Spherical Container Research Articles

Effect of air layer on PCMs melting process inside a spherical container: A numerical investigation

Efficient latent heat storage technology is getting significant interest from the researchers, scientist, and engineers who are involved in solar heating and cooling, waste heat utilization, and building energy management applications. The latter materials are employed most frequently in this connection owing to their pronounced energy storage capacity and moderate cost. The present work involves a numerical analysis for the assessment of heat transfer through paraffin wax RT42 when it is fully converted from solid to liquid phase in a spherical container with and without air layer. The interaction of the py-porosity combination was evaluated numerically with the use of ANSYS/FLUENT 16 program. The results show that the presence of a 1 mm thick air layer increased the total melting time by 33.33%, while a 2 mm thick air layer resulted in a 66.67% increase compared to the control without an air layer. In this research, it is clear that air layers play a major role in the delay of the melting of paraffin wax.

Nonlinear mechanics of phase-change-induced accretion

In this paper, we formulate a continuum theory of solidification within the context of finite-strain coupled thermoelasticity. We aim to fill a gap in the existing literature, as the existing studies on solidification typically decouple the thermal problem (the classical Stefan’s problem) from the elasticity problem, and often limit themselves to linear elasticity with small strains. Treating solidification as an accretion problem, with the growth velocity correlated with the jump in the heat flux across the boundary, it presents an initial boundary-value problem (IBVP) over a domain whose boundary location is a priori unknown. This IBVP is solved numerically for the specific example of radially inward solidification in a spherical container. Several parametric studies are conducted to compare the numerical results with the rigid cases in the literature and gain insights into the role of elastic deformations in solidification.

Experiments of Ultrasonic Positioning System with Symmetrical Array Used in Jiangmen Underground Neutrino Observatory

The experimental environment of the JUNO is a spherical container filled with a liquid scintillator (alkylbenzene) with a diameter of about 35 m. To observe neutrino interactions in alkylbenzene with photomultiplier tubes (PMTs) and to precisely measure the neutrino properties in this environment, it is necessary to design a high-precision localization system for the PMT device. In this paper, we report the design of an ultrasonic localization system with a symmetrical receiving array, based on the construction of an experimental setup that reproduces the configuration of JUNO’s environment. We show through positioning consistency and accuracy measurements that the ultrasonic localization system has a high localization accuracy and can perform effective localization in an alkylbenzene solution with 98% purity.

Effects of buoyancy on the spherical flame and explosion pressure of a CH4 mixture under dilution conditions

To determine the effects of buoyancy on the spherical flame and explosion pressure under dilution conditions, a series of explosion experiments were conducted in a 20-L spherical container. The schlieren technique was used to record CH4 flames to assess the buoyancy effect. The change in the explosion pressure was recorded and correlated with the flame shape to analyze the explosion characteristics. The methane explosion occurred in two stages: initial ignition and flame development. During initial ignition, the addition of CO2 caused the flame buoyancy to increase considerably. Flames with different buoyancies had different shapes, such as spherical, ellipsoidal, and “ω” shapes. The radius of the flame at 12 mm may serve as the threshold for the onset of buoyancy effects; once the radius exceeds this value, the flame could deform due to buoyancy effects. Increasing the added CO2 concentration caused the buoyancy effect to be enhanced and appear at a very low radius of the flame. The combined effects of buoyancy and dilution reduced the flame expansion speed. The difference between the horizontal and upward expansion speeds linearly increased with the CO2 concentration. At a high CO2 concentration, the flame stagnated at speeds below 0.5 m/s. During flame development, CO2 addition made the flame surface smoother. Suppressing the cellular flame structure delayed the maximum explosion pressure rise rate and reduced the pressure peak. A coupled analysis of the flame shape and the maximum explosion pressure rise rate showed a dense cellular structure for a high explosion pressure rise rate and a smooth flame surface for a low maximum explosion pressure rise rate. The size and number of cellular structures for different mixtures were similar at a fixed maximum explosion pressure rise rate.

