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Biochar-based composite phase change materials (PCMs) are gaining popularity in thermal energy storage (TES) applications. Organic PCMs derived from fatty acids are favored for their affordability and variable melting temperatures based on carbon chain length. Understanding the interaction between different carbon-length fatty acid PCMs and porous biochar is crucial for optimizing thermal performance. Thus, this study explored the interaction between PCMs of decanoic acid (DA) and octadecanoic acid (OA) with banana peel (BP) biochar. Experimental results showed that shorter carbon chain of DA enhanced thermal properties and surface compactness compared to OA. BP-DA had higher loading efficiency and PCMs ratio, resulting in superior thermal cycle endurance and latent heat ratio. The molecular dynamics suggest that longer carbon chains affect the mean square displacement (MSD) curves, reducing the self-diffusion coefficients of BP-DA. This is due to DA's high loading rate, which occupies more space within BP biochar structure, thus limiting its diffusion capacity. Enhanced hydrogen bonding constrained DA's thermal motion during phase transition, restricting atom mobility within BP. With temperature elevations, BP-DA exhibits lesser fractional free volume than BP-OA, due to lower molecular mass. This research highlights how carbon chain length influences composite PCMs performance, offering insights for efficient TES system design. [ABSTRACT FROM AUTHOR]

Phase Change Materials (PCMs) have got widespread attention in thermal energy storage (TES) applications as a result of their wide operational temperature range, high energy storage density, and prolonged life cycle at a reasonable cost. They offer a practical solution to mitigate the building energy consumption, addressing interior temperature fluctuations and enhancing demand-side management through the incorporation of renewable energy and off-peak power. This study focuses on evaluating the influence of PCMs on the performance of radiant heating and cooling systems. Based on conducting a comprehensive review, this study explores the current challenges associated with PCM utilization in these systems. The analysis discloses noteworthy discoveries and potential advantages, paving the way for further investigation and wider adoption of PCMs in the construction industry. Notably, the incorporation of a 10-mm PCM resulted in a 2.4% annual reduction in heating energy consumption in comparison with the existing structures. Furthermore, utilizing a 20–50-mm PCM could yield annual heating energy savings ranging from 7.3 to 15.3%. N-eicosane emerges as the most effective PCM for floor heating, achieving an optimal floor temperature and contributing to a substantial 43% reduction in heating energy consumption. Ultimately, radiant floor systems demonstrate the potential to reduce energy consumption by up to 8% and 4% in a comparison with commercial heating and cooling systems, respectively. [ABSTRACT FROM AUTHOR]

From the huge unexplored potential of non-paraffin organic compounds with exceptional thermal energy storage characteristics, this study identifies two novel eutectic PCM of margaric acid–behenic acid (MB) and palmitic acid–behenic acid (PB) with a melting temperature of 62.47 °C and 62.62 °C with high melting enthalpies of 170.66 J g-1 and 188.86 J g-1, respectively. To analyse the effects of nano-enhancement and with an objective of improved thermophysical characteristics, multi-walled carbon nanotubes were added over varying concentrations (0.5%, 1% and 1.5% of mass). Initial thermal conductivities of 0.134 W m-1 K-1 and 0.138 W m-1 K-1 were improved with the addition of nanoparticles to 0.312 W m-1 K-1 and 0.305 W m-1 K-1, reporting a 132.8% and 122.46% for MB and PB eutectic mixtures, respectively. Contrary to the usual trend, a highly significant and advantageous increment in melting enthalpy was also observed for both MB and PB eutectic mixtures by 21.9% and 15.8%, respectively. Further, the chemical stability, optical characteristics and thermal stability of the eutectic mixtures were analysed to ensure compatibility towards thermal energy storage applications. [ABSTRACT FROM AUTHOR]

A promising solution for challenges in thermal energy storage (TES) and its management is the use of phase change materials (PCMs). The ionic liquids (ILs) offer a unique properties that make them proper candidates for a number of energy related applications. The IL based PCMs are an important category of novel materials that significantly contribute to the efficient use and conservation of solar energy and wasted heat. This work presents a new family of ionic liquids (ILs) 2-hydroxyethylammonium, bis (2-hydroxyethyl) ammonium, and tris (2-hydroxyethyl) ammonium laurate as PCMs for the first time operating in the temperature range of 50–150 °C, and offer a safe and inexpensive capacity. The latent heat of fusion values were 147.13, 131.95 and 113.54 kJ·kg−1 for the [HEA]Lau, [DHEA]Lau and [THEA]Lau, respectively. Also, the thermal stability was obtained to be 99% for the [HEA]Lau. Finally, the thermal-to-electric energy conversion is performed using a homemade electronic data gathering and processing instrument with a PCMs (synthesized ILs) container cell and a commercial thermoelectric generator (TEG) device to record the real-time generated electric energy. The recorded output voltage (open circuit case) of TEG device versus time was measured that demonstrated that after turning off the thermal energy source, the proposed system provides the electric energy for a while (more than 2 h). [ABSTRACT FROM AUTHOR]

The appropriate storage, transportation, and utilization of wood-based fuels, including woodchips, pellets, and sawdust, in the energy production process, depends on their efficient drying. Traditional drying methods include limitations such as high thermal losses, inefficient heat transfer, and sustainability issues. These barriers, coupled with the high costs and complexities of maintaining the desired moisture content, underscore the need for innovative solutions. This study introduces a novel approach to wood fuel drying through the integration of phase-change materials (PCMs) with hybrid solar drying systems, aimed at enhancing thermal efficiency and sustainability. Employing coconut oil as the PCM, experiments were performed under a consistent artificial radiation of 755 W m−2. The hybrid system demonstrated the capability to retain approximately 200 watts of useful heat for three hours post-radiation, marking a significant improvement in heat storage. Our findings reveal peak thermal and exergy efficiencies of 30–35% and 13–14%, respectively. An economic and environmental analysis predicts a system lifespan of five years, with the cost of generating one kilogram of hot air at 0.0058 EUR and an annual CO2 emission of 64.09 kg. This research offers a cost-effective and environmentally friendly method for wood fuel drying, presenting a significant advancement for large-scale producers and setting a benchmark for further exploration of wood fuel drying technologies. [ABSTRACT FROM AUTHOR]

