Thermal Features Research Articles

EFFECT OF THE NANOFLUID FLOW AND EXTENDED SURFACES ON AN ABRUPT EXPANSION TUBE REGARDING THERMODYNAMIC IRREVERSIBILITY

Numerous scientists have examined circular dimpled surfaces, tubes, and other approaches for enhancing heat transfer. Moreover, the dimples' angle of attack has a substantial effect on the tube's flow and thermal features. This numerical study presents a novel approach to enhancing heat transfer rate in a tube subjected to constant heat flux by incorporating a surface dimpling strategy and evaluates three different tube layouts with elliptical dimpled fins for different working fluids such as DW and Al<sub>2</sub>O<sub>3</sub>/DW nanofluid (φ = 0.5-1.0%) by using ANSYS Fluent v2020R2 under laminar flow conditions. Under identical circumstances, the thermal performances of proposed designs are compared to those of a smooth tube, and the influence of the elliptical dimpled fin angle of attack on these parameters is determined for different Reynolds numbers (1000 ≤ Re ≤ 2000). When comparing the Nusselt number of a tube with/without elliptical dimpled fins, it is found that EDT 1 performed better. Lower Reynolds numbers are shown to result in a greater friction factor. Besides, elliptical dimpled fins promote flow mixing within the tube and the establishment of a thermal boundary layer. At a 135° attack angle (EDT 1), the 1.0% Al<sub>2</sub>O<sub>3</sub>/DW nanofluid is found to be the best-performing nanofluid in the dimpled tube, improving Nu by up to 44.56%. Furthermore, ff presented an increase of 29.18% when comparing ST and EDT 1 flowing 1.0% Al<sub>2</sub>O<sub>3</sub>/DW at Re = 2000, while total S<sub>gen</sub> is diminished by 37.75% in the same conditions.

Geochemistry of Cold Springs in Geothermal Exploration Stage – Case Study of Candi Umbul Telomoyo, Central Java

Cold springs in geothermal fields are often overlooked during the exploration stage. The best practice of geothermal exploration suggests thermal manifestation as an indicator of a geothermal system in the subsurface. This common practice neglects cold springs as valuable information points related to the system. Thermal-contaminated cold springs can be helpful to indicate the presence of inferred geothermal activity below the surface during the exploration stage. It becomes important where thermal features are absent or limited, as in Candi Umbul Telomoyo. Candi Dukuh, Candi Umbul, and Pakis Dadu thermal springs are located at the periphery of the Telomoyo Volcanic Complex, at relatively low altitude. Those thermal springs are used to construct the existing conceptual models of the geothermal system. In this study, the authors tried to consider the presence of slightly acidic cold springs (pH 5.24-5.61). Located within the Suropati Depression in the North, and the flank of Mt. Telomoyo in the South, both Keningar and Sendang Ari Wulan cold springs are located at higher altitude with higher TDS and are enriched in Cl and SO4 compared to the others. These cold springs are associated with the argillic alteration zone and observed to have iron oxide deposition at the discharge area. Sendang Ari Wulan fluid is plotted at the same zone as the thermal springs on Na-Cl•SO4 facies of the Piper diagram, while Keningar fluid is plotted on HCO3-Ca•Mg facies are similar to other cold springs. Although Sendang Ari Wulan shows a better correlation to the thermal springs, based on Piper diagram, both Keningar and Sendang Ari Wulan cold springs are classified as HCO3-SO4 and SO4-HCO3-Cl. These observations show the possibility of contamination of the geothermal system occurring below the Keningar and Sendang Ari Wulan cold springs, which is higher than the thermal springs. This interpretation is supported by the anomaly of high Hg and CO2 surrounding the acidic Keningar and Sendang Ari Wulan cold springs, three temperature gradient wells that prove the presence of three times higher-than-normal geothermal gradient. The research concludes that cold springs data are indeed useful in aiding the interpretation, especially during the exploration stage.

