Phase change materials generally suffer from low thermal conductivity. To address this, the application of TPMS skeletons for optimizing PCM phase change is investigated to explore the efficiency enhancement of energy storage units. While isotropic TPMS architectures have been documented, their fixed topology often fails to match the anisotropic heat flux distribution typical of practical storage environments, preventing the full exploitation of the thermal transport potential inherent in TPMS structures. In this study, an anisotropic multi-directional gradient TPMS architecture is developed to regulate directional heat transport. Lattice Boltzmann simulations are employed to analyze the impact of different structures on energy storage efficiency. Compared to the traditional isotropic skeleton, an anisotropic architecture with reduced pores in the conduction direction and enlarged pores in the convection region increases energy storage efficiency by 13.8%. This performance is further enhanced through multi-dimensional porosity gradients. Specifically, the dual-gradient design achieves a 17.1% efficiency improvement over the isotropic case by optimizing heat delivery to stagnant zones, while the triple-gradient design attains a 22.4% total efficiency gain by effectively balancing lateral conduction and central convection. These findings provide a framework for optimizing phase change energy storage units via tailored architectural design.

This study proposes a novel annular heat exchange channel for shell-and-tube thermal energy storage (TES) systems to address the low heat transfer efficiency inherent in conventional straight-tube designs. The primary novelty of this configuration lies in its ability to simultaneously induce inward and outward melting fronts, thereby accelerating natural convection. A three-dimensional numerical model was developed to investigate the transient melting behavior and heat storage mechanisms of the phase change material (paraffin). The thermal performance was systematically evaluated under three distinct spatial configurations of the annular channel: Location-1 (near-center), Location-2 (center), and Location-3 (far-center). The major findings indicate that the novel annular design reduces the total melting time by up to 88.8 % compared to traditional straight-tube systems. Furthermore, comparative analysis reveals that the radial distance of the channel is not monotonically beneficial, confirming the existence of an optimal critical position. The optimal configuration (Location3) shortens the melting time by 72.7 % and increases the average heat storage rate by 71.2 % relative to Location-1. This research clearly demonstrates the underlying physical mechanisms of the new channel and provides quantitative guidance for the structural optimization of high-efficiency phase change TES technologies.

The evolution of the mushy zone is essential for elucidating the interfacial heat-transfer mechanisms in solidliquid phase change. However, experimental investigations on the mushy zone, especially the quantitative analysis of the spatiotemporal characteristics of the mushy zone under natural convection, are scarce in the literature. To address this gap, this study developed an experimental system that combines visible and infrared imaging to visualize and quantify the mushy zone during paraffin melting in a side-heated rectangular enclosure. Image post-processing technology was employed to extract and properly analyze the complex mushy zone, quantifying its width, average migration rate, and temperature gradient. Experimental results show that natural convection significantly impacts mushy zone evolution. Its morphology exhibits obvious nonlinear curvature, characterized by a narrower top and a wider bottom. Both the average migration rate and temperature gradient of the mushy zone vary significantly along the height of the enclosure. Compared to the bottom characteristic baseline, the average migration rate of the mush-solid interface at the upper characteristic baseline is approximately 9 times greater (0.62 mm/min) than the bottom baseline, and the temperature gradient increased to nearly double (1.46 degrees C/mm). In addition, changes in the heat-source temperature significantly affect the evolution of the mushy zone. As the temperature rose from 52 degrees C to 58 degrees C, the maximum width of the mushy zone decreased by 36%, and its average migration rate increased by 30%. These findings will provide significant experimental validation for enhancing multi-physics coupled heat transfer models and offer insights into the mechanisms of solid-liquid phase change.

The solidification process of composite phase-change materials (CPCMs) influences phase-change energy storage. The solidification of pure paraffin and CPCMs containing metal skeletons is investigated by experimental study. A solid-liquid phase-change platform was established to analyze the solidification characteristics of CPCMs. Internal temperature measurements revealed that metal skeletons significantly accelerate paraffin solidification, with the X-positive gradient skeleton achieving the shortest time of 97.8 min at cold-source temperatures of 5 degrees C. Lower cold-source temperatures increase the solidification rate. The temperature variation inside the CPCMs would be divided into three main stages, which is the quick cooling stage of the liquid phase, the solid-liquid coexistence stage, and the cooling stage of the solid phase. Notably, the duration of the solid-liquid coexistence stage is shortened as the cold source temperature decreases. The minimum duration of 31.25 min occurs at the point of the skeleton's center when temperature of cold source is 5 degrees C. A small temperature rise occurs during the solid-liquid coexistence stage of the solidification process, which is about 0.55 degrees C. Thermal non-equilibrium effects between skeletons and phase change materials are found to be significant and complex, with multiple peaks and valleys. Local thermal non-equilibrium effect becomes more pronounced when cold source temperatures are lower.