Temperature control system based on organic phase change materials (PCMs) has attracted tremendous attention in medical applications owing to the obvious advantages of large heat storage, accurate temperature controlling, ease of modification, etc. In order to fully utilize the advantages of organic PCMs for better application in biomedicine, it is often necessary to encapsulate PCMs to improve their shortcomings (such as instability in form, biosafety, biocompatibility, etc.). Encapsulation techniques of PCMs can achieve the leakage free to enhance the biocompatibility and form stability. In addition, in order to be suitable for different biomedical application scenarios, more functionality needs to be given to PCM microcapsule by using modification, chemical grafting, and polymerization methods. However, in the field of biomedicine, the current researches on the biocompatibility and functional design of organic PCMs in the encapsulation process are relatively fragmented. For the reason, this review systematically summarizes the encapsulation strategies of organic PCMs including core–shell encapsulation, physical adsorption, 3D structure, and covalent bonding. Moreover, the biocompatibility and functionalization design concepts of form-stable organic PCMs are discussed in detail for improving therapeutic effect. In addition, the applications in terms of medical field (e.g., medical textiles, drug delivery, cold chain transportation of pharmaceutical preparation, medical device) are thoroughly presented based on detailed investigations. This review will provide profound insights into the encapsulation and functionalization strategies of form-stable organic PCMs and their medical applications. [ABSTRACT FROM AUTHOR]

This paper proposes a new correlation to evaluate the heat transfer coefficient between a vertical wall containing a phase change material (PCM) and air in a square enclosure. This correlation was determined in order to simulate the transient process during PCM discharge and its effect on the heat transfer inside the cavity without using complex CFD models. A 2D CFD model based on the resolution of Navier–Stokes and energy equations inside the air and the PCM was previously validated. It was used to generate numerical data in order to build the proposed heat transfer correlation. The new correlation is Nu = 0.186 · Ra 0.28 θ 0.271 Ste 0.022 valid for: 10 5 ≤ Ra ≤ 4.310 7 , 0.05 ≤ θ ≤ 1 and 0.05 ≤ ste ≤ 0.6 . The accuracy of the proposed correlation versus the correlations established without phase change is analysed through a simplified model considering only the PCM layer and replacing the air cavity by a flux condition with an appropriate heat transfer coefficient. The relative error being lower than 1%, the new correlation shows a better agreement with the CFD results than existing correlations. [ABSTRACT FROM AUTHOR]

This paper aims to compare the performance and efficiency of fluid-driven (FD) and solid-state (SS) systems, which are used for solar heating using parabolic trough. Sodium nitrite (NaNO2) was considered as phase change material (PCM) and both storages had the same storage capacity. To evaluate system performance, constant heating of 1 kW was provided to both systems to replicate solar energy. The fluid-driven system showed maximum efficiency of around 47% as compared to 20% of solid-state system. Although the operating temperature of FD is higher than SS, as temperature increases flow rate of fluid also increases in FD which results in reducing the melting time of PCM. FD shows potential for providing better efficiency and can help utilize solar energy during evening/night when no sun is present. [ABSTRACT FROM AUTHOR]

In high-energy-demand regions, such as the Arctic, the building sector is focused on reducing the carbon footprint and mitigating environmental impact. To achieve this, phase change materials (PCMs) are being investigated for thermal energy storage due to their high latent heat of fusion. However, their limited applications arise from poor thermal conductivity. In addressing this issue, the research delves into the preparation and characterization of nano-PCMs. These materials, synthesized in a laboratory setting, exhibit enhanced thermal performance compared to pure PCMs, attributed to the incorporation of nanoparticles in the material composition. Therefore, in the study, three paraffins with different melting temperatures (10, 15 and 18 °C) are modified by incorporating titanium oxide at various concentrations (0.05, 0.1, 0.2 and 0.5 mass%). Thermal conductivity and latent heat capacity measurements were undertaken using a thermal conductivity measuring apparatus and differential scanning calorimetry, respectively. The aim was to evaluate the enhanced performance of the modified PCMs in comparison with pure PCMs and to assess their suitability for cold climate regions. Results showed that nanoparticle incorporation increased thermal conductivity by up to 37%, albeit with a slight reduction in latent heat capacity of up to 12%. Among the samples, RT18 exhibited the most significant improvement in thermal conductivity, while RT10 experienced a minor decrease in enthalpy values. Ultimately, RT10 was identified as the optimal PCM option for cold climates, as its phase change temperature range aligns with the outdoor temperatures in the Arctic. [ABSTRACT FROM AUTHOR]

The low thermal conductivity and liquid-phase leakage of phase change materials seriously hinder their large-scale applications. Porous materials have been identified as an effective way to address the leakage and provide a thermally conductive network. Therefore, we designed an expanded graphite-based multifunctional composite phase change thermal storage materials for personal thermal management and antimicrobial in medical protection. Expanded graphite (EG) was used as the matrix, silver nanowires (Ag NWs) as the functional enhancement materials, and n-octadecane (OD) as the thermal storage materials. OD and Ag NWs were adsorbed in the porous structure of EG by vacuum-assisted impregnation. Finally, EG/Ag NWs/OD were combined with non-woven fabrics (N) by one-step hot pressing method to obtain EG/Ag NWs/OD-N composite with excellent comprehensive performance. With the mass ratio of EG to Ag NWs of 13:7, EG/Ag NWs/OD-N exhibited a thermal conductivity of 2.0130 W m−1 K−1, which was improved by 1070.3% compared with pure OD. EG/Ag NWs/OD-N has a melting enthalpy of 137.85 J·g−1 and a crystallization enthalpy of 128.97 J·g−1. In addition, EG/Ag NWs/OD-N display great antibacterial properties, thermal cycling stability, shape stability, and cycling persistence and showed excellent temperature control in protective clothing applications, offering great potential for large-scale applications. [ABSTRACT FROM AUTHOR]

It is possible to store heat energy and extract it from materials in the form of internal energy changes such as sensible heat, latent heat, and thermo-chemistry, or in any combination of these three. In systems of insensible heat storage, energy is stored by raising the temperature of the medium to which it is being stored. During the process of heat absorption and release, this system makes use of the heat capacity of materials as well as variations in the temperature of those materials. The quantity of energy that is deposited within the system is dependent on the specific heat of the medium, as well as variations in temperature and the amount of medium that is used. The principle behind the operation of latent heat storage is that the storage medium absorbs or releases heat depending on whether or not it is undergoing a phase transition from solid to liquid, liquid to gas, or vice versa. Beeswax is a naturally occurring phase change material (PCM) that has its greatest phase transition enthalpy in the temperature range of 60–68 °C. It has the potential to be used in a wide number of applications that include the storage of thermal energy. Researchers are interested in the durability and temperature resistance of beeswax. This study aims to deliver a comprehensive review that provides a rundown of experimental, numerical, and experimental and numerical studies on beeswax and Nanoparticles-beeswax as PCM for thermal energy storage (TES). The review will also provide a summary of recent developments in research. This article also discusses a few other concerns pertaining to setting up, researching parameters, and discovering results. Studies on beeswax are presently being conducted, and based on the results of the most recent one, suggestions have been made for other research projects to be carried out. [ABSTRACT FROM AUTHOR]

