Phase Change Research Articles

Design and performance assessment of a solar photovoltaic panel integrated with heat pipes and bio-based phase change material: A hybrid passive cooling strategy

This study investigates the effectiveness of an indirect passive cooling solution for photovoltaic (PV) panels using flattened heat pipes (FHPs) and phase change material (PCM). An innovative passive cooling design is proposed to cool a PV panel using multiple FHPs with a thin graphite sheet between the PV panel and the FHPs. Five experimental cases are examined under varying heat flux loads. Case O serves as the baseline with no cooling system, while Cases 1 to 4 feature different configurations of FHPs and aluminum sheets, with PCM heat sinks added in Cases 2 and 4. The investigation focuses on temperature profiles, temperature reductions, and final temperatures of the PV panel, especially at the end of a 4-hour experimental period when the PCM is fully melted. The results show significant temperature reductions in Case 1 compared to the baseline, with further improvement in Case 2 due to the PCM heat sink. Temperature reductions in Cases 2 and 4 are consistently higher than in Cases 1 and 3, demonstrating the enhanced cooling potential of PCM. Case 4 achieves the highest temperature reduction of 37.0 °C, followed by Case 2 with 34.9 °C under a radiative heat flux of 1000 W/m2. Using 4 FHPs (Cases 1 and 2) is economically justified, offering comparable cooling performance to 8 FHPs (Cases 3 and 4), thus ensuring cost-effectiveness and reducing material usage by over 50 %. A maximum enhancement in PV electrical efficiency of 17.3 % is achieved in Case 2 during PCM phase change with a radiative heat flux of 1000 W/m2.

Polystyrene shell-based “coconut-like” and “pomegranate-like” microencapsulated phase change materials: Formation mechanism, thermal conductivity/stability enhancement and their application in thermal management

Encapsulation of phase change materials (PCMs) using polystyrene (PS) can be an effective solution to the leakage of PCMs, but the low thermal conductivity/stability of the prepared microencapsulated phase change materials (MEPCMs) remain unresolved. Here, we investigated the formation mechanism of PS shell-based MEPCMs via Pickering emulsion polymerization: coconut-like and pomegranate-like MEPCMs were obtained for the first time before and after the introduction of divinylbenzene (DVB), and the thermal conductivity and stability of the former were lower than that of the latter with the same graphene nanosheets (GNSs). Among them, MEPCM-4–7 wt% GNSs (St:DVB=1:1) has the highest thermal conductivity of 0.9358 W∙m−1∙k−1 (222.47 % higher than MEPCM without GNSs) and optimal anti-leakage performance. The thermal stability (thermogravimetric results) is slightly weaker than MEPCM-3–7 wt% GNSs (St:DVB=5:1), but has the highest thermal reliability (the melting enthalpy only decreases by 0.19 % after 100 cycles). The phase change composites (PCCs) was prepared by dispersing MEPCMs in PDMS matrix and applied to the simulated chip thermal management, which can achieve a 10.85 % decrease in the chip equilibrium temperature compared with PDMS. The method of improving the heat transfer properties and thermal stability of MEPCMs based on their structure provides a new idea to solve the problem of low thermal conductivity and stability of MEPCMs, and the prepared PCCs show great potential for practical applications in the field of thermal management.

Cooling performance enhanced by integrating multicomponent phase change material and compression spring into air-cooled battery module

In order to improve the cooling efficiency and temperature consistency of the air-cooled prismatic battery module, a novel multicomponent phase change material-spring plate (MPCM-SP) was developed in this work. The MPCM was formed by combining lauric acid (LA), polyethylene glycol (PEG), palmitic acid (PA), and carboxylated multi-walled carbon nanotubes (MWCNT-COOH). The melting temperature of MPCM can be adjusted within the range 37 °C to 65 °C, and the associated latent heat of phase change varied from 159 J∙g−1 to 209 J∙g−1. The optimized proportions of LA, PEG, PA, and MWCNT-COOH achieved through multiple-objective optimization were 65.55 %, 7.07 %, 25.38 %, and 2.00 %, respectively. The cooling performance of the MPCM-SP was examined by experimental verification and numerical evaluation. The inclusion of MPCM-SP in the air-cooling system resulted in a reduction of 3.41 °C, 3.74 °C, and 3.32 °C in the maximum temperatures of the U-shaped, Z-shaped, and I-shaped battery modules, respectively. Moreover, the temperature difference was decreased by 3.60 °C, 3.16 °C, and 2.42 °C, respectively. Additionally, in comparison to a single battery, a battery equipped with MPCM-SP had a 32.8 % reduction in thermal deformation in the thickness direction under a thermal expansion coefficient of 4.06 × 10-6 K−1.

