Energy Shell Research Articles

Modeling and topology optimization of cylindrical shells with partial CLD treatment

This paper presents a unified modeling approach for cylindrical shells with partial constrained layer damping (CLD) treatment under general boundary conditions, followed by topology optimization studies of the CLD layout to realize desired damping performance. Initially, the equations of motion for cylindrical shells are formulated using the Rayleigh–Ritz method. Donnell’s shell theory is used to calculate the elastic strain energy of shells. Artificial springs are applied to represent general boundary conditions. Then, the evolutionary structural optimization method is employed to achieve optimal distribution of CLD. The proposed model is validated by comparing present results with those from literature and finite element simulations. With the validated modeling approach, the vibration characteristics of cylindrical shells with partial CLD treatment are studied. And the effectiveness of proposed topology optimization method is investigated comprehensively regarding different thickness ratios of constraining layer to viscoelastic layer under various boundary conditions.

Numerical investigation of using helical fins for the enhancement of the charging process of a latent heat thermal energy storage system

This paper is focused on the enhancement of the thermal performance of a vertically oriented shell and tube latent heat thermal energy storage (LHTES) system by using helical fins. In order to see the improvement made by using the helical fin in a LHTES unit, the performance of the helically finned LHTES system has been compared with those of axially finned LHTES system, and no finned LHTES system. The length of the helical fin in the helically finned LHTES system is considered equal to the total length of the four axial fins used in the axially finned LHTES system and the net volume of the PCM is supposed to be identical for all studied cases. Three different temperatures of 345 K, 355 K, 365 K have been considered for the inner tube wall. Results revealed that for the helically finned TESS, the total melting time of the PCM can be reduced up to 18.25%, 21.5% and 16.75% in comparison with axially finned LHTES system for the inner tube wall temperatures of 345, 355 and 365 K, respectively. The presence of a helical fin causes the penetration of the heat into the core of the PCM inside the container and the motion of the molten PCM will be affected by the result of the buoyancy forces and the centrifugal force. Thus, there will be both transverse convection and longitudinal convection for the helically finned LHTES system. Besides, for the helically finned LHTES system, the PCM receives the needed heat for its full melting (charging) in less time compared to the axially finned LHTES system. This is due to the helicity of the molten PCM and also the formation of the vorticities due to the existence of the helical fin which contributes to deeper penetration of the heat and melt front.

A nano-compression model to characterize the elastic properties of core–shell structured microspheres

Nano-compression is a convenient approach for investigating the elastic modulus of microcapsule shells by compressing a core–shell structured microsphere between two parallel plates in nanoscale. A nano-compression model was developed through energy minimization, which avoids determining the complicated load distribution at interface. The total potential energy of microcapsule includes the work done by compression load and the strain energy of shell and core. By minimizing the total potential energy, the correlation among the compression load, the compression displacement, and the elastic and geometric parameters of microcapsules was derived. With this model, the shell elastic modulus then can be evaluated by fitting the loading responses of microcapsules. To validate the proposed model, nano-compression tests were conducted on PMMA microcapsules. The elastic moduli for PMMA shells evaluated by the nano-compression model agree well with the reference value with a maximum relative error of -12.12%. The elastic moduli of the PMMA shells determined by the nano-compression model were then used in finite element simulations to predict the compression load–displacement curves, which show good agreement with those measured in experiments with a relative error within ±9.64%.

Enhanced laser-energy coupling with small-spot distributed phase plates (SG5-650) in OMEGA DT cryogenic target implosions

Cryogenic deuterium–tritium ice target implosions on OMEGA with new small-spot (SG5-650) distributed phase plates (DPPs) achieved an (11±4)% increase in energy coupling compared to implosions with larger-spot SG5-850 DPPs by decreasing the ratio of the laser spot diameter to the target diameter from 0.93 to 0.75. The SG5-650 DPPs provide a focus spot size of 674 μm, which is defined as the diameter that encircles 95% of the measured beam energy compared to 834 μm for the SG5-850, which are the standard DPPs in cryogenic target implosions on OMEGA. The hydrodynamic efficiency, defined as the ratio of the kinetic energy in the imploding shell to the laser energy, increased from 4.5% to 5.0% based on radiation-hydrodynamic calculations benchmarked to shell trajectory and bang-time measurements. The higher coupling came with a trade-off of an increased hot-electron production as well as increased hydrodynamic instabilities seeded by a larger mode-10 amplitude from the beam port geometry, both of which may have reduced the fusion neutron production and areal density.

