Solidification Process Of Materials Research Articles

Performance enhancement of latent heat thermal energy storage system by using spiral fins in phase change material solidification process

Latent heat thermal energy storage systems (LHTESS) have recently gained attention due to the critical demand for clean energy production and storage. The influence of spiral fins on the performance augmentation of a vertical tube-shell LHTESS in the solidification process was studied numerically. Different formation of fins which includes the quadruple, triple, double and single fins were studied. Amount of phase change material (PCM) mass inside the PCM enclosure was preserved equal in all cases and the length of the fins were adjusted for different fin numbers to keep the surface of heat transfer constant to find the optimized fin number. The phase change process was simulated by adopting the enthalpy-porosity technique. It was observed that the triple fin case outperformed other cases and the single fin case showed the least enhancement. When comparing the different cases while the heat transfer surface was kept constant, the triple fin case shows better performance in terms of time averaged Nusselt number and total solidification time respectively. It was revealed that the performance enhancement was not directly proportional with the number of fins and there was a trade-off between fin number and length of each fin.

Investigation of phase change material solidification process in a LHTESS in the presence of fins with variable thickness and hybrid nanoparticles

Present study deals with performance improvement of Latent Heat Thermal Energy Storage Systems (LHTESS) with Phase Change Material (PCM) during the solidification process. The released thermal energy during the solid-liquid phase change is stored in LHTESS. Due to poor thermal conductivity of conventional PCMs, Al2O3-Go hybrid nanoparticles are dispersed into the pure PCM to make Hybrid Nano-Enhanced Phase Change material (HNEPCM). Moreover, fins with variable thickness are applied to expedite the solidification process. In this paper, separate analyzes are investigated for evaluating the effects of adding fins and hybrid nanoparticles. At first, the influence of fin geometric parameters on the solidification acceleration is analyzed, and the best fin configuration is determined using Response Surface Method (RSM) optimization. Then, the influence of dispersing hybrid nanoparticles with different volume fractions into the pure PCM on the solidification rate is reviewed. Also, the outcomes of accelerating the solidification process by using fins and hybrid nanoparticles are compared together. In this study, the unsteady governing equations of the solidification process are solved numerically using standard Galerkin Finite Element Method (FEM). Results depicted that employing optimized fin results in higher solid fraction rate in comparison with dispersing hybrid nanoparticles into the PCM.

Investigations of Energy Density Effects on Forming Accuracy and Mechanical Properties of Inconel 718 Fabricated by LENS Process

The amount of heat input, expressed as energy density, is one of the key parameters for laser additive manufacturing process. It will affect the melt pool dynamics, such as melt pool/powder interaction and temperature distribution, during the material solidification process, thus exerting an important influence on the forming accuracy and properties of the fabricated part. This paper investigates the effect of energy density on the forming accuracy and physical/mechanical properties of Inconel 718 part fabricated by LENS technique. Specifically, geometrical accuracy and relative density are measured with thin wall specimens. Surface roughness test is performed with block specimens. Based on the experimental results of the forming accuracy, relative density, and surface roughness, the suggested energy density ranges from 83.33 J/mm2 to 137.5 J/mm2.

Local Exact Controllability of Two-Phase Field Solidification Systems with Few Controls

We analyze a control problem for a phase field system modeling the solidification process of materials that allow two different types of crystallization coupled to a Navier–Stokes system and a nonlinear heat equation, with a reduced number of controls. We prove that this system is locally exactly controllable to suitable trajectories, with controls acting only on the motion and heat equations.

Discharging process of a finned heat pipe–assisted thermal energy storage system with high temperature phase change material

This paper presents the results of a numerical study conducted to investigate the discharging process of a latent heat thermal energy storage system assisted by finned heat pipes. A two-dimensional finite volume based numerical model along with enthalpy-porosity technique is employed to simulate the phase change of storage media during the discharging mode. The thermal energy storage system in this study consists of a square container, finned heat pipes, and potassium nitrate (KNO3) as the phase change material. The charging process of the same thermal energy storage system was reported in an early paper by the authors. This paper reports the results of discharging process of the thermal energy storage system. The influences of heat pipe spacing, fin geometry and quantities as well as the effects of natural convection heat transfer on the thermal performance of the storage system were studied. The results indicate that the phase change material solidification process is hardly affected by the natural convection. Decreasing the heat pipe spacing results in faster discharging process and higher container base wall temperature. Increasing the fins length does not change the discharging time but yields higher base wall temperature. Using more fins also accelerates the discharging process and increases the container base wall temperature.

