Solid Phase Change Research Articles

A novel photocurable polymeric solid–solid phase change material for intelligent temperature regulators

The advancement of solid–solid phase change materials (SSPCMs) with crystalline segments embedded onto crosslinked polymer backbones offers a promising solution to the leakage problems associated with traditional phase change materials. Despite its potential, this technology faces challenges, including energy-intensive synthesis processes of SSPCMs and difficulties in custom designing materials for confined spaces. Herein, we introduce a novel strategy for the rapid preparation of polyurethane acrylate-based SSPCMs via UV-initiated polymerization. By leveraging crystalline segments from polyethylene glycol, the resulting SSPCM exhibits an impressive enthalpy of 110.4 J⋅g−1, enabling seamless transitions from rigid to soft states during solid–solid phase changes. When applied in portable electronic devices, this SSPCM can be synthesized in-situ to meet various size requirements, demonstrating exceptional temperature regulation performance based on latent thermal energy storage mechanisms. Furthermore, by integrating thin layers of carbon nanotubes (CNTs) onto the rough surfaces of SSPCM films and employing a face-to-face configuration to convert temperature-sensitive mechanical changes into electric resistance variations, we have engineered high-temperature alarms for SSPCM-based temperature regulators. The advantages of this preparation strategy, combined with the thermal regulation capabilities and innovative temperature alarm design, underscore the significant potential for intelligent and adaptive applications of SSPCMs in advanced technological landscapes.

The Effect of the Surrounding Matrix on Spin Transition Nanoparticles: How Shell Characteristics Alter Core Elastic Properties in Core‐Shell Particles

A surrounding matrix is known to alter nanoparticle spin transitions, the solid state structural phase changes associated with transitions between high spin (HS) and low spin(LS) states. To better quantify how the spin transition solid and surrounding matrix interact, several series of core‐shell particles were prepared based on RbxCo[Fe(CN)6]z∙nH2O, RbCoFe‐PBA, as spin transition core with isostructural shells of different compositions and thicknesses. Synchrotron PXRD through the thermal high HS to LS, the LS to photoexcited high spin (PXHS), and thermal PXHS to LS transitions, show the activation energy is lowered as shells become thicker and stiffer. Calorimetry data coupled with transition state theory analysis indicate the core stiffens in the core‐shell particles relative to the uncoated particles. The conclusion is supported by microstrain analysis that shows stiffer shells limit the extent to which the core distorts as individual sites transition, leading to the lower activation energy. Finally, differences in lattice mismatch with different shell materials are shown to alter the mechanism by which the transition progresses.

Enhancing building energy efficiency: Innovations in glazing systems utilizing solid-solid phase change materials

This study investigates the energy efficiency of a double-glazing window (DGW) integrating a solid–solid phase change material (SSPCM) with limited thickness, applied to the inner glass pane within the air gap. Numerical model, validated against experimental data, is developed using a finite volume method in ANSYS Fluent. In this model, the Discrete Ordinates (DO) model is applied to simulate radiation, while the enthalpy-porosity approach is used to capture the solidification and melting processes in the phase change material. With this model, the energy performance of the system is analyzed under various transient temperature values (10 to 30 °C) and ranges (1 to 5 °C) during the coldest and hottest days of the year, as well as during cloudy and sunny days in Montreal (Dfb), Vancouver (Cfb), and Miami (Aw). According to the obtained results in Montreal, the DGW-SSPCM system consistently saves energy under summer sunny conditions, with optimal performance when the SSPCM remains transparent. However, it incurs energy losses in cloudy days, where the energy lost is 2.3 times greater than the energy saved in sunny days. In Vancouver, the system shows consistent energy savings, particularly at Tc = 30 °C, with average savings of 20.5 kJ (23 %) under summer sunny conditions. The system is most beneficial in Vancouver, where winter energy savings in cloudy days (50.6 kJ) are 7.1 times greater than the losses in sunny days (7.1 kJ). In Miami, the system results in energy losses by 60 % and 5 % (at Tc = 30 °C) under both summer sunny and cloudy conditions, respectively, indicating unsuitability for its climate. During winter sunny conditions, all three cities experience energy losses, with Vancouver showing the lowest of 7.1 kJ (3 %) and Montreal the highest of 64.4 kJ (19 %) at Tc = 30 °C. In winter cloudy conditions, the system saves energy in all cities, with the highest savings in Miami of 54.5 kJ (26 %) at Tc = 30 °C. Overall, the SSPCM-DGW system has proven to be beneficial in Vancouver across various conditions in terms of energy and visual performance. These findings highlight the necessity of considering localized climate factors when designing and implementing energy-efficient glazing systems. Finally, the SSPCM-DGW system has provided complete visual clarity during office hours, making it more suitable for commercial buildings.

