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The simple wickless structure and strong heat transfer potential of pulsating heat pipes (PHP) have prompted widespread interest in transferring heat from electronic devices. This work proposes a novel single-turn PHP with convergent and divergent shaped additional branches (ABs) (C-PHP and D-PHP) in the evaporator section, which could increase latent heat transfer in the evaporator by minimizing the saturation temperature and improving the unidirectional flow and thermal performance of PHP. Numerical simulations were performed using computational fluid dynamics (CFD) techniques to understand the thermo-hydrodynamics and properties of the proposed novel PHPs. This study provides the outcomes of novel PHPs and a comparison with the performance of traditional PHP (T-PHP) without AB and straight AB PHP (S-PHP). The results demonstrated that the startup time of novel C-PHP and D-PHP were improved by 32.6% and 22.4%, respectively, compared to the T-PHP, "stopovers" and "local flow reversals" are minimized by the use of AB. The average flow velocity of novel C-PHP and D-PHP was improved by 16% when compared to T-PHP and 11.4% compared to S-PHP, the directional component in C-PHP is substantially stronger than S-PHP and D-PHP. [ABSTRACT FROM AUTHOR]

The present study numerically investigates the energy and exergy analysis of solidification of phase change materials within a double tube and triple tube latent heat storage unit using ANSYS Fluent. Double tube and triple tube thermal energy storage system's thermal characteristics are examined using MXene nano‐enhanced phase change material to determine system efficiency, discharged energy, heat transfer rate, exergy destruction, entropy generation number, exergetic efficiency, liquid fraction, solidification temperature contours. The result revealed that the double tube thermal energy storage with pure cetyl alcohol PCM has 14.76% lower discharge exergy than MXene‐based nano‐enhanced phase change material in pure solidification. In a triple tube thermal energy storage system, the solidification time for MXene‐based nano‐enhanced phase change material is impressively reduced by 54.76% compared to a double tube system using pure phase change material. At a Fourier number of 0.00672, MXene nano‐enhanced phase change material exhibits an 11.69% higher Stefan number (St) than cetyl alcohol phase change material in a double tube thermal energy storage system. At 2400 s, pure phase change material and MXene nano‐enhanced phase change material generated 3.14% and 4.88% less entropy than pure cetyl alcohol in the triple tube thermal energy storage system. During the pure solidification process in a double tube thermal energy storage system, pure cetyl alcohol experiences 7.60% higher exergy destruction compared to MXene nano‐enhanced phase change material at a solidification time of 2400 s. In a triple tube thermal energy storage system, the discharging temperature for pure cetyl alcohol phase change material is 2.92% lower than that in a double tube system. Double tube thermal energy storage with pure cetyl alcohol discharged more efficiently over 2400 s. The triple tube thermal energy storage system solidified cetyl alcohol PCM 20.83% faster than pure phase change material due to MXene nanoparticles' better thermophysical properties. Thus, MXene‐based nano‐enhanced cetyl alcohol phase change material solidifies faster per volume in a triple tube thermal energy storage latent heat system. [ABSTRACT FROM AUTHOR]

Melting and solidification of a phase change material (PCM) is investigated experimentally by applying a partial filling strategy to the hybrid enhancement of heat pipe–metal foam (HP‐MF) in a vertical cylinder. HP‐MF enhancement can improve the heat transfer capacity of the PCM system as it combines HP's efficient heat transfer capacity with MF's highly effective thermal conductivity capability. The experimental results demonstrate that the partial filling strategy in the melting and solidification of HP‐MF PCM can be optimized for effective MF utilization in the HP‐MF PCM system. A filling ratio of 83% of MF in HP‐MF PCM shows almost identical total melting and solidification along with a temperature distribution to that of an HP‐MF PCM (95% porosity, 20 pore density [PPI]). It is plausible to conclude that the removal of 33% or less mass had no significant effect on the overall melting process of HP‐MF PCM. It should be noted that the HP‐MF PCM system's HP heat transfer efficiency significantly decreased during the melting process when the MF filling ratio was 37.5% and 12.5%. [ABSTRACT FROM AUTHOR]

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This document discusses the optimization of operating conditions for battery thermal management systems (BTMS) in electric vehicles. The operational temperature of lithium-ion batteries has a significant impact on their efficiency and safety. The ideal temperature range for efficient operation is 20-40 °C, with a recommended temperature difference between batteries of no more than 5 °C. Researchers have explored various methods to regulate battery temperature, including using phase change materials (PCM) and heat dissipation techniques. These studies aim to improve battery performance in both low and high-temperature environments and prevent thermal runaway. The findings from these studies can contribute to the development of more efficient BTMS for lithium batteries. [Extracted from the article]

• Four common latent heat functional fluids are described and compared. • Summarizes the current methods for determining the stability of PCMEs. • The mechanism and solution to the stability of PCMEs are analyzed. • The mechanism, inhibition method and research on PCME supercooling are concluded. • An overview of the latest research progress of PCMEs in various fields. As the global environment continues to deteriorate and temperatures gradually rise, it has been realized that the utilization of renewable energy is one of the most effective measures to mitigate global warming. Thermal energy storage plays a crucial role in the energy mix, and phase change materials are among the most significant and effective methods of thermal energy utilization. Phase change material emulsions, as fluid-phase phase change materials, play a significant role in thermal energy storage and heat transfer. However, issues related to stability and supercooling hinder the practical application of phase change material emulsions. Consequently, this paper explores the current research status of stability and supercooling mechanisms and technologies. Firstly, this paper provides a brief overview of the fundamental concepts of phase change material emulsions. Then, it addresses the challenges related to controlling the stability of phase change material emulsions and the issue of significant supercooling. The paper elaborates on relevant research findings in detail, mechanisms, evaluation criteria, and potential solutions. Finally, the paper outlines the research progress of phase change material emulsions in the fields of solar energy, construction, and thermal management, demonstrating their potential to advance renewable energy and various industrial sectors. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive three-dimensional Computational Fluid Dynamics (CFD) analysis of the pre-cooling process of a Type B LNG tank using various refrigerants, including liquid nitrogen (LN), nitrogen gas (NG), liquefied natural gas (LNG), boil-off gas (BOG), and their combinations. The simulation model accounts for phase change (through the mixture multiphase model), convective heat transfer, and conjugate heat exchange between the fluid and the tank structure. The results indicate that liquid nitrogen is the most efficient refrigerant, achieving the highest cooling rate through both latent and sensible heat. LNG also demonstrated a relatively high cooling rate, 79% of that of liquid nitrogen. Gas-only pre-cooling schemes relying solely on sensible heat exhibited slower cooling rates, with BOG achieved 79.4% of the cooling rate of NG. Mixed refrigerants such as NG + LN and BOG + LNG can achieve comparable, while slightly slower, cooling than the pure liquid refrigerants, outperforming gas-only strategies. A further assessment of the heat transfer coefficient suggests the mixed cooling schemes have almost identical heat transfer coefficient on the inner tank surface to the liquid cooling scheme, over 5% higher than the gas refrigerants. The study also highlighted the uneven temperature distribution within the tank due to the bulkhead's blockage effect, which can induce significant thermal stress and potentially compromise structural integrity. Mixed schemes exhibit thermal gradients higher than those of gas schemes but lower than those of liquid schemes, while achieving cooling speeds comparable to liquid schemes if the inlet velocity of the refrigerants is properly configured. These findings offer valuable insights for developing safer and more efficient pre-cooling procedures for Type B LNG tanks and similar cryogenic storage tanks. [ABSTRACT FROM AUTHOR]

