Melting Efficiency Research Articles

Melting and solidification in periodically modulated thermal convection

Melting and solidification in periodically time-modulated thermal convection are relevant for numerous natural and engineering systems, for example, glacial melting under periodic sun radiation and latent thermal energy storage under periodically pulsating heating. It is highly relevant for the estimation of melt rate and melt efficiency management. However, even the dynamics of a solid–liquid interface shape subjected to a simple sinusoidal heating has not yet been investigated in detail. In this paper, we offer a better understanding of the modulation frequency dependence of the melting and solidification front. We numerically investigate periodic melting and solidification in turbulent convective flow with the solid above and the melted liquid below, and sinusoidal heating at the bottom plate with the mean temperature equal to the melting temperature. We investigate how the periodic heating can prevent the full solidification, and the resulting flow structures and the quasi-equilibrium interface height. We further study the dependence on the heating modulation frequency. As the frequency decreases, we found two distinct regimes, which are ‘partially solid’ and ‘fully solid’. In the fully solid regime, the liquid freezes completely, and the effect of the modulation is limited. In the partially solid regime, the solid partially melts, and a steady or unsteady solid–liquid interface forms depending on the frequency. The interface height can be derived based on the energy balance through the interface. In the partially solid regime, the interface height oscillates periodically, following the frequency of modulation. Here, we propose a perturbation approach that can predict the dependency of the oscillation amplitude on the modulation frequency.

Process parameter optimization for selective laser melting Ti-6Al-4V with high layer thickness

Increasing the layer thickness is an important method to increase the forming efficiency of selective laser melting (SLM) but affects the forming quality. In this work, a single track and cube sample with an 80µm layer thickness was fabricated by SLM, and then the relative density, hardness, defects, and forming efficiency were studied. It is found that the morphology of the single tracks changes significantly with the change of scanning speed. Fewer defects appear on the top surface and cross section with scanning speed below 850mm/s. However, the defects increase significantly with further increasing scanning speed. Furthermore, the relative density of the Ti-6Al-4V can reach 99.89% when the scanning speed is 800mm/s. The Vickers hardness is highest when the scanning speed is 500mm/s with the top surface of 402 HV and the side surface of 378 HV. An increase of scanning speed not only causes larger balling particles, but also results in making an appearance of micro-cracks. The increase in layer thickness leads to insufficient energy density, which affects the occurrence of lack of fusion concurrently. Element evaporation occurs at low scanning speeds, which can increase defects in the sample. The appropriate process parameters are the laser power of 300W, the scanning speed of 800mm/s, and hatch distance of 0.17mm. At this time, the forming efficiency is as high as 8.96 mm3/s.

Thermal performance and flash point analyses of concentrator photovoltaic (CPV) system using multiple types of PCMs and various panel inclination angles under the effect of a constant heat flux

This numerical study conducts a comparative analysis of various phase change materials (PCMs) including Lauric Acid, Paraffin, RT 24, RT 31, RT 35, RT 38, RT 42, RT 47, RT 50, and Lithium Nitrate Trihydrate (LiNO3.3H2O) to assess their suitability for optimizing the thermal management of a solar concentrator photovoltaic (CPV) system. The analysis focuses on the temperature regulation capabilities, melting dynamics of the used PCMs, along the electrical efficiency of the CPV system across a range of inclination angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) under a constant heat flux of 1000 W/m². The research aims to identify the most effective solutions for enhancing the efficiency and reliability of solar concentrator systems. Key considerations such as PCM’s flash points, liquid fraction and convective behavior are addressed for each PCM type. Numerical results obtained using ANSYS Fluent indicate that Lithium Nitrate Trihydrate (LiNO3.3H2O) outperformed most paraffin-based PCMs, such as RT 24 and RT 35, with around 24 % higher electrical efficiency. Although Lauric Acid was approximately 19.5 % less efficient than Lithium Nitrate Trihydrate, it offered superior long-term thermal stability due to its slower melting rate and phase change temperature of 43–44°C, taking 45.33 % longer to melt compared to Paraffin RT 24. RT 50, with its higher melting temperature of 50°C, provided a balance between melting period and efficiency, making it an ideal PCM for applications requiring both moderate efficiency and sustained thermal regulation.