In this paper, homogeneous metal skeleton and gradient porosity skeleton are constructed by three-periodic minimal surface method ( TPMS). Based on the pore scale, the finite element method is used to simulate the solidification process with the solidification process of pure paraffin cavity, and investigate the influence law of the skeleton structure in the solidification of composite phase change material. Through the comprehensive analysis of solid-liquid phase change interface, overall solid phase rate, Nu number of cold source wall and cold storage performance, the following conclusion was obtained: Adding TPMS skeleton to the phase change cavity and the porosity of 0.78 phase change cavity was 94.1% shorter than the solidification time of pure paraffin phase change cavity, and the cooling storage rate was increased by 12.98 times. At the average porosity of 0.84, the porosity increases the solidification time of the cavity along the positive direction of x is the shortest, reducing the solidification time by 93.5%, and increasing the cooling storage rate by 12.60 times; the solidification time by 12.23% and the cooling storage rate by 15.3%.

The intermittency and volatility of renewable energy can be effectively addressed by phase change energy storage technology. Understanding the physical processes within the mushy zone is critical to grasping the underlying thermal storage mechanisms. In this study, the descending and melting processes of particle groups in the mushy zone were numerically simulated using the Finite Element Method (FEM). The fluid-solid interactions were resolved with the Arbitrary Lagrangian-Eulerian (ALE) method. The coupling between motion and phase change during the descent of particle groups is highly complex. Particle group motion is influenced by gravity, inter-particle repulsion, wall repulsion, and interactions with the fluid. In the descent process, particle descent and deflection occur simultaneously, with the larger particle playing a dominant role. When the larger particle is at the bottom of the three-particle group, its maximum velocity is 20.6 mm/s, which is 21.3 % higher than when it is placed at the top of the particle group. The flow field is driven by the motion of the particle group. The motion of the particle group, affected by its number and arrangement, influences the melting process. The average solid fraction of the five-particle group is 12.43 % higher in melting compared to the three-particle group, at t = 8 s. When the spacing is 5 mm, the solid fraction of the three-particle group is 30.95 % less than the solid fraction of the five-particle group, at t = 9 s. This research is helpful to comprehend the heat transfer mechanism of phase change within the mushy zone.

The solid-liquid phase change is a highly promising energy storage technology. However, the low thermal conductivity of phase change materials (PCMs) significantly limits the efficiency of energy storage. The addition of metal skeletons is very important in improving the heat transfer properties of the phase change process. In this study, the complex skeleton models with multi-gradient pore structures are generated using the Quartet Structure Generation Set (QSGS) method. Employing a two-zone model of the mushy zone, the three-dimensional lattice Boltzmann method (LBM) is utilized to investigate the solid-liquid phase change of PCMs containing porous skeletons with different directional gradients. The influences of skeleton gradients, including porosity gradient and pore density, on heat and mass transfer and the migration evolution characteristics of the mushy zone are discussed in detail. Results indicate that the direction of the porosity gradient has a significant impact on the phase change process. The horizontal negative gradient enhances thermal conductivity, resulting in a higher melting rate and a thinner mushy zone, whereas a horizontal positive gradient leads to a thicker mushy zone and a lower melting rate. The complete melting time for the horizontal negative gradient skeleton is reduced by 12.8% compared to the horizontal positive gradient skeleton. Additionally, variations in the vertical porosity gradient also affect the melting rate of PCMs, with a vertical negative gradient reducing the complete melting time by 11.4% compared to a vertical positive gradient. The gradient variations in pore density also influence heat transfer in phase change process, and the negative gradient in the horizontal direction enhances heat transfer more effectively than the positive gradient. The enhancing effect of the gradient pore density is further strengthened with increasing porosity. This study will provide a foundation for further exploration of the impact of QSGS skeletons on phase change process.