Direct tensile failures of concrete with various moisture contents and sizes at low temperatures via mesoscale simulations with ice explicit modelling

The enhancement of mechanical properties of concrete meso-components and the interaction caused by non-uniform deformation as well as phase change can cause significant changes in the macro-mechanical performances of concrete at low temperatures. Based on the action mechanism of the above low-temperature effect, this paper established a thermal-mechanical sequential coupled simulation method with explicit modelling of pore ice at the mesoscale level to quantitatively investigate the direct tensile failures and the corresponding size effect of concrete with four structural sizes (D75, D150, D225 and D300) and three moisture contents (2.0 %, 4.0 % and 6.0 %) at different temperatures (20, −30, −60 and −90°C), in term of failure mode, deformation curve, peak strength and residual strength. The numerical results show that the direct tensile peak strength performs an obvious low-temperature enhancement effect due to the more damaged aggregates and more areas being in a state of multi-axial stress caused by low-temperature non-uniform stress field. However, with the decreasing temperature, the residual strength shows a decrease trend and the trend slows down with the increasing moisture content. Besides, as the temperature drops from 20°C to −90°C, both the size effects on direct tensile peak strength and residual strength are strengthened (with the increase approaches nearly 200 % for peak strength while 33 % for residual strength). Finally, a modified size effect theoretical model was developed considering the quantitative coupling effects of low temperature and moisture content. The present research results can provide a reference for the performance evaluation and safe design of large-sized concrete exposed to low-temperature environments.

Silicon porous disc featured parabolic trough collector functioned with paraffin: Thermal performance study

The advancement of renewable solar energy has potential for industrial heat exchanger applications, and its performance is enhanced by using nanofluid. Besides, the losses of heat during the energy transfer from solar to heat exchanger limit thermal performance and lead to reduced thermal efficiency. The conventional solar system functioning with nanofluid needs to be upgraded with an advanced thermal management system to limit energy loss and enrich the thermal performance of the overall system. The investigation aims to enrich the thermal performance of a parabolic trough solar collector (PTC), which features silicon porous discs and phase change material (PCM-paraffin). During the investigation, the flow of fluid ranged from 100 to 200 LPH with an interval of 50 LPH. Influences of silicon porous disc and phase change material melting phase on fluid temperature, temperature, energy stored, and thermal efficiency of the present system are experimentally investigated, and its values are related to conventional absorber performance without porous material and phase change material. The output results prove the significance of silicon porous and phase change material related to conventional absorber systems. The parabolic solar collector functioned with silicon porous material with phase change material phase on 200LPH spotted superior thermal performance including fluid temperature, PCM temperature, energy stored by phase change material, and average thermal & exergy efficiency of 84.2 °C, 98.5 °C 599.7 kJ, and 73.8 % & 15.1 %. These findings underscore the promising potential of porous medium absorbers in significantly elevating the efficiency of parabolic trough collector systems.

Preparation, characterization, and thermal cycling analyses of nanocomposite phase change materials for hot climate energy storage applications

Preparation, characterization, and thermal cycling analyses of nanocomposite phase change materials for hot climate energy storage applications

Magnetohydrodynamic double diffusion natural convection of power-law Non-Newtonian Nano-Encapsulated phase change materials in a trapezoidal enclosure

Magnetohydrodynamic double diffusion natural convection of power-law Non-Newtonian Nano-Encapsulated phase change materials in a trapezoidal enclosure

Thickness dependence and crystallization properties of amorphous GeTe thin films on silicon dioxide

Radio frequency magnetron sputtering was used to prepare the amorphous GeTe thin films on silicon dioxide and the thickness effects on the crystallization behavior were investigated. With the film thickness reducing, the crystallization temperature, crystallization activation energy, amorphous and crystalline resistance increase remarkably, indicating the great improvement in thermal stability and power consumption. Ozawa’s model was used to estimate the crystallization kinetics of GeTe thin films, it shows that nucleation and grain growth occur simultaneously, and grain growth dominates ultimately. XRD analysis demonstrated that the grain size can be reduced and the crystallization process of GeTe thin film can be inhibited with the film thickness decreasing. Furthermore, the thinner film has smaller resistance drift index and surface roughness, which are beneficial to improve the reliability of storage device. T-type phase change memory devices based on 25 nm GeTe thin film were fabricated by 0.13 μm CMOS technology, and the current–voltage and resistance-voltage characteristics demonstrate the excellent electrical performance, including the fast resistance switching between SET and RESET processes, low threshold current and voltage. All the results proved the strong dependency relationships between the crystallization properties and film thickness of GeTe thin film, which paves the way for developing high-density phase change memory in the fields of big data and artificial intelligence.

