Journal of Thermal Analysis and Calorimetry最新文献

The utilization of nanofluids in thermal engineering presents a promising avenue for addressing high-temperature challenges. Similarly, many industries still use air-cooled intercoolers for multistage air compressors which results in lower efficiency of the system. This study explores the application of Al₂O₃ nanoparticles mixed with water as a base fluid to analyze the effect of intercooling in a two-stage reciprocating air compressor. The study employs a shell and tube heat exchanger with parallel and counter flow conditions. The computational analysis, facilitated by computational fluid dynamic software compares the thermal conductivity and heat transfer rates of water and Alumina Oxide based nanofluid to an air-intercooled system. Additionally, the study evaluates the isothermal and volumetric efficiency of the compressor, along with the work requirements for its low-pressure and high-pressure cylinders without using a chiller or external medium. While, achieving ideal intercooling conditions remains elusive in practical experiments, ongoing research focuses on enhancing intercooler efficiency through various nanofluid techniques. The findings suggest notable enhancements in isothermal efficiency by 7.18% and reductions in work input by 3.4% for the air compressor under specified parameters.

Pyrotechnics are among the energetic materials that have wide applications in various military and civilian fields. Thermal behavior and thermal stability are the very important properties of pyrotechnics. The thermal stability of a pyrotechnic shows the scope of application as well as safety. Thermal analysis methods such as TGA, DTA, and DSC are used to obtain information on the thermal behavior and thermal stability of pyrotechnics. The first review in the field of thermal analysis of pyrotechnics was published by P.G. LAYE and E.L. CHARSLEY in Thermochimica Acta Journal in 1987. The results of thermal analysis of pyrotechnics containing molybdenum trioxide, lead oxides, nitrates, perchlorates and chlorates, dichromates and chromates have been reviewed and discussed in mentioned paper. Over time, investigating the thermal behavior of pyrotechnics can be useful for scientists in this scientific field. It is possible to consider various divisions for pyrotechnics based on the type of fuel, type of oxidizer, etc. In the present paper, the results of the thermal behavior of pyrotechnics are reviewed and discussed based on the type of metallic fuel including the common metals aluminum, magnesium, and Al–Mg alloy (magnalium).

This article reviews research studies on compression heat pump-assisted thermal desalination systems. The reported studies are grouped as follows: (a) compression heat pump-assisted regenerative solar still thermal desalination; (b) compression heat pump-assisted humidification–dehumidification thermal desalination; (c) compression heat pump-assisted air conditioning and thermal desalination; (d) compression heat pump-assisted vacuum thermal desalination; (e) compression heat pump-assisted membrane thermal desalination; (f) compression heat pump-assisted freezing thermal desalination; and (g) compression–absorption and compression–adsorption hybrid heat pump-assisted thermal desalination. The schematics of the new configurations are included. Moreover, the economic and environmental assessments for compression heat pump-assisted thermal desalination systems are presented. Based on the review, the current status, challenges and future research scope in the field of compression heat pump-assisted thermal desalination systems are described. This review concludes that compression heat pumps are energy-efficient heat regeneration equipment that can be integrated with thermal desalination systems to produce potable water. The details reported in this paper are useful for consultants, researchers and industrial experts working in thermal desalination.

Flat-plate solar collectors (FPSC) are commonly used for low-temperature heating applications, making system modeling and sensitivity analysis crucial. However, most sensitivity analyses for these collectors are conducted under steady-state conditions. Because of the inherently dynamic nature of ambient conditions, dynamic modeling and sensitivity analysis are needed to better understand and determinate important influencing design parameters. This study presents a comprehensive parametric analysis using a dynamic model of the solar flat-plate collector. The impact of deviations from nominal values of each parameter on system performance and final storage tank temperature is investigated. The findings reveal that pitch tube and absorber thickness significantly influence system efficiency, with a 20% deviation in each parameter resulting in a 10% efficiency change. Moreover, ambient temperature and irradiance have a high impact, causing changes of over 10%. Additionally, a multiparameter sensitivity analysis utilizing the Monte-Carlo method (MPSA) is employed to assess the relative importance of each parameter on FPSC performance. The results highlight that system efficiency is highly sensitive to absorber thickness, while tube pitch, ambient temperature and solar irradiance are crucial for tank temperature. The MPSA is further applied across various ambient temperatures (ranging from 5 to 35 degrees) to determine changes in parameter sensitivity indices. The outcomes indicate that at lower ambient temperatures, certain parameters, such as solar irradiance and tube pitch, exhibit increased sensitivity. However, the sensitivity of system efficiency to all parameters remains relatively constant across different ambient temperatures.

