Analysis Of Thermal Properties Research Articles

Statistical investigation of the widths of supra-arcade downflows observed during a solar flare

ABSTRACT Supra-arcade downflows (SADs) are dark voids descending towards the post-reconnection flare loops and exhibit obvious variation in properties like width. However, due to the lack of further statistical studies, the mechanism behind such variations hitherto remains elusive. Here, we statistically investigated widths of 81 SADs observed in one flare by the Solar Dynamics Observatory (SDO). For each of SADs, six moments were selected with equal time intervals to measure their widths at different stages of their evolution. It is found that most SADs show a roughly monotonous width decrease during their descents, while some SADs with small initial widths can have complex evolutions. 3D reconstruction results based on SDO and Solar Terrestrial Relations Observatory Ahead (STEREO-A) images and thermal properties analysis reveal that differences in magnetic and plasma environments may result in that SADs in the north are overall wider than those in the south. Additionally, correlation analysis between the width and other parameters of SADs was further conducted and revealed that (1) SADs with different initial widths show no significant differences in their temperature and density evolution characteristics; (2) SADs with small initial widths usually appear in lower heights, where more frequent collisions between SADs could lead to their intermittent acceleration, width increment, and curved trajectories. These results indicate that SADs with different initial widths are produced the same way, while different environments (magnetic field or plasma) could affect their subsequent width evolutions.

Embedded System for the Analysis of Thermal Properties of Hemoglobin

A novel embedded photoacoustic system design is described and a calculation method is proposed to determine the blood hemoglobin oxygen saturation through the thermal properties of different skin color types. A heat equation model allows a calculation procedure to determine the reflection and transmitted thermal wave amplitude for obtaining a depth profile, depending on the modulation frequency at the air-skin-subcutaneous tissue interface. Our reflection-mode photoacoustic technique involves the use of a 445 nm pulsed-laser light spot on subcutaneous tissue to obtain amplitude and phase from signals for different skin color types. The transmission and reflection temperature coefficients are fitted through a heat propagation model to estimate the thermal wave properties of blood hemoglobin. Nonlinearly amplified photoacoustic signals are modeled from the microphone and their stability analyzed by a bode diagram, as to consider overheated hemoglobin background. An dedicated electronic embedded system is thus integrated, including memory, processor and preprocessor, to provide a simple measurement technique, as compared to conventional instruments.

Numerical Analysis of Aerodynamic Thermal Properties of Hypersonic Blunt-Nosed Body with Angles of Fire

A hypersonic electromagnetic railgun projectile undergoes severe aero-heating with an increase in altitude. The purpose of this study was to investigate the characteristics of the shock layer flow field as well as the thermal environment of the blunt body wall of a hypersonic electromagnetic railgun projectile at different launching angles. The two-temperature model considers the thermal nonequilibrium effect and is introduced into the Navier–Stokes (N-S) equation, and it is solved using the finite volume method (FVM). The reliability of the calculation model in terms of thermal properties and composition production was verified against a blunted-cone-cylinder–flare (HB-2) test case. The surface temperature of the hypersonic blunt projectile was simulated using a radiation balance wall boundary. The thermal characteristics at the emission angles α = 60° and α = 45° were checked within an altitude range of 0–70 km, including the nonequilibrium effect, reaction heat release, aerodynamic heat flux, and wall temperature. The results show that the translational rotational temperature is higher than the vibrational electronic temperature, and the thermal nonequilibrium effect increases with an increase in altitude. Comparing the two launching angles, the nonequilibrium degree and reaction heat release at α = 60° were higher than those at α = 45°. The rates of exothermic reaction decreased with an increase in altitude. The heat flux along the wall of the generatrix decreased sharply from the stagnation point. With an increase in altitude, the heat flux dropped sharply from 7 MW/m2 at H = 0 km to approximately 2 MW/m2 at H = 70 km. The wall temperature distribution was similar to the heat flux distribution; however, the surface temperature decreased less rapidly than the heat flux.

Effects of intrinsic properties, particle size, bulk density, and specific gravity on thermal properties of coal dusts.

