Solidification Time Research Articles

Numerical Investigation of the Effect of the Mushy Zone Parameter and the Thermal Properties of Paraffin‐Based PCMs on Solidification Modeling Under T‐History Conditions

ABSTRACTPhase change materials (PCMs) are widely used in various critical applications because of their capacity to store thermal energy and regulate temperature effectively. A review of the literature on PCM solidification and melting simulations reveals that the accuracy of these simulations is highly dependent on the input parameters and underlying assumptions used in the software. Among the key factors influencing precise simulation results are the parameter of mushy zone () and the thermal properties of the material. This study numerically investigated the impact of the and thermal properties on the solidification behavior of a paraffin in the test tube under T‐history conditions. The analysis was conducted using the commercial CFD software ANSYS Fluent and the enthalpy‐porosity method is applied to simulation the solidification process. To accurately reflect the conditions of the T‐history experiment, radiative heat transfer between surfaces was employed for the boundary conditions, ensuring a realistic representation of the experimental setup. An evaluation of four thermal properties—thermal conductivity, density, latent heat, and specific heat—indicates that while an increase in latent heat, density, and specific heat slows down the rate of solidification, an increase in thermal conductivity has the opposite effect, accelerating the solidification process. The results further emphasize that selecting an appropriate value for is crucial for achieving accurate solidification simulations. Increasing from to enhanced the prediction accuracy of the solidification time by 10%. Additionally, the mushy zone parameter significantly affects the shape and progression of solidification. As increases, solidification in the lower layers decreases, concentrating the process more in the layers adjacent to the cold wall.

Utilizing biomass-derived activated carbon hybrids for enhanced thermal conductivity and latent heat storage in form-stabilized composite PCMs

ABSTRACT In this study, the focus was on developing multifunctional organic form-stabilized composite phase change materials (PCMs) to efficiently manage thermal energy and promote sustainable energy utilization. The novel composite PCMs were designed and synthesized by incorporating Methyl stearate (MtS) as the PCM with pristine activated carbon derived from coconut shells (CAC) and thermally enhanced CAC@Graphene nanoplatelets (GnP) hybrid matrices. Particularly, the combination of CAC90@GnP10/MtS allowed the composite PCM to exhibit excellent thermophysical responses, capitalizing on the unique properties and synergistic effects of each component. The resulting composite PCM from this combination demonstrated remarkable performance, with a high loading ratio of 70% and a latent heat of 160.87 J/g, which is 27.52% higher than that of the pristine CAC-supported PCM. The test results indicated that the chemical and crystal structure of MtS remained unaffected after the composite formation. The thermal conductivity of CAC90@GnP10/MtS was found to be 102.85% higher than CAC/MtS and 195.83% higher than MtS alone. The enhancement in thermal conductivity was further validated through observed reductions in melting and solidification times, as well as analysis using infrared thermal imaging. In conclusion, the development of these intelligent, multifunctional composite PCMs, which utilize CAC@GnP hybrids as supporter scaffolds and thermal conductivity enhancers for MtS, holds great promise for effective sustainable energy usage and thermal energy management systems in various fields like waste heat utilization, energy-saving buildings, constant temperature protection, thermal management of electronic devices, aerospace industry, textiles, automotive, and renewable energy systems.

Laser‐Based Closed‐Loop Controlled Heat Treatment for Residual Stress Relief of Additively Manufactured AlSi10Mg Components

In laser powder bed fusion of metals small melt pools with extremely short solidification times and steep temperature gradients to the surrounding material exist due to the layer‐wise and selective melting process with small areas of energy input compared to the cooler, solid ambient material. This causes high thermally induced residual stresses (RS), which can lead to the immediate rejection of the component due to critical part deformation and inhomogeneous mechanical properties under load. To prevent this, furnace‐based stress relief heat treatments are commonly applied before cutting‐off the part from the built platform. In this study a novel closed‐loop controlled laser‐based heat treatment using temperature feedback through inline pyrometer measurement is investigated, enabling a fast and highly efficient postprocess stress relief. Therefore, a laser beam is guided by a scanner optics in a meandering pattern over the top surface of AlSi10Mg cantilever specimens. It enables a decrease of near‐surface RS from 158 to 5 N mm−2, resulting in a reduction of displacement by over 90% at material affecting depths up to 3 mm and area rates of 8 to 163 mm2 s−1.