The clogging effect of nanoscale zero valent iron corrosion in bicarbonate anaerobic water on porous media: A real-time pore-scale visualization

The corrosion-induced permeability changes of nanoscale zero-valent iron (NZVI) are one of the crucial factors constraining the successful application of NZVI in the remediation of contaminated groundwater. It is of great significance to study the dynamic evolution of corrosion products of NZVI after NZVI is injected into porous media and its influence on pore plugging effect from the pore scale. Micro computed tomography (Micro-CT) imaging technology, mineralogical characterization and theoretical calculations were used to understand the details of NZVI corrosion plugging porous media at the pore scale. This study reveals the factors of NZVI corrosion plugging porous media, namely, gas production (H2) in the early and middle stages of corrosion (before 90 days) and solid phase changes (NZVI volume increase and migration) in the later stages (after 90 days). The permeability loss rate of the porous media was 66.8%, 87.3%, 79.4%, and 53.6% at the corrosion times of 30, 60, 90, and 120 days, respectively. After 90 d of corrosion, the particle size of NZVI increases by 7.9%, and the secondary minerals formed by corrosion are mainly Fe3O4/γ-Fe2O3 and FeOOH. In addition, this study also found that the migration of NZVI after 90 d was due to its corrosion reducing the magnetic attraction between particles, dissociating into smaller particles or agglomerates under the action of fluid dynamics, resulting in its redistribution in the porous medium and causing blockage. This study clarifies that NZVI corrosion plays a vital influence in affecting the permeability and clogging of porous media, providing valuable guidance for optimizing NZVI-based remediation technologies.

Colossal Barocaloric Effect in Encapsulated Solid‐Liquid Phase Change Materials

AbstractBarocaloric cooling as an emerging cooling technology offers an eco‐friendly alternative to traditional vapor compression refrigeration. Research on barocaloric materials primarily concentrates on solid–solid phase change materials (PCMs), among which plastic crystals exhibit colossal barocaloric effect. Solid‐liquid PCMs such as paraffin also exhibit giant barocaloric effect, however, their potential is often overshadowed by leakage issues. In this work, a strategy is demonstrated by encapsulating solid‐liquid PCMs into porous carbon matrixes to generate a large family of colossal barocaloric materials. In practice, by orthogonally combining paraffins with encapsulation matrixes like graphene foam, carbon nanotube foam, and carbon foam, it can be obtained composites that work without leakage issues. The significant advantage is their colossal barocaloric effect with the highest entropy value up to 570 J K−1 kg−1 in paraffin‐20@graphene foam. Moreover, the composites possess thermal conductivity up to 89.9 W m−1 K−1 in paraffin‐20@carbon foam, and tunable working temperature in the range of 270—330 K. Most importantly, this strategy, demonstrated with 5 solid‐liquid PCMs and 3 encapsulation matrixes in this work, is just the beginning. Further exploration with more materials can develop a huge family of encapsulated solid‐liquid PCMs with colossal barocaloric performance for modern cooling technology.

Robust Solid–Solid Phase Change Coating Encapsulated Glass Fiber Fabric with Electromagnetic Interference Shielding for Thermal Management and Message Encryption