Flow control using hot splitter plates in the wake of a circular cylinder: A hybrid strategy

A novel and effective hybrid technique, which involves active surface heating strategies in conjunction with the use of passive splitter plates in the wake of the cylinder, is proposed. In this report, we present the results of a numerical investigation on the two-dimensional, laminar mixed convection flow over a circular cylinder with a hot rigid splitter plate attached to it on the wake side. A projection algorithm-based finite volume method is employed to obtain the solution of the coupled, nonlinear governing partial differential equations subjected to Courant–Friedrichs–Lewy conditions. The isothermal heating of the splitter plate under the influence of the gravity field generates an upward buoyancy force in the wake of the cylinder. For different length-to-diameter (L/D) ratios, the effect of heating on aerodynamic, wake, and heat transfer characteristics has been studied for a wide range of parameters; 75 ≤Re≤ 150, 0 ≤Ri≤ 1, and 0.5 ≤L/D≤ 1 at Pr = 0.7. It is observed that the hot splitter plate would bring about conspicuous changes such as asymmetry in the vortex shedding behind the cylinder at low Reynolds numbers. The outcomes demonstrate a notable improvement in convective heat transfer and drag, with gains of up to 7% and 15%, respectively. It is found that the rate of heat transfer and vortex shedding frequency decrease with an increase in L/D ratio. Correlations for the estimation of Strouhal number and Nusselt number have also been proposed which helps provide a more thorough understanding of thermal and aerodynamic features of the hybrid approach.

In vitro assessment of Momordica charantia/Hypericum perforatum oils loaded PCL/Collagen fibers: Novel scaffold for tissue engineering.

The research on tissue engineering applications has been progressing to manufacture ideal tissue scaffold biomaterials. In this study, a double-layered electrospun biofiber scaffold biomaterial including Polycaprolactone (PCL)/Collagen (COL) fibrous inner layer and PCL/ Momordica charantia (MC) and Hypericum perforatum (HP) oils fibrous outer layer was developed to manufacture a functional, novel tissue scaffold with the advantageous mechanical and biological properties. The main approach was to combine the natural perspective using medicinal oils with an engineering point of view to fabricate a potential functional scaffold for tissue engineering. Medicinal plants MC and HP are rich in functional oils and incorporation of them in a tissue scaffold will unveil their potential to augment both new tissue formation and wound healing. In this study, a novel double-layered scaffold prototype was fabricated using electrospinning technique with two PCL fiber layers, first is composed of collagen, and second is composed of oils extracted from medicinal plants. Initially, the composition of plant oils was analyzed. Thereafter the biofiber scaffold layers were fabricated and were evaluated in terms of morphology, physicochemistry, thermal and mechanical features, wettability, in vitro bio-degradability. Double-layered scaffold prototype was further analyzed in terms of in vitro biocompatibility and antibacterial effect. The medicinal oils blend provided antioxidant and antibacterial properties to the novel PCL/Oils layer. The results signify that inner PCL/COL layer exhibited advanced biodegradability of 8.5% compared to PCL and enhanced wettability with 11.7° contact angle. Strength of scaffold prototype was 5.98 N/mm2 thanks to the elastic PCL fibrous matrix. The double-layered functional biofiber scaffold enabled 92% viability after 72 h contact with fibroblast cells and furthermore provided feasible attachment sites for the cells. The functional scaffold prototype's noteworthy mechanical, chemical, and biological features enable it to be suggested as a different novel biomaterial with the potential to be utilized in tissue engineering applications.

Thermal stability and crystallization kinetic of Se-Te-Ag glassy alloys and thick films for electronic devices