Utilizing phase change materials (PCMs) in passive energy-saving wall panels to regulate indoor temperatures during hot seasons can improve people's thermal comfort and reduce the energy consumption of air conditioning systems. This study is based on the hot summer and warm winter climatic characteristics of Hainan. According to local meteorological data and residents' living habits, a suitable phase change temperature of approximately 28 °C was determined. A composite PCM of paraffin and stearic acid n-butyl ester was prepared and tested for thermal performance. Encased in an aluminum box with non-penetrating aluminum rods to enhance heat transfer, the phase change panel was applied to the inner side of exterior walls. Thermal tests demonstrated that increasing the mass ratio of stearic acid n-butyl ester to paraffin lowers the melting point and latent heat. At a 3:7 mass ratio, the melting point of the composite PCM was 28.30 °C, and the latent heat was 128.26 J/g. The 20 mm thick panel maintained a stable phase change process, with unheated surface temperatures between 28 °C and 29 °C for up to 180 min. Compared to panels without aluminum rods, those with rods exhibited a 20% longer phase change time, extended heat transfer paths, and reduced liquid-phase convective heat transfer rates, demonstrating improved PCM utilization. Therefore, the phase change panel with non-penetrating aluminum rods exhibits excellent insulation and temperature control properties. [ABSTRACT FROM AUTHOR]

This study aims to use beeswax, a readily available and cost-effective organic material, as a novel phase change material (PCM) within blends of low-density polyethylene (LDPE) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS). LDPE and SEBS act as support materials to prevent beeswax leakage. The physicochemical properties of new blended phase change materials (B-PCM) were determined using an X-ray diffractometer and an infrared spectrometer, confirming the absence of a chemical reaction within the materials. A scanning electron microscope was used for microstructural analysis, indicating that the interconnection of the structure allowed better thermal conductivity. Thermal gravimetric analysis revealed enhanced thermal stability for the B-PCM when combined with SEBS, especially within its operating temperature range. Analysis of phase change temperature and latent heat with differential scanning calorimetry showed no major difference in the melting point of the various PCM blends created. During the melting/solidification process, the B-PCMs possess excellent performance as characterized by W70/P30 (112.45 J.g−1) > W70/P20/S10 (94.28 J.g−1) > W70/P10/S20 (96.21 J.g−1) of latent heat storage. Additionally, the blends tend to reduce supercooling compared to pure beeswax. During heating and cooling cycles, the B-PCM exhibited minimal leakage and degradation, especially in blends containing SEBS. In comparison to the rapid temperature drop observed during the cooling process of W70/P30, the temperature decline of W70/P30 was slower and longer, as demonstrated by infrared thermography. The addition of LDPE to the PCM reduced melting time, indicating an improvement in the thermal energy storage reaction time to the demand. According to the obtained findings, increasing the SEBS concentration in the composite increased the thermal stability of the resulting PCM blends significantly. Despite the challenges mentioned earlier, SEBS proved to be an effective encapsulating material for beeswax, whereas LDPE served well as a supporting material. Leak tests were performed to find the ideal mass ratio, and weight loss was analyzed after multiple cycles of cooling and heating at 70 °C. The morphology, thermal characteristics, and chemical composition of the beeswax/LDPE/SEBS composite were all examined. Beeswax proves to be a highly effective phase change material for storing thermal energy within LDPE/SEBS blends. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) present opportunities for efficient thermal management due to their high latent heat of melting. However, a fundamental challenge for PCM cooling is the presence of a growing liquid layer of relatively low thermal conductivity melted PCM that limits heat transfer. Dynamic phase change material (dynPCM) uses an applied pressure to pump away the melt layer and achieve a thin liquid layer, ensuring high heat transfer for extended periods. This paper investigates heat transfer during dynPCM cooling when the heated surface has extended features made from high thermal conductivity copper (Cu). Using experiments and finite element simulations, we investigate the heat transfer performance of dynPCM paraffin wax on finned Cu surfaces. A total of 102 transient temperature measurements characterize the performance of dynPCM with extended surfaces and compare the performance with other cooling methods including hybrid PCM and air cooling. The study examines the effects of fin geometry, applied power (20–65 W), and pressure (0.97–12.5 kPa). For dynPCM on a finned surface and a heating power of 65 W, the thermal conductance is 0.45 W/cm2-K, compared to 0.22 W/cm2-K for dynPCM on a flat surface and 0.10 W/cm2-K for hybrid PCM. The heat transfer is highest at the fin tips where the melt layer is thinnest, providing valuable design guidelines for future high performance dynPCM cooling technologies. [ABSTRACT FROM AUTHOR]

Achieving simultaneous control over temperature and humidity through a single direct expansion air conditioner would be advantageous, especially considering its widespread use in residential buildings. Traditional control strategies fail to achieve satisfactory control performance due to the nature of complexity and cross-decoupling of the system. Therefore, this research paper presents the advancement of a feedforward decoupling control scheme designed for a direct expansion air conditioning unit to effectively control both temperature and humidity. To facilitate the controller design, a dynamic model considering both sensible and latent heat transfers was developed and verified. The thermal responses of the coupled system were analyzed and their correlation coefficients also examined. Through identifying the transfer function model of the coupled system, a feedforward decoupling controller with two compensators was designed. The proposed decoupling control scheme was tested using the developed model as the plant to be controlled. Test results showed that, in comparison to the transitional PID based dual single-input and single-output controller, the proposed decoupling control scheme was capable of eliminating the interactions between indoor air temperature and humidity under variable speed operation, and realizing the simultaneous control over indoor air temperature and humidity with a desirable control performance. [ABSTRACT FROM AUTHOR]