AbstractElectromagnetic interference (EMI) shielding composites with both thermal response/management functions and message transfer/encryption behavior are ideal for use in fields such as aerospace, construction engineering, and military equipment. In this work, a self‐cross‐linking supramolecular solid–solid phase change polyethylene glycol (ScPEG) coating is prepared based on multiple hydrogen bonds, which is used for encapsulating glass fiber fabric (GFF) modified with silver nanowires (AgNWs). The solid–solid phase change coating is obtained through the hydrolysis‐condensation of PEG with a reactive silanol end group. Polyethylene glycol molecular chains can store and release heat by switching between the crystalline and amorphous state. The silanol groups can form supramolecular networks through the physical cross‐linking of multiple hydrogen bonds, resulting in an excellent thermal stability. In particular, hydrogen bonds between ScPEG and AgNW‐modified GFF (A‐GFF) enhance interfacial interactions, and the resulting robust structure enables an efficient stress transfer. ScPEG‐coated A‐GFF can achieve a tensile strength of up to 191 MPa and a tunable EMI shielding effectiveness (SE) of 40 to 72 dB depending on the number of fabric layers. Moreover, the fabric exhibits a flexible thermal response characteristic, an outstanding thermal management capability, and potential message encryption behavior.

A Novel Concept of Nano-Enhanced Phase Change Material.

In the actual context of growing concerns over sustainability and energy efficiency, Phase Change Materials (PCMs) have gained attention as promising solutions for enhancing energy storage and release efficiency. On another hand, materials based on graphene oxide (GO) have proven antibacterial activity, biocompatibility, efficiency in microbial growth inhibition, and pollutant removal. Integrating nanoparticles into PCMs and creating Nano-Enhanced Phase Change Materials (NEPCMs) have opened new horizons for optimizing the performance of these systems and sustainable development. The key objective of this work is to gain insight into NECPMs, which are used in solar wall systems to enhance solar energy storage. Paraffin RT31 was mixed with Cu nanoparticles, graphene oxide (GO), and Cu-decorated GO (Cu@GO) at loading ratios ranging from 1% to 4% (w/w nanoparticles with respect to RT31). The compositions were characterized through Differential Scanning Calorimetry (DSC) and rheology tests. The decoration of the carbon-based nanoparticles was performed using the ultrasonication procedure, and the decoration efficiency was confirmed through X-ray Photoelectron Spectroscopy (XPS). The rheologic measurements were performed to correlate the flow behavior of the NEPCM with their composition at various temperatures. The study methodically investigated these composites' latent heat values, phase change peak temperatures, and solidification phase change temperatures. Compared to pure paraffin, the solidification of the formulations obtained using Cu@GO exhibits the largest increase in latent heat, with a 12.07% growth at a concentration of 2%. Additionally, at a 4% concentration of NEPCM, the largest increase in thermal conductivity was attained, namely 12.5%.

Theoretical study of solidification phase change heat and mass transfer with thermal resistance and convection subjected to a time-dependent boundary condition

The solidification of phase-change materials (PCMs) is a key process that occurs commonly in materials science and metallurgy, such as in the casting of alloys and energy management systems. There is a lot of literature in this area that assumes the PCMs are in close contact with the heat source or sink. However, a non-freezing wall frequently encloses them in practical situations. This work presents a phase change problem that describes the solidification of a semi-infinite PCM with thermal resistance. We assume that time-dependent heat flux drives the solidification process. The PCM first convert into mush and then into solid, which leads to a three-region problem. The current study accounts for both conduction as well as convection heat transfer mechanisms. Unfortunately, the exact solution to such problems with time-dependent flux-type boundary conditions may not be possible. Thus, there is considerable interest in deriving the analytical solution. The space–time transformation yields the analytical solution to the problem. A numerical example of Al−Cu alloy with 5%Cu is presented to demonstrate the current study. Thermal resistance shows a pronounced impact on the temperature field. Lower thermal resistance offers faster solidification rate. It is found that as the heat transfer constant increases, the rate of propagation of solid–mush and mush–solid interfaces gets enhanced. In addition, the growth of thermal resistance is of linear nature, with variation in the value of Q. The solidified region has higher concentration than the mush region. The current study is applicable to both eutectic systems and solid solution alloys.