Increasing frequency of extreme weather conditions due to global climate change is threatening citrus orchards. Young seedlings and some citrus varieties like lemons are especially susceptible to frost damage. Many orchards have installed expensive wind machines that use electricity to ward off cold air. When the temperature falls below −4 °C, even for several hours in a year, frost damage can kill citrus trees, thus causing serious economic loses. In this experimental study, we developed new phase change material (PCM) packages for passive solar protection of citrus trees from frost damage. Aqueous solutions of ethanol, ethylene glycol, and propylene glycol were evaluated as three PCMs due to their suitable chemical properties and abundance. Flexible packaging for the PCMs that can be easily applied to citrus trees were developed, and thermal protection performance of developed packages were tested on citrus seedlings. Supercooling of PCMs was seen as a problem during the tests, which was solved by adding a nucleating agent based on silver iodide developed in our laboratory. Results show that the ethanol containing PCM provided the longest thermal protection and succeeded in keeping seedling temperatures within the target interval for 10.5 h, while ethylene glycol and propylene glycol containing PCM packages provided 6.9 and 6.0 h of protection, respectively. [ABSTRACT FROM AUTHOR]

The use of latent heat energy storage can minimize the consumption of conventional fuels. The application of latent heat energy storage using phase-change materials (PCMs) can contribute to domestic energy demand without polluting the environment. This study is planned to provide more information to design latent heat energy storage systems for industrial and domestic applications. The study includes the comparison of the latent heat storage or melting of PCM in concentric and hairpin heat exchangers. The study also includes the effect of PCM type on the melting process. The numerical results obtained show an increase in heat transfer which is achieved by decreasing the diameter and increasing the length of the high-temperature fluid (HTF). The rate and the amount of energy stored are also found to be improved. The melting time is inversely proportional to thermal diffusivity. In this study, the thermal diffusivity is the highest for RT 50 (1.2 × 10–7 m2 s−1); hence, the melting time for RT 50 is the lowest (86 min for Stefan number 0.35). Also, the melting time is directly proportional to viscosity. For RT 35, the viscosity is the highest (0.023 kg m−1. sec), and the rate of melting is the lowest (146 min for Stefan number 0.35). The evaluated energy storage capacity of hairpin and concentric heat exchangers is 455 and 140 W, respectively. Hence, the storage capacity is 3.25 times higher for the hairpin heat exchanger compared to the concentric heat exchanger. On the other hand, phase-change materials with a sizeable latent heat value can store more energy but the rate of energy stored depends on the temperature difference between high-temperature fluid and the initial temperature of phase-change materials. Therefore, an effective energy storage system can be proposed through numerical analysis. [ABSTRACT FROM AUTHOR]

Thermal energy storage systems (TESS) have emerged as significant global concerns in the design and optimization of devices and processes aimed at maximizing energy utilization, minimizing energy loss, and reducing dependence on fossil fuel energy for both environmental and economic reasons. Phase change materials (PCMs) are widely recognized as promising candidates due to their high latent heat storage (LHS) capacity. This review thoroughly evaluates the computational fluid dynamics (CFD) studies conducted in various sections, encompassing materials, modeling, simulation, as well as the results, advantages, and disadvantages of these works. The study is organized into three distinct sections. The first section discusses the applications of PCMs in various areas, including lithium-ion batteries, solar applications, building applications, electronics, and heating and cooling systems. The second section provides a comprehensive summary of cylindrical, rectangular, spherical, arbitrary shapes, and packed-bed geometries employed in TESS. The third section investigates the different types of materials used as PCMs. Based on the findings of this study, it can be concluded that industrial applications of hybrid nanocomposites incorporating PCMs in different geometries pose challenges, particularly in three-dimensional (3D) settings, where instability becomes a significant concern. Hence, further research and investigation are necessary to address these challenges adequately. In conclusion, this study serves as a reference review for future research endeavors in the field of simulating various PCMs in different geometries and applications. It provides valuable insights into the current state of knowledge, highlights potential areas for improvement, and offers guidance for advancing simulation techniques related to PCMs. [ABSTRACT FROM AUTHOR]

Novel core-shell nanostructures containing renewable capric acid (CA) core (as a high potential phase change material) and TiO2 (as a highly stable shell) were synthesized using a solgel method for thermal energy storage. Remarkably, CA, a fatty acid available in some vegetable oils, is a renewable phase change material with no undesired environmental impacts. A central composite design of response surface methodology was implemented to determine the effect of the mass ratio of CA/TNBT and the pH value on the encapsulation ratio. As the quadratic mathematical model was used to optimize the process parameters, the maximum encapsulation ratio of 56.67% was achieved, where the CA/TNBT mass ratio was 8.10, and the pH value was 2.65. The measured thermal properties indicated that NEPCMs melt at 31.1 °C with a latent heat of 88.8 J g−1 and solidify at 28.9 °C with a latent heat of 84.23 J g−1. The chemical structure and crystalline phase were measured using Fourier transformation infrared spectroscope and X-ray diffractometer. The thermal stability of the NEPCMs was analyzed by a thermogravimetric analyzer. According to the morphological images, the nanocapsules showed almost spherical shapes with an average size of 100–500 nm. The thermal cycling tests show the high thermal reliability of NEPCMs after the 50th melting/solidifying cycle. The results indicated that the prepared NEPCMs have good thermal stability and reliability for thermal energy storage; hence, they can be applied in building energy conservation and air-conditioning systems. [ABSTRACT FROM AUTHOR]

In this study, cetyl alcohol (CA) (CH3(CH2)15OH), which is a fatty alcohol, was microencapsulated by the coacervation method with the titanium-n-butoxide (TNBO). Firstly, at the beginning of the experimental process by thermal and structural analyses, the CA was determined as having a phase change material (PCM) property, then it was microencapsulated with TNBO. In the second step of the study, barite, boron nitride, marble powder, and fly ash were separately added to prepare a series of microencapsulated with TNBO. Lastly, structural and thermal properties of both microencapsulated PCM and composite supported microencapsulated PCMs (CSM-PCMs) have been analyzed by FTIR, DSC, TGA, and SEM devices. Surprisingly, the SEM image of CA turned from torn fiber structure into a particulate structure in the form of groundnut in the SEM images of the microencapsulated CA-Ti taken at different magnifications. After the thermal cycling test, the same analyses have been made before and after thermal cycling to compare the structural and thermal properties. It has been investigated whether to use as insulation material. It is concluded that the most suitable samples, compared with structural and thermal properties, are barite (B) and boron nitride (BN) with microencapsulated samples. The obtained results are shown that CATi-B and CATi-BN are CSM-PCMs and could be suggested in terms of thermal energy storage in buildings as promising PCMs. [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]

