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As an advanced energy storage technology, the compressed CO2 energy storage system (CCES) has been widely studied for its advantages of high efficiency and low investment cost. However, the current literature has been mainly focused on the TC-CCES and SC-CCES, which operate in high-pressure conditions, increasing investment costs and bringing operation risks. Meanwhile, some studies based on the phase-change CO2 energy storage system also have had the disadvantages of low efficiency and the extra necessity of heat or cooling sources. To overcome the above problems, this paper proposes an innovative compressed CO2 phase-change energy storage system. During the energy charge process, molten salt and water are used to store heat with a smaller temperature difference in heat exchangers, and high-pressure CO2 is reserved in liquid form. During the energy discharge process, throttle expansion is applied to realize the evaporation at room temperature, and CO2 absorbs the reserved heat to improve the power capacity in the turbine and the system energy storage efficiency. The thermodynamic and exergoeconomic studies are performed firstly by using MATLAB. Then, the parametric study based on energy storage efficiency, system unit product cost, and exergy destruction is analyzed. The results show that energy storage efficiency can be improved by lifting liquid CO2 pressure as well as compressor and turbine isentropic efficiencies, and CO2 evaporation pressure has the optimal pressure point. The system unit product cost can be reduced by decreasing liquid CO2 pressure and compressor isentropic efficiency, while CO2 evaporation pressure and turbine isentropic efficiency both have optimal points. Finally, the optimization of two performances is performed by NSGA-II, and they can reach 75.30% and 41.17 $/GJ, respectively. Moreover, the optimal energy storage efficiency is obviously higher than that of other energy storage technologies, indicating the great advantage of the proposed system. This study provides an innovative research method for a new type of large-scale energy storage system. [ABSTRACT FROM AUTHOR]

Given two phases in equilibrium in a porous solid, the heavy phase lying above the light phase in a gravitational field, we stabilize this adverse density arrangement by heating from below and derive a formula for how steep the temperature gradient must be to do this. The input temperature gradient has two effects on the stability of our system. Its effect on the heat convection is destabilizing, its effect on the heat conduction at the surface is stabilizing. By directing our attention to the case of zero growth rate, we obtain the critical value of the input temperature gradient as it depends on the permeability of the porous solid, the density difference across the surface, the distance between the planes bounding our system, and the physical properties. Our problem makes connections to the Bénard problem where it has two, one, or no critical points, and to the Rayleigh–Taylor problem where it has no critical points. [ABSTRACT FROM AUTHOR]

With escalating energy demands, solar power stands out for its abundance and renewable advantages, presenting a paramount sustainable solution. Herein, we tactically incorporate phase change material (PCM) into solar energy systems, resulting in substantial enhancements in energy storage and utilization. Through numerical simulations, the thermal dynamics and phase change processes associated with various heating methodologies are investigated, aiming to achieve optimal thermal performance and energy efficiency. Detailed analysis of temperature dynamics within the PCM under two distinct heating methods reveals pivotal thermal fluctuations in both the PCM and water during heat release. The results indicate that bottom heating promptly induces rayleigh convection, resulting in a uniform temperature and a stable phase interface, which are desirable for heat transfer. In contrast, central tube heating concentrates heat transfer in the upper PCM layer, leading to an uneven phase interface and thermal stratification. Configurations with two horizontally aligned heating tubes result in a 36% reduction in melting duration compared to the single central tube setup, highlighting enhanced efficiency. Additionally, the bottom heating approach demonstrates improved energy storage efficiency in both the initial and second heating cycles. These findings highlight the potential of PCM-integrated combined heating systems for solar energy capture, confirming their efficiency and practicality in addressing modern household energy demands. [ABSTRACT FROM AUTHOR]

A reconfigurable metasurface constitutes an important block of future adaptive and smart nanophotonic applications, such as adaptive cooling in spacecraft. In this paper, we introduce a new modeling approach for the fast design of tunable and reconfigurable metasurface structures using a convolutional deep learning network. The metasurface structure is modeled as a multilayer image tensor to model material properties as image maps. We avoid the dimensionality mismatch problem using the operating wavelength as an input to the network. As a case study, we model the response of a reconfigurable absorber that employs the phase transition of vanadium dioxide in the mid-infrared spectrum. The feed-forward model is used as a surrogate model and is subsequently employed within a pattern search optimization process to design a passive adaptive cooling surface leveraging the phase transition of vanadium dioxide. The results indicate that our model delivers an accurate prediction of the metasurface response using a relatively small training dataset. The proposed patterned vanadium dioxide metasurface achieved a 28% saving in coating thickness compared to the literature while maintaining reasonable emissivity contrast at 0.43. Moreover, our design approach was able to overcome the non-uniqueness problem by generating multiple patterns that satisfy the design objectives. The proposed adaptive metasurface can potentially serve as a core block for passive spacecraft cooling applications. We also believe that our design approach can be extended to cover a wider range of applications. [ABSTRACT FROM AUTHOR]