Ionization energy and valence electron orbital binding energy of superheavy element Og(<i>Z</i> = 118) and its homologs

The ionization energy of the superheavy element Og (<i>Z</i> = 118) and its homolog elements Ar, Kr, Xe, Rn, and their ions are systematically calculated by using the GRASP2K program based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method, taking into account relativistic effects, electron correlation effects between valence shell electrons, quantum electrodynamics effects, and Breit interaction. To reduce the uncertainty of the ionization energy derived from electron correlation effects which are not fully considered, the ionization potential of the superheavy element Og<sup>0–2+</sup> and its homolog element Rn<sup>0–2+</sup> are extrapolated by the extrapolation method. The ionization energy of extrapolated Rn<sup>0–5+</sup> and Og<sup>5+</sup> coincide well with experimental and other theoretical values. These results can be used to predict the unknown physical and chemical properties of the atoms and compounds of the superheavy element Og. In addition, the calculation results of the electron orbital binding energy of the atomic valence shell of the superheavy element Og and its homolog elements Ar, Kr, Xe, and Rn under relativistic and non-relativistic conditions show that owing to the relativistic effect, there occur strong orbital contraction phenomena in the 7s orbital and 7p<sub>1/2</sub> orbital and strong splitting phenomena in the 7p<sub>1/2 </sub> orbital and 7p<sub>3/2</sub> orbital of Og, which may cause the physical and chemical properties of the superheavy element Og to differ from those of other homologs.

Ionization energy and valence electron orbital binding energy of the superheavy element Og(Z=118) and its homologs

The ionization energy of the superheavy element Og (Z=118) and its homolog elements Ar, Kr, Xe, Rn, and their ions were systematically calculated using the GRASP2K program based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method, taking into account relativistic effects, electron correlation effects between valence shell electrons (VV), quantum electrodynamics (QED) effects, and Breit interaction. To reduce the uncertainty of the ionization energy derived from electron correlation effects which are not fully considered, the ionization potential of the superheavy element Og<sup>0-2+</sup> and its homolog element Rn<sup>0-2+</sup> are extrapolated by the extrapolation method. The ionization energy of extrapolated Rn<sup>0-5+</sup> and Og<sup>5+</sup> coincides well with experimental and other theoretical values. These results can be used to predict the unknown physical and chemical properties of the atoms and compounds of the superheavy element Og. In addition, the calculation of the electron orbital binding energy of the atomic valence shell of the superheavy element Og and its homolog elements Ar, Kr, Xe, and Rn under relativistic and non-relativistic conditions shows that due to the relativistic effect, there is a strong orbital contraction phenomenon in the 7s and 7p<sub>1/2</sub> orbitals and a strong splitting phenomenon occurs in the 7p<sub>1/2</sub>and 7p<sub>3/2</sub> orbitals of Og, which may cause the physical and chemical properties of the superheavy element Og to be different from other homologs.

From nematic shells to nematic droplets: energetics and defect transitions.

In this work, we investigate the possibility of inducing valence transitions, i.e. transitions between different defect configurations, by transforming a nematic shell into a nematic droplet. Our shells are liquid crystal droplets containing a smaller aqueous droplet inside, which are suspended in an aqueous phase. When osmotically de-swelling the inner droplet, the shell progressively increases its thickness until it eventually becomes a single droplet. During the process, the shell energy landscape evolves, triggering a response in the system. We observe two different scenarios. Either the inner droplet progressively shrinks and disappears, inducing a defect reorganization, or it is expelled from the shell at a critical radius of the inner droplet, abruptly changing the geometry of the system. We use numerical simulations and modeling to investigate the origin of these behaviors. We find that the selected route depends on the defect structure and the energetics of the system as it evolves. The critical inner radius and time for expulsion depend on the osmotic pressure of the outer phase, suggesting that the flow through the shell plays a role in the process.