Herein, free cooling an application of thermal energy storage is investigated through theoretical observations of air being cooled after passing over encapsulated phase change material (PCM). The impact of encapsulation geometry changes from circular to; rectangular, square, and elliptical shapes is studied for the PCM solidification and melting cycles. The study is performed for sp24, sp26, and sp29 PCM types with and without the inclusion of CuO and Al2O3 nanoparticles (NPs). A transient mathematical model for heat transfer behavior of airflow over the encapsulation is constructed and solved using Ansys 20.2 software. It is found that the rectangular-shaped PCM encapsulation with CuO nano-enhanced PCM has the shortest complete melting (~ 1–2 h) and complete solidification times (~ 3–9.3 h). Nanoparticle enhancement improves the rate of melting by a maximum of 11.56% with Al2O3 NPs and by 6.12% with CuO NPs at an inlet airflow temperature of 313 K. A maximum outlet air-temperature drop of ~ 3.1 K occurs in the cylindrical geometry with CuO nano-enhancement and the highest Nusselt number is obtained at similar conditions. From this study it is recommended to use either sp24 or sp26 PCMs mixed with nano-alumina and encapsulated within rectangular containers for free cooling applications. [ABSTRACT FROM AUTHOR]

A series of form-stable polyethylene glycol/activated carbon (AC) composites were prepared via a vacuum-assisted infiltration method, where polyethylene glycol (PEG) was used as an organic phase change material (PCM) and AC was used as an inorganic supporting matrix to prevent the leakage of the PCM during phase change period. The chemical structural, thermal properties, thermal stability, and reliability of PEG/AC composite PCMs (CPCMs) with various mass loadings of PEG2000 was investigated by N2 adsorption analyzer, Fourier transformation infrared (FT–IR) spectrometer, differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA), respectively. The form stability and thermal energy storage and release properties of PEG/AC CPCMs were also experimentally studied. The results showed that PEG/AC CPCM with 80 mass% PEG2000 loading displayed reasonable latent heat, suitable phase transition temperature, good thermal reliability, enhanced thermal conductivity, and thermal energy storage and release performances, as well as excellent form stability, which are suitable for the practical applications of PCMs for thermal energy storage. [ABSTRACT FROM AUTHOR]

The use of phase change materials (PCMs) for thermal storage, thermal management, and thermal insulation has been widespread for many years. Thermal storage systems (TES) based on PCMs can be improved and optimized by adding nanoparticles (NPs) to them. Throughout this study, PCM nanocomposites (NCs) based on paraffin wax (PW) loaded by anatase titania (TiO2) NPs were fabricated and characterized to examine their thermal performance as phase change materials. The as-synthesized TiO2 NPs were obtained by hydrolysis technique and showed a well-defined spherical shape with a diameter in the nanoscale range and a crystallite size ~ 22.75 nm. Throughout the used concentrations of TiO2 NPs, 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.5%, the morphological feature for the PW/TiO2 NCs revealed a good dispersion of NPs in PW. The non-isothermal differential scanning calorimetry (DSC) measurements at a constant heating rate of 10 °C min−1 were used in order to get the melting point (Tm), latent heat of fusion (LH), and latent heat rate (LHR) as a function of TiO2 NP concentrations for the investigated PW/TiO2 NCs. Both LH and LHR values for PW/TiO2 NCs are higher than those obtained for a pure PW sample. The significant enhancement in LH and LHR values for PW/TiO2 NCs was found to be 21.2% and 134.3% in comparison with the pure PW sample, respectively. The thermal stability of the investigated PW/TiO2 NCs was examined using thermal gravimetric (TG) scans. It is found that the thermal stability varies with TiO2 NP concentrations with a non-monotonic trend. At concentrations up to 0.25 mass%, the thermal stability improved. For concentrations over 0.25 mass%, the degradation process became rapid. [ABSTRACT FROM AUTHOR]

In this research, the effects of activated carbon from corncob (ACC) biomass as the supporting material were investigated on leakage problem and thermal properties of palmitic acid (PA) as a phase change material (PCM) for thermal energy storage, using the impregnation method. The leakage test demonstrated that the addition of ACC significantly reduced the leakage of PA. Furthermore, it was evident from ATR-FTIR spectra and XRD results that PA and ACC did not undergo any chemical reactions, and the crystal structure of PA was not changed, while the ACC was amorphous. According to the SEM result, ACC had a porous structure, and its increase in PA caused a larger pore volume and a higher specific surface area, which could prevent the leakage of PA. The thermal stability of the composites was measured by TGA. The results revealed that the addition of ACC slightly accelerated the pyrolysis of PA, improved the thermal conductivity of PA, and had enough thermal stability below 150 °C to be suitable for building and solar thermal energy storage applications. DSC analysis of the form-stable PCM showed a melting temperature of 61.25 °C and a melting latent heat of 81.57 J g−1, and demonstrated high thermal reliability after 10 cycles, indicating excellent energy storage capacity. The BET test revealed that the ACC with 1364.70 m2 g−1 have a great potential to use for supporting material, and the composites were mesoporous, which prevented the leakage of PA. [ABSTRACT FROM AUTHOR]

In the present numerical analysis, the influences of incorporating a central plate into the enclosure of a phase change material (PCM) on the solidification enhancement of a latent heat energy storage system are explored numerically. This study focuses mainly on determining the role of the central plate in enhancing the PCM discharging process. To evaluate the capability of the central plate in enhancing the PCM phase change process, various scenarios are considered in the present study. Firstly, the solidification performances of the states with no fin as well as uniform fins without the inserted central plate are compared with the discharging capability of the case equipped with the central plate. The liquid fraction as well as the PCM temperature contours are compared to assess the effectiveness of the central plate location on the PCM discharging mode, secondly. After the case with the best thermal performance is determined, the influences of adding the uniform fins and central plate into the PCM enclosure are investigated simultaneously. Then, the impacts of various configurations, namely the inline and staggered scenarios, on the PCM discharging phenomenon are analyzed in the central plate presence. As the last step, the effects of various PCMs on discharging mode of the thermal unit are studied to evaluate the PCM role in enhancing the discharging process. The numerical results reveal that the influences of the central plate incorporation on improving the solidification performance are greater than that of the melting case in the absence of the uniform fins. Time saving percentages of case VII (case with the central plate and uniform fins) compared to the no-fin case are 68.91, 71.02, and 74.84% for RT-35, RT-35HC, and n-eicosane, respectively. Furthermore, the case with RT-35HC as the PCM experienced the highest discharging rate compared to other cases. [ABSTRACT FROM AUTHOR]