As an advanced energy storage technology, the compressed CO2 energy storage system (CCES) has been widely studied for its advantages of high efficiency and low investment cost. However, the current literature has been mainly focused on the TC-CCES and SC-CCES, which operate in high-pressure conditions, increasing investment costs and bringing operation risks. Meanwhile, some studies based on the phase-change CO2 energy storage system also have had the disadvantages of low efficiency and the extra necessity of heat or cooling sources. To overcome the above problems, this paper proposes an innovative compressed CO2 phase-change energy storage system. During the energy charge process, molten salt and water are used to store heat with a smaller temperature difference in heat exchangers, and high-pressure CO2 is reserved in liquid form. During the energy discharge process, throttle expansion is applied to realize the evaporation at room temperature, and CO2 absorbs the reserved heat to improve the power capacity in the turbine and the system energy storage efficiency. The thermodynamic and exergoeconomic studies are performed firstly by using MATLAB. Then, the parametric study based on energy storage efficiency, system unit product cost, and exergy destruction is analyzed. The results show that energy storage efficiency can be improved by lifting liquid CO2 pressure as well as compressor and turbine isentropic efficiencies, and CO2 evaporation pressure has the optimal pressure point. The system unit product cost can be reduced by decreasing liquid CO2 pressure and compressor isentropic efficiency, while CO2 evaporation pressure and turbine isentropic efficiency both have optimal points. Finally, the optimization of two performances is performed by NSGA-II, and they can reach 75.30% and 41.17 $/GJ, respectively. Moreover, the optimal energy storage efficiency is obviously higher than that of other energy storage technologies, indicating the great advantage of the proposed system. This study provides an innovative research method for a new type of large-scale energy storage system.

With escalating energy demands, solar power stands out for its abundance and renewable advantages, presenting a paramount sustainable solution. Herein, we tactically incorporate phase change material (PCM) into solar energy systems, resulting in substantial enhancements in energy storage and utilization. Through numerical simulations, the thermal dynamics and phase change processes associated with various heating methodologies are investigated, aiming to achieve optimal thermal performance and energy efficiency. Detailed analysis of temperature dynamics within the PCM under two distinct heating methods reveals pivotal thermal fluctuations in both the PCM and water during heat release. The results indicate that bottom heating promptly induces rayleigh convection, resulting in a uniform temperature and a stable phase interface, which are desirable for heat transfer. In contrast, central tube heating concentrates heat transfer in the upper PCM layer, leading to an uneven phase interface and thermal stratification. Configurations with two horizontally aligned heating tubes result in a 36% reduction in melting duration compared to the single central tube setup, highlighting enhanced efficiency. Additionally, the bottom heating approach demonstrates improved energy storage efficiency in both the initial and second heating cycles. These findings highlight the potential of PCM-integrated combined heating systems for solar energy capture, confirming their efficiency and practicality in addressing modern household energy demands.

The heat transfer performance of the evaporator significantly affects the heat transfer capacity of the loop heat pipe (LHP). The vapor blanket can be formed once the vapor penetrates the wick especially at high heat flux, resulting in an unsaturated state of the wick and deteriorating the evaporator performance. It is crucial to understand the liquid–vapor behavior for enhancing the LHP performance by investigating the fundamental heat and mass transfer in the wick with phase-change. However, previous modeling studies only considered a single-phase flow or complete saturation in the wick, and the capillary effect on the fluid states was rarely taken into account. The present work developed two mathematical models based on the assumptions of saturated and unsaturated wicks. The fluid states were analyzed at the liquid–vapor interface under the consideration of the capillary effect, and a pore-scale evaporation model was applied to study the phase change behavior and interfacial heat and mass transfer. The relative permeability was introduced to describe the two-phase flow in the porous wick, and the capillary force was modeled as a function of the local saturation in the two-phase region. The temperature results calculated by the models were compared with the experimental results, and the assumption that the vapor penetration leads to deterioration of evaporator performance at high heat flux was validated. Vapor blanket thickness can be estimated through the saturation profile, which provides a simple and effective method. It was also found that the capillary number ω was the key factor affecting the thickness of the vapor blanket. The greater the ω , the faster the vapor blanket thickness increases. [ABSTRACT FROM AUTHOR]

Herein, we design an optoelectronic device using phase-change materials (PCMs) and assess its ability to possess two functionalities: the perfect absorption of photonic metasurfaces and the high-density storage capability of electronic memories. Both functionalities are evaluated experimentally and via simulations. Such bifunctionalities are achieved according to the phase-transformation extent of the designed hybrid that comprises a phase-change stack having Si/SiO 2 /Au/Ge 2 Sb 2 Te 5 (GST)/indium tin oxide (ITO) and a conductive PtSi probe. The use of PCM layers either in a full crystalline or an amorphous phase causes perfect absorption. The resonant wavelength of the device can be dynamically changed by modulating the phase-change extent of the PCM layer. Generating a continuous crystalline region or separated crystalline bits inside the amorphous GST exhibits a larger tuneability of the phase-change extent than forming separated amorphous bits inside the crystalline GST, and allows for a wider bandwidth of 300 nm for perfect absorber applications. Forming amorphous bit array inside crystalline background yields discernible optical reading contrast when compared to forming a crystalline bit array. The amorphous bit array configuration has an areal density of ～500 Gbits/inch2, data rate of 5 Mbits/s, and energy consumption of 92 pJ/bit. These values render the configuration attractive for probe storage applications. Such a designed hybrid with the ability to process data photonically and store data electronically exhibit its promising for highly integrated metasurface and superb compact electro-optical computing device. [ABSTRACT FROM AUTHOR]

A reconfigurable metasurface constitutes an important block of future adaptive and smart nanophotonic applications, such as adaptive cooling in spacecraft. In this paper, we introduce a new modeling approach for the fast design of tunable and reconfigurable metasurface structures using a convolutional deep learning network. The metasurface structure is modeled as a multilayer image tensor to model material properties as image maps. We avoid the dimensionality mismatch problem using the operating wavelength as an input to the network. As a case study, we model the response of a reconfigurable absorber that employs the phase transition of vanadium dioxide in the mid-infrared spectrum. The feed-forward model is used as a surrogate model and is subsequently employed within a pattern search optimization process to design a passive adaptive cooling surface leveraging the phase transition of vanadium dioxide. The results indicate that our model delivers an accurate prediction of the metasurface response using a relatively small training dataset. The proposed patterned vanadium dioxide metasurface achieved a 28% saving in coating thickness compared to the literature while maintaining reasonable emissivity contrast at 0.43. Moreover, our design approach was able to overcome the non-uniqueness problem by generating multiple patterns that satisfy the design objectives. The proposed adaptive metasurface can potentially serve as a core block for passive spacecraft cooling applications. We also believe that our design approach can be extended to cover a wider range of applications.