Hydrodynamic Analysis of Pipelines Transporting Capsule for Onshore Applications

Abstract— Rapid depletion of energy resources hasimmensely affected the cargo transportation industry.Efforts have been made to develop newer economic andenvironmental friendly modes for this purpose. Bulk solidscan be transported for long distances effectively in pipelines.Raw materials can be stored in spherical containers(commonly known as capsules) transported through thepipeline. For economical and efficient design of anytransportation mode, both the local flow characteristics andthe global performance parameters need to be investigated.Published literature is severely limited in establishing theeffects of local flow features on system characteristics ofHydraulic Capsule Pipelines (HCPs). The present study focuses on using a well-validatedComputational Fluid Dynamics (CFD) based solver tosimulate the unsteady turbulent flow of a sphericalcapsule as a simplified case in HCPs for onshoreapplications. A novel numerical model has beenemployed in the present study with the aid of thedynamic mesh technique for calculating the pressureand the velocity variations within such pipelines. Thenumerical model comprises a straight test section. Thenumerical model for capsule flow yields realisticresults for the global flow parameters as compared tothe experimental data from the test rig developed inthe present study. The influence of the carrying fluid(water) on the capsule has been verified by estimatingthe shear forces and the friction coefficient. Inaddition, novel models have been developed forpredicting the wet friction coefficient considering thestart-up effect in such systems.

Natural Convection in a Spherical Porous Annulus with Diathermal Partition Wall

The influence of the diathermal partition wall on natural convection in a fluid-saturated porous medium has been numerically studied in the present paper. A concentric diathermal wall of infinitesimal thickness is inserted in the fluid-saturated spherical porous annulus. Due to the flow symmetry along the vertical axis, only half of the sphere is considered for simulation. A Successive Accelerated Replacement Scheme has been used to solve the Darcy flow model using the finite difference method. The average Nusselt number value decreases with the presence of a partition wall within the fluid-saturated spherical porous annulus. The percentage decrease in average Nusselt number value depends upon the position of the diathermal wall within the width of the spherical annulus. There is about a 50% reduction in the average Nusselt number with a diathermal partition wall for the cases considered in this work. The results of the present investigation will help in the proper design of porous insulation in spherical porous containers for the storage of thermal energy.

Investigation into the ignition sensitivity and detonation kinetics of Al/RDX energetic dust

Given the prevalence of Al/RDX energetic dust in industrial production, this study investigates their ignition safety and explosion hazards using Hartmann tubes and 20 L spherical explosion containers. The minimum ignition energy (MIE) increases from 20 mJ to 55 mJ as RDX content increases, indicating that adding RDX enlarges the effective particle size of the dust, thereby reducing its ignition sensitivity. A logistic regression model was used to develop a fitting equation for ignition probability, correlating dust concentration and ignition energy. The flame propagation velocity and explosion pressure of the energetic dust initially increase and then decrease with increasing RDX content. Optimal combustion characteristics were observed at 20 % RDX, with the maximum flame propagation velocity of 101 m s−1. However, the peak flame temperature decreases with increasing RDX content. The maximum explosion pressure and maximum explosion index at 1.77 MPa and 186.99 MPa m s−1 respectively, at 40 % RDX content. These findings highlight that 20 % RDX content yields the best combustion characteristics, while 40 % RDX content offers the maximum explosive potential, providing valuable insights for enhancing safety measures in industrial applications involving energetic dusts.

Before the Dressel 20: pottery workshops and olive oil amphorae of the Guadalquivir valley between the Late Republic and Augustan-Tiberian times

Abstract The Baetican Dressel 20 is probably the most widely diffused amphora of the Roman period, found in large quantities throughout all the Roman and nearby territories. It is the most powerful evidence of the importance of the olive oil trade for Roman society and of olive oil's extraordinary production in the Baetican countryside. This wide diffusion of the amphora and, in some ways, its ubiquity at many archaeological sites, have hindered the study of the early stages of Baetican olive oil production and diffusion. The protagonists were not these spherical containers, commonly stamped up until the late 3rd c. CE, but previous models that evolved rapidly after their origins in Late Republican times. In this paper, we aim to analyze not only the formal characteristics and evolution of these peculiar and still unstandardized containers, but also other aspects linked to their production, as well as the scope of their diffusion.