Experimental Performance Evaluation of a Dual-purpose Photovoltaic-thermal System with Phase Change Material for Passive Heating and Cooling

Photovoltaic thermal technology (PVT) is gaining increasing attention due to its improved performance and reliability made possible by continuous technological advances. Despite these significant advances, the potential of PVT modules to simultaneously heat, cool and generate electricity passively remains unexplored. In this study, we developed a dual-purpose PVT collector that can passively heat and cool to improve both electrical efficiency and thermal energy management, without relying on external power supply. By using CaCl2-6H2O as an inorganic phase change material (PCM), the latent heat of fusion of the PCM passively cools the circulating air and thus improves the electrical efficiency of the PVT module. The cooling and heating performance of the system was analyzed using CFD (Computational Fluid Dynamics) simulations conducted with ANSYS FLUENT. Subsequently, the experimental performance of the system was evaluated in two periods — September and December — in a greenhouse under the climate conditions of Tehran, Iran. The results showed an 11.28% increase in cooling efficiency and a 4.23% improvement in power generation efficiency for the PVT-PCM collector, while an 18.86% improvement in heating efficiency was achieved over a longer period. In September, the observed cooling efficiency was12.92%,1.64% below the value predicted by the simulations. While the simulations calculated a heating efficiency of 20.31%, the tests conducted in December showed an actual efficiency of 18.86%. During the night-time heating, the PCM solidified in 130 minutes, while the simulations predicted a solidification time of 120 minutes. The predicted and actual values showed a strong correlation, with an R-squared value of 0.9923. These results underline the effectiveness of the passive cooling and heating system in greenhouses and demonstrate its ability to improve electrical efficiency.

Numerical investigation on consecutive charging and discharging of PCM with Modified longitudinal fins in shell and tube thermal energy storage

This study proposes six modified longitudinal fins in a shell and tube heat exchanger unit to see how the modification affects the charging and discharging of PCM. The proposed cases are modifications to the traditional rectangular shape (Case 1), employing a tapering shape (Case 2), inverse tapering shape (Case 3), herringbone wavy shape (Case 4), convex shape (Case 5), and constricted shape (Case 6). A two-dimensional computational model is applied by applying the enthalpy-porosity method. Transient simulations are conducted with the inclusion of the natural convection effect for melting and solidification. The influence of the proposed designs on the solid-liquid interface is evaluated by observing liquid fraction and temperature distribution. The cases are compared by the total time for phase transition and time savings percentage. It is found that Case 4 (herringbone wavy shape) stands out over all the cases in terms of total phase transition time, melting time and solidification time, showing a better performance by 10.93 %, 8.48 % and 12.31 % improvement respectively, compared to the traditional rectangular case (Case 1). On the other hand, the convex shape (Case 5) performed the worst, even decrease in percentage by 3.55 %, 5.88 % and 5.04 %, in terms of full cycle completion time, melting time and solidification time, against the base case.

Comparison of Different Numerical Models for Solidification of Paraffin-Based PCMs and Evaluation of the Effect of Variable Mushy Zone Constant

The impact of the mushy zone parameter (Amushy) and the chosen numerical model during the solidification of a commercial paraffin-type phase change material (PCM) in a vertical cylinder under T-history conditions was examined through numerical simulations. The cooling process was modeled using three methods implemented in the CFD software ANSYS Fluent 2020 R2: the enthalpy–porosity method, the apparent heat capacity (AHC) method, and a new model proposed by the authors which incorporates heat capacity directly into ANSYS Fluent. To accurately define the boundary conditions, radiative heat transfer between surfaces was taken into account. Furthermore, the influence of the mushy zone parameter on the simulation accuracy and solidification rate was investigated, with the parameter being treated as a function of the liquid fraction. The results indicate that the proposed model aligns closely with experimental data regarding cooling temperature, offering better predictions compared to the other models. It was observed that temperature varies with time but not with position, suggesting that this model more effectively satisfies the lumped system condition—an essential characteristic of the T-history experiment—compared to the other methods. Additionally, the analysis showed that a higher mushy zone parameter enhances the accuracy of simulations and predicts a shorter solidification time; approximately 11% for the E-p and 7% for the AHC model. Using a variable mushy zone parameter based on the liquid fraction also produced similar results, resulting in an increased solidification rate.