The present work has examined the thermal features of glassy chacogenide materials Se0.75-xTe0.25Agx (x = 0, 2, 4, 6, 8, 10 at %). The thermal stability of these compositions has been assessed under non-isothermal conditions using Differential Scanning Calorimetry (DSC), which has been used to find the glass transition temperature (Tg), the initial crystallization temperature (Tin), the temperature corresponding to the top of the crystallization rate (Tp), and the melting temperature (Tm). In addition, the kinetic parameter Kr(T) was given as an additional sign of thermal stability. Among these compositions, it was discovered that Se0.71Te0.25Ag0.04 had the best glass-forming ability and glass-thermal stability. The average coordination numbers of the considered samples have been discussed in relation to these results. Additionally, we measured the sheet resistivity, ρ, whose thickness is equivalent to 1000 nm at heating rate 5 K/min, in this work to study the crystallization kinetics of thick films of Se0.75-xTe0.25Agx (x = 0, 2, 4, 6, 8, 10 at %) in the temperature range of 300 to 625 K. This range was sufficient to draw attention to two substantial areas in the resistivity versus temperature curve, and the derivation of resistivity as a function of temperature established that the films under study only had one crystallization region.

Thermal Analysis of Radiator Using Sustainable Graphene oxide Nanofluid Mixture of Ethylene Glycol and Water

The purpose of the research is to determine if adding grapheme oxide (GO) fluids combined with EG (ethylene glycol) or water might boost the transfer of heat in automobile radiators. Radiators are essential parts of car cooling systems; they dissipate extra heat that the engine produces. The capacity of conventional coolants to transport temperature is limited, including Glycol and water. The ability to conduct heat may be improved with the use of nanoparticles fluids, which are basically solutions of particles in a base liquidize. This technique uses ethylene glycol and water to create a nanoparticles fluid by dispersing GO particles. Using experiments, the resilience or thermal features of the nanoparticle fluids are described. Next, utilizing an early version radiators arrangement, many heat transfer tests are carried out. In comparison to traditional coolants, the radiator’s ability to dissipate heat in various functioning circumstances has been assessed while utilizing the GO nanoparticles fluids together. Comparing the radiator’s heat transfer efficiency with plain ethylene glycol (or water, initial results indicate the addition with GO nanoparticles fluids improves it. Increased thermal conductivity in the nanoparticles fluids combination results in more efficient heat dissipation. For the purpose of to ensure the efficient utilization of the nanoparticles fluids on car cooling mechanisms, it is further evaluated for durability during extended exposure to elevated temperatures. The continued attempts to provide cutting-edge cooling systems for automotive applications are aided by this study. The results indicate that the use of GO nanoparticles fluids in conjunction with conventional coolants has a chance to improve car radiator thermal transfer or general efficiency. It is advised to carry out greater refinement and calibration research to fully realize the potential advantages of this unique coolant composition.

Cascading Machine Learning to Monitor Volcanic Thermal Activity Using Orbital Infrared Data: From Detection to Quantitative Evaluation

Several satellite missions are currently available to provide thermal infrared data at different spatial resolutions and revisit time. Furthermore, new missions are planned thus enabling to keep a nearly continuous ‘eye’ on thermal volcanic activity around the world. This massive volume of data requires the development of artificial intelligence (AI) techniques for the automatic processing of satellite data in order to extract significant information about volcano conditions in a short time. Here, we propose a robust machine learning approach to accurately detect, recognize and quantify high-temperature volcanic features using Sentinel-2 MultiSpectral Instrument (S2-MSI) imagery. We use the entire archive of high spatial resolution satellite data containing more than 6000 S2-MSI scenes at ten different volcanoes around the world. Combining a ‘top-down’ cascading architecture, two different machine learning models, a scene classifier (SqueezeNet) and a pixel-based segmentation model (random forest), we achieved a very high accuracy, namely 95%. These results show that the cascading approach can be applied in near-real time to any available satellite image, providing a full description of the scene, with an important contribution to the monitoring, mapping and characterization of volcanic thermal features.

Habitat Characteristics, Distribution, and Abundance of Cicindelidia haemorrhagica (LeConte) (Coleoptera: Cicindelidae) in Yellowstone National Park.