Solid Foam Insertion to Increase PCM-Based Thermal Energy Storage System Efficiency: Experimental Test and Numerical Simulation of Spherical Macrocapsules

Phase change materials (PCMs) are an interesting solution to increase the efficiency of thermal energy storage (TES) systems. The present work explores, with an experimental and computational study, the behavior of a paraffin wax encapsulated in a spherical containment system during the melting and solidification phases. The experimental tests were conducted by immersing the spherical capsule in a thermostatic water bath at different temperatures and measuring the temperatures at four different points inside the capsule. A two-dimensional CFD model of the sphere was then applied to investigate the effect of the insertion of a solid foam into the sphere to increase the system’s responsiveness under demanding conditions. In addition, an analysis of the solidification process considering two different wall materials (HDPE and aluminum) with different thermal conductivity was performed. The results suggest that embedded foams can represent a useful tool to increase the efficiency of a PCM-based TES, but, at the same time, they also highlight that a considerable increase in thermal conductivity is required to achieve significant advantages with respect to pure PCM systems.

Experimental thermal performance of deionized water and iron oxide nanofluid for cold thermal storage.

Phase change materials enhance the thermal comfort of buildings by utilizing stored thermal energy. In large air-conditioning systems, ice storage plays a crucial role in managing peak power loads. This experimental study explores the freezing characteristics of deionized water containing suspended iron oxide nanoparticles in spherical containers for cold storage. The synthesized nanofluid phase change material (NFPCM) was investigated for its freezing behavior under surrounding fluid temperatures of - 2°C and - 6°C. The uniformity in charging of NFPCM is the unique feature prevalent in the first quarter of the charging, with 50% mass frozen observed. An increased surface heat flux of 200% was achieved using NFPCM at Tsurr = -6°C. The chiller operational time is optimally reduced by 75% by considering twice the container design's phase change materials. Adding iron oxide nanoparticles and partial charging is suitable for uniform heat transfer for the shorter freezing duration in cooling applications. The novelty of the present study is that the proposed NFPCM nearly nullifies the subcooling effects of deionized water without using nucleating agents. This NFPCM appreciably enhances power competence, yielding large-scale air-conditioning systems' desired economic impact and sustainability. The reported results align with Sustainable Development Goals (7-Affordable and Clean Energy and 13-Climate Action).

An efficient solution space exploring and descent method for packing equal spheres in a sphere

The problem of packing equal spheres in a spherical container is a classic global optimization problem, which has attracted enormous studies in academia and found various applications in industry. This problem is computationally very challenging, and many efforts focus on small-scale instances with the number of spherical items less than 200 in the literature. In this work, we propose an efficient local search heuristic algorithm named solution space exploring and descent for solving this problem, which can quantify the solution’s quality to determine the number of exploring actions and quickly discover a high-quality configuration. Besides, we propose an adaptive neighbor item maintenance method to speed up the convergence of the continuous optimization process and reduce the time consumption. Computational experiments on a large number of benchmark instances with 5≤n≤400 spherical items show that our algorithm significantly outperforms the state-of-the-art algorithm. Specifically, our algorithm improves 274 best-known results and matches 84 best-known results out of the 396 well-known benchmark instances.

Breaking the size constraint for nano cages using annular patchy particles.

Engineering structures like nanocages, shells, and containers, by self-assembly of colloids is a challenging problem. One of the main challenges is to define the shape of the individual subunits to control the radius of the closed shell structures. In this work, we have proposed a simple model for the subunit, which comprises a spheroidal or spherical hardcore decorated with an annular patch. The self-assembly of these building blocks leads to the formation of monodispersed spherical cages (close shells) or containers (curved clusters). For a spheroid with a given bonding range, the curvature of the shell is analytically related to only the patch angle of the building blocks and independent of the shape of the subunits. This model with only one control parameter can be used to engineer cages with the desired radius, which also have been verified using thermodynamic calculations. In the phase diagram of the system, 4 phases are identified which includes gas, closed shell, partially closed (containers) shell and percolated structures. When the diameters of the spherical cages formed are small, we observe an icosahedral symmetry similar to virus capsids. We also observed that the kinetics of the cage formation is very similar to the nucleation and growth kinetics of viruses and is the key factor in determining the yield of closed shells.

