Solid Particles Research Articles

Thermal Cycling Test of Solar Salt in Contact with Sustainable Solid Particles for Concentrating Solar Power (CSP) Plants

Thermal energy storage (TES) is crucial in bridging the gap between energy demand and supply globally. Concentrated Solar Power (CSP) plants, employing molten salts for thermal storage, stand as an advanced TES technology. However, molten salts have drawbacks like corrosion, solidification at lower temperatures, and high costs. To overcome these limitations, research is focusing on alternative TES materials such as ceramic particles. These solids match molten salts in energy density and can withstand higher temperatures, making them well-suited for CSP systems. This study revolves around subjecting Solar Salt alone and Solar Salt alongside Volcanic Ash (VA) and Electric Arc Furnace Slag (EAFS) to a comprehensive thermal cycling test. This test is designed to assess the compatibility over the thermal cycles of the Solar Salt and the Solar Salt in contact with these solids in a CSP plant with a thermocline configuration. With a final thermal and chemical evaluation, our observations indicate that EAFS and VA demonstrate promising compatibility but an increase in the reduction rate of the Solar Salt due to a catalyst effect from EAFS in contact with the salt. No discernible alterations were detected in the properties of either the solid materials or solar salt when combined.

A Novel Simulation Model for Multiple Solid Particle Erosion in Micro-blasting Process of Ti-6Al-4V Dental Implant Alloy Considering Actual Geometry of Impacting Particles

A Novel Simulation Model for Multiple Solid Particle Erosion in Micro-blasting Process of Ti-6Al-4V Dental Implant Alloy Considering Actual Geometry of Impacting Particles

Investigation on drawdown process of light-floating particles in a pilot scale cup-shaped blade agitator

The novel cup-shaped blade agitator with pilot scale was successfully applied in light-floating particles drawdown dispersion under high solid content (40 vt.%) for the first time. The drawdown dispersion effect of cup-shaped blade agitator was systematically investigated, by integrating the CFD simulation, the research unveils the impact mechanisms of flow conditions within the agitator on particle drawdown and dispersion, under various structural and operational parameters of the cup-shaped blade (CB) impeller. The optimum structure for CB was determined as CB2, with impeller deflection angle of -30°, and impeller diameter of 0.43 m. Under this structure, the CB agitator exhibits the best performance and can complete drawdown dispersion of light-floating particles at high solid concentration exceeding 40 vt.%. Besides, at lower solid particle volume concentration (Cv), both Njd and Pjd increase with increasing Cv. Interestingly, after Cv exceeds 10%, Njd and Pjd decrease as Cv continues to rise. Comparing with traditional impeller RT and PBT, the CB impeller is more competitive. Finally, dimensionless correlations of Njd and Pjd were established to provide practical guidance for application and optimization of CB agitator.

Performance degradation model and life prediction method of spool pair caused by erosion wear

The erosion of solid particles in the fluid causes the wear of the metering edge of the spool pair, resulting in a decrease in system performance. This paper aims to develop a general method to evaluate performance degradation and life prediction of spool pairs induced by erosion. Considering the diversity of influencing factors and the complexity of operating conditions, traditional numerical calculation methods will consume huge computational costs. It is difficult to qualitatively and quantitatively analyze the evolution of metering edge by numerical calculation. The erosion prediction model (EPM) constructed by machine learning methods can be used to predict the wear profile discretized in time and space. Combined with the mathematical model of the valve-controlled cylinder, a performance degradation model (PDM) that can simulate real-time working conditions is established. Through the data exchange and iterative update between EPM and PDM, a complete digital platform for the calculation of slide valve durability is constructed. After comparing with the experimental results, it can be concluded that the proposed method can realize the performance degradation evaluation and life prediction of the spool pair caused by erosion wear under continuous working conditions.

Materials and methods for the microencapsulation of substances of food and agricultural interest

Microencapsulation involves trapping solid, liquid, or gas particles within an inert cover to protect them from the environment. This technique has numerous biotechnological applications in the food, agricultural, pharmaceutical, and other industries. Microcapsules are relevant for obtaining viable products and optimizing their efficacy, stability, safety, and ease of application. There is a wide range of coating materials and techniques used to microencapsulate various substances of interest. This article presents a review of encapsulating materials and microencapsulation methods used in the food and agricultural industries.