The addition of a metal skeleton significantly improves the heat storage/release rate of composite phase‐change materials (PCMs), taking as a critical factor in extending their application potential. When the numerical simulation with conventional thermal equilibrium model is used for high computational efficiency, its applicability is constrained in scenarios requiring precise characterization of heat transfer. To improve the simulation accuracy, the concept of contact thermal resistance, which refers to the heat transfer resistance between two adjacent objects, is introduced to construct the local thermal nonequilibrium (LTNE) model in the article. A V‐shaped nonuniform skeleton is proposed by combining several single‐directional gradient units. The comparison of numerical simulation with experimental results shows that the improved LTNE model achieves higher accuracy, with optimal agreement at a contact thermal resistance of 2.5 × 10 −4 m 2 K W −1 . The average relative error in total melting time with experimental data is significantly reduced from 16.67% to 2.00%, compared with the conventional thermal equilibrium model. The V‐shaped nonuniform skeleton is superior to the uniform skeleton with a reduction of 29.41% in melting time. This study provides an effective way to establish an accurate model of the melting process of composite PCMs.

Embedding a skeleton in an organic phase change material changes its heat transfer properties. The melting process of a composite phase change material embedded respectively with nylon, stainless steel, and aluminum alloy skeleton was investigated experimentally, and the effect of the skeleton material on the phase change process was analyzed in detail. The evolution of the phase-change interface was captured using visible-light imaging, and the temperature field distribution was obtained using an infrared camera. The temperature variations inside the composite phase change material were measured using high-precision thermocouples. The local thermal non-equilibrium effect between the skeleton and phase change material was analyzed using the difference between the temperatures of the skeleton surface and paraffin close to the surface. The results showed that the metal skeleton accelerated the migration of the phase change interface, whereas the nylon skeleton retarded the phase change process, in contrast to the pure phase change material. The complete melting time and energy storage rate of the composite phase change material with the aluminum alloy were lesser (53%) and 59.6% higher than those of the pure phase change material, respectively. The local thermal non-equilibrium effects in the melting process of composite phase change material with different material skeletons were significantly different. The larger the thermal conductivity ratio between the skeleton and phase change material, the more significant the thermal non-equilibrium effect. The maximum thermal non-equilibrium effect in the melting process of the composite phase change material with aluminum alloy skeleton was 1.59celcius.

Investigating the motion process of paraffin particle under a mesoscopic scale is very helpful to master the heat transfer mechanism of the mushy zone in solid-liquid phase change. Prior researches predominantly focused on either particle motion or phase change, without accounting for their coupling. In this study, the threedimensional finite element method is used to solve the motion and heat transfer of the particle, taking into account the coupling of motion and phase change. The moving grid is employed to trace the interface of moving particles and liquid using the Arbitrary Lagrangian-Euler method, which is able to calculate flow and heat transfer in fluid region and allow grid deformation in solid region. The results indicate that uneven fluid velocity around the particles results in non-uniform temperature gradients on particle's surface. In areas with larger temperature gradient, it melts more quickly and its deformation is obvious. The maximum is located at particle orientation angle 30 degrees. degrees . Changing the size and direction of fluid velocity will reinforce or inhibit the movement of particle. The changing time of motion direction when fluid velocity is-0.03 m/s shorten 2.7 times than when fluid velocity is-0.01 m/s. The initial temperature of the surrounding fluid has a positive relationship with the particle melting rate. The channel width affects significantly the motion and melting of particle. The initial position of particle has an important effect on it's falling movement, and the closer is close to the wall of channel, the greater the displacement of left and right movement.

The application of phase change materials (PCMs) in prefabricated buildings plays an important role in green building energy savings. In this paper, the wall with a phase change interlayer is composed of common building materials, and a phase change interlayer is filled with paraffin and nylon solid skeletons printed using 3D technology. The ordinary wall as the reference object is made of only common building materials, and its dimensions are the same as those of the composite wall with PCM interlayer. A comparison of unsteady heat transfer characteristics between ordinary wall and wall with a phase change interlayer is studied experimentally by infrared image and accurate temperature measurement. The experimental results show that the thickness, position of the phase change interlayer, and heating temperature have an important impact on the thermal insulating performance of the wall. According to the experimental data, when the interlayer thickness is 3 cm and located on the inner side of the wall with a heating temperature of 55 degrees C, the wall not only has the desired insulation performance but also has a high utilization rate of phase change materials. The research results provide a basis for further improvement of the wall by proposing a new application of phase change materials in prefabricated buildings.