Solar energy is the most plentiful renewable energy source that has the capability to keep up with the growing demand. When the sun's energy is not available, thermal energy storage (TES) using phase change material (PCM) is a promising technique for storage and utilization. However, PCM's low thermal conductivity may limit its use. The use of nanomaterials to enhance the thermal conductivity is one of the prominent solutions to overcome this issue. This research work reports that graphene nanoparticles (0.1%, 0.3%, 0.5%, 0.7% and 1% mass) enhanced paraffin wax (PW) to improve the thermophysical properties and transmittance capability. Thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR) and ultra-violet visible spectroscope (UV–VIS) were used for the characterization of the base PCM and nano-enhanced phase change materials (NePCM) composites. A significant improvement of 110% in thermal conductivity was obtained at 0.7% mass ratio compared to base PW without compromising the prepared composites' latent heat storage (LHS) capacity. TGA and FTIR outcomes demonstrated excellent thermal and chemical stability, respectively. To check the thermal reliability of composite, the PW and nanocomposite were subjected to repeated thermal cycling. The outcome evidence that the NePCM composite had consistent thermal energy storage properties even after repeated thermal cycles. The composite's light transmission was drastically lowered by 56.34% (PW/Gr-0.5) compared to base PW, resulting in PW/Gr composite has better thermal reliability in relation to thermal conductivity and LHS than base PCM, which can be used specifically in photovoltaic thermal systems and TES. [ABSTRACT FROM AUTHOR]

Leakage, low thermal conductivity and flammability are the crucial factors that severely restrain the applications of the organic phase change material (PCM). A series of nanocomposite phase change material (HNTs-PCM) was prepared by dispersing halloysite nanotubes (HNTs) in capric acid (CA) with various mass fraction loadings (0.5%, 0.75%, 1% and 2%) through a blending method. The FTIR indicated that HNTs-PCM are only physically combined by HNTs and capric acid. The leakproof test showed that HNTs can inhibit the leakage of PCM. And the diameters of PCM with 0.75% HNTs are 4.3 cm and 3.2 cm at 35 °C and 45 °C. Among all samples, PCM with 0.75% HNTs possessed the best dispersivity. Hot-wire technique and infrared thermal imager proved that the addition of HNTs improves the thermal energy storage efficiency of PCM. The melting time and setting time were decreased by 46.67% and 43.65%. The DSC suggested that the melting peak temperatures and latent heat of HNTs-PCM reduced from 32.85 to 32.40 °C and 147.65 J g−1 to 137.65 J g−1 when the mass fraction of HNTs increased from 0 to 2%. The cone calorimeter test indicated that the HNTs restrain the heat and smoke release of rigid polyurethane foam composite containing HNTs-PCM during the combustion process. The peak of heat release rate and total heat release were decreased to 295.82 kW m−2 and 157.50 MJ m−2 after adding HNTs. Besides, the total smoke production decreased to 23.49 m2. These tests revealed that the HNTs have the potential to enhance the thermal storage capacity, leakage resistance and flame-retardant properties of PCM. [ABSTRACT FROM AUTHOR]

Over the years, incredible evolution has been framed in developing particle-induced discrete simulation techniques over conventional continuum approaches. In particular, the lattice Boltzmann method (LBM) originated from a flexible and robust computational tool for scientific research and various practical applications. LBM is based on a mesoscopic approach that acts as a bridge between the microscale and macroscale, offering distinct features in the accuracy of simulations and numerical efficiency. LBM has been successfully employed over a broad aspect of disciplines, encompassing biomedicine, geothermal energy, flow physics, materials, chemistry, medical treatment, storage of energy, and several engineering disciplines. Meanwhile, phase change materials (PCMs) are extensively utilized in thermal energy storage (TES) systems as they can absorb and release heat throughout the phase change process. Moreover, phase change heat transfer (HT) has a substantial occurrence in industrial and domestic activities. It is expected to enhance the thermal transport rate between HT fluid and PCMs for the confinement of a larger amount of heat. This current work aims to provide a comprehensive review of LBM for thermo-fluids concentrating on thermal flows and PCM. It also enlightens a brief insight into the LBM formulation of heat transfer for PCMs under various external force conditions and the implementation of boundary conditions for PCMs. In addition, it also introduces the study and examination of the existing TES systems comprising PCMs for various applications. [ABSTRACT FROM AUTHOR]

In the present study, various phase change materials (PCMs) in combination with thermoelectric device were evaluated to storage solar energy and generate electricity. The PCMs were Rubitherm 35HC and Rubitherm 42, as industrial PCMs, along with margarine, sheep fat oil, and coconut oil, as edible PCMs. The main aim was to improve energy storage and cost-effective continuity of electricity generation in the absence of radiation by PCM with a longer shelf life. The results showed that energy storage materials can significantly impact electricity generation, particularly in the absence of radiation. Also, the storage efficiencies of different PCMs varied significantly when honeycomb fins were used. As a result, Rubitherm 35HC achieved the best performance with a storage efficiency of 71%, while sheep fat oil had the worst performance with a storage efficiency of 27%. Also, Coconut oil, margarine, and Rubitherm 42 recorded the storage efficiencies of 36%, 29%, and 47%, respectively. Rubitherm 35 not only significantly enhanced the energy storage efficiency but also resulted in a notable augmentation of voltage production by over 200%, compared to the circumstance when no PCM is used. Furthermore, the incorporation of honeycomb fins further amplifies this percentage to 222%. [ABSTRACT FROM AUTHOR]

Common phase change materials (PCMs) have serious shortages, and the most important one is the low thermal conductivity. This issue makes the phase change process a time-consuming period that decreases the performance of thermal storage units. This paper concentrated on improving energy and exergy performance with the aid of an air–PCM heat exchanger, which could be employed for free cooling of buildings. For the heat exchanger, the PCM of Rubitherm 22 °C high capacity (RT22HC) and the nanoparticles of multi-wall carbon nanotube were employed. The initial charging and discharging experiments showed that due to thermal conductivity enhancement, melting and solidification periods decreased using nano-PCM with three concentrations of 0.1, 0.2, and 0.5 mass% compared to the PCM without nanoparticles. Moreover, the highest exergy and energy efficiencies were obtained for the case of nano-PCM 0.5 mass% during the charging process and the values were 11.03 and 21.33%, respectively. Experiments with nano-PCM 0.5 mass% were accomplished during three continuous days. The results demonstrated that the heat obtained from nano-PCM 0.5 mass% encapsulations varied with weather conditions. In addition, the output energy and exergy rose with sunrise and fell with sunset. Finally, an economic analysis was carried out for cold climate conditions. The results indicated that the whole invested capital expenditures will return in the ninth year of exploitation. [ABSTRACT FROM AUTHOR]