We observed the tiger beetle species, Cicindelidia haemorrhagica (LeConte), foraging in and reproducing near the thermal pools of Yellowstone National Park (YNP). Although this species was recorded in YNP more than 130 years ago, its distribution, ecology, and association with thermal features are unknown. Therefore, we examined the distribution and habitat characteristics of C. haemorrhagica and evaluated methods for studying its abundance. Given the extreme environments in which these beetles live, typical methods to estimate abundance are challenging. We used a series of presence/absence studies and observations to assess distribution and recorded temperature and pH measurements to determine habitat characteristics. We also conducted visual counts, light trapping, and mark/recapture experiments to assess abundance. The inability to capture C. haemorrhagica with lights led to a phototaxis experiment, which showed minimal attraction to light. Cicindelidia haemorrhagica was found throughout YNP, but it was exclusively associated with thermal springs. The thermal springs ranged from pH 2.7 to 9.0 with temperatures from 29.1 to 75.0 °C and had varying metal concentrations in soil and water. However, all thermal springs with C. haemorrhagica had barren soil with a gradual slope toward the thermal water. Specifically, habitats were thermal pools with gradual margins (a less than five-degree slope) and thermal (i.e., heated) soils for larval burrows by thermal springs or pools. Population sizes of C. haemorrhagica ranged between 500 and 1500 individuals based on visual counts.

Mixed convection phenomenon for hybrid nanofluid flow exterior to a vertical spinning cylinder with binary chemical reaction and activation energy

The study of hybrid nanofluids over spinning cylindrical configurations is widely used in numerous engineering and technological applications. Compared to conventional coolants, nanofluids explore superior thermal conductivities and thereby promote outstanding heat transport capabilities. In this study, hybrid nanofluid flow and thermal transmission across a vertical spinning cylinder are examined in the presence of an externally applied transverse magnetic field. The working fluids used are Ag/water nanofluid and Al2O3-Ag/water hybrid nanofluid. The analysis of heat transmission is carried out in the presence of slip and convective conditions, nonlinear thermal radiation, activation energy, and viscous dissipation. Partial differential equations (PDEs) are used to model the physical situation and are subsequently transformed into ordinary differential equations (ODEs). Through the use of MATLAB's bvp4c technique for ODEs, graphical and computational results are produced and validated with previously reported studies. The important findings are that the flow field diminishes as the magnetic field parameter and Reynolds number increase. Further, for larger levels of nano particle's fraction and thermal Biot number, the thermal features increase. Moreover, it is noted that the mass diffusion rate is lowered by the system's activation energy.

Irreversibility and nanomaterials shape consequences on peristalsis of magneto hybrid nanofluid via curved configuration with homogeneous–heterogeneous chemical reactions

Over the last decade, research on nanofluids has grown at a breakneck pace. As part of their nanofluid research, researchers have recently attempted to use hybrid nanofluids, made by combining different nanomaterials. The novelty of this analysis is to inspect the consequences of entropy generation on the peristalsis of a hybrid nano-liquid via a curved conduit with homogeneous and heterogeneous chemical reactions. Hybrid nanofluid is formed of copper and iron oxide nanomaterials added to water. Furthermore, the simplified model also considered the Hall current, viscous dissipation, and electrical resistance heating effects. The Hamilton–Crosser thermal conductivity model is used to study the nanomaterials shape effects (i.e. sphere, platelet, and blade) on the thermal features of hybrid nano-liquids. Mathematical expressions for the flow problem are simplified by employing the small wave and Reynolds numbers assumptions, which are then resolved analytically and numerically. Analytical results are used to scrutinize the impacts of several included quantities on the flow and thermal characteristics, chemically reactive concentration, and entropy creation. It is found that with a rise in Hartmann number, the velocity reduces, whereas an improvement is noted in temperature and entropy production for large values of Hartmann number. The noteworthy discoveries indicate that hybrid nano-liquids exhibit enhanced thermal efficiency when compared to conventional nanofluids. Specifically, the introduction of a small quantity of ferrous oxide nanoparticles into the copper–water nanofluid led to less than 2% increase in the thermal transport rate. Additionally, it was observed that spherical-shaped nanoparticles generate more heat in comparison to platelets and blade-shaped nanoparticles. Furthermore, the homogenous reaction parameter and Schmidt number lead to a drop in the concentration profile.