Sb2S3/AlGaAs-based reconfigurable metasurface for dynamic polarization and directionality control of quantum emitter emission.

In this article, we report, to the best of our knowledge, for the first time, phase change material (PCM)-based reconfigurable metasurfaces for tailoring different degrees of freedom (DoF) of the quantum emitter (QE) emission, namely polarization and directionality, two key controlling factors in applications such as quantum computing, communication, and chiral optics. We have used a hybrid plasmon-QE coupled bullseye grating system utilizing the unexplored concept of composite nano-antennas in quantum photonics as the basic building block of the structures. Carefully engineered azimuthal width profile of the Sb2S3/AlGaAs composite ridge and selectively controlled transition of PCM (Sb2S3) states provide dynamic control over the amplitude and phase of the scattered radiation. Based on this methodology, we have designed five different metasurfaces for on-demand switching of target DoFs of QE emission, ensuring high collection efficiency due to the near-field coupling scheme. The first two metasurfaces switch the majority of the outgoing radiation from radially polarized to circularly polarized, whereas the next two switch the direction of circularly polarized outgoing radiation by a maximum of 9.23° while maintaining the spin state (or polarization chirality) in the simulation environment. The third metasurface category is capable of on-demand generation and separation of opposite spin states of outgoing radiation by 11.48° utilizing the selectively controlled phase transition of Sb2S3. Such reconfigurable multi-dimensional manipulation of QE radiation has not been investigated previously. This work proves the vast potential of active metasurfaces to modify the DoFs of QE emission, paving the way for high-dimensional quantum sources for high-speed quantum communication, higher dimensional quantum processing, and switchable chiral optics.

Bridging Innovations of Phase Change Heat Transfer to Electrochemical Gas Evolution Reactions.

Bubbles play a ubiquitous role in electrochemical gas evolution reactions. However, a mechanistic understanding of how bubbles affect the energy efficiency of electrochemical processes remains limited to date, impeding effective approaches to further boost the performance of gas evolution systems. From a perspective of the analogy between heat and mass transfer, bubbles in electrochemical gas evolution reactions exhibit highly similar dynamic behaviors to them in the liquid-vapor phase change. Recent developments of liquid-vapor phase change systems have substantially advanced the fundamental knowledge of bubbles, leading to unprecedented enhancement of heat transfer performance. In this Review, we aim to elucidate a promising opportunity of understanding bubble dynamics in electrochemical gas evolution reactions through a lens of phase change heat transfer. We first provide a background about key parallels between electrochemical gas evolution reactions and phase change heat transfer. Then, we discuss bubble dynamics in gas evolution systems across multiple length scales, with an emphasis on exciting research problems inspired by new insights gained from liquid-vapor phase change systems. Lastly, we review advances in engineered surfaces for manipulating bubbles to enhance heat and mass transfer, providing an outlook on the design of high-performance gas evolving electrodes.

Water retention and heat storage characteristics of phase change hydrogel in cooling pavement

Phase change hydrogel (PCH) combines the heat storage characteristics of phase change material with the water retention capacity of hydrogel, showing great potential in cooling pavement applications. This study aims to investigate the water retention and heat storage properties of PCH in cooling pavement, providing new insights for mitigating the urban heat island effect. Based on the principle of osmotic pressure, polyethylene glycol (PEG) solution was actively absorbed by superabsorbent polymers (SAP) to form stable PCH. By infusing the asphalt mixture skeleton with PCH-containing phase change grouting material (PCGM), a temperature-regulating phase change grouting pavement (PCGP) can be obtained. Morphological characterization showed that PCH was uniformly distributed in PCGM and effectively locked PEG during high temperature and water absorption/release processes without leakage. PCH imparted excellent water retention properties to PCGM, with a saturation water absorption rate of 44.1 %, which is 6.2 times higher than the control group, and a water retention rate of 34.31 % after heating at 60 °C for 12 hours. Furthermore, PCGM exhibited considerable heat storage performance, with a melting enthalpy of 15.74 J/g and a crystallization enthalpy of 12.07 J/g. Based on these, PCGP demonstrated outstanding temperature-regulating ability, reducing surface temperatures by 9.3 °C and 11.6 °C under dry and saturated conditions, respectively, compared to control pavement. In conclusion, this study provides a theoretical basis for the development of novel cooling pavement materials and shows great potential for its wide application in urban infrastructure construction.

