Melting Characteristics Research Articles

Hydrochemical Dynamics of River Flow in a Mountain River (Katun River as an Example)

It is noted that the efficiency of protection and rational use of water resources decreases due to uncertainty of information about spontaneously changing indicators of their quality, uniqueness of such variability and, consequently, due to impossibility to develop uniform rules of economic use of water bodies and watercourses. It is shown that these problems arise not only in water bodies subjected to intensive anthropogenic impact, but also in those remaining in practically natural conditions. The results of the authors' studies of the rivers of the Altai Mountains are presented, where such features of melt (freshly formed) water as structural shifts in time series of its quality indicators, clustering of volatility, non-seasonal cyclicity and long memory of time series were discovered. It was concluded that it is necessary to take into account not only external conditions but also intrinsic dynamic characteristics of water flow to assess water composition and properties in order to reliably predict its quality and ensure efficient water use.

Thermal Performance Enhancement With Melting Effect of Nickel Foam and MXene Nano-Enhanced Phase Change Material Composite-Based Thermal Energy Storages

Abstract This research explores the numerical investigation of melting processes in duplex and triplex tube latent heat thermal energy storage (LHTES) systems utilizing phase change material (PCM) enhanced with nickel foam and MXene nanoparticles. By incorporating a nickel foam/PCM/MXene (5% v/v) composite, the research scrutinizes the effects on melting characteristics, Stefan and Fourier numbers, and thermal behavior of both duplex tube thermal energy storage (DuT-TES) and triplex tube thermal energy storage (TrT-TES) configurations. A comprehensive analysis encompassing liquid fraction, melting temperature contours across varying melting durations, exergy destruction, exergetic efficiency, system efficiency, and the stored energy is conducted. The findings indicate that systems employing nickel foam/PCM–MXene composite exhibit superior performance compared to those utilizing nickel foam/PCM or pure PCM, resulting in a notable reduction in melting time. Furthermore, it is observed that the stored exergy of nickel foam/PCM composite surpasses that of pure cetyl alcohol PCM. In TrT-TES systems, melting with nickel foam/PCM composite occurs 58.82% faster than in DuT-TES systems. The stored energy of TrT-TES employing nickel foam/PCM and nickel foam/PCM/MXene composite is 4.55% and 3.69% greater, respectively, than that of DuT-TES systems. DuT-TES with nickel foam/PCM/MXene also achieves a 44.86% higher system efficiency at 90 s than nickel foam/PCM. Notably, the melting process with nickel foam/PCM/MXene in TrT-TES occurs 60.26% faster than in DuT-TES. Consequently, TrT-TES systems employing nickel foam/PCM/MXene composite demonstrate superior potential for latent heat thermal storage compared to DuT-TES systems.

Anisotropic Shock Response of 3,4-Dinitropyrazole Revealed by First-Principles Calculations.

DNP (3,4-dinitropyrazole) has attracted much interest due to its promising melting characteristics and high detonation performances, such as low melting point, high density, high detonation velocity, and low sensitivity. In this work, first-principles molecular dynamics (MD) simulations were performed to investigate the anisotropic shock response of DNP in conjunction with the multiscale shock technique (MSST). The initial decomposition mechanism was revealed through the evolution of the chemical reaction and product analysis. Independent gradients based on the Hirshfeld partition (IGMH) method showed that van der Waals forces mainly exist between the layered structures. Chemical reaction analyses revealed four major initial decomposition reactions for the DNP molecule. At different shock velocities, the molecules in were more inclined to undergo H dissociation reactions, whereas the molecules in were more inclined to undergo nitro-dissociation reactions. Product analysis showed that the faster the shock velocities, the earlier the DNP molecules completely disappeared. Furthermore, N2 and CO2 were mainly produced by the ring-opening reaction, and their numbers in were higher than in , indicating that the ring-opening reaction was more easy to occur in . The ring-opening reaction mainly occurred in , suggesting that was more decomposable than . The fitting results of the state equation showed that the theoretical detonation pressures for and are close to the experimental value. These results could help to increase the understanding of shock-induced anisotropy in energetic materials.