This study presents a one-dimensional mathematical model developed to simulate multi-zone thermal storage systems using phase change materials (PCMs). The model enables precise analysis of temperature distribution in the layered storage based on several PCM configurations and properties. It is distinguished by its adaptability to various tank geometries and the number of PCM capsules, enabling its application under diverse operating conditions. By simplifying the implementation of heat transfer processes that depend on the shape of the capsule and the thermal properties of the PCM, the computation time can be reduced to a level that makes simulations over longer periods feasible. Experimental validation confirmed the accuracy of the model, with deviations below 6%, underscoring its practical applicability. The study demonstrates that individual layering in the storage tank can be achieved by filling it with PCMs of different melting points without compromising the maximum storage capacity. It is shown that including a PCM layer can maintain the outlet temperature 20% longer while storing 14% more energy. The results point out the model's potential to improve the performance of thermal storage systems through targeted PCM layer configurations. The model serves as the basis for the planning and optimization of these systems. [ABSTRACT FROM AUTHOR]

Elastocaloric cooling is emerging as a promising alternative to conventional vapor compression systems due to its potential for energy savings and significant temperature lift compared to other solid-state cooling technologies. This technology harnesses the latent heat associated with the martensitic phase transition of shape memory alloys to generate the desired cooling or heating effect. This paper comprehensively reviews the fundamentals of elastocaloric cooling systems, including the thermodynamics cycle and various materials used. It also presents the latest advancements in elastocaloric systems, focusing on heat transfer enhancement, actuator development, and prototype summaries. Additionally, this paper introduces a new non-dimensional performance parameter to evaluate different elastocaloric prototypes and discusses key aspects necessary to achieve potentially high-performance elastocaloric devices. Finally, we propose an approach for future elastocaloric device development. [ABSTRACT FROM AUTHOR]

The objective of the current study is to investigate the importance of entropy generation and thermal radiation on the patterns of velocity, isentropic lines, and temperature contours within a thermal energy storage device filled with magnetic nano-encapsulated phase change materials (NEPCMs). The versatile finite element method (FEM) is implemented to numerically solve the governing equations. The effects of various parameters, including the viscosity parameter, ranging from 1 to 3, the thermal conductivity parameter, ranging from 1 to 3, the Rayleigh parameter, ranging from 102 to 3 × 102, the radiation number, ranging from 0.1 to 0.5, the fusion temperature, ranging from 1.0 to 1.2, the volume fraction of NEPCMs, ranging from 2% to 6%, the Stefan number, ranging from 1 to 5, the magnetic number, ranging from 0.1 to 0.5, and the irreversibility parameter, ranging from 0.1 to 0.5, are examined in detail on the temperature contours, isentropic lines, heat capacity ratio, and velocity fields. Furthermore, the heat transfer rates at both the cold and hot walls are analyzed, and the findings are presented graphically. The results indicate that the time taken by the NEPCMs to transition from solid to liquid is prolonged inside the chamber region as the fusion temperature θf increases. Additionally, the contours of the heat capacity ratio Cr decrease with the increase in the Stefan number Ste. [ABSTRACT FROM AUTHOR]

In heating processes using superheated steam, a practical heat transfer model for predicting the change in the material temperature taking condensation/evaporation into consideration is required. This study observed the behavior of condensed water and verified a simple but practical heat transfer model to predict the heating time of materials. The one-dimensional model, which comprehensively includes the conductive, convective, radiative, and latent heat fluxes, was utilized. For simplicity, film condensation was assumed. To conduct experiments covering a wide humidity range, the humidity of the airflow was regulated by mixing superheated steam with high-temperature air. The sample material having 50 mm of length, 50 mm of width, and 10 mm of thickness was placed under this airflow, and the change in temperature over time was measured. During the initial stages of heating via superheated steam, condensation, and subsequent evaporation were observed. The time required for the evaporation of condensed water increased with the humidity, owing to the large amount of condensed water. The ending time of evaporation was successfully estimated within about −30% error. Although some modifications will be required in the future, the model is expected to be a powerful tool in various industries where superheated steam is applied. [ABSTRACT FROM AUTHOR]

Boiling is a phase change heat transfer process that transfers latent heat quickly, making it suitable for use in various heat transfer systems. An important worry for the boiling performance degradation is the durability of the artificial nano-/microporous interfaces concerning the bottom surface. This study therefore proposes a novel three-step surface creation process (chemical etching, electroplating, and sintering process). Wet/chemical etching is first used to form three distinct micro/nanostructured substrates (ES#1, 2, 3). The most effective etched substrate (ES#3) is again employed as a cathode for the electrochemical depositing process or next-of-surface manufacturing. To strengthen the link between the etched layer (ES#3) and the surface of the coating (copper-alumina), the electroplating produced substrate (ES#4) is sintered in a predetermined environment. The enhanced boiling efficiency obtained on ES#4 is attributable to the appropriate bonding among ES#3 and electroplated nanoparticles (Cu-Al2O3). By maintaining a consistent temperature across the heater's topmost layer and the fin tip, the reduction in resistance at the intermediate level brought on by appropriate binding increases the rate of heat transfer. The critical heat flux (CHF) and heat transfer coefficient (HTC) improvements for ES#4 over bare copper are 184% and 216%, respectively. Additionally, the impact of certain macro- and micro-scale restrictions on the occurrence of flow boiling heat transfer is examined. The ES#4 surface showed better stability during repeated thirty testing cycles, as seen by the much smaller decline in superheat temperatures (1.2 °C) and wettability (32° to 33.7°). [ABSTRACT FROM AUTHOR]