Numerical study of shell and tube thermal energy storage system: Enhancing solidification performance with single-walled carbon nanotubes in phase change material

The coupling of Organic Rankine Cycle (ORC) and Latent Heat Thermal Energy Storage (LHTES) is a novel strategy for efficiently using solar energy. The objective of this study is to explore the solidification performance of phase change material (PCM) with single-walled carbon nanotubes (SWCNTs) for thermal management in solar energy system. The evolution of temperature and liquid fraction during the solidification process is investigated across four cases: Case 01 without SWCNTs, and Cases 02, 03, and 04 with 2 %, 3 %, and 4 % SWCNTs dispersion, respectively. By analyzing the temperature and liquid fraction contours over time, the impact of SWCNTs concentration on thermal performance is assessed. Case 01 has a total solidification time of 14,400 s. In comparison, Case 02 achieves solidification in 13,600 s, Case 03 in 13,040 s, and Case 04 in 12,500 s, reflecting time savings of 5.55 %, 9.44 %, and 13.2 %, respectively. Additionally, Case 04 exhibits the highest sensible heat release of 527.9 kJ and a total heat energy release of 2851.09 kJ. The dimensionless TES rate P′ for Case 04 is 1.26, indicating a 26 % improvement in thermal energy storage performance over the baseline. These findings underscore the effectiveness of SWCNTs-enhanced PCM in optimizing solar energy systems through enhanced heat transfer and accelerated solidification.

A Periodic Horizontal Shell-And-Tube Structure as an Efficient Latent Heat Thermal Energy Storage Unit

Thermal energy storage systems utilising phase change materials offer significantly higher energy densities compared to traditional solutions, and are therefore attracting growing interest in both research and application fields. However, the further development of this technology requires effective methods to enhance thermal efficiency. We propose a horizontal periodic shell-and-tube structure as an efficient latent heat thermal energy storage unit. This research aims to analyse heat transfer not only between the tube containing the heat transfer fluid and the phase change material but also between adjacent shell-and-tube units. The results obtained for a single cell within the periodic structure are compared with those of reference single shell-and-tube units with insulated adiabatic and highly conductive shells. The enthalpy–porosity approach, combined with the Boussinesq approximation, is applied to address the heat transfer challenges encountered during melting and solidification. The periodic horizontal shell-and-tube structure proves to be an efficient latent heat thermal energy storage unit with short melting and solidification times. In contrast, the non-periodic case with neglected conduction in the shell increases the melting and solidification times by 213.8% and 21%, respectively. The shortest melting and solidification times were recorded for the case with a periodic horizontal shell-and-tube structure and shell aspect ratios of 0.44 and 1, respectively.

Experimental investigation on the thermophysical properties and solidification characteristics of n-octadecane in a spherical capsule

A thorough understanding of the thermophysical properties of phase change materials and the natural convection effect during the phase transition process is crucial for the accurate modeling and designing latent heat storage systems. However, research findings on the thermophysical properties of n-octadecane and the natural convection effect during the solidification process remain insufficient. In this study, the thermophysical properties of n-octadecane, including latent heat, thermal conductivity, density, thermal expansion coefficient and dynamic viscosity, were systematically measured under varying temperature conditions. Subsequently, a comprehensive solidification experiment of n-octadecane in a spherical capsule was conducted to assess the temporal and spatial temperature distribution characteristics and the evolution patterns of the solidification front. Finally, numerical techniques were employed to quantify the impact of natural convection. The results indicate that, the relationship between solidification mass fraction and time follows a quartic polynomial pattern. Based on the temperature curve at the central point, the solidification process of n-octadecane can be divided into four distinct stages. The first two stages account for 98.2 % of the total heat release, with natural convection primarily concentrated in the sensible heat release stage of liquid phase, contributing only 2.3 % to the entire solidification process, making its effect essentially negligible.