Halide perovskite metasurfaces are attracting increasing interest for applications in light-emitting and display technologies. To access the wide range of colors required for these applications, the main mechanism exploited thus far has been chemical engineering of the perovskite compounds – this constitutes a significant limitation for the dynamic switching of optical response desirable in actual devices. Here we demonstrate polarization-dependent, dynamic control of structural color and emission wavelength in an all-dielectric phase-change halide perovskite nanograting metasurface, by temperature tuning. This is underpinned by the significant change in the perovskite optical constants which accompanies its phase-transition around room temperature. The functionalities demonstrated in our work bearing potential for applications in light-emitting devices, displays and spatial-light-modulators.

Phase-changing materials have recently found use as particulate fillers to engender stiffness-changing behavior in composites. In the transition from solid to liquid particles, the composite modulus can be significantly reduced, and then raised again as the particles are allowed to solidify. While the general effect of stiffness tuning in phase-changing composites has been demonstrated in a range of studies and applications, the most drastic stiffness ranges are provided by fusible metallic alloys, which are commonly subject to the formation of oxide shells on their surfaces. In this work, we examine the effect these oxide surfaces have on variable-stiffness performance, and investigate the corresponding role of particle size. In particular, we study particles of a low-melting-point metallic alloy, Field's Metal, and we also present a facile method of manufacture that allows for control of particle size. We then manufacture a set of stiffness-changing composites using these particles and characterize mechanical performance, with the aim of controlling particle size to increase the total stiffness ratio while resisting material failure. [ABSTRACT FROM AUTHOR]

Refrigerant indirect contact phase-change cooling system flows refrigerant into a cold plate and utilizes the phase-change to exchange heat with the battery. However, R134a, commonly used, is being gradually restricted due to its environmental impact. A new kind of near azeotrope mixed refrigerant R1234yf/R152a (mass ratio 60.5:39.5) is proposed under environmental protection and safety. Based on the fluid-structure interaction model, the evaluation of different indirect contact phase-change cooling systems for battery thermal management (BTM) using R1234yf/R152a is investigated. After obtaining battery (150 Ah, 3.2 V LiFePO4) parameters, heat generation power, and main test conditions through experiments, the thermal properties are numerically studied by computational fluid dynamics (CFD). At 1 C discharge rate, the temperature gradient (TG) of single battery and the maximum temperature difference (TD) among batteries are analyzed for two cases: The maximum TD among batteries of Case_b is 6.5°C lower than that of Case_a. In addition, the effect of the mixed refrigerant and traditional liquid cooling on the battery temperature is studied at different evaporation temperatures (ETs) (20°C, 25°C) and different mass flow rates (MFRs) (0.02, 0.10, and 0.18 kg/s). The results show that both the increase of inlet MFR and the reduction of inlet ET may significantly improve the battery module cooling rate. Compared with 0.02 kg/s, as the MFR increases, the temperature drop slopes to 9.56 and 11.2 at 20°C. The battery module temperature uniformity is improved with the increase of ET. Overall, the mixed refrigerant has advantages in temperature uniformity and consistency. The new mixed refrigerant plays a positive role in controlling battery temperature. [ABSTRACT FROM AUTHOR]

Phase-change optical device has recently gained tremendous interest due to its ultra-fast transmitting speed, multiplexing and large bandwidth. However, majority of phase-change optical devices are only devoted to on-chip components such as optical tensor core and optical main memory, while developing a secondary storage memory in an optical manner is rarely reported. To address this issue, we propose a novel phase-change optical memory based on plasmonic resonance effects for secondary storage applications. Such design makes use of the plasmonic dimer nanoantenna to generate plasmonic resonance inside the chalcogenide alloy, and thus enables the performance improvements in terms of energy consumption and switching speed. It is found that choosing height, radius, and separation of the plasmonic nanoantenna as 10 nm, 150 nm, and 10 nm, respectively, allows for a write/erase energies of 100 and 240 pJ and a write/erase speed of 10 ns for crystallization and amorphization processes, respectively. Such performance merits encouragingly prevail conventional secondary storage memories and thus pave a route towards the advent of all-optical computer in near future. [ABSTRACT FROM AUTHOR]