Orientation Effect of Arc Array Horizontal Tubes Inside a Phase Change Storage Unit on Melting and Solidification Characteristics

Orientation Effect of Arc Array Horizontal Tubes Inside a Phase Change Storage Unit on Melting and Solidification Characteristics

Ice thickness formation and melting characteristics of Lake Nanhu in Inner Mongolia based on the process-based model of SIMSTRAT

Ice thickness formation and melting characteristics of Lake Nanhu in Inner Mongolia based on the process-based model of SIMSTRAT

PCM melting characteristics in a sidewall-heated rectangular cavity with non-uniform longitudinal fins near the bottom

PCM melting characteristics in a sidewall-heated rectangular cavity with non-uniform longitudinal fins near the bottom

A 9R-like 2D hybrid metal halide with remarkably low melting temperature.

N-Methyl-2-hydroxy-1-ethanaminium lead iodide exhibits a low melting temperature (Tm = 99 °C) among 2D hybrid metal halides (HMHs). This discovery expands the low melting characteristics of 2D HMHs to include a stepped 9R-like structure, suggesting significant potential for melt-processing and hybrid glass formation.

Numerical study on the moving and melting characteristics of paraffin particle group

Numerical study on the moving and melting characteristics of paraffin particle group

Composition, microstructure, rheology, and meltdown behavior of commercial nondairy frozen desserts.

The demand for nondairy and plant-based products has increased, but there is still a need for more information about and improvement in these products, especially when it comes to frozen desserts. Similar to ice cream, which simultaneously is an emulsion, dispersion, and foam, nondairy frozen desserts also have a complex structure. As a starting point, 15 commercial nondairy frozen desserts, marketed as offering an ice cream-like experience, were purchased and evaluated for compositional, physical, structural, rheological, and meltdown properties. The correlations between the parameters of these characteristics were also studied. The parameters with the greatest variability in percentage terms for each property after melt-down were fat content ranging from 3.8% to 18.6%, surface tension from 26.4 to 45.4 mN·m-1, fat destabilization from 3.6% to 94.4%, yield stress from 0.0 to 25.2Pa, and final height from 0% to 77.3%. Interestingly, the maximum overrun found was about 82%, considered low compared to economy dairy ice creams. The fat content was the most significant parameter that influenced drip-through rate, height change rate, and final height. Additionally, yield stress was the only rheological parameter that correlated with the meltdown behavior, which affected only one of them, the induction time. Therefore, in the meltdown profile, the lag phase was driven by yield stress, while the fast-melting phase and the plateau phase were influenced by the fat content. Moreover, four samples presented uncommon drip-though curves, which were visually recorded. This study offers a baseline understanding of the compositional, structural, rheological, and melting characteristics of commercial nondairy frozen desserts available in the United States. PRACTICAL APPLICATION: The compositional, microstructural, rheological, and meltdown characteristics of nondairy frozen desserts available in the US market were evaluated. The information can be used for industry research and development, understanding the challenges, and advancing knowledge regarding nondairy frozen desserts.

Three-dimensional numerical simulation of melting characteristics of phase change materials embedded with various TPMS skeletons

Three-dimensional numerical simulation of melting characteristics of phase change materials embedded with various TPMS skeletons

Geochemical Characteristics of Melts from the Eastern Volcanic Belt and Sredinny Range of Kamchatka: Analysis of Evidence from Melt Inclusions

We analyzed sets of published data on the composition of glasses from melt inclusions in minerals of volcanics from the Eastern Volcanic Front and Sredinny Range of Kamchatka. A significant difference was revealed between the distribution of silica contents in the rocks and melts: intermediate compositions are most common among the rocks, whereas the melts are dominantly silicic. The distribution of major and trace element was analyzed. It was shown that the contents of some elements are environment-specific (e. g., Nb and light REE). We distinguished trace element ratios in melts that most strongly correlate with the geodynamic setting.

Enhanced casing molten salt thermal energy storage through cobblestone-fin composite: Multi-objective optimization with RSM and NSGA-II

In this paper, the thermal storage performance of molten salt phase change materials in a triplex-tube latent heat thermal energy system designed by mixing fins and pebbles is studied. Commercial Computational fluid dynamics software is utilized for simulating and analyzing the latent heat system. The influence of stone arrangement, rotating speed and heat transfer fluid temperature on the melting performance of latent heat thermal energy system is emphatically discussed. The results show that the change of pebble diameter has a significant influence on the melting characteristics of latent heat thermal energy system. When the pebble diameter is 1 mm and arranged in 3 rows and 3 columns, latent heat thermal energy system has the best heat storage effect. At the same time, the effects of rotating machinery and heat transfer fluid temperature on the thermal performance of latent heat thermal energy system are discussed. Finally, the response surface method and the non-dominated sorting genetic algorithm II are employed to optimize the design, after optimization, the system's heat storage capacity increases by 19.04 kJ, and the melting time decreases by 16.12 s. Therefore, it is suggested that the optimized latent heat thermal energy system can significantly enhance heat transfer efficiency.