The preparation of metal nanoparticles (NPs) on metal-organic frameworks (MOFs) has aroused great interest in the field of bacteriostasis. However, MOFs as nano-supports to form uniformly dispersed NPs loadings has still been in the exploratory stage. The use of Agx/Cu-BTC as nano-supports was investigated for the preparation of silver nanoparticles and their antibacterial activity. The post-synthetic exchange method was used to achieve the in situ loading of Ag NPs on copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC) nano-supports and the Agx/Cu-BTC (x = 7, 14, 21 % molar ratio) were successful synthesized. The crystal structure characteristics and the physicochemical properties of the prepared materials were analyzed by SEM, EDS, FT-IR, XRD, XPS, TG, and BET. Using Bacillus subtilis as the experimental strain and Cu-BTC as the antibacterial activity standard, the antibacterial performance of Agx/Cu-BTC was evaluated using the minimum inhibitory concentration test and the Kirby-Bauer test. According to the reaction mechanism of related antibacterial materials, a reasonable mechanism explanation was given for the antibacterial effect of Ag NPs. All characterization results demonstrated that the preparation of Ag NPs using Cu-BTC as nano-supports did not destroy the structure of Cu-BTC. Agx/Cu-BTC still maintained the ortho-octahedral structure, which demonstrated the in situ preparation of Ag NPs was achieved. With the ratio of Ag NPs increased, the specific surface area became smaller, the average pore size became larger, and the thermal stability was enhanced. Agx/Cu-BTC showed significantly stronger antibacterial activity than Cu-BTC. Among the synthesized materials, Ag21/Cu-BTC showed the strongest antibacterial activity, which was due to the more adsorption of Ag NPs onto the cell wall, causing irregular pits and damaging the cell wall and cell membrane. As a result, the cell membrane permeability was altered, allowing more nutrients to flow out of the cell. Ag NPs entered the cell causing a significant increase in the level of reactive oxygen species (ROS), leading to cell damage or death. The higher the concentration of Ag NPs, the more Ag+ was released and the stronger the antibacterial activity. Overall, the in situ preparation of Ag NPs by MOFs nano-supports has the potential to enhance the antibacterial performance of Ag NPs, making them more effective in applications.

Phase change energy storage technology has great potential for enhancing the efficient conversion and storage of energy. While triply periodic minimal surface (TPMS) structures have shown promise in improving heat transfer, research on their application in phase change heat transfer remains limited. This paper presents numerical simulations of composite phase change materials (PCMs) featuring TPMS skeletons, specifically gyroid, diamond, primitive, and I-graph and wrapped package-graph (I-WP) utilizing the lattice Boltzmann method (LBM). A comparative analysis of the effects of four TPMS skeletons on enhancing the phase change process reveals that the PCM containing the gyroid skeleton melts the fastest, with a complete melting time of 24.1% shorter than that of the PCM containing the I-WP skeleton. The PCM containing the gyroid skeleton is further simulated to explore the effects of the Rayleigh (Ra) number, Prandtl (Pr) number, and Stefan (Ste) number on the melting characteristics. Notably, the complete melting time is reduced by 60.44% when Ra is increased to 106 compared to the case with Ra at 104. Increasing the Pr number accelerates the migration of the mushy zone, resulting in fast melting. Conversely, the convective heat transfer effect from the heating surface decreases as the Ste number increases. The temperature differences caused by the local thermal non-equilibrium (LTNE) effect over time are significant and complex, with peaks becoming more pronounced nearer the heating surface. This study intends to provide theoretical support for the further development of TPMS skeletons in enhancing the phase change process.

Solid skeletons will play an important role in improving the thermal properties of phase change materials. For this reason, the efforts should be dedicated to studying the heat transfer characteristics of solid-liquid phase change with different structural skeletons. In this paper, the composite structures spliced with Gyroid and Diamond skeletons in the horizontal or vertical directions were established by using the Triply Periodic Minimal Surface method. A three-dimensional dimensionless lattice Boltzmann model of the phase change material (PCM) cavity with the spliced skeleton was developed by using the two-region model for solid-liquid phase change in the mushy zone. Based on the pore scale, the phase change heat transfer characteristics under the thermal conductivity ratio of the skeleton to PCM of 100 were analyzed in depth with constant temperature heating at the left wall surface. The results showed that the skeleton spliced in different directions has different effects on the temperature field and heat transfer characteristics of the phase change process. The (G + D)H spliced skeleton which was arranged by Gyroid and Diamond skeletons in the horizontal direction led to a faster melting rate of the PCM than the (D + G)H spliced skeleton which was arranged by Diamond and Gyroid skeletons. The promotion effect of a large porosity skeleton on the melting process of PCM was less than that of a small porosity skeleton. The dimensionless complete melting time for the cavity containing skeleton with porosity epsilon = 0.915 was increased by 35.7 % and 19.4 % compared to the cavities containing skeletons with porosity epsilon = 0.826 and 0.871, respectively. This study lays the foundation for the development and application of TPMS spliced skeletons in phase change heat storage and enhanced heat transfer technologies.