The cigar wrapper, binder and filler play different roles in cigar puffing. This work aims to conduct a comprehensive study on the pyrolysis process of cigar wrappers, binders and fillers to obtain the similarities and differences in the residue, combustibility and pyrolysis products. In the residue section, the surface microstructure of the cigar wrapper, binder and filler was scanned by the scanning electron microscope, and the elemental state composition was characterized by X-ray photoelectron spectroscopy during the combustion process. The combustibility of the cigar wrapper, binder and filler was evaluated by the mass loss rate obtained from thermogravimetric experiments and the heat release rate obtained from the microscale combustion calorimeter experiments. The pyrolysis products were analyzed by infrared spectroscopy and mass spectrometry. The research results show that the similarities between wrapper, binder and filler lie in the elemental composition, combustibility and the main components of pyrolysis products. The difference lies in the fact that the surface microstructure of the wrapper is the smoothest, while the filler is the roughest with the leaf vein. The concentration of pyrolysis products in filler is significantly higher than in wrapper and binder after 400 °C. This work analyzed the similarities and differences in their pyrolysis behavior, providing a deeper understanding of cigar pyrolysis.

The miniaturization and increasing functionality of electronic devices lead to significant heat generation, negatively impacting their performance and longevity. Efficient thermal management is crucial to maintain temperature within safe operating limits. Using nanofluids in mini-channel heat sinks and optically tuned nanofluids in agricultural greenhouses has emerged as a viable solution for active cooling. This study investigates the thermal cycling performance of PCM-based heat sinks with and without pin fins to assess their suitability for long-term thermal management applications. Thermal cycling tests are conducted on PCM-based heat sinks containing RT-42 PCM and different pin fin configurations made from aluminum 2024-T851. The tests evaluated stability under a constant 10 W heat flux during both charging and discharging phases for baseline cases without fins. The results indicate that the maximum temperature difference between the 30th and 40th thermal cycles was only 0.97 °C, representing a mere 2.08% variation. This observation highlights the ability of PCM-based heat sinks to maintain a consistent temperature profile even under repeated thermal loading conditions. The PCM-based triangular pin fin heat sink was more effective than the circular and square pin fin heat sinks. It maintained the lowest average temperature at 32.83 °C and had the lowest rate of temperature increase during charging, at 0.463 °C per minute. Furthermore, the combination of PCM and triangular fins demonstrated superior thermal stability compared to other configurations. The maximum temperature difference between the first and 40th thermal cycles for this configuration is observed at only 0.83 °C with 1.38% variation. This exceptionally low-temperature difference underscores the effectiveness of the triangular pin fin design in promoting heat dissipation and maintaining thermal stability. The results highlight the potential of PCMs to enhance the long-term performance of electronic devices by maintaining optimal operating temperatures.

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This study proposes a new method called “thermopixelgraphy” for analyzing thermal images (TI) through quantifying pixels classified as cold, neutral and hot. For this, we analyzed 30 professional male football players (27.2 ± 4.4 yrs., 69.8 ± 6.6 kg; of 9.8 ± 3.0% of body fat). Thermographic images were obtained in 13 games played in the Brazilian league. Images of the lower limbs (anterior and posterior) were obtained at three moments: M1 (24 h before); M2 (24 h after); M3 (48 h after the match). The total number of pixels in each image were quantified and classified as: (a) cold 28.0–31.0 °C; (b) neutral 31.1–33.0 °C and; (c) Hot 33.1–36.0 °C. The main results showed a higher frequency of pixels in the cold (mainly between 30 and 31 °C; n = 1551.9) and neutral zones (mainly between 32 and 33 °C; n = 2253.9) for the anterior view of the right lower limb at moment M1 and a higher frequency of pixels in the neutral (mainly between 32 and 33 °C; n = 2622.8) and hot zones (mainly between 33 and 34 °C; n = 2579.5) at moment M2 for the posterior view (M1: cold zone 30–31 °C; n = 1319.1; neutral zone 31–32 °C; n = 2835.8; M2: neutral zone 32–33 °C; n = 2939.5; and hot 33–34 °C; n = 3066.5). Similar results were observed for the left leg. In conclusion, “thermopixelgraphy” quantifies the number of pixels from TI and the image analysis process is faster, more accurate, encompasses all areas of the thigh and leg muscles, and does not require extensive prior experience from the evaluator.