Experimental investigation of shellac wax as potential bio-phase change material for medium temperature solar thermal energy storage applications

Thermal performance of shellac wax as a novel bio-phase change material (BPCM) and Therminol®-55 as heat transfer fluid (HTF) in a vertical shell and tube latent heat thermal energy storage (LHTES) unit is analyzed experimentally. Operational parameters considered, namely HTF flow rate and inlet temperature in the range of 2–5 LPM and 100–120 °C, respectively. The comprehensive study of contours and plots reveals the impact of natural convection and the progress of the melting and solidification front in the charging and discharging process. As the HTF flow rate increases, the charging rate improves considerably, and a maximum reduction in melting time is obtained as 43.6% for 4 LPM. The maximum reduction in melting time and storage efficiency are 42.2% and 73.4%, respectively, at 120 °C and 4 LPM. However, the discharging process's increased flow rate has no significant effect on solidification and discharge efficiency, which attributes the dominant mode of heat transfer is conduction during the solidification. Shellac wax storage efficiency is comparable to existing paraffin wax, stearic acid and palmitic acid-based LHTES unit. In this regard, shellac wax can be a potential Bio-PCM for medium temperature range (60–80 °C) solar thermal applications such as domestic water heating and food drying.

Optimization of Nano-Additive Characteristics to Improve the Efficiency of a Shell and Tube Thermal Energy Storage System Using a Hybrid Procedure: DOE, ANN, MCDM, MOO, and CFD Modeling

Using nano-enhanced phase change material (NePCM) rather than pure PCM significantly affects the melting/solidification duration and the stored energy, which are two critical design parameters for latent heat thermal energy storage (LHTES) systems. The present article employs a hybrid procedure based on the design of experiments (DOE), computational fluid dynamics (CFD), artificial neural networks (ANNs), multi-objective optimization (MOO), and multi-criteria decision making (MCDM) to optimize the properties of nano-additives dispersed in a shell and tube LHTES system containing paraffin wax as a phase change material (PCM). Four important properties of nano-additives were considered as optimization variables: volume fraction and thermophysical properties, precisely, specific heat, density, and thermal conductivity. The primary objective was to simultaneously reduce the melting duration and increase the total stored energy. To this end, a five-step hybrid optimization process is presented in this paper. In the first step, the DOE technique is used to design the required simulations for the optimal search of the design space. The second step simulates the melting process through a CFD approach. The third step, which utilizes ANNs, presents polynomial models for objective functions in terms of optimization variables. MOO is used in the fourth step to generate a set of optimal Pareto points. Finally, in the fifth step, selected optimal points with various features are provided using various MCDM methods. The results indicate that nearly 97% of the Pareto points in the considered shell and tube LHTES system had a nano-additive thermal conductivity greater than 180 Wm−1K−1. Furthermore, the density of nano-additives was observed to be greater than 9950 kgm−3 for approximately 86% of the optimal solutions. Additionally, approximately 95% of optimal points had a nano-additive specific heat of greater than 795 Jkg−1K−1.

Tunable Performance of Quantum Dot-MoS2 Hybrid Photodetectors via Interface Engineering.

Heterostructures of quantum dots (QDs) and two-dimensional (2D) materials show promising potential for photodetection applications owing to their combination of high optical absorption and good in-plane carrier mobility. In this work, the performance of QD-2D photodetectors is tuned by band engineering. Devices are fabricated by coating MoS2 nanosheets with InP QDs, type-I core-shell InP/ZnS QDs, and type-II core-shell InP/CdS QDs. Comparative spectroscopic and photoelectric studies of different hybrids show that the energy band alignment and shell thickness can influence the efficiency of charge transfer (CT), energy transfer (ET), and defect-related processes between QDs and MoS2. Benefiting from efficient CT between the QDs and MoS2, a significant enhancement of responsivity and detectivity is observed in thick-shell InP/CdS QD-MoS2 devices. Our results demonstrate the feasibility of using core-shell QDs for regulating the ET and CT efficiency in heterostructures and highlight the importance of interface band design in QD-2D and other low-dimensional photodetectors.