(Invited) Overview of Ionic Liquid Electrolytes Doped with δ-Metal Halides for Advanced Post-Lithium-Ion Batteries

Humankind is currently facing a global transition towards a green electrification of both energy production and transportation. There is an urgent need to find new approaches for the storage of energy derived from renewable sources, such as solar irradiation, wind and waves. In addition, electric cars require energy storage or conversion systems capable of providing engine power. To these ends, secondary batteries are an attractive and viable solution, especially in the form of the relatively mature Li-ion technology. Unfortunately, Li power sources suffer from high cost, low Li earth-crust abundance, and toxicity of their electrochemical components (e.g., the Co-based cathodes). Such disadvantages demand the exploration of new energy storage devices based on alternative chemistries (e.g., Na, Mg, Ca).Since their discovery [1-5], electrolytes based on disordered or delta metal halide salts (e.g., δ-MgCl2, δ-LiCl, δ-MgI2) have received widespread attention due to their intriguing physical-chemical properties. Subsequently, electrolytes comprised of ionic liquid solvents dispersing various δ-metal halide salts were investigated [6-9]. These latter ion-conducting systems are characterized by: (i) very high room-temperature ionic conductivity; (ii) wide thermal, chemical and electrochemical stability; and (iii) high coulombic efficiency and very low overpotentials in the metal deposition and stripping processes.In this contribution, a comparison of different families of ionic liquids will be proposed. In particular, the effects of the use of δ-metal halide salts (e.g., δ-MgCl2, δ-LiCl, and δ-NaCl) on the thermal stability, vibrational features, and electrochemical properties of the resulting electrolytes will be considered. The conductivity mechanisms will be analyzed side-by-side, revealing how ionic conductivity is modulated by the metal ions (e.g., Mg2+, Li+, Na+), on the basis of broadband electrical spectroscopy results. Acknowledgments The authors acknowledge support in the form of the following grants: project “Interplay between structure, properties, relaxations and conductivity mechanism in new electrolytes for secondary Magnesium batteries” (Grant Agreement W911NF-21-1-0347-(78622-CH-INT)) of the U.S. Army Research Office; project “ACHILLES” (prot. BIRD219831) of the University of Padua; project “VIDICAT” (Grant Agreement 829145) of the FET-Open call of Horizon 2020; project “Polymer electrolytes for Sodium Batteries” (Grant Agreement 72957-00 01) sponsored by Natrion Inc. and the CUNY Sensor CAT.

Improving flowability of the propellant prepared by solventless extrusion process by integration dendrimer and investigation on its thermal, sensitivity, and combustion features

A mixed nitrate ester propellant composed of nitrocellulose, nitroglycerin, triethylene glycol dinitrate, and dendrimer DP-2 was studied to explore the effects of DP-2 on the rheological properties of the propellant during the solventless extrusion process. The results showed that the apparent shear viscosity of the propellant decreased gradually with the increased mass fraction of the DP-2 from 0 wt% to 2 wt%. Additionally, it was evident that the inclusion of 0.5 wt% DP-2 leads to a notable decrease in both the apparent shear viscosity of the propellant and the torque of screw by over 50%. However, in contrast to the change in fluidity observed from 0 wt% to 0.5 wt%, the enhancement trend of propellant fluidity becomes less significant as the DP-2 content continues to increase. The effects of DP-2 on thermal properties, chemical stability, mechanical sensitivity, mechanical property, and combustion behavior of the propellant were comprehensively assessed. The results demonstrated that DP-2 exhibited promising potential as a flow modification additive for the manufacture of the propellant by solventless extrusion process.