Roadmap for the Development of Transition Metal Oxide Cathodes for Rechargeable Zinc-Ion Batteries

Continued efforts towards the decarbonization of the power sector through an uptake of renewable energy generation, namely solar and wind, play a key role in the fight against climate change. However, due to their variable nature, the simultaneous implementation of energy storage solutions capable of ensuring a reliable delivery of energy at any time of day is of the utmost importance. Aqueous rechargeable zinc-ion batteries (RZIBs) are a promising technology for this end. Offering several advantages over lithium-ion batteries in terms of cost, environmental impact, and material abundance, the investment in RZIB research continues to grow. However, the realization of commercial RZIBs is currently hindered by the lack of cathode materials with adequate performance for long-term storage solutions. This is the case for manganese (e.g., MnO2, Mn2O3, Mn3O4) and vanadium (e.g., V2O5, VO2) based oxides, which exhibit considerable capacity fade during realistic charge and discharge times. While simple transition metal oxides (MyOx, M=transition metal) are one of the most studied classes of materials for RZIB cathodes, a literature survey shows that there are still many unexplored redox active elements and redox pairs which may be employed in next-generation RZIBs. Therefore, to accelerate the discovery of these novel cathode systems, we mapped the theoretical Zn intercalation potential for simple oxides from 12 different transition metals using Density Functional Theory (DFT) calculated thermodynamic properties. The screened elements were chosen upon considering their commercial availability, toxicity, price, and existence of previously reported structures containing zinc. During the present analysis, the feasibility of Zn intercalation for each system was accounted for by analyzing the atomic arrangement in the charged and discharged phases. Experimentally obtained Pourbaix Diagrams were also used to probe the electrochemical stability of the cathodes in aqueous solution, with the possibility of electrolyte degradation (oxygen or hydrogen evolution reaction) and competing reactions (metal dissolution or solid phase change) also considered. Experimental validation of the computationally predicted potentials was also done for select materials. The result for the 35+ redox pairs evaluated in this study provides a clear roadmap for the future development of RZIBs cathodes.

3D Numerical Modeling to Assess the Energy Performance of Solid–Solid Phase Change Materials in Glazing Systems

This research investigates the energy efficiency of a novel double-glazing system incorporating solid–solid phase change materials (SSPCMs), which offer significant advantages over traditional liquid–solid phase change materials. The primary objective of this study is to develop a 3D numerical model using the finite volume method, which will be followed by a parametric study under real climatic boundary conditions. A proposed double-glazing setup featuring a 2 mm layer of SSPCM applied on the inner glass pane within the air gap is modeled and analyzed. The simulations consider various transient temperatures and ranges of the SSPCM to evaluate the energy performance of the system under different weather conditions of Miami, FL during the coldest and hottest days of the year, both in sunny and cloudy conditions. The results demonstrate a notable improvement in energy performance compared to standard double-glazing windows (DGWs), with the most efficient SSPCM configuration exhibiting a phase transition temperature and range of 25 °C and 1 °C, respectively. This configuration achieved energy savings of 24%, 26%, and 23% during summer sunny, winter sunny, and winter cloudy days, respectively, relative to DGWs during cooling and heating degree hours. However, a 3% energy loss was observed during summer cloudy days. Overall, the findings of this study have shown the potential for energy savings by incorporating SSPCM with suitable thermophysical properties into double-glazing systems.

High reflectivity and latent heat synergetic TiO2/Cs0.33WO3-PU double-layer materials with zero transmittance

Passive Cooling Technology, as a method of achieving long-term refrigeration without the need for external energy input, has emerged as an alternative to traditional energy-intensive cooling, garnering increasing attention from academia and industry. However, current passive cooling technology faces challenges such as incomplete solar energy reflection, overcooling, and inevitable absorption of solar radiation and surrounding environmental heat. This paper presents a passive cooling bilayer film with latent heat storage capability, composed of a solid–solid phase change polyurethane (PU) matrix with added TiO2 and Cs0.33WO3.TiO2/Cs0.33WO3-PU exhibits minimal solar transmittance, with reflectance and emissivity rates of 84.46 % and 93.08 %, respectively. The solid–solid phase change matrix effectively mitigates overcooling and heat input issues, reducing temperature fluctuations and peaks, and thereby enhancing passive cooling performance. At the phase transition temperature (306 K), TiO2/Cs0.33WO3-PU achieves cooling powers of 113.77 W/m2(day time) and 173.19 W/m2(night time), the temperature can be reduced by 14.3 °C under 100 mW/cm2sunlight. Additionally, TiO2/Cs0.33WO3-PU demonstrates outstanding thermal stability and reliabitity, hydrophobicity, as well as resistance to UV aging. Moreover, it offers the flexibility to adjust the phase transition temperature and latent heat of the solid–solid phase change matrix according to specific environmental conditions. TiO2/Cs0.33WO3-PU combines passive cooling materials with phase change materials, and complements each other’s advantages. TiO2/Cs0.33WO3-PU not only improves the cooling power, but also provides a new solution to the problem of heat input and supercooling of passive cooling materials. TiO2/Cs0.33WO3-PU also provides new possibilities for the application of passive cooling materials in the fields of long-term outdoor building cooling, human heat management, food preservation and electrical equipment cooling.