Convective heat transfer into moving fluid from a heated prolate spheroid

A common assumption in heat transfer models that involve fluid-solid interactions is that solid particles have a spherical shape. However, in numerous engineering applications, it is crucial to gain insights into the heat transfer mechanisms involving non-spherical particles and flowing fluids. These processes often employ particles with altered shapes, such as elongated geometries resembling prolate spheroids.A numerical study of airflow past a stationary constrained prolate spheroid under forced convective heat transfer is performed. A large temperature difference of the spheroid's surface was maintained relative to free stream temperature. Navier-Stokes and energy equations were solved to investigate the impact of Reynolds number (Re) and aspect ratio (AR) on convective heat transfer rate and Nusselt number (Nu). We focus on a wide range of spheroids' surface temperatures up to 1500 K in our study, which has never been studied in depth before. The simulations show that the mean Nu has a positive dependence on Ts, AR, and Re.A new correlation has been introduced that calculates the average Nusselt number (Nu) for spheroidal particles without assuming an isothermal condition (where the surface temperature Ts is roughly equal to the ambient temperature T∞). The suggested correlation incorporates the influence of AR, surface temperature, and Re.

Evaluation of Improved Tribo-Performance Characteristics of MoS2 functionalized MWCNTs Hybrid reinforced Epoxy Composites for Severe Erosion Conditions

Solid particle erosion (SPE) has become a major concern for epoxy composite structures exposed to high erosion conditions. A novel erosion-resistive hybrid nanofiller molybdenum disulphide (MoS2) functionalized MWCNTs have been synthesized by hydrothermal route. Epoxy nanocomposite with MoS2 functionalized MWCNTs showed enhanced SPE resistance and mechanical properties as compared to conventional MWCNTs nanocomposites. Epoxy/MoS2/MWCNTs – 1 nanocomposite showed low erosion rate of 471mg/Kg and 132mg/Kg at 15° and 90° impact angles, whereas epoxy/MWCNTs nanocomposite showed high erosion rate of 548mg/Kg and 300mg/Kg at 15° and 90° impact angles respectively. Erosion efficiency parameter (η) was used to predict the possible erosion mechanism and was further validated using FESEM analysis.

Thermal case study of magnetic radiative flow impacts on Newtonian nanofluid over a stretchable plate in absorbent: Box approach

Nanofluid technology represents a significant breakthrough in thermal engineering, with widespread applications spanning heat exchangers, cancer treatment, and heat storage systems. Despite its success in improving heat transfer rates in diverse devices, the challenge of enhancing thermal conductivity using nanoparticles looms large. This study aims to elucidate the 2D flow of nanofluid under suction/injection over a stretching wedge. It considers factors such as Brownian and thermophoretic diffusions, nonlinear heat generation, and thermal radiation. Additionally, it examines the effects of viscous dissipation and Joule heating. Through the conversion of governing nonlinear coupled partial differential equations into a system of coupled ordinary differential equations using similarity transformations, numerical solutions are obtained via the Keller-box method. The analysis delves into the significant impacts of relevant parameters on velocity, temperature, concentration, and microorganism fields, presented graphically. Notably, the findings underscore the role of solid particles in enhancing the thermal efficiency of base fluids. These investigation outcomes are vital for controlling heat transferal rates and fluid velocities throughout a variation of manufacturing processes and industrial sectors, guaranteeing the required quality of the ending product. The perceptions garnered from this research hold capacity for a broad range of industrial purposes and carry consequences through countless engineering disciplines, mostly within the range of nanotechnology.

Effect of Air Distribution on the Transport Characteristics of Solid Particles in the Thermal Storage and Release System of Circulating Fluidized Bed

Effect of Air Distribution on the Transport Characteristics of Solid Particles in the Thermal Storage and Release System of Circulating Fluidized Bed

Coupling SPH-DEM method for simulating the dynamic response of breakwater structures under severe free surface flow

This paper introduces a novel smoothed particle hydrodynamics (SPH) - discrete element method (DEM) to enhance our understanding of the impact of free-surface flow on breakwater structures. SPH is employed to simulate incompressible fluids, while DEM is utilized to track the trajectories of solid particles. Advanced strategies including polyhedral particle modeling and contact model are adopted to enhance the model's capability in solving the dynamic behavior of irregular particle. Several cases are analyzed to validate the accuracy of coupling model, showing a high level of agreement. Additionally, the impact of wave flow on coastal breakwaters composed of irregular rocks is simulated. This work reveals that the coupling model effectively provides extensive information about the flow field and dynamic response of multi-particle systems, such as velocity, fluid force and force chain distribution. This model exhibits significant potential for analyzing the dynamic response of severe free surface flow on the multi-block structures.

