Journal of Thermal Analysis and Calorimetry最新文献

In this study, the ONNO type Schiff base ligand N, N’-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH₂) was reduced and converted into a tetradentate phenolic amine ligand, N, N′-bis(2-hydroxybenzyl)-1,3-diaminopropane (L^HH₂). First, a mononuclear [NiL^HCl(DMF)]₂(DMF) complex (I) was obtained with the reduced ligand in dimethylformamide (DMF). CoCl₂ was then added to the complex I to give the heterodinuclear [NiL^HCoCl₂(DMF)₂] complex (II). The complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction (XRD). The XRD analysis of complex I revealed that one phenolic oxygen persisted in its coordinated phenol form, while the charge of Ni(II) was observed to be neutralized by a chloride ion and a phenolate ion. The Ni(II) center ion in the complex exhibited octahedral coordination, being surrounded by two phenolic oxygens, two aminic nitrogens, an oxygen from a DMF molecule, and a chloride ion. In complex II, the Ni(II) ion was coordinated by two phenolic oxygens, two aminic nitrogen, and two DMF oxygens. The Co(II) ion was found to have a tetrahedral coordination sphere with two phenolate oxygens and two chloride ions. Thermogravimetric analysis demonstrated distinct thermal behaviors for mononuclear and heterodinuclear complexes. The mononuclear complex exhibited stability up to 210 °C and an exothermic reaction at 510 °C in an oxygen atmosphere, resembling energetic materials. The heterodinuclear complex showed higher thermal stability and a distinct decomposition pathway, influenced by Co(II) coordination. These findings highlight the significance of heterometallic coordination in thermal properties and controlled decomposition applications.

The use of natural fibers in the manufacture of composites has gained prominence due to their sustainability, low cost, and application in several areas of engineering. However, the high moisture absorption of lignocellulosic fibers still represents a significant limitation, compromising their mechanical performance and durability. This study aims to investigate the hygroscopic behavior of sugarcane bagasse composites, with and without applying a nanoparticle-based spray, using the non-destructive technique of passive infrared thermography. For this purpose, samples produced with polyurethane resin based on castor oil were tested by applying droplets of distilled water on their top surfaces. Water absorption was monitored over time using an infrared camera. A precision balance was used to measure water absorption of both samples. The results showed that the sample treated with nanoparticles presented a (text {28.74 %}) lower average water absorption rate compared with the untreated sample. However, both samples absorbed approximately the same amount of water, indicating that the nanoparticles only delayed the absorption process. The treated sample presented an absorption time of (text {13 h 48 min}), while the untreated sample presented an absorption time of (text {19 h 21 min}), with the cold region remaining on the surface for longer. The thermal analysis was associated with sample morphology and the thermal behavior of monitored regions. The proposed approach is promising because it combines sustainable materials with advanced and non-destructive characterization techniques. This study contributes by demonstrating the applicability of infrared thermography in evaluating the effectiveness of hydrophobic treatments in natural composites.

Enhancing heat transfer in double-tube heat exchangers (DTHX) improves energy efficiency, reduces equipment size and cost, and minimizes operational expenses. Due to laminar sublayer formation, DTHXs face reduced efficiency, highlighting the need for turbulence-promoting procedures and further focused research. This work highlights the novelty of using sinusoidal inner tubes with multiple wave amplitudes in DTHX, demonstrating enhanced heat transfer, exergy efficiency, and thermal performance. A numerical study is applied to examine the effects of an inner tube with a sinusoidal surface on the DTHX performance. The corrugated tubes with three different wave amplitudes are investigated and compared with a plain tube. The DTHX performance is evaluated focusing on Nusselt number, friction factor, exergy efficiency, and thermal enhancement factor. The model is validated by comparing with previous experimental results. The results show that the wavy surface enhances the Nusselt number by 80% for a 5 mm wave amplitude tube. The corrugated tube with 5 mm wave amplitude reduces the friction factor by 20% compared to 3 mm wave amplitude tube. Exergy efficiency is enhanced by 51% as the maximum heat transfer rate is obtained with the wavy surface tube. The thermal enhancement factor is enhanced by 29% with 5 mm wave amplitude tube. The temperature and velocity contours confirm higher enhancement in the heat exchanger performance with the sinusoidal tubes compared with the plain tubes.