Abstract Despite attracting increasing attention in clinic, non-invasive high-intensity focused ultrasound (HIFU) surgery still commonly suffers from tumor recurrence and even matastasis due to the generation of thermo-resistance in non-apoptotic tumor cells and adverse therapy-induced inflammation with enhanced secretion of growth factors in irradiated region. In this work, inspired by the intrinsic property that the expression of thermo-resistant heat shock proteins (HSPs) is highly dependent with adenosine triphosphate (ATP), dual-functionalized diclofenac (DC) with anti-inflammation and glycolysis-inhibition abilities was successfully co-encapsulated with phase-change dl-menthol (DLM) in poly(lactic-co-glycolic acid) nanoparticles (DC/DLM@PLGA NPs) to realize improved HIFU surgery without causing adverse inflammation. Both in vitro and in vivo studies demonstrated the great potential of DC/DLM@PLGA NPs for serving as an efficient synergistic agent for HIFU surgery, which can not only amplify HIFU ablation efficacy through DLM vaporization-induced energy deposition but also simultaneously sensitize tumor cells to hyperthermia by glycolysis inhibition as well as diminished inflammation. Thus, our study provides an efficient strategy for simultaneously improving the curative efficiency and diminishing the harmful inflammatory responses of clinical HIFU surgery. Graphical Abstract

• Physics-Informed Neural Networks (PINNs) were benchmarked for bubble evaporation. • The study considered evaporation of three working fluids (water, R-134a and FC-72). • Maximum forward-prediction error was over 5 % lower than the reference CFD solution. • Effective transfer learning produced inverse predictions within 2 % of CFD reference. In this paper, a physics-informed neural network (PINN) technique is developed to study the heat and mass transfer for the process of vapour bubble growth in a superheated liquid domain and tested using three working fluids including water, R-134a and FC-72. The work represents a novel step in the development of PINNs for phase change scenarios where surface tension effects dominate, and acts as a necessary validation stage before PINN techniques can be applied to complex boiling analysis. Initially, a forward analysis was performed using water and R-134a as working fluids. For each of these investigations, the PINN algorithm was trained on 50 % of the available CFD data. The proposed algorithm was able to accurately infer velocity fields, particularly in the near-interfacial region. The resultant circulatory flow was found to maintain the desired circular shape of the growing bubbles. As a result, when predicting the evolution of a water vapour bubble, the developed PINN algorithm produced a reduction in peak error by 0.87 % compared to CFD reference data, and 3.42 % reduction in peak error for prediction of the evolution of the R-134a vapour bubble. To test and optimise the transfer learning capabilities of the developed methodology, the evolution of an FC-72 vapour bubble in superheated FC-72 was predicted without supplying supporting observational data. For this scenario, the PINN algorithm produced a peak error within 1.3 % of the unobserved CFD reference data. The proposed approach confirms the robustness of PINN methodologies as a method of solving phase-change problems where surface tension plays a pivotal, promising to expedite parametric studies in practice. This study represents a pioneering effort in the development of PINNs for phase change by applying the current algorithm to investigate bubble growth within superheated liquid domains, serving as a basis for the application of PINNs for boiling problems and as a benchmark for inverse training strategy. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) is a debilitating condition that can result in significant functional impairment and loss of quality of life. There is a growing interest in developing new therapies for SCI, and hydrogel-based multimodal therapeutic strategies have emerged as a promising approach. They offer several advantages for SCI repair, including biocompatibility, tunable mechanical properties, low immunogenicity, and the ability to deliver therapeutic agents. This article provides an overview of the recent advances in hydrogel-based therapy strategies for SCI repair, particularly within the past three years. We summarize the SCI hydrogels with varied characteristics such as phase-change hydrogels, self-healing hydrogel, oriented fibers hydrogel, and self-assembled microspheres hydrogel, as well as different functional hydrogels such as conductive hydrogels, stimuli-responsive hydrogels, adhesive hydrogel, antioxidant hydrogel, sustained-release hydrogel, etc. The composition, preparation, and therapeutic effect of these hydrogels are briefly discussed and comprehensively evaluated. In the end, the future development of hydrogels in SCI repair is prospected to inspire more researchers to invest in this promising field. Various types of hydrogels, including phase-change hydrogels, self-healing hydrogel, oriented fibers hydrogel, and self-assembled microspheres hydrogel, as well as different functional hydrogels such as conductive hydrogels, stimuli-responsive hydrogels, are employed as biological scaffolds, combined with stem cells, exosomes, and neurotrophic factors, in the treatment of SCI. [Display omitted] [ABSTRACT FROM AUTHOR]

• Excite the Optical Tamm States effect of the top GST material through quasi-periodic photonic crystal structure coatings. • Realize the active tunable performance of multi-spectral selective narrowband absorber. • Demonstrate the highly directional absorption of the designed coatings under S polarization at 75–80°. Based on the Optical Tamm States (OTS) effect of phase-change material (PCM) Ge-Sb-Te (GST), a tunable multispectral selective narrowband absorber is proposed. The application wavelength range is combined with the solar spectral distribution in this study. Compared with other absorbers with complex shapes, this planar device is easier to manufacture, making it possible for the photolithographic, large-scale, cost-effective manufacturing process. Through the phase change of GST, the multi-spectral narrowband absorption of the harmful gas SO 2 (1.35 μm), NO 2 (1.59 μm), NO (1.91 μm) and CO (2.1 μm) of the vehicle exhaust was finally realized. Meanwhile, it shows good directivity and polarization performance in the wavelength range of 1.7–2.0 μm, and finally high S-polarization absorptivity (>90 %) at 75–80° incident angle was achieved. The present work is of potential application value in the research areas of infrared detection, energy management, information encryption and so on. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) devices, often referred to as memristors, have exhibited interesting electronic performance that could be useful to enhance the capabilities of multiple types of integrated circuits that we use in our daily lives. However, RS devices still do not fulfil the reliability requirements of most commercial applications, mainly because the switching and failure mechanisms are still not fully understood. Density functional theory (DFT) and/or molecular dynamics (MD) are simulations used to describe complex interactions between groups of atoms, and they can be employed to clarify which physical, chemical, thermal and/or electronic phenomena take place during the normal operation of RS devices, which should help to enhance their performance and reliability. In this article, we review which studies have employed DFT and/or MD in the field of RS research, focusing on which methods have been employed and which material properties have been calculated. The goal of this article is not to delve into deep mathematical and computational issues – although some fundamental knowledge is presented – but to describe which type of simulations have been carried out and why they are useful in the field of RS research. This article helps to bridge the gap between the vast group of experimentalists working in the field of RS and computational scientists developing DFT and/or MD simulations. [ABSTRACT FROM AUTHOR]