Effect of Varied Cure Temperature on the Cure Behavior, Mechanical Properties and Heat Build-Up of Solid Tire Tread Compound Containing Different Particles Sizes of Ground Tire Rubber

This work investigates the effect of variation in vulcanization temperature on the cure behavior, tensile properties, tear strength, hardness, Akron abrasion loss and heat build-up of vulcanized tire tread compound in which the total rubber was replaced with 10% and 20% ground tire rubber (GTR) of 40, 60 and 80 mesh sizes. The first step was the characterization of the GTR using optical microscopy and a thermogravimetric analyzer. The first step of mixing each rubber compound was carried out using an internal mixer (Brabender) at 60°C and 40 rev/min rotor speed and the second step was done on a two-roll mill. The mooney viscosity of each rubber compound was investigated. the cure behavior of the rubber compounds was studied at 140°C, 150°C, and 160°C respectively. Results show that the introduction of GTR reduced vulcanization time, while increased cure temperature resulted in a lower vulcanization time. No significant difference was observed in the vulcanization time at a particular temperature of the rubber sample with different particle sizes and varied amounts of GTR. The introduction of ground tire rubber in the rubber vulcanizate however resulted in decreased tensile strength, tear strength and elongation, and increased hardness, abrasion resistance, modulus and heat build-up. An increase in the vulcanization temperature from 140°C to 150°C and 160°C  did not impart a significant reduction in the tensile strength of the vulcanizates containing GTR. Vulcanization at higher temperatures resulted in reduced hardness, and modulus, slightly increased abrasion loss and increased elongation of the vulcanizates containing GTR. The heat build-up increased as the cure temperature increased. Generally, the control sample with no content of ground tire rubber exhibited the best properties. If GTR is to be introduced in rubber matrix at an amount up to 20%, the results suggest that 60 mesh size particles will impart better properties. The optimal vulcanization temperature recommended based on the findings from the work is 150°C.

Modeling of micron-sized aluminum particle combustion in hot gas flow

This paper presents a model for micron-sized aluminum (Al) particle combustion in hot oxidizing environments, forming hollow spheres. The model comprises four sub-models describing the physical and chemical processes during Al combustion: melting of the solid core, ejection of liquid Al droplets from the breaking solid shell, vaporization of liquid droplets, and ignition and establishment of vapor flame surrounding the solid particles. The model is of critical importance when the ambient gas temperature is higher than the melting point of the Al core, Tc,m, but lower than the alumina (Al2O3) shell’s melting point, Ts,m. In the model, the Al core is assumed to be surrounded by a thin, compact alumina shell that blocks the diffusion of oxidizer into the core and prevents surface reactions. The alumina shell’s cracking and liquid Al’s eruption are triggered by thermal expansion and pressure buildup in the liquid core. The splashed liquid Al droplets vaporize quickly and initiate gas-phase reactions, followed by the vaporization of the liquid Al core as the particle temperature Tp increases. Al vapor combustion heat is redistributed to simulate the gaseous flame near the particle. The model is implemented using the Lagrangian particle tracking method and is validated through simulations of micron-sized Al particle combustion in hot gas and comparison with experiments. The results can explain the formation of the sharp-edged holes on hollow aluminum oxide spheres and the ignition behavior observed in the experiments.