Thermal properties of pulverized coal govern theheat transfer and greatly influence the coal dust explosion and spontaneous combustion processes. This study measures the thermal properties of five coal samples at six distinct particle sizes using an advanced thermal property analyzer. The thermo-physical properties of coal dust positively correlated with theparticle size. Thermal conductivity, diffusivity, and specific heat capacity increased with the ash percentage, bulk density, and specific gravity of coal dust. In contrast, they negatively correlated with the fixed carbon and volatile content of coal. Empirical relations between the thermo-physical properties were developed. The thermal conductivity, diffusivity, and specific heat capacity of coal dusts varied in the range of 0.091-0.147W/mK, 0.125-0.164mm2/s, and 0.715-0.945MJ/m3K, respectively. With increase in particle size from < 38 to 500-1000µm, thermal conductivity, thermal diffusivity, and specific heat capacity increased in the range of 25.60-32.89%, 9.76-22.11%, and 9.57-20.80%, respectively, for different coal samples.

Thermal analysis of surface micromachined porous silicon membranes using the 3ω method: Implications for thermal sensing

Investigations into porous silicon thermo-resistive type thermal sensors and their advantages in speed-sensitivity trade-off relative to other comparable thermal materials are presented in this work. Porous silicon films were suspended above a silicon substrate using successive patterning and micromachining steps. The 3ω method was used in both supported and suspended configurations, allowing the analysis of both cross-plane and in-plane thermal properties of the micromachined films. By utilising a low noise, broad-frequency measurement of the in-phase and out-of-phase temperature components, thermal conductivity and thermal diffusivity were simultaneously determined. The measurements showed isotropic thermal conductivity of 0.38 ± 0.02 W/m K and 0.12 ± 0.01 W/m K, and thermal diffusivity of 0.39 ± 0.04 mm2/s and 0.23 ± 0.02 mm2/s, for the surface micromachined released porous silicon films at 50 % and 77 % porosity, respectively. The implemented suspended 3ω method leveraged a thermal model that accounted for the finite length of the heater(180 µm) and membranes (400 µm × 400 µm), eliminating the millimetre scale dimensional constraints in previous works. Use of a thermal passivation technique rendered the thermal properties of the films robust against successive photolithography and micromachining. The obtained thermal properties were utilised in finite element modelling of a thermo-resistive thermal sensor with 50 µm × 50 µm × 100 nm dimensions. The modelling results suggest that a thermal time constant of 5 ms could be achieved, comparable to that of amorphous silicon based thermal sensors but with 2–4 times larger temperature sensitivity due to smaller intrinsic thermal conductivity and heat capacity in the porous silicon films, thus achieving a significant improvement in overall speed-sensitivity trade-off.

Effect of tea polyphenols on the physicochemical, structural and digestive properties of modified high amylose corn starch.

In this study, starch-polyphenol complexes (CES-TPS complexes) were prepared using various ratios (0%, 2%, 4%, 6%, 8%, and 10%, based on starch) of tea polyphenols (TPS) and high amylose corn starch (HACS) pretreated with starch branching enzyme (SBE). It was aimed to determine the effects of TPS on the physicochemical and structural properties and digestibility of the CES-TPS complexes. Scanning electron microscopy and laser particle size analysis showed that the addition of a moderate amount of TPS will reinforce interaction force, while excessive TPS will cause a loose structural morphology, leading to an increase in starch particle size. Thermal property analysis indicated that SBE pre-treatment decreased TO, TP and TC of HACS, and the gelatinization temperature was further reduced after adding TPS. The digestion of CES-TPS complexes was investigated using an Artificial Gut analyzer; the predicted glycemic index of starch samples decreased with the addition of a low concentration of TPS (2-6%), while there was a significant increment in the pGI of starch samples when a high concentration of TPS (8-10%) was added. XRD analysis showed that the relative crystallinity of the CES-TPS complexes further increased to 21.91% and then decreased to 19.38% with the increase of TPS concentration. The ratios of 1047/1022 cm-1 presented the opposite trend to that determined by FT-IR.