The present work focuses on the development of the 3D MRT-LBM computational method to simulate a droplet formed by the condensation of a gas at a saturation temperature. The droplet falls by the effect of its volume (body force) and collides with a solid surface of parallelepiped shape for different values of 0.25 ≤ κ ≤ 0.95. This study presents the evolution of the drop from its formation on the upper cold surface until it falls on the lower wall. For this purpose, we present the behaviour of the dropwise on a horizontal surface as well as the parameters which characterise its evolution over time: its radius R, its height H, and its maximum distance during its contact with the obstacle. Moreover, the distribution of its local heat flux in 2D during its first contact with the upper face of the solid obstacle is presented for each value of κ to describe their heat exchange. [ABSTRACT FROM AUTHOR]

Despite attracting increasing attention in clinic, non-invasive high-intensity focused ultrasound (HIFU) surgery still commonly suffers from tumor recurrence and even matastasis due to the generation of thermo-resistance in non-apoptotic tumor cells and adverse therapy-induced inflammation with enhanced secretion of growth factors in irradiated region. In this work, inspired by the intrinsic property that the expression of thermo-resistant heat shock proteins (HSPs) is highly dependent with adenosine triphosphate (ATP), dual-functionalized diclofenac (DC) with anti-inflammation and glycolysis-inhibition abilities was successfully co-encapsulated with phase-change dl-menthol (DLM) in poly(lactic-co-glycolic acid) nanoparticles (DC/DLM@PLGA NPs) to realize improved HIFU surgery without causing adverse inflammation. Both in vitro and in vivo studies demonstrated the great potential of DC/DLM@PLGA NPs for serving as an efficient synergistic agent for HIFU surgery, which can not only amplify HIFU ablation efficacy through DLM vaporization-induced energy deposition but also simultaneously sensitize tumor cells to hyperthermia by glycolysis inhibition as well as diminished inflammation. Thus, our study provides an efficient strategy for simultaneously improving the curative efficiency and diminishing the harmful inflammatory responses of clinical HIFU surgery. [ABSTRACT FROM AUTHOR]

The complex internal structures and moisture states of porous materials are of great significance to heat and mass transfer, and their coupling heat and mass transfer processes widely exist in energy development and engineering heat insulation. Beyond the unilateral analysis of heat and mass transfer characteristics of porous materials under ideal conditions, the distribution parameters of porous channels, rough surface, wet states and phase-change were considered, and the fractal theory was used to deduce the expressions of the seepage coefficient and the coupling equivalent thermal conductivity of porous materials with wet phase-change rough surface. The results show that, the seepage coefficient is positively correlated with the area fractal dimension and the moisture saturation, and negatively correlated with the relative roughness and the tortuous fractal dimension. The coupling equivalent thermal conductivity is positively correlated with the seepage coefficient and the phase variable, but negatively correlated with the relative roughness. In addition, the phase variable and the gas expansion pressure difference caused by phase-change also have important effects on the coupling heat and mass transfer. [ABSTRACT FROM AUTHOR]

In this article, we are interested in flexible modeling and performing solution of transient thermal selective laser melting problems. For this, we first introduce a finite addition of matter elements method (FAMEM) to generate any wished finite sequence of thermal problems, defined in additively constructed domains. Second, we use the multiscale Arlequin frame‐work to develop a three‐level Arlequin weak‐strong formulation of each problem of the finite sequence. Two Arlequin patches are used in the latter to localize the steepest thermal gradients and the nonlinear phase‐change phenomena, allowing for fine local approximations and the localized nonlinearity treatment by an algorithm we develop. These patches are identified via the solution of a representative mono‐domain transient thermal problem. The latter is also solved with our three‐level Arlequin method for comparison of the solutions and respective performances of both approaches. Moreover, two dimensional tests consisting in the creation of a 316 L stainless steel wall and a two AlSi10Mg layers, are carried out to further enlighten our global approach and to position it with respect to literature. [ABSTRACT FROM AUTHOR]

The sheet resistance (Rs), and hence electrical resistivity of different thicknesses (200–320 nm) of As30Te60Ga10 films was measured from 490 to 600 K. Crystallization kinetics parameters of the As30Te60Ga10 films were determined in terms of the evaluated Rs for various film thicknesses. The investigated kinetics parameters were compared to obtained experimental data from differential scanning calorimetry as well as were confirmed by the X-ray diffraction and scanning electron microscope. It was found that the exothermic heat flow can be obtained from the measured surface resistance, with high accuracy, for all As30Te60Ga10 films. The crystallization kinetic parameters of As30Te60Ga10 films were determined under non-isothermal and isoconversional conditions. Besides, the activation energy required for the amorphous-crystalline transition of As30Te60Ga10 was estimated and various models of the crystallization kinetics were applied. It was observed that the Šesták-Berggren equation is more appropriate, compared to the Johnson–Mehl–Avrami equation, for describing the kinetics of crystallization in As30Te60Ga10. The obtained results could give an experimental basis for the optimization of phase-change memory in the As–Te–Ga system in terms of the sheet resistance measurement and the possibility of its application for various phase-change materials. [ABSTRACT FROM AUTHOR]