A New Type of Hydraulic Clutch with Magnetorheological Fluid: Theory and Experiment

This paper presents a new type of hydraulic clutch operating by means of magnetorheological (MR) fluids and the results achieved from both theoretical analysis and experimental measurement. A hydraulic clutch system with MR working fluid and a rotating magnetic field located was designed. The clutch was based on the principle of using a rotating magnetic field created by an alternating current electromagnet to set the MR fluid in motion. To test the hydraulic clutch with a rotating magnetic field, MR fluids were produced by our laboratory, consisting of solid iron particles of various diameters mixed with a silicone oil. With MR working fluid and a rotating magnetic core was designed. The rheological properties of the MR fluids were assessed on the basis of tests carried out with a Brookfield DV2T rheometer equipped with a magnetic device for generating a magnetic field. The characteristics of the hydraulic clutch were tested on a specially built test stand. It was found that the torque transmitted by the clutch increased with the rotational speed of the magnetic field and with a lower rotational speed of the beaker in which the working fluid was placed. It was also found that the greatest torque occurred with the working fluid with the highest iron content. Based on the analysis of the structure and characteristics of the clutch in which the magnetic field is used, it has been shown that the design of the developed clutch is similar to that of an induction clutch, and its characteristics correspond to the characteristics of the eddy current clutch. Therefore, the proposed new clutch with MR fluid and rotating magnetic field can be applied to stationary power transmission systems in a manner similar to an eddy current clutch.

Secondary crushing of droplets of water-oil emulsions

When fuel oil is supplied to an accurate chamber, its spraying process takes place due to injectors and sprinkler devices. This process is called primary droplet crushing. It is often not enough to burn fuel efficiently. Since the size of fuel droplets in the combustion chamber often reaches several millimeters, which increases underburning and leads to uneven burnout. In such cases, it is advisable to use secondary crushing of water-oil fuel droplets. Secondary crushing of droplets reduces the average size of droplets in the fuel spray torch by several times. At the first stage of secondary crushing of droplets, their collisions with each other in the jet are realized, after which the formed droplets are subjected to collisions with the walls of thermal equipment. At the next stage, pyrolysis of such droplets occurs at the periphery of the jet, which leads to the formation of solid particles and subsequent collisions of droplets of water-oil fuels with them. At the final stage, the formed secondary fragments are subjected to intense heating in the combustion chamber, which allows for micro-explosive grinding. The present study is aimed at studying the characteristics of secondary crushing of water-oil fuel droplets with the addition of specialized additives. The results of the conducted studies have shown that the use of an additive based on a special combination of positively and negatively charged ions reduces the size of fuel droplets by 25%. It has been found that when using such an additive, the ratio of the free surface areas of droplets increases several times with a combination of all secondary grinding modes.

Synthesis and characterization of absorption-enhanced alumina solid particle materials for direct irradiation solar-thermal conversion

Based on solar-thermal application more than 1000 °C, a novel combination of sol-gel synthesis and stepwise calcination to prepare metal-ion doped alumina composite particles as heat transfer media were proposed, enhancing solar energy absorption and lowering preparation temperature. Investigations focused on the elemental distribution, phase composition, oxidation states, optical properties and thermal stability of the composites, which were doped with Cr, Co, Cu, Fe, and Mn metal ions in a 100:5 M ratio. The first-principles calculations elucidate the mechanism behind the impact of transition metal ions on alumina’s optical properties. Results show that introducing a small quantity of metal atoms results in new impurity energy levels and electron states around EF = 0. Specifically, the band gap energy of Cu- and Mn–Al2O3 decreases from 6.017 eV to 4.464 eV and 2.170 eV, respectively. Correspondingly, the absorptivity of these composite particles increases from around 20 %–76.6 %. And Tauc analysis indicates a decrease in the optical band gap of the particle materials from 5.37 eV to a range of 2.88–4.90 eV. Additionally, doping with Mn, Fe, and Cu accelerates the in-situ formation of α-Al2O3 crystals, with a phase transition temperature below 1000 °C and a crystallinity exceeding 93 %. Thermal stability tests show that the particles are highly stable, exhibiting a mere 0.49 % mass change between 30 °C and 1200 °C. The stepwise inert annealing strategy and metal-iron doping positively influence the optical performance of alumina, synthesizing long-term high-temperature stable alumina ceramic particles with absorptance enhancement and a low α-Al2O3 phase transition temperature. These attributes make a favorable choice for solar-thermal applications in direct irradiation.