Dynamic regulation of the photothermal conversion performances of nano-enhanced phase change material composited with ceramic foam subjected to external fields

This study aims to comparatively analyze the melting characteristics of magnetic Fe3O4 nano-enhanced phase change materials (NEPCM) assisted by optimum filling strategies of Al2O3 foam ceramics, ultrasonic field and magnetic field under solar radiation. A visualization experimental platform consisting of an ultrasonic field, a magnetic field, and infrared thermography is constructed and used to evaluate in detail the evolution of the melting front, the temperature distribution, and the heat transfer mechanism under different experimental conditions in a square cavity. The results show that the 1 wt% NEPCM using an ultrasonic field has the highest solar energy conversion efficiency of 39.99 % among the 18 experimental groups. This suggests that the cavitation effect and acoustic flow effect induced by ultrasound with a power of 40 W periodic ultrasonic mechanical vibration improve the uniformity of the distribution of magnetic nanoparticles, resulting in improved heat transfer properties. In the experimental group where a magnetic field is applied, the downward movement of the melting interface is accelerated due to the force of the magnetic field on the Fe3O4 nanoparticle. Under the effect of localized porous filling, the solar conversion efficiency of 1 wt% NEPCM is 31.57 % and the total energy storage is as high as 14.39 kJ. With the increase of concentration, the solar conversion efficiency and total energy storage decrease gradually. However, under the simultaneous effect of magnetic field and localized porous filling, the solar conversion efficiency and energy storage show an opposite trend. From a comprehensive point of view, the application of periodic ultrasound with a power of 40 W can effectively improve the photothermal conversion capacity of the PCM.

Heat Transfer Characteristics of Cryogenically Frozen Kulfi (A Dairy Dessert)

Kulfi was frozen from concentrated milk as well as from reconstituted dry mix with solids content of 60%. The convective heat transfer coefficients during freezing of kulfi by deep freeze and cryogenic methods were determined using one-dimensional transient heat conduction equation. The heat transfer coefficient for cryogenic freezing of kulfi from milk and dry mix concentrates was 210.57 W m-2K-1 and 216.84 W m-2K-1, respectively when compared to 8.33 W m-2K-1 for conventional deep-frozen kulfi. Freezing was achieved in 267 min in deep freeze method, while it reduced to just 185-190 s under cryogenic conditions. The freezing time was predicted using empirical equations, and the prediction accuracies were compared. Cryogenic freezing was nearly 87.66 times faster than deep freezing, and Pham’s model best-predicted the freezing time. Organoleptic evaluation using fuzzy-logic revealed that the order of ranking of quality attributes of kulfi was body and texture (highly important) > melting characteristics (highly important) > flavour and taste (highly important) > colour and appearance (important), and cryogenically frozen kulfi was statistically (p<0.05) superior to conventionally frozen kulfi.

Influence of heated temperatures on PCM melting characteristics in a pneumatic-based extrusion system of fused deposition modeling: Experimental and numerical studies

With the vigorous development of three-dimensional printers, fused deposition modeling has become one of the focuses of printed products in the biomedical field. However, many raw medical materials cannot be formed into filaments. A practical solution is to compact and melt powdered synthetic biomaterials into a melting bucket with a heat source. In line with this, the present study investigates the effect of heated temperatures on the melting behaviors of phase change materials in the pneumatic-based extrusion system. A series of experiments and simulations are carried out at three different heated temperatures, i.e., 60 °C, 70 °C, and 80℃. The computed results, with a mushy zone constant of 3 × 106, display good agreement compared with experimental data. Time-evolution of temperature distribution and mass fraction and an index of the melting fraction are presented to characterize the melting behavior qualitatively and quantitatively for a baseline case of 70 °C. The obtained findings reveal thatthe melting fraction increases significantly with heated temperatures. The melting times at 60 °C and 80 °C are 64 % longer and 26.7 % shorter than that at 70 °C, respectively. The heated temperature of 70 °C is considered the optimal operating temperature, providing the best balance between melting efficiency and energy consumption. The final unmelted area remains in the lower half of the bucket regardless of these three operating temperatures. To avoid clogging issues, the time history of three heated temperatures at the bucket outlet is also monitored. The results show that outlet temperatures cannot respond immediately to the target in the early melting stage, which is prone to clogging and interrupting the printing process.