ANALYSIS AND CHARACTERIZATION OF DENDRITE STRUCTURES FROM MICROSTRUCTURE IMAGES OF MATERIAL

Digital Image processing (DIP) and Computer vision (CV) techniques have great support role in material manufacturing by providing precise insight of materials. The morphology of constituents in metal alloys basically depends on the process of solidification. The solidification method (air, oil or water) and time are the reasons for definite morphology of constituents. Dendrite structures are one of the, such morphological structures and many important properties of materials are closely related to the morphology of the dendrite. The information about solidification process of materials is a must-know information in the process of production of materials which can be extracted through characterization of dendrite structures. In this paper, an automated and robust method that comprises of image processing, computer vision and serial sectioning techniques as a means of 3D characterization of the solidified microstructures of magnesium-based alloys is presented. The phase fraction and morphologies of intermetallics of magnesium –aluminium alloy material are determined. The results obtained by proposed method are compared with the manual computations based on the Scheil–Gulliver solidification model [12,13] for the authenticity of proposed method. The comparison of results indicates that the results of the proposed method are much accurate compared to other methods. Therefore, the proposed method will enable a comprehensive understanding of solidification variables, microstructure, and properties.

Micromolding of Polymer Nanocomposites Diagnosed by Ultrasound

Miniaturized ultrasonic sensors, fabricated onto the mold insert of a micromolding (MM) machine, have been applied for real-time diagnosis of micromolding of polymer nanocomposites, nylon66 with polyhedral oligomeric silsesquioxanes (POSS) as nanofiller. The process dynamics, such as melt arrival, mold open and part detachment, were successfully monitored during molding. Ultrasound was capable of measuring peak injection pressure and material solidification process. In the pressure range between 50 and 150 MPa, the ultrasonic velocity linearly increased with a changing ratio of 2.6(m/s)/MPa. It was also found that concentration of the nanofiller (POSS) could be evaluated by using ultrasonic velocity measurement. In the concentration range of POSS between 0% and 8% the ultrasonic velocity linearly decreased with a changing ratio of 7.38(m/s)/%. The presented ultrasonic sensors and technique optimize the micromolding of nanocomposites, and improve the part quality and process efficiency by controlling mold cycle time.

The rapid solidification processing of materials: science, principles, technology, advances, and applications

The purpose of this technical manuscript is to present an explanation of rapid solidification processing in an easily understandable manner so that the technique is widely accepted and put to commercial practice by many working in the industries of materials processing and manufacturing engineering. The comprehensive review article presents a comprehensive overview of the widely accepted and used rapid solidification processes. To better, understand rapid solidification in comparison with conventional solidification, the intrinsic aspects and types of nucleation and the kinetics governing nucleation and subsequent growth of the crystal during rapid solidification are presented and discussed. The commercially viable methods for the rapid solidification processing of metal-based and even intermetallic-based composites are presented. The technically viable methods for the consolidation of rapidly solidified powders are discussed. A succinct description of notable recent advances in the technique of spray processing is presented. In the last section of this article, we highlight the key findings of selected studies in the area of rapid solidification processing of advanced metallic, intermetallics, and composite materials that have helped to advance the processing technique for emerging applications that is synchronous with advances in technology.

Inverse method with heat and entropy transport in solidification processing of materials

An inverse formulation is presented for phase change heat transfer with applications in materials processing such as casting solidification. The scheme predicts the proper transient boundary conditions in order to achieve a prescribed solid–liquid interface motion, as well as corresponding desired interface characteristics (i.e. planar interface). In addition to heat transfer, the model considers entropy transport for effective enhancement of the overall formulation. In particular, the second law of thermodynamics is applied in a corrective manner to support stable computations in the event of non-physical numerical results, such as numerical oscillations. Both heat and entropy transport models are implemented in a control-volume-based finite element formulation of the phase change governing equations. Numerical results are presented for sample problems in order to examine the performance of the inverse algorithm. These results indicate promising performance and good agreement with available analytic solutions. In the application problems, numerical stability is achieved with entropy based corrections of computations during solidification.