Optimization of solid particle erosion behavior of thermally sprayed nichrome on duplex stainless steel

Optimization of solid particle erosion behavior of thermally sprayed nichrome on duplex stainless steel

Estimating the Thermal Conductivity of Unsaturated Sand

A modified parallel model for estimating the thermal conductivity of unsaturated sand was proposed in this study. The heat conduction in the solid phase of sand depends mainly on the form of contacts between solid particles, while water bridges at the particle contacts increase the contact areas and remarkably enlarge the transfer paths of heat conduction in sandy soils. However, the thermal conductivity of the solid particle itself (λs) cannot describe the influence of the form of contacts and water bridges on heat conduction through the solid phase. In this study, the equivalent thermal conductivity of the solid particle (λes) was presented which reflected the influence of the form of contacts and water bridges between particles under dry conditions or a low degree of saturation, respectively. The relationship between λes and degree of saturation was described by hyperbolic expression. The modified model was calibrated using measured values of the thermal conductivity from published datasets, including those for 41 types of sand from 15 studies. Numerical analyses of the temperature field of the energy pile were performed and validated against laboratory measurements. The results illustrated that the modified model was more applicable than the original model for predictions of sand thermal conductivity.

Failure mechanisms of interfacial coatings (MCrAlY+8YSZ) on high temperature solid particle erosion

Failure mechanisms of interfacial coatings (MCrAlY+8YSZ) on high temperature solid particle erosion

Cost modeling of photocatalytic decomposition of atmospheric methane and nitrous oxide

Abstract The photocatalytic decomposition of atmospheric methane (CH4) and nitrous oxide (N2O) could be valuable tools for mitigating climate change; however, to date, few photocatalyst deployment strategies have had their costs modeled. Here, we construct basic cost models of three photocatalytic CH4 and N2O decomposition systems: 1) a ground-based solar system with natural airflow over photocatalyst-painted rooftops, 2) a ground-based LED-lit system with fan-driven airflow, and 3) an aerosol-based solar system on solid particles dispersed in the atmosphere. Each model takes as inputs the photocatalyst’s apparent quantum yield (AQY; a measure of how efficiently photons drive a desired chemical reaction) and the local CH4 or N2O concentration. Each model calculates an overall rate of greenhouse gas drawdown and returns a levelized cost of greenhouse gas removal per equivalent ton of carbon dioxide (tCO2e). Based on prior studies of atmospheric carbon dioxide removal, we adopt $100/tCO2e as a target cost.

We estimate that painting rooftops with photocatalysts might meet the target cost for decomposition of >10ppm CH4 with catalyst AQYs >4%. If painting and cleaning costs were reduced by a factor of ~3 from our scenario, removal of ambient CH4 could meet the cost target with AQYs >1% and removal of ambient N2O could do so with AQYs >0.1%. 
Fan-driven systems with LED illumination appear to be very challenging, achieving removal costs <$100/tCO2e only for AQYs of >10% for CH4 and >1% for N2O. Dispersing photocatalytic aerosols in the troposphere could be cost-effective with AQYs of >0.4% for ambient CH4 or >0.04% for ambient N2O. However, the mass of aerosols required is large and their side effects and social acceptability are uncertain. We note that, for any system, AQYs on the order of 1% will likely be extremely challenging to achieve with such dilute reagents.

Synthesis and coating properties of (La0.5Eu0.25Y0.25)2Zr2O7 ceramic powder

The (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) ceramic powder for spraying was prepared and synthesised by combining spray granulation and solid phase reaction phase, and a double ceramic layer structure with (La0.5Eu0.25Y0.25)2Zr2O7 ceramic surface coating and YSZ intermediate coating was prepared by atmospheric plasma spraying. Experimental characterisation revealed that the moulding state of spray granulated powders was significantly influenced by the solid content. When the solid content is small, the viscosity of the slurry is insufficient, and the prepared powder has poor formability and small overall particle size. When the solid content is large, the slurry is too viscous, which easily leads to unfavourable conditions such as sticky walls. The best formability of the pelletised powder was obtained with a solid content of 55 wt-% and a binder content of 2.0 wt-%. Compared with La2Zr2O7 (LZ) ceramics, the fracture toughness of the rare-earth co-doped modified LEYZ ceramic coating was increased by 8.4% and the bond strength was increased by 49.9%, showing good toughness and crack resistance. Moreover, LEYZ coating has significantly better resistance to solid phase particle erosion than LZ coating, with 46.3% and 45.4% reduction in erosion rate at 45° and 90°, respectively.