Research on Electric Heating Green Snow Melting and Anti-icing Technology for Tunnel, Bridge, and Culvert Entrances

This paper addresses the issue of electric heating snow melting at tunnel, bridge, and culvert entrances. It explores a novel carpet-style electric heating snow melting and anti-icing system for these areas. The study analyzes the shortcomings of existing electric heating snow melting methods and proposes effective measures for improvement. To accurately assess the characteristics of current snow melting techniques, the research considers the damage caused by traditional snow melting methods to road structures and subsequent maintenance issues, while emphasizing energy-saving and environmentally friendly technologies. The snow melting process was simulated using Star-CCM+. The results show that the new carpet-style electric heating elements significantly improve snow melting efficiency. Preheating the road surface before snow accumulation greatly reduces snow retention time, enabling timely snow and ice removal. Typically, electric heating elements in snow melting systems are installed beneath the road surface at tunnel entrances. After installation, to protect the elements and ensure smoothness, a layer of cement or another suitable material is poured over them. However, these heating elements require regular inspection or replacement, which necessitates breaking up the road surface, increasing maintenance costs, and disrupting normal traffic operations. This study overcomes these challenges by providing significant convenience for installation and maintenance work, reducing costs, and minimizing the impact on traffic operations.

Simulation of melting characteristics of thermal washing of the wax layer in the pipeline based on lattice Boltzmann method

ABSTRACT The escalation of transportation costs and the obstruction of pipelines due to wax deposition significantly impact the secure and efficient production of oil fields. The thermal washing method, characterized by its simplicity and cost-effectiveness, is widely employed for dewaxing crude oil gathering pipelines. The investigation of the melting mechanism of the wax layer during thermal washing is extremely important. In this paper, the two-zone composite model of multiphase flow-porous medium in the mushy zone is introduced into the solid-liquid phase change lattice Boltzmann model based on the enthalpy method, and the problem of circumferential inhomogeneity in the melting of the wax layer and the important influence of flow and heat transfer in the mushy zone on the thermal washing are systematically investigated. The demarcation point (γ tr) between the high and low liquid fraction zones is measured to be 0.81 by microscopic experiment. The impacts of varying γ tr and Ste numbers on wax melting at different circumferential locations are analyzed in detail. The results show that the melting efficiency of wax exhibits a nonlinear enhancement from − 90° to 90°. The melting efficiency of wax decreases with increasing γ tr for wax layers between 90° and − 45°. The melting efficiency of wax increases with higher Ste numbers at all angles. The Ste number increases from 0.42 to 5.0, and the melting efficiency of the wax layer at angles ranging from 90° to − 90° increases by factors of 2.16, 2.16, 2.20, 2.61, and 3.33 respectively. The growth of the Ste number improves the warming rate and shortens the generation time of convection at the center point of the wax layer. The research findings serve as a fundamental reference for formulating a rational and efficient thermal washing scheme.

Melting of PCM-graphite foam composites with contact thermal resistance: Pore-scale simulation

Latent heat energy storage systems have emerged as a solution to intermittency and instability in renewable energy sources, the phase transition of phase change materials (PCMs) within these systems is hindered by their poor thermal conductivity. Graphite foam, renowned for its superior thermal properties, stands as an ideal choice to improve the melting efficiency of PCMs. In the current study, the melting behavior of PCM-graphite foam composites is simulated by the pore-scale numerical simulation (PNS) by employing cubic idealized cells with spherical pores and cylindrical channels. The computed results demonstrate that the porosity and contact thermal resistance of graphite foam are key factors affecting the melting efficiency of PCMs. The full melting time (FMT) of PCMs increases with porosity, achieving a 53.1 % improvement as porosity decreases from 0.90 to 0.75. In addition, the absence of natural convection markedly diminishes the maximum melting rate of PCM, reducing it by 33.5 % to 50.3 % for porosity from 0.75 to 0.90. Notably, it needs to be emphasized that the melting rate of PCM is significantly reduced when the contact thermal resistance surpasses 1.0 × 10–4 m2·K·W−1. Compared to the idealized condition without contact thermal resistance, the dimensionless FMTs for porosities of 0.75, 0.80, 0.85, and 0.90 extend by 27.3 %, 27.1 %, 22.2 % and 23.9 % for a contact thermal resistance of 5.0 × 10–4 m2·K·W−1, respectively.