Optimization of shell and tube thermal energy storage unit based on the effects of adding fins, nanoparticles and rotational mechanism

According to the high storage capacity of latent heat thermal energy storage (LHTES) systems, finding a suitable solution to compensate for the weakness of these systems is logical. The main weakness of these systems is the low thermal conductivity of phase change materials (PCMs) as the storage reservoir of thermal energy. Many methods have been proposed previously to overcome this limitation. Most of these methods can be divided into three types that including changes in the geometric configurations, improving thermophysical properties of PCMs and applying external conditions to improve the LHTES systems' performance. Nonetheless, limited studies have been conducted with combination approaches between these methods. In line with this, the present study investigates the effect of combining three different types of improvement methods in the applicable ranges simultaneously. These methods are selected based on utilizing three different ways to heat transfer rate enhancement. So that these ways include increasing heat transfer area (by adding fins), increasing natural convection effect (by adding rotational mechanism) and improving the thermal conductivity of PCM (by adding Cu nanoparticles). Results show that the combination of these methods has a significant effect on the improving performance of LHTES system during charge and discharge processes. So that increasing productivity of each method leads to decreasing melting and solidification times and following this heat transfer rate enhancement. Based on comparing results, rotational speed increment has the highest effect on increasing heat transfer rate in charge and discharge processes. Moreover, since storage and release capacities are important parameters in the LHTES systems, to shed further light on the impact of utilizing combination methods on reducing these capacities, an optimization process is conducted by the response surface methodology (RSM). Optimization results present an optimal case based on the highest heat transfer rate with the highest storage and release capacities in charge and discharge process. Comparing results between simple and optimal cases show that applying optimal conditions leads to enhancing heat transfer rate significantly based on decreasing melting and solidification time at about 74% and 70%. While based on this comparison, storage and release capacities are reduced by just 2.5% and 4.1%, respectively.

Modified hybrid CdSe/ZnS quantum dots and their size dependent unique characteristics

In this study, CdSe-based hybrid CdSe/ZnS quantum dots were synthesized. Their optical properties have been proven using absorption and luminescence spectroscopy methods. After the ZnS shell was grown on the surface shell of CdSe nanoparticles, the photoluminescence stability and shelf life of the quantum dots increased significantly. The energy of the outer shell has increased. Absorption and luminescence spectra shifted to a shorter wavelength range. The size of the nucleus decreased from 3.7 nm to 2.8 nm. The surface was stabilized with oleic acid as an active ligand. After stabilization with the surfactant, the average total hydrodynamic size of the nanoparticles increased.

Experimental and numerical investigation of melting/solidification of nano-enhanced phase change materials in shell & tube thermal energy storage systems

In this work, the melting/solidification process of the nano-enhanced phase change materials (NePCM) was investigated experimentally and numerically using a horizontal shell & tube heat exchanger equipped with longitudinal fins. The NePCM was prepared by dispersing titanium dioxide nanoparticles (TiO2NPs) in stearic acid (SA). The effect of geometry parameters and nano particle content on melting/solidification rate of PCM were investigated. The results showed that using longitudinal fins could reduce the required time for melting and solidification by around 54% and 76%, compared to the system without fins, respectively. while the greatest effect of adding the TiO2-NPs was related to unfinned tube heat exchanger, which reduced the required time by 6% and 8% for melting and solidification, respectively. Furthermore, it was concluded that adding nanoparticles could offer its positive effect for enhancing the melting rate only while using unfinned tube heat exchanger.

Relationships between Molecular Structure of Carbohydrates and Their Dynamic Hydration Shells Revealed by Terahertz Time-Domain Spectroscopy.