Boiling of the coolant at the hot surface provides relatively better cooling by absorbing latent heat along with convection heat transfer as compared to heat transfer under single-phase conditions. In boiling, the orientation of heated surface also plays a crucial role. Downward facing boiling is complex than upward facing boiling, as the detachment of the bubble inhibited due to the heater surface orientation. Consequently, the bubble residence time and interaction with other bubbles are different in such boiling conditions. Our experiments on a large downward facing flat surface (100 × 400 mm2) revealed unexplored boiling phenomena. The boiling process is dominated by a complex engulfing phenomenon, which is rarely reported in the past. The engulfing phenomena have been captured using high-speed photography, wherein, at low heat fluxes, it is observed that larger bubbles engulf small bubbles by opening their mouth and swallowing the small bubbles. However, at higher heat fluxes, this phenomenon disappears. A larger vapor blanket is formed due to engulfing of bubbles, which may lead to departure from nucleate boiling. This engulfing behavior depends on the heat flux and subcooling. With the increase in heat flux, it is found that the rate of vapor engulfing increases. We have attempted to explain the science behind such engulfing phenomenon based on the capillary pressure difference. These results are consistent at various subcooling. This research provides new insights into nucleate boiling and may help in developing advanced mathematical models for accurate heat transfer prediction on downward facing nucleate boiling. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) using phase change materials (PCMs) is one of the potential solutions for stockpiling thermal energy and utilizing it for different applications, which results in effective energy usage. The main drawback of organic PCMs in practical applications is poor heat transfer due to low thermal conductivity (TC). Therefore, investigations into nano-enhanced PCMs are being explored to improve their thermophysical properties. In this work, the various thermophysical characteristics of nano-enhanced lauryl alcohol as a PCM were investigated using carbon-based and metallic nanoparticles. The results indicated that the addition of nanoparticles improved its thermal properties and affected other physical properties, such as viscosity. The latent heat was degraded with the addition of nanoparticles. The results revealed that by adding MWCNTs and CuO nanoparticles, a maximum of 82.6% and 49.6% improvement in TC was achieved, respectively. The maximum drop in latent heat during melting and freezing for the PCM with MWCNTs was about 10.1% and 9.3%, respectively, whereas for the PCM with CuO, they were about 11% and 10.3%, respectively. The lowest supercooling for the PCM with MWCNTs and CuO nanoparticles was 8.6 and 8.3 °C, respectively. The present work confirms that nano-enhanced PCMs can be a potential material for storing thermal energy for various applications. [ABSTRACT FROM AUTHOR]

Loop heat pipe (LHP) encased in phase change material (PCM) incorporated annular to catalytic converter (CC) is proposed to augment the performance of the "thermal energy storage" (TES). LHP are designed to extract surplus heat from the exhaust discharge, thereby reducing the amount of exhaust heat emitted into the atmosphere. A four-cylinder IC engine's CC is considered with Mg70Zn24.9Al5.1, paraffin oil as PCM and working fluid for the heat pipe are evaluated. A comparative experimental investigation was performed considering two models for CC with and without heat pipe integrated in the TES for (i) distribution of average PCM temperature (ii) energy, exergy efficiency and distribution (iii) effectiveness (iv) instantaneous waste heat recovered during heat storage. Transient cycles at 2000 r/min with varying load conditions were run considering city drive conditions. Heat storage for CC with heat pipe encased in TES was found to be 35% faster, whereas discharge time for CC without heat pipe developed in TES was found to be longer. For melt fraction 1, maximum exergy efficiencies of 71% and 69% were observed for the TES unit with and without heat pipe. Heat pipes are observed to help extract a considerable amount of surplus heat from exhaust and reduce the exhaust gas outlet temperature released into the atmosphere by nearly 130 – 40°C under various load circumstances. [ABSTRACT FROM AUTHOR]

With the growing demand for photovoltaic (PV) systems as a source of energy generation that produces no greenhouse gas emissions, effective strategies are needed to address the inherent inefficiencies of PV systems. These systems typically absorb only approximately 15% of solar energy and experience performance degradation due to temperature increases during operation. To address these issues, PV–thermal (PVT) technology, which combines PV with a thermal absorber to dissipate excess heat and convert it into additional thermal energy, is being rapidly developed. This review presents an overview of various PVT technologies designed to prevent overheating in operational systems and to enhance heat transfer from the solar cells to the absorber. The methods explored include innovative absorber designs that focus on increasing the heat transfer contact surface, using mini/microchannels for improved heat transfer contiguity, and substituting traditional metal materials with polymers to reduce construction costs while utilizing polymer flexibility. The review also discusses incorporating phase change materials for latent heat absorption and using nanofluids as coolant mediums, which offer higher thermal conductivity than pure water. This review highlights significant observations and challenges associated with absorber design, mini/microchannels, polymer materials, phase change materials, and nanofluids in terms of PV waste heat dissipation. It includes a summary of relevant numerical and experimental studies to facilitate comparisons of each development approach. [ABSTRACT FROM AUTHOR]

Compared to sensible heat storage, latent heat storage provides higher energy density due to the enthalpy difference of the storage medium undergoing a phase change. However, the heat storage capability of phase change materials is opposed by low thermal conductivity. To enable sufficient heat transfer within a latent heat storage unit, phase change materials can be used in combination with a metallic matrix. One approach is the infiltration of phase change materials into additively manufactured metallic lattice structures. In this work, the fabrication of aluminum lattice structures through laser powder bed fusion is described. During fabrication, the cell size and the strut diameter were varied to obtain specimens of different geometries. To obtain the thermal conductivity of the fabricated lattices, measurements were conducted based on the transient plane source method. Additionally, finite element simulations were carried out to evaluate the effect of fabrication and measurement uncertainties. The thermal conductivity of the fabricated lattices was found to be between 3 W/(m·K) and 130 W/(m·K). The numerically and analytically performed calculations provide good estimations of the experimentally obtained data. [ABSTRACT FROM AUTHOR]

Boiling heat transfer, as an efficient heat transfer approach, that can absorb a large amount of latent heat during the vaporization, is especially suitable for heat transfer occasions with high heat flux demands. Experimental studies show that the surface tension coefficient of pure water can be reduced sharply (up to 25%) when it is magnetized by a magnetic field applied externally. In this paper, magnetized water (MW) was used as the work fluid to conduct boiling heat transfer experiments, to explore the influence of magnetization on the boiling characteristics of pure water. The electromagnetic device was used to magnetize water, and then the MW was used as the work-fluid of boiling heat transfer experiments, the bubble dynamic behavior of the MW boiling was captured by a video camera, and the characteristics and mechanism were analyzed. It was found that at the same conditions, the boiling of MW can produce more vapor bubbles of smaller size than the water without magnetization, which leads to a higher heat-transfer efficiency. This indicates that magnetization can enhance the boiling heat transfer of pure water. Furthermore, the thermal conditions required by magnetized water when the boiling is started are lower than the non-magnetized water boiling, which means the earlier start of nucleate pool boiling when using the MW. [ABSTRACT FROM AUTHOR]

