and heating applications like radiant walls, ceilings, and floors. The study emphasizes the importance of considering occupant preferences, building characteristics, and energy efficiency when choosing the most suitable heating and cooling systems for different indoor environments. Stand-alone and hybrid applications of radiant heating/cooling and displacement systems can enhance thermal comfort performance, with the exception of specific cases requiring a high thermal load or ventilation rate.