Comparative experimental study of the effect of loading rate on the typical mechanical properties of bubble and clear ice cubes

Icing is a common liquid–solid phase change process that usually has negative effects. Bubbles will form in ice since air is significantly less soluble in ice than it is in water and these bubbles will affect the mechanical properties of ice cubes. To quantitatively investigate the effect of air bubbles on the mechanical strength of ice cubes, an experimental setup is built to explore the mechanical strength and modulus of clear and bubble ice cubes at different loading rates. The results show that even a low volume fraction of air bubbles in the ice cubes as low as 1.98% can have a significant effect on their mechanical properties. The weakening of tensile, compressive and bending strengths by air bubbles is almost less than 20%, while the weakening of shear strength by air bubbles reaches almost 60%. The effect of air bubbles on the four typical mechanical moduli does not exceed 20%. This research helps to optimize the de-icing technique and also provides methods and ideas for preparing ice.

Single‐step preparation of intrinsic solid–solid phase change materials with excellent anti‐leakage and form‐stable performance

AbstractPhase change materials (PCM) often encounter severe problems of leakage and shape collapse concerns. Chemical modification methods, utilizing chemical bonds to bind phase change molecular chains, have the potential to address the above‐mentioned problems radically. However, this approach often entails the use of expensive raw materials and complex processes. Therefore, a simple one‐pot preparation method had been reported using earth‐abundant and inexpensive octadecyl methacrylate (OMA) and 1,6‐hexanediol diacrylate (HD) as raw materials to prepare PCM with a molecular structure of cross‐linked polymer main chains and phase change side chains through free radical polymerization. Owing to the three‐dimensional polymer main chain structure, it exhibited excellent leakage‐proof performance, maintaining its form‐stable nature at 70°C with no obvious leakage observed during the phase change process, confirming it to be an excellent intrinsic solid–solid PCM (SSPCM). Additionally, the introduction of the cross linking segment significantly improves its thermal stability, and the 50% degradation temperature increased significantly from 228.8 to 355.9°C. Moreover, the latent heat increased with the decrease of the crosslinking density until the molar ratio of HD/OMA was reduced to 1/40 and then tended to reach constant. At the optimal ratio the latent heat of SSPCM can reach 88.23 J g−1. Excessive crosslinking density will affect the stacking tightness of molecular chains during the crystallization process, thereby reducing the latent heat.

Bis(dialkylammonium)-based hybrid organic–inorganic ionic materials as solid–solid phase change materials

The application of phase change materials (PCMs) in thermal energy storage (TES) systems is often restricted by challenges such as volume expansion, phase segregation, stability issues and potential leakage, particularly prominent in conventional solid–liquid PCMs. In response to these limitations, solid–solid PCMs have emerged as a promising alternative, garnering increasing attention. While both organic and inorganic solid–solid PCMs have been extensively studied, hybrid organic/inorganic materials represent a distinct class of solid–solid PCMs that have recently garnered significant interest due to their inherent properties such as high thermal stability, non-flammability or long cycle life. Organic-inorganic layered perovskites are emerging as potential good solid–solid PCMs as they present energetic solid–solid transitions and high thermal stability. In this work we propose the synthesis and thorough thermal characterization and cyclability of a series of new hybrid organic–inorganic ionic materials based on n-dialkylamines of different lengths (C8, C10, C12 and C18) with general formula of the type 2[(CnH2n+1)2NH2][MX4], using three different tetrachlorometalates anions ([FeCl4]2-, [MnCl4]2- and [CuCl4]2-). Among the new ionic materials prepared six of them have shown solid–solid transition enthalpies higher than 100 J/g. In particular, the 3 bearing the secondary n-dioctadecylamines as cations have shown unprecedent solid–solid transitions enthalpies ca. 90 °C, for this kind of ionic materials of 167.5 J/g, 157.7 J/g and 146.9 J/g for [DODA]2[MnCl4], [DODA]2[CuCl4] and [DODA]2[FeCl4] respectively. In addition, the latter ionic materials have undergone reliability tests showing excellent performance up to 500 heating/cooling cycles.