The heat transfer performance of the evaporator significantly affects the heat transfer capacity of the loop heat pipe (LHP). The vapor blanket can be formed once the vapor penetrates the wick especially at high heat flux, resulting in an unsaturated state of the wick and deteriorating the evaporator performance. It is crucial to understand the liquid–vapor behavior for enhancing the LHP performance by investigating the fundamental heat and mass transfer in the wick with phase-change. However, previous modeling studies only considered a single-phase flow or complete saturation in the wick, and the capillary effect on the fluid states was rarely taken into account. The present work developed two mathematical models based on the assumptions of saturated and unsaturated wicks. The fluid states were analyzed at the liquid–vapor interface under the consideration of the capillary effect, and a pore-scale evaporation model was applied to study the phase change behavior and interfacial heat and mass transfer. The relative permeability was introduced to describe the two-phase flow in the porous wick, and the capillary force was modeled as a function of the local saturation in the two-phase region. The temperature results calculated by the models were compared with the experimental results, and the assumption that the vapor penetration leads to deterioration of evaporator performance at high heat flux was validated. Vapor blanket thickness can be estimated through the saturation profile, which provides a simple and effective method. It was also found that the capillary number ω was the key factor affecting the thickness of the vapor blanket. The greater the ω, the faster the vapor blanket thickness increases.

Dynamic terahertz devices are vital for the next generation of wireless communication, sensing, and non-destructive imaging technologies. Metasurfaces have emerged as a paradigm-shifting platform, offering varied functionalities, miniaturization, and simplified fabrication compared to their 3D counterparts. However, the presence of in-plane mirror symmetry and reduced degree of freedom impose fundamental limitations on achieving advanced chiral response, beamforming, and reconfiguration capabilities. In this work, a platform composed of electrically actuated resonators that can be colossally reconfigured between planar and 3D geometries is demonstrated. To illustrate the platform, metadevices with 3D Split Ring Resonators are fabricated, wherein two counteracting driving forces are combined: i) folding induced by stress mismatch, which enables non-volatile state design and ii) unfolding triggered by the strain associated with insulator-to-metal transition in VO 2 , which facilitates volatile structural reconfiguration. This large structural reconfiguration space allows for resonance mode switching, widely tunable magnetic and electric polarizabilities, and increased frequency agility. Moreover, the unique properties of VO 2 , such as the hysteretic nature of its phase transition is harnessed to demonstrate a multi-state memory. Therefore, these VO 2 integrated metadevices are highly attractive for the realization of 6G communication devices such as reconfigurable intelligent surfaces, holographic beam formers, and spatial light modulators., (© 2024 Wiley‐VCH GmbH.)

Summary: Evaporation, boiling, and condensation are fundamental liquid-vapor phase-change heat transfer processes and have been utilized in many conventional and emerging energy systems. Recent advances in the manipulation of interface wetting and heterogeneous nucleation using micro/nano-structured surfaces have enabled exciting two-phase flow dynamics and heat transfer enhancement. However, independently manipulating droplets, bubbles, or liquid films through surface modification has encountered bottlenecks. In this Perspective, we discuss an emerging strategy where droplets/bubbles are coupled with a liquid film to control fluid dynamics for minimizing the thermal resistance between the liquid-vapor interface and solid substrate, thus significantly enhancing the heat transfer performance beyond the state of the art.

Electrical probe memory has received considerable attention during the last decade due to its prospective potential for the future mass storage device. However, the electrical probe device with conventional diamond-like carbon capping and bottom layers encounters with large interfacial contact resistance and difficulty to match the experimentally measured properties, while its analog with titanium nitride capping and bottom layers also faces serious heat dissipation through either probe and silicon substrate. Therefore, the feasibility of using indium tin oxide (ITO) media for the capping and bottom layers of the electrical probe device is investigated by tailoring the thickness and electrothermal properties of the ITO capping and bottom layers within experimentally established range and subsequently calculating the resultant temperature at several predefined points based on a previously developed three-dimensional model. To meet the required temperature and to fit the experimentally reported values, the thickness, electrical conductivity, and thermal conductivity of the ITO capping and bottom layers are found to be 5 nm, 103 Ω−1 m−1, 0.84 W m−1 K−1, and 200 nm, 1.25 × 106 Ω−1 m−1, 0.84 W m−1 K−1, respectively. The practicality of using this optimized device to achieve ultrahigh density, ultralow energy consumption, ultrafast switching speed, low interfacial contact resistance, and high thermal reliability has also been demonstrated.

The Special Issue entitled “Novel Numerical Methods in Heat and Mass Transfer” focuses on such issues as CFD modeling of fluid flow, heat transfer characteristics, mass transfer, phase-change and heat exchangers. The Guest Editors of this Special Issue, under the support and auspices of the publishing house, and through its editors, invited the authors to publish their latest achievements in the area of numerical methods used in the area of heat and mass transfer. A short overview of the successful invited submission articles devoted to the above-mentioned subject is presented with the hope that these valuable works will be of interest to a wide range of readers, as the topic is important and worth further scientific attention.