Featured Application: This study proposes a novel concept for designing thermal energy storage tanks applying biomimetics to enhance heat transfer without the need for fins. Thermal energy storage (TES) systems play a very important part in addressing the energy crisis. Therefore, numerous researchers are striving to improve the efficiency of TES tanks. The TES technology has the potential to reach new heights when the biological behavior of nature is incorporated into the design of TES tanks. By mimicking the branched vein pattern observed in plants and animals, the heat transfer fluid (HTF) tube of a TES tank can enhance the heat transfer surface area, hence improving its thermal efficiency without the need to add other enhancements of heat transfer methods. Accordingly, in this study, a unique additive-manufacturing-based bio-inspired TES tank was designed, developed, and tested. A customized testing setup was used to assess the bio-inspired TES tank's thermal performance. A comparison was made between the bio-inspired TES tank and a conventional shell-and-tube TES tank. The latent TES system's thermal performance was significantly enhanced by the biomimetic approach for the design of a TES tank, even before the optimization of its design. The results showed that, compared to the shell-and-tube TES tank, the bio-inspired TES tank had a higher discharging rate and needed 52% less time to release the stored heat. [ABSTRACT FROM AUTHOR]

An ouzo droplet is a multicomponent liquid comprising ethanol, water, and anise oil, each possessing distinct thermophysical properties, volatility, and mutual miscibility. Evaporation leads to the complex physicochemical process of coupled mass and heat transfer, spontaneous emulsification, and liquid–liquid phase separation, known as the ouzo effect. An acoustically levitated ouzo droplet undergoes five characteristic stages of evaporation based on temporal temperature variation. Such levitated droplet shows a significantly longer lifespan upon evaporation because of the thermal isolation in air, as well as a drastic initial cooling. Sessile droplets, on the other hand, have heat transferred from the surroundings via the substrate to replenish latent heat of vaporization. A conductive substrate thus helps the droplet to stay close to the ambience and a shorter lifespan. A rudimentary theoretical model based on dimensional analysis is developed and shows consistency with measurements. [ABSTRACT FROM AUTHOR]

This study explores the influence of angle of attack (AOA) on the icing distribution characteristics of asymmetric blade airfoil (DU97) surfaces for wind turbines under icing conditions by numerical simulation. The findings demonstrate a consistence between the simulated ice shapes and experimental data. The ice thickness distribution on the lower surface of the leading edge exhibits a trend of first rising and then declining along the chord direction while showing a gradually decreasing trend on the upper surface. The ice distribution range on the upper surface of the trailing edge is broader than that on the lower surface. The peak ice thickness at the trailing edge rises significantly as AOA increases from 5° to 10°, and at the leading edge raises dramatically at droplet sizes of 30–40 μm and wind speeds of 5–10 m/s. The peak ice thickness is more significantly influenced by AOA than by ambient temperature due to the combined effect of airflow characteristics induced by AOA and latent heat (phase change) and sensible heat (thermal convection and thermal radiation) caused by ambient temperature. The findings offer valuable insights into the flow and heat transfer physics, and can operate as references for wind turbine anti/de-icing technology. [ABSTRACT FROM AUTHOR]

Phase-changing materials are nowadays getting global attention on account of their ability to store excess energy. Solar thermal energy can be stored in phase changing material (PCM) in the forms of latent and sensible heat. The stored energy can be suitably utilized for other applications such as space heating and cooling, water heating, and further industrial processing where low-temperature heat energy is required. The presented work attempts to evaluate past, present, and future trends in the development of energy storage materials and their encapsulation techniques for efficient utilization of the available energy. Hybrid PCM with nanoparticles has excellent potential to tailor thermo-physical properties and uplift the efficiency of energy storage systems. Synergistic use of PCM with nanomicromaterial can further improve the capacity of energy storage system along with the charging and discharging efficiencies of the system. Impacts of the size of particle, concentration ratio, and shape of particle have been studied to assess their effectiveness in enhancing storage efficiency of the systems. Waste heat recovered and stored in energy storage materials can undoubtedly improve the total energy availability of the source, thus enhancing the exergy efficiency with simultaneous reduction in the entropy generation rate. Core-shell nanoparticles can further improve the optical absorptance spectra towards an infrared region of thermal energy. Paraffin wax-based NEPCMs with graphene nanoplatelets achieve 2.14 W/(m·K) thermal conductivity, enabling faster and more efficient heat transmission and lowering charging and discharging times for thermal storage devices. [ABSTRACT FROM AUTHOR]

• Review various methods of ice slurry preparation and its research progress. • Summarize the research progress of flow and transfer characteristics of ice slurry. • Describe the research status of ice slurry in fruit and vegetable precooling systems. • Discuss the nonnegligible problems of the precooling of ice slurry. Ice slurry is a phase change refrigerant with a high latent heat of melting and good flow properties. Ice slurry has been applied to fruit and vegetable precooling systems after harvest and garnered widespread attention. To expand the applicability of ice slurry precooling technology, conventional ice slurry preparation methods, including supercooling, wall scraping, fluidized bed, direct contact, and vacuum techniques, are reviewed; moreover, the advantages and limitations of each method are discussed. In addition, the flow and heat transfer properties of ice slurry are provided. Furthermore, recent progress in the research on the flow and heat transfer properties of ice slurry is summarized, and the application and future development trends regarding the precooling of fruits and vegetables are discussed according to the precooling mechanisms of fruits and vegetables. [ABSTRACT FROM AUTHOR]

Lava domes form during effusive eruptions due to an extrusion of highly viscous magmas from volcanic vents. In this paper we present a numerical study of the lava dome growth at Volcán de Colima, Mexico during 2007–2009. The mathematical model treats the lava dome extrusion dynamics as a thermomechanical problem. The equations of motion, continuity and heat transfer are solved with the relevant boundary and initial conditions in the assumption that magma viscosity depends on the volume fraction of crystals and temperature. We perform several sets of numerical experiments to analyse the internal structure of the lava dome (i.e. the distributions of the temperature, crystal content, viscosity and velocity) depending on various heat sources and thermal boundary conditions. Although the lava dome growth at Volcán de Colima during short (a few months) dome-building episodes can be explained by an isothermal model of lava extrusion with the viscosity depending on the volume fraction of crystals, we show here that cooling plays a significant role during long (up to several years) episodes of dome building. A carapace develops as a response to a convective cooling at the lava dome–air interface. The carapace becomes thicker if the radiative heat loss at the interface is also considered. The thick carapace influences the lava dome dynamics preventing its lateral advancement. The release of the latent heat of crystallization leads to an increase of the temperatures in the lava dome interior and to a relative flattening of the dome. Meanwhile, the heat source due to viscous dissipation inside the lava dome is negligible, and it does not influence the lava dome growth. The developed thermomechanical model of the lava dome dynamics at Volcán de Colima can be used elsewhere to analyse effusive eruptions, dome morphology and carapace evolution including its failure potentially leading to pyroclastic flow hazards. [ABSTRACT FROM AUTHOR]