Mechanically strong, healable, and recyclable supramolecular solid–solid phase change materials with high thermal conductivity for thermal energy storage

Conventional polymeric solid–solid phase change materials (SSPCMs) have garnered significant attention in the development of state-of-the-art latent heat storage (LHS) systems. However, the industrial application of polymeric SSPCMs is compromised by inferior mechanical properties and intrinsic low thermal conductivity. In addition, they are unable to be recycled and self-healed due to permanently cross-linked structures. In this study, a series of healable and recyclable supramolecular SSPCMs (PEG4K-Bx-PEG6K), possessing robust tensile strength (∼22.90 MPa), excellent strain-at-break (∼733.62 %), and high toughness (∼120.05 MJ/m3), are designed and developed by incorporating dynamic boroxines and hydrogen bonds. Because of the reversibility of dynamic boroxines and hydrogen bonds, the PEG4K-Bx-PEG6K was able to be healable and conveniently processed into packaging bag. More importantly, the PEG4K-Bx-PEG6K also possessed high thermal storage capacity (98.03 J/g), and excellent thermal shape memory capability. To achieve efficient heat transfer, an orientated solar thermal composite with high thermal conductivity was fabricated by compression-induced repetitive stacking of oriented graphene nanosheets (GNs) layers in PEG4K-Bx-PEG6K. Thanks to the efficient heat conduction of oriented GNs layers in the composite, the directional thermal conductivity of composite was up to 3.639 W/mK at 5 wt% loading of GNs. Combining the above excellent heat conduction, the solar thermal composite developed in this work offered efficient solar thermal conversion, fast transportation and storage of the harvested thermal energy.

Saturated phase change threshold of plume flow gas species under low temperature and rarefied environment

Gas species in high altitude plume flow are all exposed to low temperature, thus making possible phase change processes on those other than H2O vapor. In order to obtain saturated threshold of gas species, which is normally abundant in plume flow, this study establishes Gibbs phase calculation method for CO2, CO, H2, and N2. The non-continuum effect caused by rarefied gas environment is quantitatively calculated by ratio between molecular free path scale and characteristic length of investigated object. Validation on Gibbs method is guaranteed by comparison between calculated results and data from American National Standards Institute (ANSI), while non-continuum effect method is verified by revealing essential reason for gas-solid phase change processes resembling droplet condensation phenomenon observed in high altitude environment. According to the results, non-continuum effect only influences gas-solid boundary. Phase change for rarefied gas species can only occur under low temperature. Saturated threshold deflects toward solid phase region below specific molecules number density, thus decreasing gas to solid phase change trend. Both increasing on characteristic length and existence of other gas components contamination decreases non-continuum effect. Variation on non-continuum effect shows biggest influence on CO2 saturated phase change threshold, while shows smallest influence on that of N2.

Influence of biomass fly ash on durability of self-consolidating cement-tailings grout: Resistance to freeze-thaw cycles and sulfate attack

The durability of backfills is a crucial factor in maintaining the long-term stability of the mine backfill area. Partial replacement of cement by biomass fly ash (BFA) is a cost-effective and sustainable way for viscosity control of self-consolidating cement-tailings grouts (CTG), however, the unfavorable changes of pore structure may affect the durability during the service life. This study investigates the resistance of self-consolidating CTGs to 90 freeze-thaw cycles and 180 days sulfate attack, with and without BFA addition. The mechanical properties and relative dynamic modulus of CTGs were measured and analyzed during the exposure to freeze-thaw cycles and sulfate attack. The changes in pore structure, solid phase, and microstructure were also studied. The results demonstrate that the role of 30 % BFA addition on resistance to freeze-thaw cycles and sulfate highly depends on the water-to-binder ratios of hardened CTGs. At a low water-to-binder ratio of 0.6, the addition of BFA can enhance the performance of concrete in terms of its resistance to freeze-thaw cycles and sulfate attacks. At the water-to-binder ratios of 0.8 and 1.0, BFA can increase the resistance to sulfate attack but degrades the performance after freeze-thaw cycles. At a high water-to-binder ratio of 1.2, the addition of BFA reduces resistance to freeze-thaw cycles and sulfate attack. The varying effects of BFA with different water-to-binder ratios are attributed to the pore structures. When the water-to-binder ratio is 0.6, the CTG containing BFA exhibits the best resistance to freeze-thaw cycles and sulfate attack. This provides insights into the design and application of novel self-consolidating CTGs in engineering sites.