The effect of quasi-static pressure on strain growth in an elastic ring

Regarding strain growth, the influence of quasi-static pressure on the strain growth of a plane-strain ring is investigated using a simplified pressure model that incorporates quasi-static pressure, combining with Mathieu equation, SDoF equation and numerical simulation. The results demonstrate that after considering quasi-static pressure, the mechanism of strain growth in a plane-strain ring remains as a nonlinear coupling between bending and breathing modes. It is inadequate to accurately predict the generation of bending mode solely based on the initial velocity in Mathieu equation. If pure triangular pulse fails to excite strain growth, it is still possible for the plane-strain ring to experience strain growth caused by quasi-static pressure. Furthermore, higher peak pressures of triangular pulses correspond to smaller magnitudes of quasi-static pressure required to trigger the bending mode. The compression displacement significantly affects the response and strain growth in a plane-strain ring. When considering quasi-static pressure effects, observing strain growth becomes more likely when compression displacement exists; conversely, without compression displacement, likelihood of strain growth occurrence diminishes. These findings have implications for designing cylindrical and spherical explosion containers.

Experimental investigation and simulation of the phase change process of enhanced paraffin by MWCNTs in a spherical container

This study investigates the enhancement of phase change materials (PCMs) by incorporating highly thermally conductive carbon-based nanoparticles (multi-walled carbon nanotubes (MWCNTs)) into paraffin wax (PW) and the effect of added nanoparticles on the phase change process by experiments and numerical investigations.The melting and solidification processes were studied while melting was performed in a constant temperature oil bath and solidification in different fluid media (oil, water, and atmospheric air). Various parameters such as temperature distribution, liquid fraction, density, electrical conductivity, and thermal conductivity were measured for the PCM enclosed in a spherical container.The results show that adding nanoparticles to paraffin decreased the melting time by 9% and 14% for MWCNTs with 8 nm and 10–20 nm diameter, respectively. It also led to a decrease in solidification time of 23% for MWCNTs with a diameter of 8 nm and 28% for MWCNTs with a 10–20 nm diameter. Notably, the nanoparticles significantly impacted the solidification process more than melting.Additionally, this study shows that reducing the container's diameter from 68 to 48 mm resulted in a 40% reduction in melting time and a 47% reduction in solidification time. Changing the surrounding medium from oil to air and water further reduced solidification time by 16% and 48%, respectively.

Investigation on synergistic suppression of hydrogen explosion behaviors by ethylene and carbon dioxide

Hydrogen is getting more and more attention, but hydrogen safety is the foundation of the hydrogen economy. In this paper, 1.5% ethylene cooperates with carbon dioxide to suppress hydrogen explosions at normal temperature and pressure in a spherical container. The purpose of this paper is to solve the problem of the large amounts of traditional suppression materials needed to suppress hydrogen explosions. The experimental and simulation results show that 1.5% ethylene quenched active free radicals by cutting off chain reactions and suppressing hydrogen explosions with the endothermic and oxygen dilution effects of carbon dioxide. Even though 1.5% ethylene initially enhanced lean hydrogen explosions, the final experimental results showed that the synergistic effect of 1.5% ethylene and carbon dioxide demonstrated better performance, and the addition of carbon dioxide was reduced by up to 28%. This strategy offers new ideas for enhancing the capabilities of traditional suppression materials and preventing hydrogen explosions.

Inhibition effect of NH4H2PO4 on explosion flame propagation of aluminum alloy dust cloud

To investigate the inhibitory effect of NH4H2PO4 on the flame propagation of aluminum alloy dust clouds, experiments were conducted in cylindrical vertical ducts. High-speed cameras were employed to capture the explosion flames of aluminum alloy dust clouds under the coupled effect of NH4H2PO4 with different concentrations and particle sizes. The flame propagation behavior of NH4H2PO4/aluminum alloy dust was analyzed, and mathematical models were developed to describe the maximum distance and maximum velocity of NH4H2PO4 inhibition on the flame propagation of aluminum alloy dust clouds. Additionally, the inhibition characteristics of NH4H2PO4 on aluminum alloy dust explosions were studied in a 20 L spherical explosion container, and the thermal decomposition properties of NH4H2PO4 and aluminum alloy particles were investigated using a simultaneous thermal analyzer. Furthermore, the inhibition process of NH4H2PO4 on aluminum alloy dust was explored. The results demonstrate that the concentration of NH4H2PO4 has a greater impact on the inhibition effect on aluminum alloy dust, while the particle size has a smaller influence. Generally, as the concentration of NH4H2PO4 increases, the flame propagation distance and flame development rate decrease, leading to an enhanced inhibitory effect. The addition of NH4H2PO4 slows down the peak pressure of aluminum alloy dust explosions, resulting in a longer duration and smaller peak values of the “double-peak” pressure structure. When the particle size of NH4H2PO4 decreases and the concentration increases, the possibility of the “double-peak” structure decreases, forming a single-peak structure with lower peak values and pressure rise rates. The decomposition temperature of NH4H2PO4 precedes the combustion temperature of aluminum alloy particles. NH4H2PO4 absorbs thermal energy from the reaction system, exerting an inhibitory effect on aluminum alloy dust. The research findings provide valuable references for optimizing explosion suppression parameters and improving powder explosion suppression techniques.