The phenomenon of bioconvection in nanofluid flows represents a significant interdisciplinary research area that combines fluid dynamics, biotechnology, and nanotechnology. Understanding the interplay between biological organisms and nanoparticle-laden fluids is crucial for various applications in engineering, medicine, and environmental science. This study aims to scrutinize the production of entropy in bioconvective Sutterby nanomaterial flow over porous rotating disk. Impacts of surface roughness and Lorentz force are considered in relation to momentum. Mathematical expressions for energy and mass concentration are developed accounting Brownian and thermophoretic features of nanoparticles. Effects of thermal radiation and internal fluid friction are further measured in the thermal transport equation. Boundary layer norms are considered throughout modeling. PDEs demonstrating the flow are altered into ODEs via transformations. The numerical scheme Runge–Kutta-Fehlberg(RKF-45) is implemented via NDSolve code in Mathematica. The impacts of dominant parameters of flow on velocity, motile density, concentration, temperature, Bejan number, and irreversibility are deliberated. Physical quantities are studied numerically through tables. Results reveal that for larger magnetic and surface porosity variables velocity diminishes. The thermal field escalates for greater magnetic variable while it declines for higher Prandtl number. Entropy enhances for up surging values of radiation, diffusion, and Brinkman variables.

This research investigates methods to enhance the efficiency of solar ponds as sustainable energy storage systems by leveraging phase change materials (PCMs) and nanoparticles. Solar ponds often suffer from reduced performance during hot summer months due to high temperatures, which limit their overall efficiency. This study focuses on the impact of adding candle soot-derived carbon nanoparticles at different mass fractions (1 mass%, 2 mass%, and 3 mass%) on the thermal performance, storage capacity, and efficiency of solar ponds. Conducted over a seventy-five-day experimental period, the study reveals that the average temperature of the lower convective zone (LCZ) increased by 15.3% with the use of PCM and by 28.3% with the addition of PCM containing 2 mass% carbon soot, compared to traditional solar ponds. The incorporation of paraffin wax and carbon soot significantly improves energy storage capacity, enhances thermal efficiency, and reduces convection losses. These findings demonstrate that PCMs combined with candle soot nanoparticles can effectively enhance the efficiency and performance of solar ponds, offering a promising approach for optimizing solar energy storage systems.

This paper presents a comprehensive review of the most significant and recent technologies that have been integrated with solar dryers, demonstrating a notable enhancement in the performance of solar dryers. The majority of review articles in this field that have been published have concentrated on the application of solar drying for food preservation in agricultural industries. Numerous researchers have found gaps at the component level and suggested different modifications to solar thermal collectors to enhance drying efficiency. Various technologies that have been created and put into use have effectively and efficiently optimized the energy requirements. Nevertheless, there are not many studies that concentrate on the possible integration strategies in different industries where drying is a crucial step in the production process. This study presents a comprehensive overview of the key drying processes used in different industries to provide readers a sense of the current status of existing technologies and the on-going research being done in the topic of sun drying. To develop innovative drying systems for large-scale enterprises that can be used to other industrial settings, it has been suggested that solar drying be integrated with the current drying techniques. This paper discusses how solar energy is used in the food sector, with a focus on solar air heaters and how they are integrated into solar drying processes. This will help industries and researchers make the drying process compatible with solar energy. This study also offers an alternative viewpoint by examining and contrasting solar dryers based on the many designs that are employed, as well as strategies to increase the solar dryer's efficiency, shorten its drying time, and improve its overall performance. Additionally, this study shows how various solar drying methods such as using gravel, sand, paraffin wax, etc. affect the rate at which moisture is removed based on sensible and latent heating.