The Special Issue entitled "Novel Numerical Methods in Heat and Mass Transfer" focuses on such issues as CFD modeling of fluid flow, heat transfer characteristics, mass transfer, phase-change and heat exchangers. The Guest Editors of this Special Issue, under the support and auspices of the publishing house, and through its editors, invited the authors to publish their latest achievements in the area of numerical methods used in the area of heat and mass transfer. A short overview of the successful invited submission articles devoted to the above-mentioned subject is presented with the hope that these valuable works will be of interest to a wide range of readers, as the topic is important and worth further scientific attention. [ABSTRACT FROM AUTHOR]

Melting and solidification processes are often affected by natural convection of the liquid, posing a multi-physics problem involving fluid flow, convective and diffusive heat transfer, and phase-change reactions. Enthalpy methods formulate this convection-coupled phase-change problem on a single computational domain. The governing equations can be solved accurately with a monolithic approach using mixed finite elements and Newton's method. Previously, the monolithic approach has relied on adaptive mesh refinement to regularize local nonlinearities at phase interfaces. This contribution instead separates mesh refinement from nonlinear problem regularization and provides a continuation procedure which robustly obtains accurate solutions on the tested 2D uniform meshes. A flexible and extensible open source implementation is provided. The code is formally verified to accurately solve the governing equations in time and in 2D space, and convergence rates are shown. Two benchmark simulations are presented in detail with comparison to experimental data sets and corresponding results from the literature, one for the melting of octadecane and another for the freezing of water. Sensitivities to key numerical parameters are presented. For the case of freezing water, effective reduction of numerical errors from these key parameters is successfully demonstrated. Two more simulations are briefly presented, one for melting at a higher Rayleigh number and one for melting gallium. [ABSTRACT FROM AUTHOR]

Four-terminal, inline, indirectly heated phase-change switches (IPCS) have emerged as great contenders for reconfigurable radio frequency (RF) integrated circuits, providing state-of-the-art cutoff frequency thanks to their built-in dc-RF decoupling. However, the switching of IPCS devices is determined by their temperature which is challenging to predict. In this article, we present a physics-based compact model of the IPCS, validated by finite-element method simulations and measurements of IPCS devices. The model accurately predicts the thermal and electrical dynamics of the device by considering the changes in heater resistance, contact resistance, and parasitic capacitance. The complete model is implemented in Verilog-A, and a downloadable version is freely available at the nanoHUB.org. We show how the compact model can be used for rapid device evaluation and optimization between RF performance and energy efficiency. Nanosecond electrical thermometry of the heater for varying pulses during IPCS device operation and RF measurements is used to experimentally validate the model. [ABSTRACT FROM AUTHOR]

Nanostructures on heat transfer surfaces can enhance micro/nanoscale phase-change heat transfer processes. To understand the enhancement mechanisms provided by nanostructures, evaporation processes of nanoscale liquid films on periodic sinusoidal-shaped surfaces were investigated via molecular dynamics simulations. By changing the amplitudes (A) and periods (T) of the curves describing the sinusoidal shapes, which possess shapes similar to j(x)=h0+Asin(2πx/T), sinusoidal surfaces of different sizes were constructed. An unevaporated region always existed on the copper plate for all surfaces during phase-change processes. Moreover, we calculated the interfacial thermal resistances and the mismatches between the vibrational density of states of the solid and liquid for different surfaces. The results show that the argon temperature changes and evaporation rates during the phase-change process on sinusoidal surfaces are higher than those on flat surfaces, and these results increase with the increase in amplitudes and the decrease in periods within certain limits mainly because of the thermal resistance decrease at the solid-liquid interface. Furthermore, the corresponding mismatches between the vibrational density of states of the solid and liquid also decrease, which indicates that the existence of sinusoidal nanostructures enhances the heat transfer of the phase-change process. [ABSTRACT FROM AUTHOR]

Effortless separation without damage to the substrates is highly advantageous for the recovery and recycling of expensive electronic components in display devices. In this study, we present an approach for separating transparent adhesive films from substrates using phase-change core-shell nanocapsules. The nanocapsules are prepared from poly(methyl methacrylate) (PMMA) nanoparticles via the encapsulation of methylcyclohexane (MCH). The evaporated MCHs facilitated the detachment of adhesive films through micro-bubble generation after thermal treatment, leading to the effortless separation of the adhesive layer. The newly fabricated adhesive film with phase-change nanocapsules resulted in high transmittance, with an excellent debonding efficiency after thermal treatment. [ABSTRACT FROM AUTHOR]

The blade-type phase-change random access memory (PCRAM) has recently attained considerable interest due to its potential for providing low programming current, while its interfacial resistance (IR) characteristics that play an important role in temperature and programming current for conventional PCRAMs is yet to be deeply studied. To achieve this, a completely 3-D electro-thermal and phase-transformation model with inclusions of thermal boundary resistance (TBR) and electrical IR (EIR) at different layered interfaces were developed to assess the influence of the IRs on phase-transformation kinetics. It was found that the TBR at the chalcogenide/insulation interface as well as interfacial size dominates the resulting programming current that is almost independent of the TBR and EIR at chalcogenide/heater interface. In this case, an optimized blade-type device having platinum silicide heater and superlattice insulated encapsulation was proposed, allowing for a 38% reduction on “SET” current and a 40% reduction on “RESET” current, respectively. [ABSTRACT FROM AUTHOR]

Linear radio-frequency (RF) switches are highly desired in wireless system front ends. Here, we report electro-thermal measurements and modeling of an indirectly heated phase change RF switch (IPCS). We study the energy-efficiency of the IPCS device by electro-thermal modeling and show that its layer design is crucial to reduce its switching power. Thermally optimized SbTe-based IPCS devices switch at a record-low power of ~8 mW/ $\mu \text{m}^{2}$ , approaching the efficiency limit of such indirectly heated devices. [ABSTRACT FROM AUTHOR]