The low ability of phase change material (PCM) to transfer thermal energy has created a serious challenge for the development of latent heat storage (LHTES) units. Embedding foam with high thermal conductivity material like copper has attracted significant attention. Besides, high porosity, lightweight, and easy usage are other important benefits of copper. However, its higher cost and decreasing effective volume of PCM led to the creation of amendments in the foam design. Employment of the foam in the form of fin or foam fin has emerged as an alternative method to benefit from the advantages of porous material and overcome its defects. In this study, various LHTES units with different numbers of foam fins have been simulated numerically and compared with pure PCM and fully foam PCM enclosures. Two practical boundary conditions including constant temperature and constant heat flux were examined for the designed systems. The obtained results demonstrated that foam fins have a remarkable effect on the thermal performance enhancement of LHTES under constant temperature boundary condition. For LHTES with six foam fins, 42% and 30% reductions in melting time were achieved for both types of boundary conditions including constant temperature and heat flux, respectively. At the beginning of charging process, a significant enhancement of input heat rate was proved for LHTES with 6 foam fins and fully foam up to 112% and 155%, respectively. In addition, the foam fins method provided some free volume of PCM to permit the falling out of natural convection of molten PCM. [ABSTRACT FROM AUTHOR]

Copyright of EMERG: Energy. Environment. Efficiency. Resources. Globalization is the property of Romanian National Committee of World Energy Council and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phase-change materials (PCMs) can be used to develop thermal energy storage systems as they absorb large amount of latent heat nearly at a constant temperature when changing phase from a solid to a liquid. To prevent leakage when in a liquid state, PCM is shape stabilized in a polymer matrix of high-density polyethylene (HDPE). The present research explores the injection-molded mechanical and thermal properties of different PCM/HDPE composite ratios. The tensile strength and modulus of elasticity at room temperature and with the PCM fully melted within the composite are measured. Additionally, the hardness, latent heat of fusion, phase-change temperature, and thermal conductivity are investigated. An analysis of microstructures of the composite is used to support the findings. The PCM within the PCM/HDPE composite gives it the benefit of thermal storage but causes a decrease in mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, the work is concerned with the study of moving boundary based on non-classical heat equation that includes a time dependent heat flux and convection. The latent heat is represented as a function of the moving interface. Mathematical model accounts for a control function varying with heat flux. We have obtained the explicit solution of the given mathematical model in the presence of convection and a control function. The Legendre wavelet Galerkin approach (LWGA) is used to solve the mathematical problem. In a particular case, our numerical results were compared with previous results and found to be in excellent agreement. Moreover, the current numerical technique is more efficient and accurate in comparison to the previous available method. An extensive analysis of the problem parameters is presented. It is found that the control function offers a significant contribution during the melting or freezing of a PCM. A greater value of the heat flux accelerates the rate of propagation of interface. Convection heat transfer increases the speed of the interface. Results obtained from the current study are expected to improve the fundamental understanding of heat transfer and aid in sublimation and desorption like physical phenomena. [ABSTRACT FROM AUTHOR]

The objective of this review paper is to implement and investigate of micro‐nano bubble technology for enhancement of condensation heat transfer. Micro‐nano bubbles dispersions in aqueous solutions can stay for a substantial time. As an example, 20 micron size micro‐nano bubbles take daily to rise one meter. Because the inertia force of fluid current exceeds the buoyant force, any currents within a large vessel would be anticipated to entrain kind of micro‐nano bubble dispersion. Micro‐nano bubbles will vaporize hotter water toward the center of the plume and convert that extra heat of transition to the cold wall, where it will condense the vapors and release latent heat if the condenser is arranged in the micro‐nano bubble‐assisted airlift configuration. [ABSTRACT FROM AUTHOR]

The melting behavior of a phase change material (lauric acid) placed in various shaped cavities having an inner heated tube is studied numerically. The present investigation concerns the influence of various shaped cavities and the position of the tube on the melting rate and heat transfer process of the phase change material. Finite element method has been employed to solve the governing differential equation along with boundary conditions. The PARADISO package solves the algebraic systems of equations deriving from spatial and temporal discretization. It is notably successful in solving unsymmetrical sparse matrixes using an LU-based decomposition strategy. The average Nusselt number in the inner tube is determined to confirm whether the melting process is convection dominant or conduction dominant. The result shows that the trapezoidal-shaped cavity with an eccentricity of inner tube can enhance the melting fraction compared to the annular-shaped cavity with a central inner tube, annular-shaped cavity with an eccentric inner tube, and trapezoidal-shaped cavity with a central inner tube by 67%, 12%, and 40%, respectively. The results show that the shape of the cavity and proper positioning of the inner tube can influence the melting phenomenon and therefore improves the charging rate appreciably. [ABSTRACT FROM AUTHOR]

Flue gas after wet desulfurization contains a large quantity of water vapor, as well as a small amount of fine particulate matter, acid and other pollutants. Direct emissions will cause haze and environmental pollution. Flue gas condenser can effectively recover latent heat of vaporization and remove these pollutants. However, the traditional flue gas condenser has disadvantages such as large volume, low heat exchange efficiency and easy blockage. To overcome these problems, a new type narrow gap heat exchanger, which is easy to detach and clean, is proposed. Then, the flue gas condensation characteristic is experimentally investigated. The factors including velocity and temperature of flue gas, flow and temperature of cooling water are studied on heat transfer coefficient and the condensation rate. The results indicate that the overall heat transfer coefficient is seven times of convection heat transfer coefficient, and the condensation rate can reach more than 60%. As the cooling water temperature increases, the condensation rate and condensation heat transfer coefficient gradually decrease. With the increasing of the flue gas velocity, condensation rate gradually decreases and condensation heat transfer coefficient gradually increases. Finally, the dimensionless correlation of Nusselt number is carried out, and the error is within 10%. [ABSTRACT FROM AUTHOR]