Exploring the antimicrobial, antioxidant and cytotoxic activities of organyltellurium (IV) complexes incorporating 2‐hydroxy‐1‐naphthaldehyde schiff base ligand: Synthesis, spectroscopic investigations and theoretical studies

In this study, Schiff base ligand 1,1′‐((propane‐1,3‐diylbis [azaneylylidene]) bis (methaneylylidene))bis (naphthalen‐2‐ol) based Organyltellurium (IV) complexes were synthesized with formulae C32H27ClN2O3Te (5a)\C31H25ClN2O3Te (5b)\C32H27ClN2O3Te (5c)\ C39H34N2O4Te (5d)\ C37H30N2O4Te (5e)\ C39H34N2O4Te (5f) for acquiring a potential therapeutic agent. The synthesized compounds were characterized by ultraviolet–visible (UV–Vis), FT‐IR, 1H‐NMR, 13C‐NMR, mass spectrometry, molar conductance, elemental analysis, powder X‐ray diffraction and EDAX, which states that the tetradentate Schiff base ligand (HNDP) coordinated via oxygen and nitrogen atom with tellurium giving hexa‐coordinated tellurium (IV) complexes. The thermal features of the ligand and complexes were studied using thermal (TGA and DTG) technique. The biochemical behavior of the Schiff base and its complexes was assessed by examining their reactivity against various microbial strains, DPPH free radicals as well as normal and cancer cells. The complex 5c exhibited the highest inhibition activity against bacterial strains while complex 5f showed the strongest inhibition activity against fungal strains. Complexes 5e and 5f displayed the most effective suppression of DPPH free radicals. The results of in vitro cytotoxicity study revealed that complex 5a demonstrated moderate cytotoxic effect on the L929 cell lines. Complex 5c displayed a significant cytotoxic effect on the PC3 cell line. Moreover, complex 5a, 5c and 5e exhibited the best cytotoxic activity against the Saos‐2 cell line. Additionally, the structural forms of synthesized compounds were elucidated by DFT study. Furthermore, pharmacokinetic ADMET properties were estimated for their drug similarity behavior. The results advocate that complexes can be utilized as biological drugs.

A novel numerical note on the enhanced thermal features of water-ethylene glycol mixture due to hybrid nanoparticles (MnZnFe2O4 – Ag) over a magnetized stretching surface

In this article, we presented a numerical solution of steady-state magnetohydrodynamic (MHD) flow of an incompressible, electrically conducting Casson hybrid nanofluid through a stretching surface under the incitement of viscous dissipation, heat generation and induced magnetism. A viscous mixture of water and ethylene glycol ( W : E G = 60 % : 40 % ) is considered as a base fluid. Enhanced thermal aspects of the working fluid due to suspended manganese zinc ferrite ( MnZnFe 2 O 4 ) and silver ( Ag ) nanoparticles are analyzed by successive over relaxation iterative method. A self-similar procedure is adopted to obtain dimensionless system of governing equations. Order reduction and finite differences discretization of nonlinear coupled differential equations lead to the approximate solution of proposed problem. Impacts of various dominant parameters on the hybridized Casson fluid are examined through the graphs sketched for the functions of velocity, temperature, and induced magnetism. Skin friction coefficient and thermal transfer characteristics at the stretching surface have been simultaneously observed via tabular data prepared for pure nanofluid ( Ag-WEG ) as well as for hybrid nanofluid ( MnZnFe 2 O 4 -Ag/WEG ). It is perceived that induced magnetic field tends to decline the Nusselt number while exhibits a significant growth in the surface drag. Moreover, a significant enhancement in temperature of working fluid has been observed due to Eckert number and heat generation parameter. This decisive role of enhanced thermal features will help to improve industrial growth, waste-water treatment, and automobiles engine efficiency.

A lightweight network based on local–global feature fusion for real-time industrial invisible gas detection with infrared thermography