Experimental study on snow melting and deicing of carbon fiber heating roads considering thermal insulation conditions

The electrothermal method for snow melting and deicing in road engineering provides efficient deicing. To improve the ice melting efficiency of carbon fiber heating cables, employing extruded polystyrene foam board (XPS)、polyethylene foam cotton (PEF) as insulation materials under the carbon fiber heating wire could reduce heat transfer to the lower layers of the road structure. Road model tests were conducted under various conditions to analyze how different heat insulation conditions、environmental temperatures affect road snow melting and ice melting. The results indicate that the placement of the heat insulation layer significantly affects the temperature fluctuation range between its upper and lower layers.The ice melting rate increases by 25∼50 % compared to pavement structures with no heat insulation layer. When heat insulation material is incorporated into the road structure layer, under preheated conditions, snow with a thickness of 0.2 cm on the surface of the plate heat insulation model can completely melt within 2.5 h, reducing the effective ice-melting time by 40∼51.7 %. A comparison of the thermal performance of the two insulation materials under various conditions reveals that the XPS plate is more suitable as an insulation layer compared to other materials.

Reducing the environmental footprint of glass manufacturing

AbstractThe glass industry is a significant source of greenhouse gas emissions due to its energy consumption profile and the use of fossil fuels in the manufacturing process. Most of the energy to produce glass is consumed in the process of treating raw materials to elevated temperatures, usually above 1500°C. Glass manufacturing also generates significant environmental impacts, such as greenhouse gas emissions, air pollution, water consumption, and waste generation. Therefore, improving the sustainability of glass manufacturing is a significant challenge for the industry and society. There are ways to reduce the energy consumption and emissions of glass melting, such as recycling glass, using oxy‐fuel burners, improving furnace insulation and design, and adopting electric melting technologies. These methods can help save energy, lower costs, and enhance the sustainability and environmental footprint of the glass industry. However, the industry faces challenges and barriers, such as technical feasibility, economic viability, capital investment, and market acceptance. More research and development must be invested to improve the energy efficiency and environmental performance of glass melting. The objective of this paper is to provide an overview of the growth glass industry has made over the past 30 years and the remaining challenges for sustainable glass manufacturing with a focus on the fiberglass segment. Sharing of procedural methods, technical approaches, and results can help enable the global glass industry in our future sustainability challenges. The fiberglass segment included a broad technical view including glass chemistry development, product development, new industry codes and standards, melting development, computational fluid dynamic modeling, life cycle assessments, and sustainability goals linked to capital planning. The net result delivered a significant reduction in environmental emissions at the global enterprise scale. The implemented changes have taken decades, significant investments, and resources to plan and develop. Practices reviewed and implemented can help drive collaboration and commonality within the glass industry to achieve sustainability goals. Action is needed now if the glass industry is to meet global government demands of reducing carbon emissions by 55% by 2030 and zero carbon emissions by 2050 in alignment with the Paris Agreement on decarbonization.

High-Safety Lithium-Ion Battery Separator with Adjustable Temperature Function Inspired by the Sugar Gourd Structure.