The geochronology and cooling history of type 7 chondrites: Insights into the early impact events on chondritic parent body

Type 7 chondrites, which record a higher degree of heating process than typical type 3 to type 6 chondrites, are characterized with textures and petrography of partial melting. Understanding the timing and cooling history of incipient melting event for type 7 chondrites could provide insights into the complex thermal process of the early solar system. Here, we studied two chondrites NWA 12272 and NWA 11021. Both samples display partial melting characteristics of LL chondrites, including interconnected plagioclase/high-Ca pyroxene network, zoned plagioclase and lack of chondrules, which concurs with their classification of LL7 chondrites in the Meteoritical Bulletin Database. The 53Mn-53Cr isotopic data of NWA 12272, determined by mineral separates and bulk samples, yielded an isochron with a 53Mn/55Mn ratio of (1.40 ± 0.59) × 10-6 and a corresponding absolute age of 4558.8 ± 2.3 Ma (anchored to D’Orbigny angrite). Combined with the cooling rate estimated by the integration of REE-in-two-pyroxene thermometry and two-pyroxene thermometry, Mn-Cr isochron age of 4558.8 ± 2.3 Ma and Ca-phosphate Pb-Pb age of 4517 ± 6 Ma, we suggest that NWA 12272 experienced a two-stage cooling process after the incipient melting: it exposed to a relatively cold environment with a rapid cooling rate of ∼ 30-100°C/yr at 1150–1000 °C, and soon reburied with a slower cooling rate of ∼ 13 °C/Ma at 1000–475 °C. Although the Mn-Cr isotopic study was not conducted for NWA 11021, the average Ca-phosphate Pb-Pb age of 4509 ± 7 Ma and high-temperature cooling rate (∼1-30°C/yr) of NWA 11021 are indistinguishable from or slightly lower than those of NWA 12272. Assuming NWA 11021 cooled from the same incipient melting event as NWA 12272, it could have recorded a similar two-stage cooling process. We suggest that the studied LL7 chondrites were most likely formed in the early solar system when additional impact heat overlapped on the “heated” type 5–6 chondrites. Integrated with the previous cooling rates of LL6-7 chondrites, the prevailing two-stage cooling rates of LL chondrites provide compelling evidence for the fragmentation-re-accretion process in the early history of LL chondrite parent body. This early impact event also happened in other ordinary chondrite groups and some iron meteorites.

Effect of Fin Configuration on the Early Stage of the Melting Process of a Phase Change Material

Thermal storage systems are essential for optimizing energy resource utilization, particularly in the current context where sustainability and efficiency are critical. Phase Change materials (PCMs) offer a promising solution for improving thermal management efficiency without additional power consumption. Considering that the low thermal conductivity of phase change materials (PCMs) is a limiting factor for heat transfer, this study employs the enthalpy-porosity method to analyze the melting characteristics of a high-Prandtl number PCM. Additionally, this study investigated the effect of varying the number of fins in the heat sink on the heat transfer rate. The material melting process was modeled by considering buoyancy effects and treating the flow as incompressible, Newtonian, transient, and laminar. Lauric acid was selected as the working material with temperature-dependent properties that were incorporated into the simulations for greater accuracy. Three different heat sink configurations were analyzed, varying the number of fins from 5 to 10 and their lengths from 0.02 meters to 0.04 meters. The objective was to optimize the cooling performance using aluminum, which was selected for its excellent balance of lightweight properties and high thermal conductivity. This analysis aimed to assess how these variations in the fin count and dimensions affect the overall heat dissipation efficiency and thermal management of the system. The inclusion of a finned heat sink within a heat exchanger has demonstrated significant efficiency, particularly in regions with substantial boundary layer development, resulting in enhanced heat transfer. These findings highlight the effectiveness of using finned heat sinks in these regions. However, an interesting observation emerged regarding the effect of increasing the number of fins over long periods. Although initially beneficial, a larger number of fins eventually led to a reduced performance over time, notably affecting the thermal storage capacity and molten liquid mass production. Additionally, this study elucidates the influence of natural convection on thermal boundary layer development, highlighting the complexity of the heat transfer processes.