The detection of industrial invisible gas plays a vital role in preventing environmental pollution and fire accidents. Optical gas imaging (OGI) with infrared thermography is widely used in the field of gas leak monitoring and treatment by visualizing gases to quickly and accurately detect and locate the gas leak sources. However, this method still relies on manual visual inspection. Existing automatic visual gas detection methods suffer from insufficient gas feature extraction and high computational cost due to the indistinct gas features in thermal images. To address these problems, we propose a new lightweight network specialized for thermal gas feature extraction, namely GasViT, sufficiently extracting gas features at very low computational cost by local–global feature fusion. Specifically, two new feature extraction modules Multi-scale Fusion Feature Attention (MsFFA) and Multi-head Linear Self-attention (MhLSa) are proposed for GasViT. MsFFA enhances the gas local feature extraction ability by constructing multi-scale channel and spatial feature fusion maps, enabling the network to focus on more valid local information. MhLSa complements the gas global features with very low computational cost by efficiently encoding the global information of the image in terms of the innovative linear self-attention mechanism. Our experimental results on the self-made Industrial Invisible Gas (IIG) Dataset show GasViT achieves 82.7% mAP50, significantly outperforming the state-of-the-art lightweight networks. Moreover, GasViT achieves 33 FPS real-time detection with a running memory footprint of only 47.2 MB on edge computing devices, making it extremely suitable for portable and embedded detection devices than existing methods to cover gas leakage detection in complex and hazardous industrial scenarios.

Organic/carbon and organic/carbon-metal composite phase change material for thermoelectric generator: Experimental evaluation

Phase change materials (PCMs) are regarded as a promising choice for thermal energy storage and thermal regulation applications owing to their extensive range of operational temperature. Nevertheless, the effective utilization of PCMs is primarily limited by their inadequate thermal conductivity. Present study investigates the efficacy of employing graphene (Gr) mono nanoparticles and graphene-silver (Gr:Ag) hybrid nanoparticles as an approach to enhance thermal features and establish a comparative analysis in energy storage performance of organic phase change material (PCM). The comparative study suggest the addition of 0.8 weight% (wt%) of hybrid Gr:Ag nanoparticles (NPs) enhanced the thermal conductivity of PCM (RT54HC) by 96 %, while 0.8 wt% addition of mono graphene NPs increases thermal conductivity by 83 %. Hybridization of Ag nanoparticle over Gr nanoparticle surface ensures uniform dispersion of nanoparticle into the PCM matrix overcoming the issue of floating in graphene mono nanoparticle and settling in silver nanoparticle. Subsequently, energy storage enthalpy of nanocomposite PCM with 0.8 wt% NPs of Gr and Gr:Ag nanoparticle results in increase in latent heat by 11 % and 8.5 % respectively. Likewise, inclusion of Gr nanoparticles resulted in a decrease in optical transmissibility by 71 %, while Gr:Ag hybrid nanoparticles led to a slightly lower decrease of 65 %. The composites also exhibited a minor alteration in their thermo-physical properties following 500 thermal cycles, thus validating the reliability of prepared nanoparticle enhanced PCMs. Further, hybrid nanocomposite applied in thermoelectric generator (TEG) that produced 425 mV in comparison to base PCM 325 mV. Therefore, the prepared nanocomposites, with their established capabilities, have the potential to make a substantial contribution to the advancement of energy storage requirements in the future.

Phenothiazine-based oxime ester as a photobase generator for thiol-acrylate reactions

In this work, a previously designed and synthesized phenothiazine-based oxime ester was investigated as a photobase generator for the formation of thiol-acrylate networks through the polymerization of thiol-acrylate reactions and more appealingly the base-catalyzed thiol-acrylate Michael addition reactions. This system accomplished a complete disappearance and a full conversion of the characteristic acrylate peak within 10 min of irradiation with a light-emitting diode (λ = 405 nm) or within 1 or 2 min of the same irradiation source and 24 h of heat exposure (T = 60 °C). Photobase generation was evidenced using phenol red as a pH-indicator, enabling to confirm the production of methyl amine (CH3NH2) as initiating species. Photoinitiation mechanism through which base reactive species are produced and the reactions by which the thiol-acrylate polymerization proceeds were investigated according to the base detection experiments, the obtained real-time Fourier transform infrared spectroscopy results, and according to the general photochemical base-generation reactions of oxime-esters. Finally, differential scanning calorimetry scans and Shore A and Shore D hardness experiments have been performed on the polymers obtained to examine their thermal properties and surface hardness features.