As the power core of an electric vehicle, the performance of lithium-ion batteries (LIBs) is directly related to the vehicle quality and driving range. However, the charge-discharge performance and cycling performance are affected by the temperature. Excessive temperature can cause internal short circuits and even lead to safety issues, such as thermal runaway. The separator plays a crucial role in protecting the battery from regular operation, preventing direct touch between the cathode and the anode while allowing the transport of lithium ions. In this study, we have designed a thermoregulating separator in the shape of calabash, which uses melamine-encapsulated paraffin phase change material (PCM) with a wide enthalpy (0-168.52 J g-1) to dissipate the heat generated inside the battery promptly. Under extra-long-use conditions, the heat emitted by the battery is absorbed by the PCM without causing a significant temperature rise that triggers thermal runaway. The PCM separator can effectively suppress the temperature increase caused by battery penetration. Due to the unique structure of the PCM, the battery is short-circuited; it can significantly delay the internal temperature rise of the battery and quickly dissipate the heat, which is consistent with the characteristics of natural calabash in nutrient absorption and water diffusion, improving the melting and heat storage efficiency of the PCM. The design of the phase change separator provides an effective reference for overheat protection and improved safety in lithium-ion batteries.

Influence of variable gravity on the phase change material for enclosed vertical channels with helical fins

This study numerically investigates the influence of variable gravity on the melting behaviour of a phase change material (PCM- paraffin wax RT27) contained within an enclosed vertical channel under different gravity conditions, specifically those found on the Earth, the Moon, and under the microgravity environments. Furthermore, the impacts of incorporating various number of helical fins within the PCM unit under different gravitational conditions are assessed for the first time. The findings indicate that the melting efficiency of PCM is considerably affected by the reduced gravity conditions, due to changes in the natural convection, velocity, and temperature; the melting time is twice as long under the moon-gravity conditions and sixfold longer under the microgravity conditions compared to the earth-gravity. It is also observed that reduced efficiency can be remedied by the insertion of fins into the PCM unit. The breakdown of the natural convection vortices with different number and orientation of fins expedites the melting process for all gravity conditions thus leading to improved performance in melting and energy storage.

Experimental study of the performance of a heat exchanger for a new desalination-cooling technique using ice slurry: A proof of concept

Ice slurry was used to produce desalinated water and cold energy simultaneously. The process involved partially freezing seawater to separate the ice from the brine. Then, freshwater is produced by recovering heat from seawater to melt the ice. This paper focused on the kinetics and efficiency of ice melting in direct contact with a finned-tube heat exchanger. The melting performances were analysed as a function of the quantity of ice, the salt water flow rate and the state of the ice during melting. It was found that increasing the salt water flow rate by 33 % increased the melting efficiency by 33 % and decreased the melting time by 15 %. Increasing the quantity of ice by 36 % decreased the melting efficiency by 6 % and increased the melting time by 24 %. The use of weights impacted melting efficiency differently depending on the state of the ice (compacted, watered).

Analysis of temperature stress and critical heating temperature for hydronic airport pavement

The hydronic heated pavement system has been widely used for snow and ice removal in airports and other transportation infrastructure facilities because of its good snow melting efficiency and environment friendliness. However, the study of the temperature stress distribution in hydronic pavement and the corresponding critical operation method shows many insufficiencies, which allows security problems during system operation. This paper investigated the temperature stress of the hydronic pavement near the pipes with a 3D finite element model. This model was validated by the measured temperature stress in a full-scale hydronic snow melting experiment system. The locations of the maximum compressive and the time-varying tensile stress in the hydronic pavement were reported. The maximum temperature stresses of the hydronic pavement with various design and operation parameters were compared, and the sensitive parameters were proposed. In particular, the critical fluid temperature with various design and weather parameters was presented by comparing the maximum temperature stress in the pavement with the failure strength of concrete material. The findings show the maximum compressive stress appears near the hydronic pipe, and the maximum tensile stress appears at the midpoint between two adjacent pipes after heating for 2 h. Maximum tensile stress increases with pipe embedded depth, pipe diameter, fluid temperature, and pavement capacity, but decreases with air temperature and pipe spacing. To ensure the safety of hydronic pavement, the critical fluid temperature under different conditions is controlled within the range from 38 °C to 77 °C.