In the present work, the effect of natural convection caused by immiscible intermediate fluid on melting process in a horizontal shell-and-tube latent heat storage is examined numerically. The intermediate fluid is placed between the section filled with phase change material and the storage outer hot wall (as heat source). Water is considered as the intermediate fluid to transfer heat from the hot wall to PCM (n-octadecane) by the buoyancy impact of heated water. Water and the liquid phase of the n-octadecane are immiscible. Numerical analysis is performed employing the enthalpy-porosity method with the assistance of a commercial CFD code, ANSYS FLUENT 18.2, based on the finite volume method. The present work consists of two parts. In the first part, a simple 2D latent heat storage with various volume proportions of water as intermediate fluid, including; 25, 50, 75, and 100%, is considered. In the second part, the effect of the number and arrangement of heat transfer fluid channels is evaluated and analyzed. In all investigated models, the volume of the storage is constant and the amount of the PCM varies. The solid PCM was subcooled to 1 ℃, and the temperature of the surface of the storage was maintained at 329 K. The pertinent dimensionless parameters, including; Prandtl, Rayleigh, and Stefan numbers, are 59.5, 6.3 × 108, and 0.27, respectively. The results depicted that the maximum saved energy inside the proposed latent heat storage belongs to the case with 50% of storage volume capacity filled by water. Moreover, the case with four heat transfer fluid tubes indicated the highest absorbed energy, and among them, the four tubes with diamond pattern arrangement stored the highest amount of energy. [ABSTRACT FROM AUTHOR]

A novel frosting model based on Burton–Cabrera–Frank theory is developed. The proposed model contains correction factors for the amount of desublimation (βinn and βsf) and a parameter related to effective diffusivity in frost (F). βinn should be set to approximately 10-3 because of the impact of released latent heat and vapor consumption due to desublimation at nearby interfaces, and the growing ability of ice crystals depending on their crystallographic orientation. In addition, F should be set to approximately 5 to account for the effect of complex transportation of water vapor in frost. Without considering this effect, the frost becomes dense only near the surface. The density distribution becomes inconsistent with experimental findings. This compromises calculation accuracy. Moreover, calculations are performed to validate our model under the following frosting conditions: 243.15 K ≤ Tp ≤ 263.15 K and 8 g/m³ ≤ ρv ≤ 16 g/m³, where Tp is the cold plate temperature, and ρv is the absolute humidity. The results show that the present model can predict the frost mass and average frost thickness with a maximum error of less than 15% at 600 s under a wide range of conditions. [ABSTRACT FROM AUTHOR]

In order to optimize the heat transfer characteristics of regenerative evaporative coolers under different climatic conditions and provide reference data for numerical simulation research. The dynamic coupling of heat and humidity parameters of the air flow in the regenerative evaporative cooler is the fundamental factor affecting the efficiency of evaporative heat transfer, and mastering its law can guide the structure optimization of the heat exchanger. In this paper, a simulation model is constructed based on the structure of regenerative evaporative cooler, and the variation of heat and humidity parameters in the airflow passage is studied by numerical simulation method with the application background of representative cities at home and abroad under different climate conditions. It is found that the relative humidity increases rapidly in the wet channel, and the length of 40 cm wet channel can meet the full evaporation demand under most working conditions. The evaporation cooling effect is greatly affected by the inlet air parameters, and the saturation degree of ambient air has a significant influence on the cooling effect. Keeping the latent heat exchange process in the high efficiency evaporation section and the sensible heat exchange process in the high temperature difference section of the channel can effectively improve the heat exchange efficiency of the evaporative cooler and shorten the length of the heat exchanger. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) system is the most eminent storage method that aids in the power generation. Latent heat storage (LHS) is on the rapid mark‐up that fosters the TES with the utilization of the phase transition of a material to store the heat. Typically the phase change materials (PCM) are used in the LHS system to store the energy. During the material's phase transition, thermal energy is stored and released. Nevertheless, the low thermal conductivity of the PCM in the LHS is susceptible to deteriorate the charging and discharging of the thermal energy. Hence there is a necessity to enhance the thermal performance of the LHS system, on which various studies have been done. Therefore this paper aims in providing a review on the enhancements of the LHS system with improved heat transfer rate and heat transfer enhancement techniques in the PCM for better efficiency. A comprehensive review on the LHS system component is provided to make an emphasis on the heat transfer enhancement rate and storage time. Various characterizations and categories of the PCM are provided to intensify the outcomes of the review as PCMs are most viable materials for storing thermal energy. In addition the recent researches on the integration of PCM with other materials are also discussed that help in the improvements of the thermal conductivity of the PCM. The selection parameters of the PCM materials are also discussed in brief to avoid the poor performance of the PCMs. The heat transfer analysis methods are analyzed to improve the efficiency and reduce the heat loss. Finally, advancements in the future trends for the enhancement of heat transfer is provided. [ABSTRACT FROM AUTHOR]

Long-term measurements of permafrost temperatures do not provide a complete picture of the Arctic subsurface thermal regime. Regions with warmer permafrost often show little to no long-term change in ground temperature due to the uptake and release of latent heat during freezing and thawing. Thus, regions where the least warming is observed may also be the most vulnerable to permafrost degradation. Since direct measurements of ice and liquid water contents in the permafrost layer are not widely available, thermal modeling of the subsurface plays a crucial role in understanding how permafrost responds to changes in the local energy balance. In this work, we first analyze trends in observed air and permafrost temperatures at four sites within the continuous permafrost zone, where we find substantial variation in the apparent relationship between long-term changes in permafrost temperatures (0.02–0.16 Kyr-1) and air temperature (0.09–0.11 Kyr-1). We then apply recently developed Bayesian inversion methods to link observed changes in borehole temperatures to unobserved changes in latent heat and active layer thickness using a transient model of heat conduction with phase change. Our results suggest that the degree to which recent warming trends correlate with permafrost thaw depends strongly on both soil freezing characteristics and historical climatology. At the warmest site, a 9 m borehole near Ny-Ålesund, Svalbard, modeled active layer thickness increases by an average of 13 ± 1 cmK-1 rise in mean annual ground temperature. In stark contrast, modeled rates of thaw at one of the colder sites, a borehole on Samoylov Island in the Lena River delta, appear far less sensitive to temperature change, with a negligible effect of 1 ± 1 cmK-1. Although our study is limited to just four sites, the results urge caution in the interpretation and comparison of warming trends in Arctic boreholes, indicating significant uncertainty in their implications for the current and future thermal state of permafrost. [ABSTRACT FROM AUTHOR]