Innovative Approaches to Thermal Management in Next-Generation Electronics

In conclusion, the analysis and measurement of thermal properties are crucial for a wide range of applications in science, technology, and industry. For energy efficiency optimisation, the design of sophisticated materials, and the creation of cutting-edge technologies, it is essential to comprehend how heat is transmitted and handled within materials. Researchers can precisely evaluate thermal conductivity, heat capacity, and other thermal parameters using a variety of experimental methodologies, including both conventional and cutting-edge technologies. This enables accurate material characterisation and performance evaluation. The landscape of thermal management and energy conversion has been significantly shaped by nanostructured materials. Their distinct nanoscale characteristics provide chances to modify thermal behaviour, boost effectiveness, and add new features. Researchers are able to manage heat conduction, phonon behaviour, and charge transport through the use of designed nanostructures, which has led to breakthroughs in a variety of industries, including electronics, energy storage, thermoelectric devices, and more. In addition to promoting energy efficiency and waste heat recovery, these developments pave the path for sustainable solutions to the world’s rising energy needs and environmental problems. We are on the verge of ground-breaking discoveries that have the potential to restructure industries, enhance energy sustainability, and pave the way for a more effective and linked society as we continue to investigate and harness the complex behaviour of heat within materials.

Mitigating phosphoric acid migration in high temperature polymer electrolyte membrane fuel cells with hydrophobic polysilsesquioxane-based binders

Binders prepared through crosslinking of organosilsesquioxanes were subjected to various physical, thermal, and electrochemical property analyses for high temperature polymer electrolyte membrane fuel cells.

Analysis of phase stability, elastic, electronic, thermal, and optical properties of Sc1-xYxN via ab initio methods.

Understanding the physical properties of a material is crucial to know its applicability for practical applications. In this study, we investigate the phase stability, elastic, electronic, thermal, and optical properties of the ternary alloying of the scandium and yttrium nitrides (Sc1-xYxN) for different compositions. To do so, we apply a "density functional theory (DFT)" based scheme of calculations named as "full potential (FP) linearized (L) augmented plane wave plus local orbitals (APW + lo) method" realized in the WIEN2k computational package. At first, the phase stability of the investigated compositions of the mentioned alloy is determined. The analysis of our calculations shows that Sc1-xYxN alloy is stable in rock salt crystal structure for all investigated compositions. Next to that, the elastic properties of the rock-salt phase of the studied ternary alloy Sc1-xYxN at all above said compositions were done at the level of "Wu-Cohen generalized gradient approximation (Wu-GGA)" within DFT. However, Trans-Blaha (TB) approximation of the "modified Becke-Johson (mBJ)" potential is also used in combination with Wu-GGA where the thermal properties are calculated at the level of the "quasi-harmonic Debye model." The obtained results for the absorption coefficients, and optical bandgap, represent that the title alloy may be a suitable candidate for the applications in optoelectronic devices.

Characterization of a Thermal Insulating Material Based on a Wheat Straw and Recycled Paper Cellulose to Be Applied in Buildings by Blowing Method

The thermal envelope is a key component of a building’s energy efficiency. Therefore, considerable efforts have been made to develop thermal insulating materials with a better performance than the existing products. However, in the current climate change scenario, these materials must be sustainable, principally during their production stage. In this context, the use of recycled raw materials and agro-industrial waste can be the basis of a material with a low environmental impact and a good thermal performance. In this study, cellulose and wheat straw were characterized. Then, they were mixed in different proportions and densities and the best thermal behavior was selected. The materials were chemically analyzed by TAPPI 2007, thermogravimetric and infrared spectroscopy, together with the measurement of their thermal conductivity with a thermal property analyzer based on the transient line heat source method. The results show that both raw materials are chemically similar to each other. When mixed, they have a thermal conductivity ranging from 0.031 to 0.036 (W/mK), being comparable with several conventional thermal insulators. On the other hand, to achieve the commercial use of this material, an installation through a blowing process has been proposed and proves to be highly promising, achieving a proper density and efficiency in its application.