The development of a new composite phase change material (PCM) was accomplished by using n-eicosane, which was belonging to the paraffins. For this goal, hexagonal boron nitride (h-BN)-loaded macroporous foams were synthesized by emulsion-templating method. The resulting foams were used as supporting materials in the preparation of n-eicosane-based composite PCMs that have improved thermal conduction property. The h-BN was synthesized as additive with the aim of thermal conductivity enhancement, and the porous supporting materials were obtained by polymerization of high internal phase emulsions (HIPEs) at various loadings of h-BN nano-fillers (0, 1, 5 and 9 mass/%). The h-BN, h-BN-loaded macroporous polyHIPE foams (MPFs) and composite PCMs were fully characterized by SEM, BET, FT-IR, TG and DSC analysis techniques. Furthermore, leak-proof and phase-change properties of composite PCMs were tested in addition to investigation of thermal behavior with a thermal performance test. The highest thermal energy storage (TES) capacity among the produced n-eicosane-based h-BN-loaded MPFs was belonging to 1 mass/% h-BN-loaded composite PCM having 79 J g−1 latent heat of melting and 38.79 °C melting temperature; the composite was also comprised of the supporting matrix with highest specific surface area. Based on the results, thermally conduction enhanced n-eicosane-based composite PCMs are promising materials for thermal management applications, such as electronic package and electronics cooling, with thanks to high latent heats (range between 72.2 and 79 J g−1) and convenient phase transition temperature as well as anti-leakage property. [ABSTRACT FROM AUTHOR]

The technical importance of paraffins as phase change materials (PCM) in heat storage systems increases. Knowledge on the thermal conductivity of paraffins is necessary for the design and optimization of heat storage systems. However, for most paraffins solely the thermal conductivity of the liquid state has been sufficiently investigated. For the solid state, precise thermal conductivity data are only known for a few paraffins, while only generalized values are available for the remainder, some of which contradict each other. In this study, a measurement setup based on the modified guarded hot plate method is developed. It is used to investigate the thermal conductivity of several paraffines in the solid state, including pure n-docosane and its compounds with different types and concentrations of graphite. For n-docosane in the solid state, the thermal conductivity is determined to be 0.49 W m−1 K−1. A particle size of 200 μm with a spherical shape turns out to be optimal to increase the thermal conductivity. This allows the thermal conductivity of a compound with 10% graphite to increase by a factor of three compared to the pure paraffin. Furthermore, significant differences to thermal conductivity data from the literature are found. [ABSTRACT FROM AUTHOR]

The most common type of thermal energy storage material is phase change material (PCM). Because of their low thermal conductivity values and the liquid leaks caused by the transition phase from the solid to the liquid state, these materials have limited applications. To make these materials applicable in a variety of applications, their stabilization within a composite material must be improved. Lauric acid is a saturated fatty acid organic PCM with high latent heat, good chemical and thermal stability, and little supercooling and pollution. To address the leakage issue, expanded organophilic clay treated with cationic surfactant (CTAB) and lauric acid graft-modified cellulose nanofibers were added. In order to increase thermal insulation and lower energy consumption, composite materials based on cement, organophilic clay, and modified cellulose nanofibers were created in this study. These materials are used as shape-stable materials in the building industry. The thermal conductivity of the PCM composite samples increases in direct proportion to the percentages of organophilic clay added, according to research on the thermal behavior of the materials created. The findings indicate that the S5 sample has a thermal conductivity of the order of 0.115 (W m−1 K−1) and that the reduction in thermal conductivity reached 60%. This allows for the best thermal insulation performance due to the prepared material's stability heat, making the material promising for thermal energy storage. The results of the (DSC) thermal properties revealed that the fusion temperature and latent heat of the composite materials were 21.56 °C and 88.5 J g−1, respectively, and supercooling degrees for the nanofiber cellulose–lauric acid composite decreased to 13.99 °C compared to 20.28 °C for pure lauric acid. The FTIR and XRD techniques confirmed the production of the organophilic clay. The addition of clay to the nanofiber cellulose–lauric acid composite material solves the leakage impacts with the phase change material. [ABSTRACT FROM AUTHOR]

Devices of solar water desalination confront many problems including the low thermal properties of phase change materials (PCMs) such as heat transfer, storage of heat capacity, charging and discharging capability. Thus, these properties need to be improved by using a simple and novel procedure. So, incorporation and dispersion of hybrid nano-powders inside PCMs is considered a simple and novel procedure to improve the thermal properties of solar water desalination devices. The present article is focused on incorporating different nano-powders of MWCNTs and Al2O3 inside PCMs to improve the thermal characteristics of solar water desalination applications. Different nano-powders of MWCNTs and Al2O3 have been incorporated as: (i) 1.0 mass% Al2O3, (ii) 1.0 mass% MWCNTs, and (iii) hybrid 1.0 mass% of Al2O3 + 1.0 mass% MWCNTs, inside a constant amount of 250 gm RT-65HC paraffin wax. An innovative prototype was designed and produced to measure the thermal characteristics of solar water desalination devices. Various analyses have been carried out to study the influence of nano-powders scattering on the morphological, microstructural observations, chemical and thermal characteristics, including SEM, XRD, FT-IR, TGA, DSC, thermal conductivity, and infrared thermography. Microstructural observations showed that the excellent dispersion of nano-powders was at hybrid nano-additives of 1.0 mass% MWCNTs + 1.0 mass% Al2O3 inside PCMs. The uniform scattering of hybrid 1.0 mass% MWCNTs + 1.0 mass% Al2O3 inside PCMs assists to eliminate any defects. Finally, thermal characteristics of hybrid nano-additives phase change materials (NAPCMs) were improved specially in thermal stability, latent heat temperature, and thermal conductivity at 89%, 80%, and 32.8%, respectively. [ABSTRACT FROM AUTHOR]

In this study, microcapsules based on Cu2O containing different phase change materials (PCM) were prepared and characterized. The elemental, structural and electronic properties of the Cu2O-based microcapsules were characterized using several techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and Fourier-transform infrared spectroscopy. In addition, the thermal properties of the microcapsules prepared were characterized in order to analyse their possible application as a thermal energy storage medium. Heating/cooling cycles using a differential scanning calorimetry technique were performed, and the phase change temperature and enthalpy were estimated. We observed good stability after the cycles. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 14.8% for the paraffin wax-based microcapsules. Finally, isobaric specific heat was measured to evaluate the storage capability of the encapsulated PCMs with regard to pure Cu2O to evaluate their possible application as a thermal storage system. An increase of around 140% was found in the isobaric specific heat for the microcapsules based on paraffin wax with regard to pure Cu2O. [ABSTRACT FROM AUTHOR]