CEMENT COMPOSITES WITH THE ADDITION OF PHASE-CHANGE MATERIALS AS INNOVATIVE CONSTRUCTION MATERIALS FOR MAINTAINING A PLEASANT LIVING ENVIRONMENT

The aim of this work was to investigate the possibility of the addition of phase-change material (PCM) to mortar mixtures and its effect on the material’s mechanical and thermal properties. This work included the preparation of mortar mixtures with two different water-to-cement (w/c) ratios as well as various PCM volume-fraction additions. The main objectives were to determine the effect of the w/c ratio as well as the PCM addition on the mechanical properties of the mortars after (3, 7, and 28) d of curing. Additionally, we examined the microstructure of the prepared mortar composites and evaluated their thermal behaviour. Microstructural analysis revealed the uniform distribution of PCM microcapsules throughout the mortar matrix, which contributes to the efficient storage and release of thermal energy. Thermal properties were analysed by repeated heating and cooling cycles of the mortar composites. The repeatability of the cyclic testing results showed a reversible melting and solidification phase change of the PCM and indicated the potential use of such composites as an energy-efficient building material. The study highlighted the potential incorporation of the PCM into mortar mixtures to improve their thermal properties while maintaining the mechanical integrity. The research findings provide valuable insight into the development of sustainable building materials with greater energy efficiency and structural reliability.

Optimal design on fin-metal foam hybrid structure for melting and solidification phase change storage: An experimental and numerical study

A fin-metal foam composite structure is employed in the phase change energy storage coupled Organic Rankine Cycle system to enhance thermal performance. The 3-D numerical model is validated through an experimental system to analyze the impact of metal foam parameters and fluctuating heat source parameters (amplitude and half-period) on the system's storage-release process during heat source fluctuation. According to the Taguchi method, metal foam porosity significantly influences the total storage-release time. An increase in porosity leads to a continuous increase in the total storage-release time, while an increase in PPI and a decrease in heat source amplitude initially increase and then decrease the total storage-release time. Under constant metal foam PPI (10) and porosity (0.97), Case T (half period = 60 and amplitude = 1.0) demonstrates a 2.04 % increase in average heat transfer rate and a 1.78 % reduction in total storage-release time compared to Case 0 (constant heat source). The average heat release rate sees a 4.23 % increase, while total heat storage and heat release rise by 0.96 % and 1.87 %. The research has specific technical significance for the photothermal application of phase change energy storage technology to the variability and unpredictability of solar energy.

Applying isovolumic steam capsule as new thermal energy storage unit

In order to make up the inefficiencies of liquid–solid phase change material (PCM) such as low latent heat and low heat transfer rate, the possibility of adopting water steam as the phase change material is explored. Although great volume change occurs during the gas–liquid phase-changing, the specific latent heat is at least one order of magnitude larger than that of liquid–solid phase-changing. To minimize the adverse effect of the great volume change during vaporization or condensation, the steam can be accommodated inside sealed vessel with sturdy shell. In this study, an isovolumic steam capsule (ISC) was made by filling a cylinder with a small amount of liquid water and then heated and boiled to extinguish the non-condensable gas (NCG) before sealing it. Thermodynamic analysis shows the thermal energy contained in the isovolumic steam capsule per unit volume increases in approximately an exponential manner with the increase of temperature due to the evaporation of liquid, and can reach several times that of liquid–solid phase change material, demonstrating great potential as energy storage material. The heat transfer experiments show that the energy charging and discharging rates increase with the temperature difference. There exists thermodynamic non-equilibrium during heat transfer and the deviation from saturation enlarges with increasing temperature difference and non-condensable gas concentration. For both charging (vaporization) and discharging (condensation), a higher non-condensable gas concentration in the steam exhibits larger heat transfer rate in the beginning, but smaller heat transfer rate in the later stage. The mechanism of vaporization and condensation in the isovolumic steam capsule awaits to be further clarified.