Thermal storage performance of a novel shell-and-tube latent heat storage system: Active role of inner tube improvement and fin distribution optimization

This study presents a numerical analysis of the melting process in a shell-and-tube latent heat thermal energy storage (LHTES) system, featuring a twisted elliptical inner tube with annular fins. Utilizing paraffin as the phase change material (PCM) and water as the heat transfer fluid (HTF), this research examines the impact of varying twist degrees, fin quantity and fin distribution on the system's thermal performance during melting process. The analysis of the melting process includes complete melting time, temperature, and the contour of the solid-liquid interface. Notably, the study identifies that both fin quantity and distribution play a significant role in the melting process. The findings indicate that an optimal configuration, comprising a 720° twisted degree, 11 fins, and a base number a of 0.80, enhances the melting efficiency of the LHTES system by 156.44 % and reduces ineffective heat loss by 41.36 %. These results highlight the potential advantages of the twisted elliptical inner tube structure and propose an innovative approach with an exponentially non-uniform fin distribution, marking an advancement in the field of thermal energy storage.

Evaluation of Melting Efficiency in Cold Wire Gas Metal Arc Welding Using 1020 Steel as Substrate

A key welding parameter to quantify in the welding process is the ratio of the heat required to melt the weld metal versus the total energy delivered to the weld, and this is referred to as the melting efficiency. It is generally expected that the productivity of the welding process is linked to this melting efficiency, with more productive processes typically having higher melting efficiency. A comparison is made between the melting efficiency in standard gas metal arc welding (GMAW) and cold wire gas metal arc welding (CW-GMAW) for the three primary transfer modes: short-circuit, globular, and spray regime. CW-GMAW specimens presented higher melting efficiency than GMAW for all transfer modes. Moreover, an increase in plate thickness in the spray transfer regime caused the melting efficiency to increase, contrary to what is expected.

Directly depositing highly densified and uniform Cu-Cr pseudobinary alloy

Cu-Cr pseudobinary alloys have excellent electrical properties and are widely used in many industries. Laser additive manufacturing can effectively avoid the shortcomings of traditional methods for preparing Cu-Cr alloys. However, the high reflection of Cu powder to laser energy brings difficulties to industrial practice. The assembled Cu powder is used as raw material to absorb more laser energy through the outer layer of Cr powder, thereby improving the melting efficiency of the powder and the quality of the molten pool. Laser remelting of unmelted Cr powder can inhibit the uneven nucleation and growth of precipitated Cr, and improve the uniformity of electrical conductivity and element distribution. This study provides a new idea for the preparation of high-performance Cu alloys.

Research on thermal efficiency and weld forming coefficient prediction of ultra-high strength steel welded joint under different energy inputs

As an ultra-high strength steel, Al–Si coated 22MnB5 hot stamping steel is widely used in the manufacturing of body-in-white structural parts. Compared with traditional welding technology, laser welding is widely used in the field of automobile body-in-white manufacturing due to its high energy density, small heat affected zone, and high weld quality. For ultra-high strength steel laser welded joints, the weld forming coefficient is an important index to reflect the welding quality. In order to investigate the influence of weld forming coefficient on the Al content and the thermal efficiency, laser welding experiments of ultra-high strength steel under different laser energy inputs are carried out. The melting of the base metal and coating under different laser energy inputs is also considered. Particle swarm optimization (PSO) algorithm is introduced into radial basis function (RBF) neural network model to optimize the central parameters as the RBF neural network model alone is not sufficient in predicting the outcomes. The results shows that if the laser power density is constant (7 × 105 W/cm2), when laser energy inputs are 400 J/cm to 1200 J/cm, the Al content in welded joints is 1.458%–1.886%, the melting efficiency of welded joints is 0.23–0.26, the energy conversion efficiency of welded joints is 0.45–0.46. When the laser energy inputs are lower than 522 J/cm, the Al content of the laser welded joint increases gradually. When the laser energy inputs are higher than 522 J/cm, the Al content of the laser welded joint decreases. The root mean square error(RMSE) of PSO-optimized RBF neural network testing sets prediction results is 0.1551, R-square (R2) is 0.771 and mean absolute percentage error (MAPE) is 2.758%. The prediction accuracy of the PSO-optimized RBF neural network model for the upper surface weld width, waist weld width, and lower surface weld width is 93.9%, 91.1%, and 92.2%.