Despite more than a century of research on the hydration of biomolecules, the hydration of carbohydrates is insufficiently studied. An approach to studying dynamic hydration shells of carbohydrates in aqueous solutions based on terahertz time-domain spectroscopy assay is developed in the current work. Monosaccharides (glucose, galactose, galacturonic acid) and polysaccharides (dextran, amylopectin, polygalacturonic acid) solutions were studied. The contribution of the dissolved carbohydrates was subtracted from the measured dielectric permittivities of aqueous solutions based on the corresponding effective medium models. The obtained dielectric permittivities of the water phase were used to calculate the parameters describing intermolecular relaxation and oscillatory processes in water. It is established that all of the analyzed carbohydrates lead to the increase of the binding degree of water. Hydration shells of monosaccharides are characterized by elevated numbers of hydrogen bonds and their mean energies compared to undisturbed water, as well as by elevated numbers and the lifetime of free water molecules. The axial orientation of the OH(4) group of sugar facilitates a wider distribution of hydrogen bond energies in hydration shells compared to equatorial orientation. The presence of the carboxylic group affects water structure significantly. The hydration of polysaccharides is less apparent than that of monosaccharides, and it depends on the type of glycosidic bonds.

Potential energy surfaces and fission fragment mass yields of even-even superheavy nuclei * *Supported by the Polish National Science Center (2018/30/Q/ST2/00185) and the National Natural Science Foundation of China (11961131010, 11790325)

Potential energy surfaces and fission barriers of superheavy nuclei are analyzed in a macroscopic-microscopic model. The Lublin-Strasbourg Drop (LSD) model is used to obtain the macroscopic part of the energy, whereas the shell and pairing energy corrections are evaluated using the Yukawa-folded potential; a standard flooding technique is utilized to determine barrier heights. A Fourier shape parametrization containing only three deformation parameters is shown to effectively reproduce the nuclear shapes of nuclei approaching fission. In addition, a non-axial degree of freedom is taken into account to better describe the structure of nuclei around the ground state and in the saddle region. In addition to the symmetric fission valley, a new highly asymmetric fission mode is predicted in most superheavy nuclei. The fission fragment mass distributions of the considered nuclei are obtained by solving 3D Langevin equations.

Parametric scaling of a magnetic field-reversed conducting coil assembly for radiation shielding

• The geometric scalability of a novel form of active magnetic shield is analyzed • This scalable shield offers an expandable shell of concentrated magnetic energy • Tabletop experiments verify computational models of amplifying and canceling magnetic flux We explore the design scalability of an active magnetic shield for protecting against isotropic radiation, such as galactic cosmic rays in deep space. Each shield is composed of two concentric, elliptical layers of circular conducting coils, each arranged like lines of latitude on a globe, with the current modulated to amplify the magnetic field in the layer between the ellipses, and canceling within. The efficacy of this field-reversed array for creating a shell of magnetic energy to protect a central object from isotropic radiation is explored using quantitative analyses of incident particle momentum. The parametric scalings are verified through ANSYS magnetostatic modeling and corresponding 3D-printed test article demonstrations matching vector magnetic field models. The quantitative parameters utilized here can be applied to constrain and optimize magnetic shielding requirements of this type with respect to size, maximum current, total number of coils, and mass. We will also demonstrate that these parametric scalings can help design future experimental tests of this shield type for deflecting any class of incident radiation.

Numerical Study for the Tube Rotation Effect on Melting Process in Shell and Tube Latent Heat Energy Storage LHES System

Although renewable energy systems have become an interesting global issue, it is not continuous either daily or seasonally. Latent heat energy storage (LHES) is one of the suitable solutions for this problem. LHES becomes a basic element in renewable energy systems. LHES compensate for the energy lack when these systems are at low production conditions. The present work considered a shell and tube LHES for numerical investigation of the tube rotation influence on the melting process. The simulation and calculations were carried out using ANSYS Fluent software. Paraffin wax represents the phase change material (PCM) in this work, while water was selected to be the heat transfer fluid (HTF). The calculations were carried out for 9 rpm tube rotation case as well as the stationary case. The results show a slight increase in the liquid content of phase change material PCM due to tube rotation. The enhancement percentage in liquid content was 3.5% for 6 hrs charging process. The heat transfer in the axial direction was small relative to that in the radial direction.