The effect of post-bond heat treatment on microstructure and mechanical properties of a two-step heating transient liquid-phase bonding IN738LC

ABSTRACT This study evaluated the bonding of a Ni-based superalloy, Inconel 738LC, using two-step heating and conventional TLP bonding techniques using a foil of BNi-2 filler alloy with a thickness of 70 μm. The bonds were processed. The first step at 1160 °C for 1 min and the second step at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 minutes), and the conventional TLP process at 1120 °C for 80 min. It was inferred from the results of microstructural examinations that the joints contained eutectic product constituents that formed an athermal solidified zone (ASZ) during the bonding time of 50 min. It was also found that 80 min was required to complete isothermal solidification in the two-step TLP bonding employed in this study, whereas isothermal solidification was incomplete in conventional TLP for 80 min. The time necessary to complete the isothermal solidification was lowered using two-step TLP bonding. The microstructure after being subjected to a two-stage postbond heat treatment, becomes close to the base metals. As a result, homogenizing microstructure forms throughout the joint. The heat-treated sample contained a much greater amount of the γ′ phase generated at the bond location, resulting in increased shear strength and hardness of the bond.

Optimization of antenna-shaped fins configuration for enhanced solidification in triplex thermal energy storage systems with radiative heat transfer

The objective of this study is to enhance the rate of solidification of Phase Change Materials (PCMs) in Latent Thermal Energy Storage Systems (LTESSs) by incorporating hybrid nanoparticles (MoS2-Fe3O4) and utilizing a unique optimized antenna-shaped fin configuration in a triplex-tube energy storage device. The problem was solved by applying the Finite Element Method (FEM), considering some numerical analysis. For studying the effects of a variety of angles and dimensions of antenna-shaped fins with a radiation parameter during the process of solidification, a computational model validated by historical experimental data is developed. This paper will present an analysis of the effect of different angles and dimensions of antenna-shaped fins in conjunction with the radiation parameter during the solidification process. Results show that the full solidification time (FTS) decreases by 51 % when Rd = 1 compared to zero radiation, indicating a significant improvement in the efficiency of the solidification process. Furthermore, at 4000 s, the average temperatures for Rd = 0 and Rd = 1 differ, showing a noticeable drop of 4.51°. Furthermore, using Taguchi and Response Surface Methodology (RSM), the optimal settings were determined to minimize the full solidification time in the triplex-tube LHESS. Interestingly, a highly accurate and precise correlation for FST was established.

Optimization of a cold thermal energy storage system with micro heat pipe arrays by statistical approach: Taguchi method and response surface method

Cold thermal energy storage (CTES) technology is one of effective ways to utilize renewable energy and shift peak power load. In this paper, a novel CTES device using micro heat pipe arrays is numerically studied and optimized. Firstly, the Taguchi method is adopted to quantitatively analyze the contribution ratio (CR) of fin parameters to solidification and melting time, as well as compactness factor. Fin height has the highest CR of approximately 70 % for solidification and melting time, while fin thickness with the highest CR of 58.88 % for the compactness factor. Then, the response surface method is used to uncover the interactive effects of fin parameters and operation parameters. Next, multi-criteria optimization is performed by minimizing solidification time and heat exchange temperature difference, and maximizing the compactness factor. Compared with the original structure, the solidification time of optimized structure is reduced by 26.59 % with small heat exchange temperature difference of 4 °C and great compactness factor of 0.8219. Additionally, the phase change front of the original and the optimized CTES device are compared and analyzed to further reveal the reason for the performance improvement of the device. The research results provide inspiration and data support for the practical application of CTES.

In situ X-ray imaging and quantitative analysis of balling during laser powder bed fusion of 316L at high layer thickness

Balling is the main surface defect in additive manufacturing, leading to surface roughness and uneven powder deposition. Through the in-situ X-ray imaging technology, the melting process of high layer thickness 316L powder under different process parameters was investigated in real time in this work. We systematically elaborate the complex formation mechanism of balling at high layer thickness, and the key mechanism underlies the splatter’s coalescence during the flight and solidification stages. The frequent spatters coalescence dominates the large-size balling. The spatter coalescence event was roughly quantified, and the coalescence rate ranges from 42.42 % to 73.04 %. The swing of the irregular balls and jumping of the regular small balls were observed, and the solidification time ranges from 10 ms to 20 ms. Moreover, the detailed morphological parameters including the contact angle and counts of the spatter were clarified, and the algebraic equations about the contact angle and the volumetric energy density were established. This study provides a systematical understanding of the balling phenomenon during laser powder bed fusion of 316L at high layer thickness.