High performance flexible phase change hydrogel applied to thermal management of new cigarette device

To address the thermal management challenges of new heat-not-burn (HNB) cigarette devices, this study aims to enhance overall energy conversion efficiency while maintaining unchanged battery capacity. The goal is to minimize heat dissipation and reduce the temperature of the device's housing that contacts the user. In this research, CaCl2·6H2O (CCH) was selected as the phase change material (PCM), and a polyacrylamide (PAM) phase change hydrogel encapsulating CCH was prepared via in-situ polymerization. Additionally, konjac glucomannan (KGM) was incorporated into the three-dimensional network structure of PAM through hydrogen bonding to promote the formation of a porous gel structure. CNTs-CuO composites, featuring in-situ generated CuO nanoparticles on carbon nanotubes (CNTs), were synthesized using a microwave hydrothermal method and employed to enhance the thermal conductivity of the phase change hydrogel.This study demonstrates that the three-dimensional porous network structure of the hydrogel not only provides effective encapsulation protection for CCH and maintains high latent heat (144.9 J/g), but also imparts excellent flexibility and stability to the composites. The incorporation of CNTs-CuO composites introduces efficient heat transfer channels, significantly increasing the thermal conductivity of the hydrogels by approximately 37 % (0.687 W·m−1·K−1). Moreover, the hydrogel composites exhibit exceptional temperature regulation properties.The innovative design and preparation of these hydrated salt-based flexible hydrogel composites offer a novel approach in the fields of thermal management and energy storage. This material demonstrates practical applications not only in HNB devices but also in various thermal management systems, such as wearable electronics, battery thermal management, and electronic device cooling. Furthermore, its application in energy storage systems, including thermal energy storage units and smart textiles, underscores its broad applicability and significance.

Biomimetic bilayer phase change hydrogels with enhanced water adsorption and desorption for evaporative cooling

Hygroscopic hydrogels, reliable carriers for water-based evaporative materials, undergo shrinkage after evaporative cooling, and the consequent reduction in hygroscopic sites can significantly impair their recyclability in cooling period. To realize cyclic evaporative cooling for rapid regeneration and evaporation, bilayer phase change hydrogel (BPH) concept combining an upper layer of hygroscopic polymer film (CaCl2@ carboxymethyl cellulose/konjac glucomannan films, CaCl2@CMC/KGM, MAF) with a lower layer of hygroscopic hydrogel (CaCl2@poly(vinyl alcohol)/sodium tetraborate decahydrate hydrogel, CaCl2@PVA/Borax, PCH), is presented in this paper. The high liquid–vapor phase change enthalpy of BPH (1274 J/g) enables it to continuously and rapidly remove heat. Benefiting from the MAF hygroscopic porous skeleton, the saturated BPH exhibited a faster water evaporation rate (2.15 kg m−2 h−1) and comparable water vapor transmission rate (1.61 kg m−2 h−1) at 50 °C. After being heated at 50 °C for 1 h, BPH requires 9h to regain its initial mass at 25 °C, 90 % RH. Fifteen moisture adsorption–desorption cycles demonstrate the excellent cyclic regeneration capability of BPH. COMSOL Multiphysics simulation results indicate that evaporative cooling in BPH provides excellent heat dissipation (reduced by about 27 °C). BPH reduces the peak temperatures of a mobile phone by 7.8 °C while charging and 6.5 °C while gaming. This design will contribute to the future cooling of heat-related devices and global sustainability.

Thermal behavior of coated powder during directed energy deposition (DED)

In powder-based additive manufacturing (AM), the quality of the feedstock material is critical for obtaining enhanced mechanical properties. Recently, the application of coated powders during directed energy deposition (DED) has been prompted by the goal of fabricating composite and functional materials in-situ. The complex temperature and momentum fields established during DED render direct experimental characterization of coated powder behavior challenging. To address this challenge, this study reports on the thermal behavior of coated powders during interactions with the molten pool by constructing three-dimensional heat transfer and phase distribution models using the finite elements method (FEM). Transient temperature and phase distributions were calculated for coated and uncoated stainless steel 316L and ZnAl powders under various particle size, coating thickness, molten pool temperature, and coating material conditions. Particle residence time values were extracted from the calculations, defined as time spent by the particle before a phase change. The results show large variations in particle residence time (85 μs to 2670 μs for stainless steel 316L particles, and 48 μs to infinity for ZnAl particles) as a function of the variables considered, especially the thermal diffusivity of the coating materials, thereby highlighting the potential value of coatings as an additional design parameter in DED. Significant increases in particle residence time for both stainless steel 316L and ZnAl particles were found when contact angle increases from 0° (submergence regime) to 180° (floating regime).