Stability and Thermal Conductivity of Mono and Hybrid Nanoparticles Dispersion in Double-End Capped PAG Lubricant

Stable nanolubricant mixtures are interrelated with thermal conductivity enhancement, thus improving heat transfer performance in automotive air conditioning (AAC) systems. This paper studies the stability and thermal conductivity of double-end capped polyalkylene glycol (PAG)-based nanolubricants specially designed for R1234yf refrigerant. Mono nanolubricants (Al2O3/PAG and SiO2/PAG) and hybrid nanolubricants (Al2O3–SiO2/PAG) were prepared using a two-step preparation method at different volume concentrations of 0.01 to 0.05%. The stability of these nanolubricants was observed by visual, UV-Vis spectrophotometer, and zeta potential. Thermal conductivity (k) was measured from 30 to 70 °C using a C-Therm thermal properties analyser. The results from the stability analysis show that all nanolubricants were confirmed in excellent stability conditions for more than six months with minimum visual sedimentation, more than 70% concentration ratio, and zeta potentials greater than 60 mV. The Al2O3–SiO2/PAG samples recorded the highest values of thermal conductivity increment, followed by the Al2O3/PAG and SiO2/PAG samples with 2.0%, 1.7%, and 1.5% enhancement. Hybrid nanolubricants have been shown to have greater potential in the AAC system because of their excellent stability and better property enhancement in thermal conductivity.

Synthesis and characterization of sulfonated poly(eugenol-co-allyleugenol) membranes for proton exchange membrane fuel cells

The research of sulfonated eugenol-allyleugenol copolymer (SPEAE) based membrane for fuel cell from eugenol derivate had been conducted. First, eugenol was reacted with various weights of allyl eugenol to form eugenol-allyleugenol copolymer (PEAE). Determination of the optimum composition of PEAE was done by testing the swelling properties. Then, PEAE was sulfonated using concentrated sulfuric acid with time variations of 1, 2, 3, 4, and 5 h to form SPEAE. The SPEAE produced was tested for the degree of sulfonation, water uptake, cation exchange capacity, and membrane proton conductivity. In addition, the characteristics of the PEAE and SPEAE copolymer membranes were also analyzed using FTIR spectrophotometers, 1H-NMR, TGA, and DSC. The results showed that the copolymerization of eugenol:allyleugenol (EG:AEG) with a ratio of 10:1 gave the lowest swelling degree. The best SPEAE copolymer was obtained from sulfonation for 2 h with yield, degree of sulfonation, water absorption value, proton conductivity, and cation exchange capacity of 90.6%, 12.87%, 50.7%, 1.83 × 10−5 S cm−1 and 0.356 meq/g, respectively. FTIR analysis shows the formation of PEAE with the loss of the vinyl eugenol groups used to form the polymer and shows the formation of SPEAE in the presence of sulfonate groups from the sulfonation reaction. 1H-NMR also confirmed the presence of the PEAE and SPEAE copolymers. In addition, analysis of thermal properties with TGA and DSC also showed that sulfonate treatment could improve membrane stability.

Oscillatory thermal response test using heating cables: A novel method for in situ thermal property analysis

In situ subsurface thermal conductivity (λ) and thermal diffusivity (α) are critical parameters to design ground-coupled heat pump systems (GCHP). λ is conventionally determined from thermal response tests (TRT), whereas α is commonly selected from literature data or with laboratory analyses. Alternatively, both thermal properties can be assessed independently with an oscillatory thermal response test (O-TRT), which consists of heating the subsurface at an oscillatory rate and monitoring the resulting thermal perturbation. Due to their flexibility and relatively small radius, heating cables can be used to carry out tests in shallow unconsolidated deposits in the scope of horizontal GCHP design. The duration of the tests is short compared to vertical ground heat exchangers (fractions of a day) since the thermal resistance between the heating cable and the soil is negligible. The objective of this work was to develop an apparatus and an analytical approach to assess λ and α from an O-TRT carried out in shallow unconsolidated deposits. Nine different O-TRTs were performed in the lab for a dry standard material and five O-TRTs were performed in situ in a natural sandy deposit. After validation via numerical modelling, results show that the analytical approach using correction factors allowed the estimation of λ and α with an accuracy of < 2%. The study demonstrates that O-TRTs are a useful method to estimate both λ and α. Further testing in other reference materials and with different apparatus configurations is needed to enhance the experimental setup and extend O-TRTs towards new applications.