Incorporating numerical method for analyzing the conduction heat transfer during solidification loading nanoparticles

This study examines the freezing within a tank with a curved cold surface, integrating an innovative use of fins. The addition of fins and the careful introduction of nanomaterial knowingly enhance solidification efficiency, with potential applications in areas such as cryopreservation and thermal energy storage. To further optimize the solidification process, various types and concentrations of nano-powders were dispersed into the water, serving as heat transfer enhancers. The mathematical model was refined through specific assumptions, leading to the derivation of two principal equations. These equations were then effectively solved using the Galerkin method, offering a novel optimization approach for solidification. The enhancement in conductivity due to the modifications plays a key role in improving the productivity of the system. Furthermore, the addition of nanoparticles resulted in a notable extension of freezing time around 26.71 %. The use of an adaptive grid method during grid generation, coupled with the successful verification of the final model, strengthens the reliability of the research. By increasing the parameter "m" (shape factor) from 4.8 to 8.6, the solidification time was reduced by approximately 6.96 %, demonstrating a significant improvement in the system's efficiency.

Design a Gating System for an Aluminum Cast Three-Way Pipe in Sand Casting

The study of aluminum casting work with market demand in the metal casting industry, designing a gating system in aluminum casting using a three-way pipe-shaped sand mold workpiece as a basic shape template in metal casting, namely a flat-face core box with a core. The gating system has a metal inlet with design variables including the pouring height, pouring basin cross-sectional area, rest basin cross-sectional area, running system cross-sectional area and inlet cross-sectional area. From the studying and designing, actual casting experiments were conducted and simulation behavior was analyzed using Cast-Designer software to make decisions and find appropriate design approaches from analyzing simulation results including liquid metal filling time, molten metal flow behavior, metal solidification time and shrinkage porosity formation of the workpiece. The results of the casting experiment and behavior simulation were able to cast the pipe workpiece which is a flat-face core box mold. The analysis results from the software can be used for actual pouring, where the fully cast mold successfully produced a complete workpiece. This can be a guideline for future improvements to reduce the shrinkage of actual cast workpieces.

Influence of adjustable ring modes on molten pool behavior and microstructure of Al–Si coated boron steel in fiber laser welding

The influence of adjustable ring modes on the phase transition and microstructural evolution in conduction mode laser welding of Al–Si coated boron steel was investigated. Distinct geometric variations and molten pool behavior were observed through a ring-shaped beam effect. The ring beam introduced by ring-beam-mode (RBM) and dual-beam-mode (DBM) laser welding inhibited Al segregation into the fusion zone (FZ). The ring beam caused the Al molten particles to be driven towards the outer boundaries of the weld pool. A ring-beam-mode (RBM) and a dual-beam-mode (DBM) laser welding inhibited Al segregation into the FZ, resulting from a minimal temperature gradient and extension of the solidification time. Phase transition calculations demonstrated that a mount of residual ferrite within the FZ is significantly correlated with the Al concentration at specific temperature points, indicating a predominant role of a central-beam-mode (CBM) FZ in δ-ferrite formation. The RBM and DBM effectively suppressed Al segregation into the FZ, leading to a reduction in ferrite formation and the development of a refined microstructure characterized by a uniform and high density of geometrically necessary dislocations. Electron backscattered diffraction (EBSD) analysis revealed a higher proportion of low-angle grain boundaries in the RBM and DBM, attributed to the unique thermal distribution induced by the ring beam. These findings highlight the critical role of beam mode in tailoring the microstructure and properties of laser welds in Al–Si coated boron steel.

Fins-nanoparticle combination for phase change material enhancement in a triplex tube heat exchanger: A numerical approach to thermal sustainability

Many phase change materials exhibit low thermal conductivity, leading to incomplete melting and solidification processes. To address this issue, researchers have numerically explored the integration of alumina nanoparticles (Al2O3) with paraffin (RT82), a phase change material with a solidification temperature of 65 °C, in a triplex-tube heat exchanger. The phase change material model with internal longitudinal fins employed the both-sides freezing technique and was conducted using Ansys Fluent software, employing the enthalpy-porosity method within a finite-volume framework to model the phase change material behavior during both melting and solidification phases. This methodology aims to significantly improve the thermal performance of thermal energy storage systems by enhancing heat transfer efficiency within the phase change material (PCM), thereby ensuring more effective utilization of stored thermal energy. The numerical findings show that the pure PCM completely solidified in 780 min. By dispersing 1 %, 4 %, 7 %, and 10 % of Al2O3 in the PCM, thermal conductivity improved by 3 %, 12.5 %, 22.5 %, and 32.5 %, respectively. Additionally, the inclusion of nano-PCM reduced the solidification time. This research also compares the overall energy release in two different situations: PCM with and without nanoparticles. The computer-generated simulation results closely correlated with the practical experimentation results.