As a typical carbon-based material, activated carbon (AC) has satisfied adsorption performance and is of great significance in the field of volatile organic compounds (VOCs) pollutants removal. In order to further reveal the optimization mechanism of AC adsorption performance, coconut shell-based AC was selected as the research object, and different concentrations of HNO3 coupled with microwave were used for rapid modification and activation. The characteristic changes of pore structure and surface chemical of AC before and after rapid modification were analyzed, and the performance changes of VOCs absorption were discussed from the perspective of reaction kinetics. The pore structure and surface chemical properties of before and after modification were analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmeta-Teller (BET) analysis, Fourier Transform Infrared Spectroscopy (FTIR), and Boehm titration. The results showed that HNO3 coupled with microwave could significantly eliminate impurities in the pores of AC. After impregnation in HNO3 at a concentration of 1.5 mol L−1 and under microwave irradiation of 900 W, the number of micropore on the surface of samples increased slightly. When the impregnation concentration of HNO3 continued to increase, the two adjacent pore structures of the samples merged, which lead to a large decrease in the number of micropore and a corresponding increase in the proportion of mesoporous. Meanwhile, the specific surface area SBET of the modified NAC-6 sample increased to 1,140.40 m2 g−1, and the total acidic oxygen-containing functional groups on the surface increased by 0.459 mmol g−1 compared to that of the unmodified raw carbon. Furthermore, by analyzing the experimental results of formaldehyde adsorption on AC samples, it was concluded that the saturated adsorption capacity of the modified NAC-6 sample was 43% higher than that of the raw carbon. This study provides a more convenient and faster modification method for AC in the field of gas phase pollutants purification, which is helpful to realize the practical engineering application of AC with high efficiency, energy saving and sustainable.

将金属骨架加入到纯相变材料(石蜡)制备复合相变材料,以纯相变材料、复合相变材料为研究对象,建立数学模型.采用有限元软件模拟相变材料的熔化过程.结果表明:均匀、x、y、z-复合相变材料完全熔化时间分别为460 s、660 s、460 s、470 s,减小x方向圆柱骨架半径可使完全熔化时间增加43％,减小y方向的圆柱骨架半径对完全熔化时间无影响,减小z方向圆柱骨架半径可使完全熔化时间增加2％.在相同时间内,复合相变材料的液相率明显高于纯相变材料,纯相变材料、均匀、xy-复合相变材料完全熔化时间分别为1245 s、460 s、355 s,均匀、xy-复合相变材料的完全熔化时间分别比纯相变材料缩短了 63.1％、71.5％.研究表明,金属骨架的加入可明显改善换热状况,xy-复合相变材料在强化换热方面优于均匀-复合相变材料.

Hydrogen energy is considered to be the most potential "ultimate energy source" due to its high combustion calorific value, cleanliness, and pollution-free characteristics. Furthermore, the production of hydrogen via the electrolysis of water has the advantages of simplicity, high efficiency, environmentally safe, and high-purity hydrogen. However, it is also associated with issues such as high-power consumption for the reaction and limited large-scale application of noble metal catalysts. Metal-organic frameworks (MOFs) are porous composite materials composed of metal ions and organic functional groups through orderly coordination with large specific surface areas and large porosity. Herein, we focus on the research status of MOFs and their transition metal derivatives for electrocatalytic water splitting to produce hydrogen and briefly describe the reaction mechanism and evaluation parameters of the electrocatalytic hydrogen evolution and oxygen evolution reactions. Furthermore, the relationship between the catalytic behavior and catalytic activity of different MOF-based catalysts and their morphology, elemental composition, and synthetic strategy is analyzed and discussed. The reasons for the excellent activity and poor stability of the original MOF materials for the electrolysis of water reaction are shown through analysis, and using various means to improve the catalytic activity by changing the electronic structure, active sites, and charge transfer rate, MOF-based catalysts were obtained. Finally, we present perspectives on the future development of MOFs for the electrocatalytic decomposition of water.