Preparation and photothermal properties of latent functional thermal fluid based on size-controllable phase change nanocapsules

To improve the solar heat utilization efficiency of working fluid in direct solar collector, a novel latent functional thermal fluid (LFTF) based on self-designed 1-octadecanol@silica phase change nanocapsules (NEPCMs) with excellent heat storage capacity and photothermal conversion efficiency were prepared. The NEPCMs prepared by sol–gel method were dispersed in water containing multi-walled carbon nanoparticles to prepare the LFTF. The prepared NEPCMs have high encapsulation efficiency (85.12 %) and melting phase change enthalpy (235.1 J/g), controllable particle size (27.13–167.30 nm), excellent thermal stability and cycle stability. The LFTF containing 10 wt% NEPCMs was considered the optimal choice for its excellent dispersion stability (zeta potential 35.63 mV), thermal storage capacity (peak specific heat capacity 5.11 J·g−1·K−1) and superior photothermal conversion efficiency (up to 98 %), which is roughly 3.29 times that of water. These results offer valuable insights for the future development of LFTF in the field of solar thermal applications.

Ethnic proximity, mobility and (non)-belonging: middle-class Singaporean migrants in China

New global multi-directional migration flows are decentering extant analyses of White expatriate migration. As migration becomes more diversified, new lines of intellectual inquiry are surfacing about the experiences of middle-class non-white expatriates. This paper uses the case study of China, which with the rise in immigration, has an increasingly diverse ‘expatriate’ population. While the visibility of White expatriates in non-white-majority host countries may compel them to adopt lifestyles segregated from the local population, expatriates of Chinese heritage in China have the (dis)advantage of blending in with the local population. This paper examines the experiences of Singaporean-Chinese migrants in China where their ethnic proximity to the Chinese can be both a boon and a bane. We present our findings in three sections addressing: first, how ethnic proximity can enable mobilities including motility and a mobile sense of belonging; second, how mobilities can condition ethnic proximity as experiences of privilege but also reminders of non-belonging; and third, how participants’ change in life phases i.e. temporalities shift meanings of proximity, mobility and mobile belonging. Through highlighting the multidimensional nature of mobilities – proximity, motility, temporalities – this paper contributes to studies of middling migration, (ethnic) proximity and mobilities.

Impact of Encapsulated Phase Change Material Additives For Improved Thermal Performance of Silicone Gel Insulation

Impact of Encapsulated Phase Change Material Additives For Improved Thermal Performance of Silicone Gel Insulation

Transient analysis and thermal design of a solar-powered cooling system for an office building: Enhancements using phase change materials and zeotropic mixtures in ejector refrigeration cycle

This study explores an innovative integration of solar energy with thermal energy storage for power production and cooling system support, utilizing phase change materials (PCMs) to enhance solar system performance, particularly for the cooling demands of an office building. The cooling load of a target office building in Ardabil City, Iran, is calculated for a typical day. Optimization is conducted using Multi-Objective Particle Swarm Optimization (MOPSO) to select the optimal zeotropic mixture as the working fluid, aimed at maximizing efficiency and minimizing heat source requirements. The system is designed to meet the needs of a two-story office building. Analysis of photovoltaic modules integrated with PCM under various parameters led to the selection of 25 PVT-PCM units in a series. The total setup includes 730 modules covering 365 m2, achieving a mass flow rate of 2.92 kg/s and supporting a 40 kW cooling load in the Ejector Refrigeration Cycle (ERC). The development of this solar-powered cooling system presents a sustainable, economically viable solution for building cooling. It demonstrates significant advancements in thermal efficiency through the strategic use of PCMs and optimized zeotropic mixtures in ejector refrigeration cycles. The system's scalable design offers a model for adapting to diverse climatic conditions, marking a notable contribution to sustainable building technologies.

A Dual Gelation Strategy Under Gravity‐Enhanced Orientation to Construct Super‐Strong and Tough Bacterial Cellulose Phase Change Fiber for Wearable Heat Supply

A Dual Gelation Strategy Under Gravity‐Enhanced Orientation to Construct Super‐Strong and Tough Bacterial Cellulose Phase Change Fiber for Wearable Heat Supply

Development of a Controlled Low-Strength Material Containing Paraffin–Rice Husk Ash Composite Phase Change Material

Development of a Controlled Low-Strength Material Containing Paraffin–Rice Husk Ash Composite Phase Change Material