The Effect of Cooling Rate on Solidification Characteristics and Grain Structure of Al-9Si Cast Alloy

A thermal analysis study is essential before the semisolid metal processing of a particular alloy. The surrounding environment, especially the cooling rate is also an important factor. This study investigated the influence of different cooling rates on the solidification characteristics and microstructure evolution of the Al-9Si cast alloy. Four cooling mediums were designed, and their cooling rates are 0.16 ℃/s, 1.0 ℃/s, 1.3 ℃/s, and 1.9 ℃/s, respectively. The results show that the primary dendrite size of the Al-9Si alloy was reduced from 162.61 μm to 86.86 μm as the cooling rate increased from 0.16 ℃/s to 1.9 ℃/s. Significant grain refinement was observed, however, the external cooling has a negligible impact on solid fraction. The optimal temperature range of the Al-9Si cast alloy for the semisolid metal processing at a solid fraction of 0.5 to 0.7 is between 554 ℃ and 563 ℃. With these thermal profiles provided, the relationship between the solid fraction and the solidification time could be expressed using the polynomial equation, which is also useful for point prediction in the subsequent semisolid metal processing.

Alternative thermal histories of Earth-like planets: Influence of key parameters

The thermal evolution of any planet can be influenced by many factors: the initial temperature profile, the distribution of specific materials within the planet, the existence or lack of a gaseous atmosphere, the effects of early and “late” collision events. Insights concerning the influence of those factors can be obtained by examining solutions to the heat equation, applied to spherical bodies. General trends identified in this work include: 1) Moderate conductive materials contribute to efficiently flatten the temperature gradients, whereas insulating materials promote the preservation of steep temperature gradients. 2) It is not necessary to invoke convection to achieve a relatively flat temperature gradient; moderately conductive materials might achieve the same result without any advective motion involved. 3) Heat transport can take place both outwards and inwards, depending on the initial distribution of temperatures. 4) If the initial temperatures near the center of a planet are low, they will tend to remain low even if heat production takes place at its middle or upper parts. 5) Gradients of temperature near the surface of a planet may not reflect temperature variations at its middle or central parts. 6) Changes of phase exert a strong influence on the evolution of temperature profiles within a planet. 7) Highly insulating atmospheric layers can be important in determining the time of solidification of the upper layer of a magma ocean but not all atmospheres are equally efficient in that respect. As a result, models that give for granted the existence of deep mantle convection on Earth are justified only in the context of models of planet formation that require high initial temperatures; the standard model of a cold solar nebula is not consistent with such deep mantle convective movements.

Solidification process modeling for energy storage by means of galerkin method utilizing nano-sized additives

In this study, a numerical method for modeling the freezing process inside a storage enclosure equipped with ψ-shaped fins has been scrutinized. The container features both square and sinusoidal walls, with ψ-shaped fins enhancing the thermal conduction within the system. Alumina nanoparticles, in both blade and cylindrical forms, have been dispersed in the water to investigate the effect of particle shape on the freezing process. The shape factor (m) is considered in the calculation of conductivity to capture the impact of different nanoparticle geometries. Additionally, a single-phase model is used for the nanomaterial formulation, with nanoparticle concentrations (φ) kept below 0.04 to ensure accurate representation. The results reveal that increasing (m) leads to a reduction in solidification time by approximately 7 %. When nanoparticles are dispersed in water, the time required for complete freezing decreases from 275.57 s to 201.95 s, representing a significant improvement. This demonstrates that the presence of nanoparticles can accelerate the freezing process by about 26.71 %. By incorporating ψ-shaped fins and optimizing nanoparticle characteristics, the study provides valuable insights into enhancing thermal conduction and reducing freezing times.