Electrical probe memory has received considerable attention during the last decade due to its prospective potential for the future mass storage device. However, the electrical probe device with conventional diamond-like carbon capping and bottom layers encounters with large interfacial contact resistance and difficulty to match the experimentally measured properties, while its analog with titanium nitride capping and bottom layers also faces serious heat dissipation through either probe and silicon substrate. Therefore, the feasibility of using indium tin oxide (ITO) media for the capping and bottom layers of the electrical probe device is investigated by tailoring the thickness and electrothermal properties of the ITO capping and bottom layers within experimentally established range and subsequently calculating the resultant temperature at several predefined points based on a previously developed three-dimensional model. To meet the required temperature and to fit the experimentally reported values, the thickness, electrical conductivity, and thermal conductivity of the ITO capping and bottom layers are found to be 5 nm, 103 Ω−1 m−1, 0.84 W m−1 K−1, and 200 nm, 1.25 × 106 Ω−1 m−1, 0.84 W m−1 K−1, respectively. The practicality of using this optimized device to achieve ultrahigh density, ultralow energy consumption, ultrafast switching speed, low interfacial contact resistance, and high thermal reliability has also been demonstrated. [ABSTRACT FROM AUTHOR]

Bubble electrospinning technology can be used for mass production of nanofibers, it has been widely used in polymer electrospinning such as PVA, PVP and PAN, but there are no reports on the preparation of composite phase-change nanofibers by this method. In this paper, the transparent solution 1(PEG was put into formic acid according to the mass fraction of 60%) was mixed with the transparent solution 2 (PA66 was put into formic acid according to the mass fraction of 15%) according to the mass ratio of 15:85 , 25:75 , 35:65 and 45:55 to prepare four kinds of spinning solutions. And the pure PA66 nanofiber membrane(PNM) and PA66/PEG composite nanofiber membrane(PGCNM) were fabricated by the improved bubble electrospinning device on the basis of bubble electrospinning device invented by He Jihuan etc Also we analyzed their surface microstructure and tested their mechanical properties, thermal properties and molecular structure. The lower the content of PA66, the smaller the adhesion granular matter on the nanofiber surface and the thicker the diameter of the nanofiber, but the surface of the nanofiber is more smooth. The PGNCM appeared double absorption peak at 1515.5 cm ^−1 and 1642 cm ^−1 and existed weak absorption peak at 3298 cm ^−1 ∼ 3302 cm ^−1 . The tensile strength and the elongation at break of the PGNCM was less than that of the PNM. The hot decomposition process of the PGNCM was composed the melting exothermic process of PEG and PA66. When the mixed ratio between PA66 and PEG was 15:85, the decomposition rate of residues between 210 ∼ 310 °C was the fastest.

• Use of exothermic thermite reactions is seen as a game-change technology to be developed for plug and abandonment of mature oil wells. • Multi-domain simulation of termite reaction using advanced chemical kinetics reproduced experimental data for temperature levels and reaction front propagation speed. • Heat losses affected the melting of the species as a small portion of alumina remained entirely solid during the reaction. Thermite reactions are self-sustained exothermic reactions commonly employed in welding processes of railway tracks, material synthesis and pyrotechnics, to mention a few applications. More recently, this reaction has been assessed to plug depleted oil wells. Motivated by the foregoing, this work numerically investigates a Fe 2 O 3 /Al thermite reaction. A two-dimensional axisymmetric domain with a thermite layer compressed between a PMMA lid and a stainless-steel disk is considered. A first-order kinetic is assumed and the reaction is controlled by the hematite consumption. A computational solver is developed based on the open-source OpenFOAM® software. Numerical results showed good agreement with experimental data for temperature levels. Numerical results further indicated thermal losses next to the thermite-steel interface. These heat losses affected the melting of the species as a small portion of alumina remained entirely solid during the reaction. [ABSTRACT FROM AUTHOR]

Four β-cyclodextrin (β-CD)/benzene derivatives gels were developed as temporary plugging agent for different formation temperature ranges. The gel was composed of β-CD as the host, benzene derivatives as the guest and 1,2-propylene glycol as solvent. The systems undergo a "sol-gel" phase transition when the temperature rises. By adding different benzene derivatives (toluene/phenol/benzoic acid) in the system, the gel temperature could be controlled between 70 and 130 ℃. And the gel turns into a solution again upon further heating. Further, FT-IR, X-ray diffractometer (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to analyze the micromorphology and phase transformation mechanism of the gel. The results confirmed that the gelling process of the four systems mainly depends on non-covalent bond action. Furthermore, the degradation rate and the plugging and permeability recovery rate were tested. The results showed that the degradation rate of the four systems were finally greater than 98%, the plugging rate was greater than 85%, and permeability recovery value was more than 98%, which can meet the requirements of fracturing temporary plugging with the formation temperature of 70 ∼ 130 ℃. [Display omitted] • The binding ability of benzene derivatives to β-cyclodextrin affects the gelation temperature. • As the temperature increases, the system is self-assembly into a three-dimensional network structure. • The "sol-gel" phase transformation mainly depends on supramolecular force rather than chemical change. • Supramolecular gel based on cyclodextrin has good temporary plugging and self-degradation effect in tight oil reservoirs. [ABSTRACT FROM AUTHOR]

Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.