Nano-sized high conductive particles are extensively used in many engineering applications to achieve enhanced thermal performance. Paraffin wax is regarded as the most promising phase change material (PCM) for energy storage applications. However, the low thermal conductivity of paraffin poses a challenge which decreases the performance of storage system. In this work, composite PCMs consisting of paraffin and copper (Cu) nanoparticles were synthesized at different mass percentages (0%, 0.5%, 1%, 2% and 3%) and the thermo-physical properties were examined experimentally. The field emission scanning electron microscope (FESEM) results showed that the dispersion of nanoparticles in the PCM is homogeneous. The differential scanning calorimeter reports revealed that the effect of nanoparticle addition on phase change temperature is insignificant. On the other hand, reduction in latent heat is observed. The addition of nanoparticles is found to be critical in prolonging the thermal degradation of the storage medium which ensures the thermal and chemical stability of nano-Cu–paraffin composites. Moreover, the thermal conductivity of solid PCM is enhanced by 7%, 14%, 24% and 30.5% with the nanoparticle loading of 0.5%, 1%, 2% and 3%, respectively. In case of liquid PCM, the enhancement is found to be 8%, 15%, 28% and 31.5% with mass fraction of 0.5%, 1%, 2% and 3%, respectively. Altogether, the obtained results have revealed that the enhanced properties make nano-Cu–paraffin composite PCM as right candidate for solar thermal energy storage. [ABSTRACT FROM AUTHOR]

The research article addresses the effect of multi-wall carbon nanotube (MWCNT) and nano-boron nitride (NBN) hybrid composite powders on thermal properties of the paraffin wax for thermal storage applications. Five different phase change material (PCM) samples were prepared with 100 paraffin wax, 99.5 paraffin wax + 0.5 MWCNT, 99.5 paraffin wax + 0.5 BN, 99 paraffin wax + 0.5 MWCT + 0.5 BN and 98 paraffin wax + 1 MWCNT + 1 BN mass percentage compositions. The size of the secondary particles MWCNT and NBN was assessed using transmission electron microscope (TEM). After PCM preparation, the morphology and distribution of the secondary particles were evaluated using field emission scanning electron microscope (FE-SEM). The phase change of MWCNT and NBN was evaluated using X-ray diffraction (XRD) technique. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermal conductivity tests were carried out on the PCMs to assess physical and thermal properties. The results revealed that hybrid nano-composite powders with paraffin wax provide better thermal conductivity of paraffin wax which increased from 0.18 to 0.31 W m−1 K−1. However, the distribution of MWCNT and NBN extended the thermal degradation of paraffin wax and solidification temperature. Increasing the mass % of MWCNT and NBN reduced the melting point of paraffin wax from 64.70 to 62.52 °C. Further, the solidification temperature of paraffin wax increased while increasing the mass % of MWCNT and NBN from 56.01 to 60.13 °C. This research revealed that thermal properties of paraffin wax were significantly increased with the increment of mass % of composite powders (MWCNT and NBN) addition. [ABSTRACT FROM AUTHOR]

In this work, a novel type of stearic acid-modified exfoliated graphite (SEG) with strong lipophilicity, rich pores and good economic efficiency is synthesized in order to improve the decline of heat storage capacity, poor dispersion stability and thermal cycle stability of paraffin (PA)-based composite phase change materials (PCMs) after multiple cycles. With a small amount (≤ 4 mass%) of SEG as a thermal performance enhancement additive, PA/SEG composite PCMs with comprehensive thermal performance is prepared. DSC, TG and other experimental analysis methods are used to evaluate the thermal performance of composite PCMs before and after multiple cycles (up to 500 cycles). It is found that the thermal conductivity of composite PCMs is more than 2 times higher than that of pure PA. Most importantly, after 500 heat storage and release cycles, the heat storage capacity of composite PCMs would hardly decrease, where the melting and cooling enthalpy of PA/SEG4 is up to 188.3 J g − 1 and 186.6 J g − 1, respectively, which are 5.5% and 4.4% higher than that of 0 cycle, and it still has outstanding dispersion stability and excellent thermal cycle stability. These results may provide a feasible strategy of successfully synthesizing novel high-performance composite PCMs and further enhancing energy storage efficiency. [ABSTRACT FROM AUTHOR]

A thermal energy storage system combined with renewable energy sources or waste heat recovery will increase the dispatchability of the energy system. It also helps to reduce the gap between supply and demand. Among available techniques, latent heat thermal energy storage systems have been an attractive area of research. Selecting a phase change and construction material is vital in designing any storage system. In the present study, corrosion characterization was performed for erythritol used in the experimental prototype. The use of erythritol to develop a storage system requires understanding its corrosion behavior with storage container material and piping system to ensure the safety of construction and enhance the system's life. Corrosion rates were determined in stainless steel and mild steel sample by gravimetric tests, measuring the mass loss after 2000 h of immersion at 140 °C in two different test conditions. Simultaneously, surface morphology and corrosion products were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray scanning (EDX). The experimental result confirms that stainless steel shows better corrosion resistance than mild steel for selected phase change material. SEM and EDX analysis shows no significant changes in the structure after 2000 h of immersion. Corrosion rates for open and closed crucible stainless steel sample have been observed at 0.003 mm y−1 and 0.004 mm y−1, respectively, whereas mild steel sample was more affected by PCM in both the open and closed crucible tests, giving 0.0221 mm y−1 and 0.0392 mm y−1. The study shows that further research is required in different operating conditions. [ABSTRACT FROM AUTHOR]