Electron beam melting efficiency at multiple hafnium e-beam processing

The method of electron beam melting and vacuum refining has clear advantages over other metallurgical methods since it enables manufacturing of refractory and chemically active metals. This study focuses on the efficiency of removing impurities from technogenic hafnium under multiple electron beam melting. Assessments are performed on the efficiency of double and triple e-beam melting processing of refractory metal hafnium. The influence of different e-beam melting technological modes on the refining effectiveness is investigated. A highest hafnium purity of 99.2% was achieved after double and triple e-beam refinements of the investigated materials, with the highest process efficiency reaching 61.58% and 51.07%, respectively.

EFFECT OF METAL FOAM FILLING POSITION AND POROSITY ON HEAT TRANSFER OF PCM: A VISUALIZED EXPERIMENTAL STUDY

The application of phase change material (PCM) in energy storage systems is limited by its low thermal conductivity. One of the effective methods to improve the thermal conductivity of PCM is to embed foam metal within it. To investigate the effects of foam metal infill position and porosity on the melting process and temperature distribution of PCM, a visualized experimental system study is built. Paraffin is employed as the PCM with a melting point of 62°C, while 85%, 90%, and 95% porosity copper foams are chosen in the experiment. The evolution of the liquid-solid phase interface and the temperature distribution in the PCM are recorded. Singlelayer filling schemes show that placing copper foam closer to the bottom accelerates melting, while double-layer schemes further optimize the melting time and temperature distribution. Additionally, decreasing the porosity of copper foam enhances heat transfer, shortening melting times. The study introduces a melting efficiency index, demonstrating that optimizing filling schemes and porosities improves the overall melting performance. When the copper foam with 90% and 85% porosity is arranged in the middle and bottom layers, respectively, the complete melting time is shortened by 38.2% and the maximum and average temperature differences are reduced by 30.0% and 45.2%, respectively, compared with pure paraffin. The findings contribute valuable insights into designing efficient PCM systems for thermal energy storage applications, emphasizing the importance of copper foam arrangement and porosity optimization.

Application of Solar Energy to Liquify Beewax

This study investigates the feasibility of using solar energy for melting recycled older combs and capping wax byproducts to create raw beeswax. The solar-driven beeswax melter is composed of a stainless steel container, a lean-to structure featuring polycarbonate sheet covers, a wooden solar heater, and parallel arrays of PV solar panels. The research contrasts three distinct approaches for melting beeswax: the conventional water bath technique, exclusive reliance on solar energy for melting, and the combination of solar energy and supplementary heat from solar panels. The traditional water bath method's effectiveness and the bulk temperature of the liquified beeswax were gauged. In the case of the solar-powered wax melting setups, the process's efficiency, the melted wax's bulk temperature, and various macroclimatic factors such as sunlight radiation, temperature, and relative humidity were documented. Based on the experimental outcomes, the beeswax melting efficiency was determined to be 73.4% for the traditional water bath method, whereas it escalated to 85.5% and 87.2% for the solar approaches, respectively. Hence, the utilization of solar techniques for beeswax melting is recommended.

An urban energy recycling system that recycles the waste heat from industry for deicing on urban road in winter-taking Harbin as an example.

Northern cities in China have frequently suffered from ice and snow disasters. On the other hand, Harbin mainly relies on coal-fired plants for heating during the winter time. However, coal-fired plants produce a significant amount of air pollution through the production of numerous hazardous gases. This thesis proposed an urban energy recycling system that uses waste gas from heating facilities to recycle waste heat and reduce air pollution in northern cities during the winter. This research made a hypothesis that wintertime ice and snow on city streets could be melted by using waste heat of waste gases from heating industries. The methodology of this research can be divided into three parts: Firstly, the principle of theenergy recycling system is designed based on investigation. Secondly, a simulation experiment is used to analyze the system's difficulties. According to the experiment, when anicy road is far away from the heating industry, ice melting efficiency is low. Finally, this research proposed a method for system improvement based on the findings of the experiment. The system's environmental and social benefits will likely lead to its future application in northern Chinese cities even if there are many application-related difficulties, such as the high cost of construction.