Quasi-Packing Different Spheres with Ratio Conditions in a Spherical Container

This paper considers the optimized packing of different spheres into a given spherical container under non-standard placement conditions. A sphere is considered placed in the container if at least a certain part of the sphere is in the container. Spheres are allowed to overlap with each other according to predefined parameters. Ratio conditions are introduced to establish correspondence between the number of packed spheres of different radii. The packing aims to maximize the total number of packed spheres subject to ratio, partial overlapping and quasi-containment conditions. A nonlinear mixed-integer optimization model is proposed for this ratio quasi-packing problem. A heuristic algorithm is developed that reduces the original problem to a sequence of continuous open dimension problems for quasi-packing scaled spheres. Computational results for finding global solutions for small instances and good feasible solutions for large instances are provided.

Life cycle cost assessment for thermal insulation of above-ground spherical container with different capacities in hot fluid storage processes

Due to environmental and economic reasons, thermal energy saving has gained more importance especially in industry. This study is concerned with the application of insulation to improve thermal energy storage in spherical shaped containers positioned high above the ground. For this purpose, the thickness of the insulation applied to spherical containers of different diameters was optimized for convection and radiation heat transfer using life cycle cost analysis. In Turkey, the mechanism of storing the thermal energy of water at different temperatures in four different climatic conditions in Turkey (Ankara, Antalya, Erzurum, and Istanbul) in a container has been investigated. The results of the study show that the optimum insulation thickness and energy savings rise as the water storage temperature and the diameter of the container increase. While there is a 46% increase in the optimum insulation thickness for the vessel diameter from 0.5m to 3m in 20 °C water, a 69% increase is achieved in 100 °C water. Similarly, 85% and 114% increases were found for the optimum insulation thickness from 20 °C to 100 °C for 0.5m and 3m, respectively. In climates with the lowest heating degree-hours (Antalya), the highest energy savings are achieved with the lowest insulation thickness. To accurately determine seasonal storage heat load, a revised heating degree-hour method using hourly solar-air temperature data is recommended. This provides a 13% increase in energy savings.

Sensitivity of predicted stresses in thick‐walled steel/ceramics spherical FGM‐structures to parameter uncertainties

AbstractThe effects of both material data uncertainties of the constituents and of volume fraction deviations from the design values caused by the manufacturing process on the forecasted stresses in a spherical container of functionally graded material (FGM) are investigated. Specifically, a steel/alumina hollow sphere subject to internal pressure and homogeneous heating is studied. It is shown that even moderate uncertainties and deviations may cause large expectation ranges of von Mises equivalent stresses, and this issue may yet predominate over the question for the most reasonable homogenization scheme(s).

Phase behavior and dynamics in a colloid-polymer mixture under spherical confinement.

From studies via molecular dynamics simulations, we report results on structure and dynamics in mixtures of active colloids and passive polymers that are confined inside a spherical container with a repulsive boundary. All interactions in the fully passive limit are chosen in such a way that in equilibrium coexistence between colloid-rich and polymer-rich phases occurs. For most part of the studies the chosen compositions give rise to Janus-like structure: nearly one side of the sphere is occupied by the colloids and the rest by the polymers. This partially wet situation mimics approximately a neutral wall in the fully passive scenario. Following the introduction of a velocity-aligning activity to the colloids, the shape of the polymer-rich domain changes to that of an ellipsoid, around the long axis of which the colloid-rich domain attains a macroscopic angular momentum. In the steady state, the orientation of this axis evolves via diffusion, magnitude of which depends upon the strength of activity, but only weakly.