Effect of dual NEPCM and tapered fins on thermal runaway control in lithium-ion batteries

This research investigates the thermal performance of dual phase change materials (PCMs) RT82 (PCM1) and RT27 (PCM2) using tapered fins and nanoparticles to improve their thermal management capabilities, specifically for controlling excessive heating in lithium-ion battery cells. The primary objective is to enhance heat transfer efficiency and melting characteristics of dual PCMs by incorporating alumina (Al2O3), molybdenum disulfide (MoS2), and single-walled carbon nanotubes (SWCNTs) nanoparticles at varying volume fractions and configuring tapered fins in different arrangements. A series of parametric studies were conducted to analyze the impact of these modifications on the thermal transport and solid-liquid transition characteristics of the PCMs. The key findings indicate that the incorporation of nano-sized particles significantly enhances the thermal conductivity of PCMs, with SWCNTs showing the highest improvement. The PCM system with 6 % SWCNTs nanoparticles exhibited a 41.85 % increase in melting characteristics compared to the baseline PCM. The study also reveals that increasing the number of fins from two to eight results in a 94.28 % increase in the melting rate for RT82 and a 50 % increase for RT27. Furthermore, the combination of increased nanoparticle concentration and fin number leads to a 12.17 % rise in melt pool temperature distribution for 2 % SWCNTs and 14.08 % for 6 % SWCNTs. The enhanced thermal conductivity and efficient heat transfer due to the synergistic effect of fins and nanoparticles result in faster phase transitions and improved temperature regulation within the system. These findings underscore the potential of optimized PCM configurations with advanced materials for superior thermal management solutions in high-heat applications, effectively extending the operational efficiency and lifespan of thermal systems like lithium-ion batteries.

Experimental study on the melting characteristics modulation of cubic ice cubes with different trace air contents under natural convection condition

Ice as a typical phase change material has the advantages of low cost, high latent heat and environmental friendliness, and the ice melting process under natural convective conditions is a fundamental study that has received wide attention. For the cubic ice cubes having different air contents, their melting characteristics becomes more complicated. The melting model of cubic ice under natural convection conditions was developed, which can accurately predict the time of the entire melting process. To validate the accuracy of the model, a series of melting experiments on cubic ice cubes are conducted and analyzed, with mass and air contents varied from 20 g to 50 g, and from 0 to 3.9 %, with a model error of less than ±20 %. Based on the maximum melt rate and the change in shape to a pyramid of cubic ice, the melting process can be divided into the initial melting, frustum-shaped, and pyramid-shaped stages. Varying the air content of the ice regulated the total melting time and the time proportion of the initial melting stage and the frustum-shaped stage of the ice. The proportion of time in the pyramid-shaped stage decreased from 64.3 % to 51.5 % for bubble ice with an air content of 3.9 % compared to clear ice. The proportion of time in the pyramid-shaped stage during the ice melting process is not significantly related to the air content and mass, and remains at approximately 27 %. Results of this study are meaningful for regulating the melting process and optimizing phase change energy storage technologies.

Technological Features of Filler Wire Melting for Arc Welding and Surfacing with the Introduction of SF6 into Protective Gas Atmosphere

On the basis of the results of experimental studies the paper establishes important patterns of dependence of the frequency of short circuits of the arc gap and the coefficient of loss of electrode metal due to spatter from the voltage on the arc and the feed rate of the filler wire during welding and surfacing with the introduction of gaseous SF6 into the Ar + CO2 protective mixture. It is proposed to introduce fluorine-containing components of SF6 directly into the protective gas mixture of 82 % Ar + 18 % CO2 in quantities not exceeding 2 %. The technology makes it possible to reduce the amount of diffusion hydrogen in the deposited metal, which is an urgent task when welding high-strength steels and materials sensitive to hydrogen embrittlement. Previously, we resolved a number of issues related to the obstacle to increasing the concentration of S in the deposited metal, which made it possible to determine the most effective concentrations of SF6 in the protective gas environment, limited to 1.5 % by volume of the total composition (Ar + CO2) + SF6. At the same time, modification of the protective gas atmosphere with the halide compound SF6 has a significant effect on the melting characteristics of the electrode wire and temperature indicators in the arc combustion zone. This is due to the high ionization potential of fluorine as a product of the high-temperature dissociation reaction of SF6. The results obtained have made it possible to determine the most effective relationships between the values of the mode parameters, as well as to study the specifics of melting the filler wire in a protective atmosphere modified with SF6. Important regularities have been established that reveal the technological features of welding and surfacing with modification of the protective atmosphere with halide compounds.