Influence of physical characteristics of graphene/Al2O3 composites employing nano particles based organic phase changing materials

In the field of energy conservation and management, PCMs are increasingly being used to store latent heat. PCMs have been infused with nanoparticles to enhance their thermal conductivity. This work presents the results of a study on the thermo-physical characteristics of an Al2O3-Graphene (Al2O3: Gr) binary composite (1 wt% Al2O3:0.5, 1, 1.5, and 2 wt% of Graphene (Gr)) with Paraffin wax (PW) as a surfactant. Thermo-gravimetric analyzer (TGA), Thermal property analyzer (TEMPOS), and UV–VIS spectrometer (UV–VIS) were all employed to characterize the materials. The latent heat capability of Paraffin Wax/Al2O3 Gr and PW/Al2O3 Graphene binary composites increased by 8.62 % and 10.02 %, as compared to Phase change material. Al2O3-1.0 and Al2O3Gr-1.0% PCMs exhibit thermal conductivities that are 130 and 180 %more than base paraffin wax. According to the Fourier Transform Infrared spectra, there was no chemical connection between the paraffin wax and nanoparticles. Thermal stability was raised by including Al2O3-Graphene particles into the paraffin wax matrix, according to TGA measurements. The produced composite's light transmission was lowered by 60.2% compared to the base PW, resulting in higher light absorption and, as a result, increased photothermal transformation. Thermal conductivity and enthalpy of the composite generate a great choice of solar photovoltaic thermal and TES systems.

Experimental Analysis of the Thermal Performance Enhancement of a Vertical Helical Coil Heat Exchanger Using Copper Oxide-Graphene (80-20%) Hybrid Nanofluid

The thermal performance enhancement of a vertical helical coil heat exchanger using distilled water-based copper oxide-graphene hybrid nanofluid has been analyzed experimentally. Accordingly, the focus of this study is the preparation of CuO-Gp (80-20%) hybrid nanoparticles-based suspensions with various mass fractions (0% ≤ wt ≤ 1%). The volume flow rate is ranged from 0.5 L·min−1 to 1.5 L·min−1 to keep the laminar flow regime (768 ≤ Re ≤ 1843) and the supplied hot fluid’s temperature was chosen to equal 50 °C. To ensure the dispersion and avoid agglomeration an ultrasound sonicator is used and the thermal conductivity is evaluated via KD2 Pro Thermal Properties Analyzer. It has been found that the increment in nanoparticles mass fraction enhances considerably the thermal conductivity and the thermal energy exchange rate. In fact, an enhancement of 23.65% in the heat transfer coefficient is obtained with wt = 0.2%, while it is as high as 79.68% for wt = 1%. Moreover, increasing Reynolds number results in a considerable augmentation of the heat transfer coefficient.

A profound analysis of structural, thermal, optical, and electrical properties of Cd50Pb30S20 composition for optoelectronic devices: implications of changes in film’s thickness

A profound analysis of structural, thermal, optical, and electrical properties of Cd50Pb30S20 composition for optoelectronic devices: implications of changes in film’s thickness

Mechanical and Thermal Properties Analysis of Recycled Concrete Aggregate on Its Fire Exposure

Concrete constructions can be badly damaged by fire, and the damage can be estimated using knowledge of material properties. The major focus on using green materials instead of traditional materials are promoted. Recycled concrete aggregates (RCA) are nominated and analyzed its mechanical and thermal properties with its fire exposure. Conclusions are when using RCA to mix natural aggregate in concrete, and it will help obtaining a better performance of concrete at high temperatures (more than 50 percent). Rich mixed RCA outperforms standard mixed RCA and natural concrete aggregate regarding fire resistance and remaining compressive strength. The effects of varying mixing percentages above 50% mixed concrete and different time effects on concrete performance are examined. It suggests the replacement of RCA is suitable for modern building construction and fire safety sector from its performance post fire residual.