Using substances of high latent heat such as phase change materials is a perfect technique in the energy storage units. Additionally, examining the heat transport and melting process for these materials is beneficial for a wide variety of solar-related applications. Therefore, this study aims to examine the time-dependent fractional melting process within inclined containers filled with Nanoparticles-enhanced Phase-Change Materials (NePCM) via the model of the enthalpy-porosity. The used NePCM is octadecane and the fractional derivatives are considered for all the time-dependent variables, namely, velocities, temperature and liquid fraction. The Caputo definition is applied to estimate the non-integer derivatives and the fractional order takes the values between 0.75 and 0.95. The solution methodology is depending on the Finite Volume technique with SIMPLE approach. The range of the Fourier number is between 0.05 and 0.4 and the resulting data is presented in terms of melting interface, liquid fraction, streamlines, isotherms and heat transfer rate. The main findings revealed that the influences of order of the fractional derivatives more significant at the higher values of the Fourier number and the melting interface points move towards the heated wall as order of the fractional derivatives is reduced. Also, at higher values of the fractional derivative's order (0.9), the maximizing of inclination angle causes a diminishing in the rate of the heat transfer. [ABSTRACT FROM AUTHOR]

Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Superheated steam acts as both a heat source and a drying medium. The study sought to predict the evolution of the moisture transport behaviour of the corn kernel at various axial distances at varying instantaneous time. The equations describing the drying phases were solved using numerical solutions with the Eulerian technique in ANSYS software. Cone geometry was used to simulate the corn kernel with initial moisture content at 20% w.b. Steam conditions were similar to what is encountered in industry, with temperatures ranging (from 120–200°C) at 1.5 m s−1 velocity. ANOVA was used to determine if there was difference between the conditions. The temporal change in moisture from the apex to the periphery varied at superheated steam temperatures 120, 160 and 200°C. At 10, 100 and 200 s the drying rate and effective moisture diffusivity of corn kernel from the centre towards the periphery differed. Post‐hoc analysis with Bonferroni adjustment revealed that moisture content (w.b.%) differed between 10 and 100 s, 10 and 200 s and 100 and 200 s. The mean difference was attributed to the drying being in the falling drying phase at 200 s and initial condensation at 10 s. Thus, at high superheated steam temperatures, dry zones can be seen as the axial distance from the apex increases toward the periphery. [ABSTRACT FROM AUTHOR]

The high latent heat of phase change materials (PCMs) makes them one of the most important sources of heat energy storage systems. However, due to the slow rate of heat transfer in these materials, using conductive materials such as fins and nanoparticles could improve the thermal efficiency of these energy storage systems. So in this article, cross‐shaped fins and Copper(II) oxide nanoparticles with different synthesized forms and various volume fractions have been employed to increase the thermal efficiency of paraffin PCMs. In this simulation, three fin models based on the installed size, the shape of the synthesized nanoparticles in brick, cylindrical, and platelet forms, and the nanoparticle volume fraction of the Copper(II) oxide is 1%–4% are studied. Increasing the volumetric ratio of nanoparticle and shape coefficient decrease the time of solidification, while increasing the length of the cross‐shaped fins raises the solidification rate and improves heat transfer. Finally, it was found that when the inner and outer walls play a role in the solidification process at the same time, the solidification rate will increase by more than 66% as more zone of the surface is exposed to cold. [ABSTRACT FROM AUTHOR]

An integration between latent heat storage unit (LHSU) and an air cooler was studied to reduce the space cooling energy consumption in telecommunications base stations (TBSS). A mathematical model was developed to address the heat transfer processes within energy storage modules and air cooler. Furthermore, a solid works simulation was used to simulate the real system virtually. A simulated annealing algorithm (SA) was utilized to maximize annual energy savings ratio which was considered a performance criterion for the proposed system. The calculations included comparisons the relative errors of air and temperature difference between the optimized using simulated annealing algorithm and tested (virtual) results which were calculated for both operation modes energy charging and energy discharging. The obtained results illustrated a remarkable improvement both relative errors and annual energy savings ratio for the study case. [ABSTRACT FROM AUTHOR]

Due to effects of moisture transfer, the hygrothermal bridge could be developed at building corners, and increase the thermal conductivity of building materials. Three different types of roof-wall corners (ring beam, double beam column and shear wall structure) were studied. When considering moisture transfer, effects of different air states, structural types and wall materials on the thermal performance of the hygrothermal bridge were evaluated and heat losses of the structure were compared. Given the periodic boundary conditions, the dynamic thermal response of the hygrothermal bridge after moisture transfer was analysed. Among three types of corners, the increase of heat flow through the most detrimental point of the ring beam structure corner was the largest (34.7%) after considering moisture transfer. The heat flow loss rate of the shear wall structure was the lowest (15.2%). When clay brick was used at the corner rather than aerated concrete for walls, a lower proportion of latent heat flow and higher (8.6%) heat flow loss rate were shown after considering moisture effects. Furthermore, the dynamic thermal response was influenced by multi-dimensional and moisture effects. The time lag was reduced with increasing humidity, while the thermal bridge effects increased the deterioration of the time lag. [ABSTRACT FROM AUTHOR]

Renewable energy resources require energy storage techniques to curb problems with intermittency. One potential solution is the use of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. Despite the high energy storage density of PCMs, their thermal response rate is restricted by low thermal conductivity. The topic of heat transfer enhancement techniques for increasing thermal performance of LHTES systems has mainly focused on passive heat transfer enhancement techniques with less attention towards active methods. Active heat transfer enhancement techniques require external power supplied to the system. In this paper, recent advances in active heat transfer enhancement techniques within LHTES systems are reviewed, including mechanical aids, vibration, jet impingement, injection, and external fields. The pertinent findings related to the field are summarized in relation to the charging and discharging processes of PCMs. Suggestions for future research are proposed, and the importance of additional energy input for storage is discussed. [ABSTRACT FROM AUTHOR]

A new model for predicting the thermal performance of a thin layer of phase change material enclosed in a multilayer structure has been developed, verified, and validated. Numerical verification includes heat transfer and solar radiation processes, while only heat transfer was considered for experimental validation. The model considers thermo-optical properties of the PCM layer using a Moving Mushy Volume Approach. The basic assumption of the proposed approach is to divide the PCM domain into sub-volumes and determine their physical state separately, which allows varying the parameters in time. Each sublayer can be in a solid, liquid, or semi-transient state (mushy) where the level of latent heat and the solid–liquid ratio is determined by a dimensionless temperature-dependent melting function. Hence, it is appropriate for use in whole-building simulation programs, where it can be applied to more precise determination of heat transfer within a transparent PCM structure. [ABSTRACT FROM AUTHOR]