A novel analytical approach to study the charging characteristics of a shell and tube thermal energy storage system

AbstractThis study presents a novel analytical solution of the phase change problem in a shell and tube arrangement of latent heat thermal energy storage (LHTES) system. The transient melting behavior of phase change material (PCM) is captured using time‐dependent boundary conditions and moving interface energy equation. An approximate mathematical model is developed with the help of dimensionless number (η), exponential integral function, Lambert W function, and Swamee and Oijha approximation. The proposed analytical solution is used for investigating the thermal performance of low, medium, and high melting temperature PCM for building, solar absorption cooling, and concentrated solar power (CSP) applications, respectively. The results obtained from the analytical approach are compared with a numerical model based on the enthalpy method. It is found that the root mean square difference between the average PCM temperature obtained from analytical solution and detailed numerical analysis is 3.3°C, 1.2°C, and 0.1°C for the low, medium, and high‐temperature systems, respectively. The temporal variation of melt front position and the effect of inner tube temperature are further investigated using the analytical solution. The mathematical model could be proposed as an effective tool for the assessment of shell and tube LHTES systems.

Dominant roles of eccentricity, fin design, and nanoparticles in performance enhancement of latent thermal energy storage unit

In this paper, numerical and experimental investigations of thermal performance enhancement of horizontal longitudinal shell and tube latent heat thermal energy storage unit (LHTESU) via eccentricity (e), fin design optimization, and nanoparticles in the phase change material (PCM) of stearic acid are presented. An enthalpy-porosity-based two-dimensional, transient numerical methodology is used after validating against the experimental results and the literature. Five different eccentric positions, e = 0.14, 0.28, 0.42, 0.56, and 0.63 are investigated by modifying the design of Y-finned tube. The eccentricity and fin design modifications improved natural convection effects as compared to concentric Y-finned tube. Thermal performances of LHTESU are analyzed on the basis of melting time, heat storage capacity, heat storage rate, and performance enhancement ratio. Based on the performance analysis, an optimum eccentric configuration of LHTESU is proposed. For optimized eccentric unit (e=0.42), a reduction of 34.14% in melting time along with 30.7% improvement in thermal energy storage rate is achieved as compared to concentric (e=0) LHTESU. The effect of temperature of the tube on PCM's melting time and heat transfer is also analyzed and two important correlations are proposed. The thermal performance of the optimized eccentric unit is further enhanced by adding nanoparticles of Al2O3 and CuO ranging from 0.5% to 10% by volume in the pure PCM. The nano-enhanced PCM with 1% of Al2O3 further improves melting and energy storage rates of optimum LHTESU by 10%.

Rational Design of Nonbonded Point Charge Models for Highly Charged Metal Cations with Lennard-Jones 12-6 Potential.

Here, we developed nonbonded point charge models using a simple Lennard-Jones (LJ) 12-6 potential for highly charged metal cations (18 trivalent and 6 tetravalent ions) for use with 11 water models of TIP3P, OPC3, SPC/E, SPC/Eb, TIP3P-FB, a99SB-disp, TIP4P-Ew, OPC, TIP4P/2005, TIP4P-D, and TIP4P-FB. The designed models simultaneously reproduce the hydration free energy (HFE) and ion-oxygen distance (IOD) in the first hydration shell with an error within 1 kcal/mol and 0.01 Å on average, respectively, and yield reasonable coordination numbers for most cations. Such performance is equivalent to the previously reported point charge models using a more complex 12-6-4 LJ-type potential, while the LJ R parameters of our models are much close to Shannon's revised effective ion radii than that of the 12-6-4 models. Our designed models overestimate the diffusion constants of several trivalent ions by 5-68%. The performance in predicting osmotic coefficients of trivalent chlorides in aqueous solution depends on the salt type. A calibration of cation-anion interacting LJ parameters reproduces the experimental osmotic coefficients of an AlCl3 solution at 0.2-3.0 mol/L. The effectiveness of our new models is further demonstrated by simulating a metalloprotein system with four force field/water combinations. This work facilitates accurate modeling of metal-containing systems by a variety of force fields and water models in aqueous solution.