Mechanical and Thermal Properties Analysis of Recycled Concrete Aggregate on Its Fire Exposure

Concrete constructions can be badly damaged by fire, and the damage can be estimated using knowledge of material properties. The major focus on using green materials instead of traditional materials are promoted. Recycled concrete aggregates (RCA) are nominated and analyzed its mechanical and thermal properties with its fire exposure. Conclusions are when using RCA to mix natural aggregate in concrete, and it will help obtaining a better performance of concrete at high temperatures (more than 50 percent). Rich mixed RCA outperforms standard mixed RCA and natural concrete aggregate regarding fire resistance and remaining compressive strength. The effects of varying mixing percentages above 50% mixed concrete and different time effects on concrete performance are examined. It suggests the replacement of RCA is suitable for modern building construction and fire safety sector from its performance post fire residual.

Performance Study of Ground Heat Exchanger Based on Thermal Conductivity of Hybrid Soil

The need for renewable energy sources has grown as the world has significantly changed, and fossil fuels have been used extensively in global perspective. As a result, renewable energy has replaced fossil fuels in many places around the world because it is better for the environment. Geothermal energy is the most efficient way to heat and cool space from all renewable energy sources. Geothermal renewable energy, in particular from ground heat exchangers (GHE), has enormous potential for use in construction (building). In order for the GHE to function appropriately (efficiently), it is critical (better) to have sufficient quantities of backfilling material. This material is used to fill the gap between the soil surrounding. The heat transfer rate from the air to the soil, which is controlled by thermal characteristics of the soil near the GHE pipe, determines the thermal performance of the GHE. Using some backfilling materials that have been thermally improved, the thermal properties of the soil around the GHE pipe can be improved as well. Therefore, the current study examines the impact of hybrid soils without moisture on the GHE performance. The hybrid soils comprise of two components: native soil and bentonite. A thermal property analyzer was used to measure the thermal conductivity of the hybrid soil. According to the study, compared to other grain sizes, native soil with a grain size of 2.0 to 2.5mm has the highest thermal conductivity value at 20% bentonite, which is 0.331 W/m.K. The effectiveness of the GHE system was assessed using a mathematical model, demonstrating that the GHE has significantly reduces temperatures along pipes with length of 0 to 16m. In a nutshell, once the thermal conductivity of hybrid soil increases, the performance of GHE will improve.

High porosity composite structures produced from poly(lactic acid)/hydroxyapatite microspheres using novel Dual Beam Laser Sintering method: Analysis of structural, mechanical and thermal properties

The paper discusses the applicability of the novel Dual Beam Laser Sintering (DBLS) method for processing of poly(lactic acid)/hydroxyapatite (PLA/HAp) composite powders. The composite microspheres were prepared using the solid-in-oil-in-water (S/O/W) emulsification technique. The three-dimensional structures made of composite microspheres with different filler content – 5 % and 10 % by weight of HAp were processed using DLBS that uses a new method of preheating the powder bed. The obtained results were compared to the case of pure PLA presented in our previous work.The quality of the powders was determined using Dry Laser Diffraction (DLS), X-Ray Computed Tomography (XCT), Revolution Powder Analysis (RPA) and Differential Scanning Calorimetry (DSC). The melt flow rate and the thermal conductivity of the microspheres were also determined. Conducted research shows that the morphology of the particle depends heavily on the HAp content which ultimately influences the powder flowability properties. Moreover, the properties of samples manufactured using DBLS were evaluated. The internal microstructure was reconstructed using XCT and the open porosity structures were revealed. The influence of both the porosity and the HAp reinforcement on the mechanical properties was observed. Additionally, a thermal DSC analysis was carried out, which allowed to assess how the filler and process parameters affect the degree of crystallinity of the obtained structures and the thermal degradation of the composite.In general, the presented study shows the possibility of designing part properties not only by means of the DBLS process parameters but also by influencing the powder material properties. Both raw material properties and process parameters affect the morphology of pores and therefore the mechanical properties of PBF processed material.