Hydrogen is becoming a promising clean energy option, and improving the efficiency of steam methane reforming remains an important challenge. In this work, a solar thermochemical reactor is analysed under different conditions by comparing the Discrete Ordinate and P1 radiation models. The reactor was tested to observe the effect of varying flow velocity, porosity, mean cell size, and heat transfer coefficients on the thermal performance of the reactor under different heat transfer and radiation models. At a flow velocity of 0.05 m s⁻¹, the Discrete Ordinate model reached a peak temperature of 1413.87 K, compared with 1342.55 K for the P1 model. Higher porosity levels also improved performance, with an average temperature of 1391.78 K, about 3% higher than at lower porosities. Under turbulent conditions, the Discrete Ordinate model continued to capture heat transfer more effectively than the P1 model. The non-equilibrium heat-transfer approach provided more realistic and uniform temperature predictions, giving an average temperature of 1389.05 K at 0.005 m s⁻¹ when paired with the Discrete Ordinate model. Overall, the results show that combining the Discrete Ordinate model with non-equilibrium heat transfer and Wu’s heat-transfer correlation gives the most reliable thermal performance assessment for high-temperature reactor applications.

This study examines the rotational magnetohydrodynamic (MHD) flow of Casson–Williamson double-diffusive engine-oil-based molybdenum disulfide (MoS₂) nanofluid over a slanted stretching sheet focusing on the combined effects of heat generation, Joule heating, and Hall currents. The mathematical model also incorporates the viscous dissipation, chemical reactions, Soret and Dufour effects. The governing partial differential equations are transformed into ordinary differential equations using similarity variables and are then tackled numerically via the spectral relaxation method (SRM). The performance of velocity, temperature, and concentration fields is evaluated by the graphical depictions in relation to the pertinent parameters, whereas the engineering quantities by tabular presentations. We found that the strong magnetic influence and mixed convection parameters caused to decrease both primary and secondary velocities. The primary velocity slowed down due to the rotational and Hall effects, while the secondary velocity was exposed an opposite trend. The strong buoyancy forces in the flow was prompted to hasten the primary flow. The temperature field was considerably magnified by thermophoresis, magnetic field, viscous dissipation, heat source, and higher nanoparticle concentration effects. Likewise, the concentration field was enlarged by the thermophoresis, but it decays with chemical reaction influence. Both primary and secondary skin frictions were decreased by the Brownian motion, magnetic field, thermophoresis and Hall effects, whereas both raised by mixed convection parameter. The effects of thermophoresis, magnetic and Brownian motion were incited to rise the Nusselt number, but it was decreased by heat source and Hall influences. Further, heat transfer rate was approximately raised up to 0.73% when dispersing 4% of MoS₂ nanoparticle into the base-fluid (engine oil).

The key to the advancement of thermal management technology lies in the optimization of control strategies. Building upon the traditional PID and fuzzy PID control, this paper presents a fuzzy PID control based on the Snow Geese Algorithm (SGA), aiming to study the refrigeration performance of the battery and the cabin under summer high-temperature conditions and the optimal cabin temperature control. The results show that when the environmental temperature was at 35 °C and 40 °C, the power battery temperature dropped to the target value of 25 °C around 1540 and 2000 s, respectively. Based on different temperature control strategies, under the environmental temperatures of 35 °C and 40 °C, the cabin temperature controlled by SGA-fuzzy PID was respectively stabilized at 25.07 °C and 24.97 °C, and the system response was superior to that of traditional PID control and fuzzy PID control. In comparison with the traditional PID control, the SGA-fuzzy PID control can increase the performance coefficient by 2.77 and 2.14%, respectively, and reduce the compressor power consumption by 0.82 and 1.51%, respectively. In comparison with the fuzzy PID control, the SGA-fuzzy PID control can increase the performance coefficient by 2.59 and 2.45%, respectively, and reduce the compressor power consumption by 0.48 and 1.39%, respectively.

This review critically examines recent advances in improving the ability of flat plate solar collectors (FPSCs), particularly focusing on passive, active, and hybrid strategies. Passive methods remain widely deployed in solar-rich regions due to their design simplicity and cost-effectiveness, while hybrid approaches that combine both active and passive techniques are emerging as promising solutions to achieve higher thermal efficiency and shorter payback periods despite increased upfront costs. Key innovations include optimisation of fluid flow pathways, incorporation of nanoparticles to boost thermal conductivity, and absorber plate modifications such as wavy geometries, which enhance thermal efficiency by up to 30% and exergy by 20% compared to conventional FPSCs. The development of spectrally selective multilayer cermet coatings demonstrates exceptional thermal stability at ultra-high temperatures (up to 650 °C), expanding the applicability of FPSCs in concentrating solar power systems. Furthermore, the integration of swirl generators and helical inserts has been shown to reduce irreversibility while improving thermo-hydraulic performance. Despite their delivery of predominantly low-grade heat, FPSCs remain one of the most sustainable and economically viable solar energy technologies, exhibiting lower embodied energy and CO₂ emissions than PV and PV/T systems. This review not only consolidates technological innovations but also highlights persisting challenges and scientific gaps, offering pathways for future research to accelerate the deployment of FPSCs in addressing global energy needs and climate change mitigation.