Heat Transfer in Simultaneously Developing Turbulent Mixed Convection Flows in Vertical Tubes

This article investigates the simultaneously developing pure turbulent mixed convective regime and compares the hydrodynamic and thermal features of both buoyancy-assisted and opposed flows in a vertical tube. Two-dimensional (2D) axisymmetric steady-state simulations were carried out for Reynolds number, 5,000–20,000; Grashof number, 1.25 × 106 to 108; and Richardson number, 0.05–0.25 for a length-to-diameter ratio of 150 with uniform heat flux boundary condition and water as the working fluid. Three Reynolds-averaged-Navier–Stokes turbulence models were compared and then the most suitable model was used for the simulations. At a given Richardson number, the friction factor and Nusselt number are lower in the case of buoyancy-assisting flow compared to buoyancy-opposing flows. Similar friction factors and heat transfer trends were obtained at a given Grashof number. At varying Grashof numbers and Richardson numbers keeping the Reynolds number constant, no discernible variations were observed for both flows. The entry length was also examined, and it has been found that the hydrodynamic and thermal entry lengths are restricted to a length-to-diameter ratio of 25 and 20 for assisting and opposing flows, respectively. Correlations were developed for both flows to quantify the friction factor, Colburn factor, and Nusselt number in terms of the Reynolds number.

Energy bandgap and thermal characteristics of non-Darcian MHD rotating hybridity nanofluid thin film flow: Nanotechnology application

Abstract The primary purpose of this research is to examine how the presence of thermal features variation affects the velocity and heat transfer rate of nanofluids composed of sodium alginate and molybdenum disulfide [Na-Alg/MoS2]m and sodium alginate and molybdenum disulfide and graphene oxide [Na-Alg/MoS2 + GO]h, respectively, flowing between two rotating, permeable plates. Both centripetal and Coriolis forces, which act on a spinning fluid, are taken into account. The impacts of magnetized force, thermal radiative flux, heat source (sinking), and varied pressure in the Darcy–Forccheimer material are considered. Using the physical vapor deposition method, single and hybridity nanofluid thin films of thickness 150 ± 5 nm may be created. The controlling mathematical equations of the suggested model are solved using the Keller-box technique in MATLAB software. The surface friction coefficient of a hybrid nanofluid is less, and the heat transfer rate is greater than that of a regular nanofluid. The rate of heat transmission is slowed by the rotational parameter. The thermal efficiency of mono nanofluids is as low as 6.16% and as high as 21.88% when compared to those of hybrid nanofluids. In particular, the findings of density functional theory (DFT) calculations reveal that the energy bandgap Δ E g Opt \Delta {E}_{{\rm{g}}}^{{\rm{Opt}}} drops from 1.641 eV for conventional nanofluid to 0.185 eV for hybridity nanofluid. Based on the findings, the addition of graphene oxide nanoparticles to the base nanofluid converts it from a semi-conductor to a hybridity nanofluid as a superconductor.

Structure, Thermal, and Mechanical Behavior of the Polysulfone Solution Impregnated Unidirectional Carbon Fiber Yarns.

The paper is devoted to the study of thermal and mechanical behavior and structural features of the polysulfone solution impregnated unidirectional carbon fiber yarns depending on fabrication conditions and appearance for optimum production method of the composites. The effect of producing conditions, such as polysulfone solution concentration, drying and post-heating temperatures, and the residual solvent content on the structure, mechanical, and thermal properties of the carbon fiber-reinforced composites was studied. The polysulfone solution impregnated carbon fiber yarns show relatively high mechanical properties, realizing up to 80% of the carbon fibers' tensile strength, which can be attributed to good wettability and uniform polymer matrix distribution throughout the entire volume of the composites. It was found that the composites impregnated with 40 wt.% of the polysulfone solution showed lower porosity and higher mechanical properties. The results of a dynamic mechanical analysis indicate that residual solvent has a significant effect on the composites' thermal behavior. The composites heated to 350 °C for a 30 min showed higher thermal stability compared to ones dried at 110 °C due to removal of residual solvent during heating. The impregnated carbon fiber yarns can be used for the further producing bulk unidirectional composites by compression molding and the proposed method can be easily transformed to continuous filament production, for example for further use in 3-D printing technology.