Cold thermal energy storage (CTES) is paramount for energy management in large building air-conditioning systems using phase change materials. In this study, the thermal transport performance of DI water is enhanced with a natural gum as a nucleating agent (gum acacia (GA)) and a high conductive nanomaterial (graphene nanoplatelets (GnPs)). The nanofluid phase change materials (NFPCMs) are prepared with different mass concentrations viz. 0.25%, 0.50%, 0.75%, and 1.00% of GnPs by a two-step synthesis method. The zeta potential, UV–visible spectrophotometry, and visual inspection methods are used to analyze the stability of NFPCM over time. The phase change enthalpy is lowered by 7.72% and 15.26% for 1.00% GnPs seeding into DI water at a heating rate of 5 Kmin−1 during heating and cooling, respectively. Thermal conductivity of NFPCM shows maximum augmentation of 10.8% (25 °C) and 54.4% (− 5 °C) owing to its highly conductive specific surface area of stable GnPs. The temperature–time history of NFPCMs is investigated during freezing experimentation in a spherical encapsulation at a surrounding bath temperature of − 7 °C. GA has a major influence on the degree of supercooling, as it causes a 47.6% drop in DI water and eliminates it at a higher mass concentration (1.00%) of GnP-NFPCM. The maximum freezing rate is reduced by 27.1% with a higher mass concentration of NFPCM compared to pure PCM. Furthermore, a significant energy-saving potential of 4 to 6% is revealed for GA-NFPCM, which shows tremendous promise for developing energy-effective thermal management with an accelerated mode of charging. [ABSTRACT FROM AUTHOR]

In order to explore the utility of barium hydroxide octahydrate (BHO) in heat storage systems, high-performance composite phase change materials (CPCMs) were prepared by mixing additives. CaCO3, MgCl2·6H2O, and MgSO4 were firstly selected as nucleating agents to reduce the supercooling degree of BHO. The enhancement of thermal conductivity by nucleating agent CaF2 was quantified. Gelatin, sodium carboxymethyl cellulose, and xanthan gum (XG) were added to inhibit phase separation. It was found that 3 mass% CaF2 reduced the supercooling degree of BHO to 0.4 °C and also made the phase change platform of solidification (PCPs) temperature most stable. It was also found that 4 mass% MgCl2·6H2O prolonged PCPs by 50.2%. The CPCM with 3 mass% XG still showed supereminent suspension stability after cycling, which hindered the phase separation. Expanded graphite (EG) was used to intensify the thermal conductivity of CPCM. After the investigation of thermal properties and microstructure, it was concluded that 4 mass% EG could increase the thermal conductivity by 3.37 times. [ABSTRACT FROM AUTHOR]

In this work to increase the thermal capacity and performance of pristine paraffin wax (phase change material), it is mixed with COOH group functionalized graphene. The various concentrations of graphene mixed with paraffin wax are 0.25 volume percent to 1 volume percent at an increment of 0.25 volume% at three different volumetric flow rates of 6.25 mL s−1, 12.5 mL s−1, and 25 mL s−1. The charging performance is analyzed, and Fourier transform infrared spectroscopy (FTIR), X ray diffraction (XRD), differential scanning calorimetric (DSC) analysis, Thermo gravimetric analysis (TGA), field effective scanning electron microscopy, with energy dispersive spectroscopy are done for characterizing chemical structure, crystal structure, enthalpy, thermal stability, and microstructure, along with elemental composition, respectively. The results indicated that with increasing percentages of COOH group functionalized graphene the charging time decreases by 6.25–25% for the HTF flow rate 6.25 mL s−1, 6.67–26.67% for HTF flow rate 12.5 mL s−1, and 15.38–38% for HTF flow rate 25 mL s−1 over pure paraffin wax owing to increasing percentage and thermal conductivity of COOH group functionalized graphene in paraffin wax. This advanced material with the help of XRD and FTIR also showed that the functionalized COOH graphene was chemically inert and did not lead to any new product being formed. Through TGA the advanced functional materials manifested that they were thermally very stable and by DSC it showed that it was having very high enthalpy of melting. [ABSTRACT FROM AUTHOR]

Desalination has emerged as a vital solution to tackle global water scarcity, and among various desalination methods, the humidification–dehumidification cycle has garnered significant attention. This study provides a detailed review of performance enhancement techniques utilized in the humidification–dehumidification desalination systems. The review highlights previous studies conducted in this area. The humidification–dehumidification cycle, its working principles, and its advantages and drawbacks are then thoroughly discussed, establishing the groundwork for comprehending the significance of performance improvement strategies. The investigated techniques for multiple facets of the humidification–dehumidification cycle are multistage humidification–dehumidification, bubble columns, phase change materials, nanofluid application, variable pressure humidification–dehumidification, ultrasonic, and other techniques such as thermoelectric application, rotating belt, multiple insert, air saturator, fogging, and desiccant wheel. Through an extensive analysis of existing studies, the review summarizes the key findings of each technique, including improvements in system efficiency, freshwater production rates, heat and mass transfer rates, thermal energy storage, and reduced fouling. The findings provide valuable insights for researchers and practitioners, facilitating the selection and implementation of the most suitable techniques to achieve sustainable and efficient water desalination. [ABSTRACT FROM AUTHOR]

Thermoregulating composites were produced by using a thermoregulating slurry (NPCS) containing nanoencapsulated phase change material (NPCM) from poly(styrene-co-divinylbenzene) as shell and the commercial paraffin Rubitherm®RT27 as core material. These composites were synthesized by using the constitutive water of the slurry as setting water and changing the NPCM/Hemihydrate (NPCM/Hem) mass ratio within 0.0–0.41. It was found that nanoparticles were uniformly dispersed into the gypsum, and the gypsum crystal morphology was tuned by the addition of the slurry. Attending to the thermal properties, these materials can work either as insulating or thermal energy storage materials, decreasing the thermal conductivity up to ~ 50%, whereas the thermal energy storage (TES) capacity is enlarged in a ~ 140%, respect to the pure gypsum, when the maximum NPCM/Hem mass ratio was used. This composite had a latent heat of 30.2 J g−1 and a heat capacity of equivalent 3.5 J g−1 K−1. Composites from a NPCM/Hem mass ratio up to 0.15 satisfied European mechanical standard EN 13,279–1 for gypsum binders and gypsum plasters and all of them, presented a bulk density higher than 0.60 g cm−3. The addition of a 41% in mass of nanocapsules allowed to save 13.5 kWh m−3 and, reducing the CO2 emissions up to 3.4 kg of CO2 per operating cycle. The use of this new material would lead to significant energy and economic savings, as well as a considerable reduction in the emission of polluting gases into the atmosphere. [ABSTRACT FROM AUTHOR]

Water crisis has been emerged as major environmental issues at global level, which involves lack of cost-effective and efficient treatment facilities of wastewater and scarcity of drinking water. Commercially available technologies such as RO plants are too expensive to be used in rural areas or remote areas that lack of reliable power supply. Therefore, application of solar energy for water purification such as solar still is gaining much interest due to their efficient utilization for residential and commercial application for the treatment of saline as well as industrial wastewater. Presently, research work for the efficient design with productivity enhancement of the solar still is very much popular and focused area of work. This review article provides the technological advancements in different designs of solar still (active and passive) with the productivity of water. The assessment of thermal energy storage materials and the use of nanofluids for the energy and productivity enhancement for better utilization of solar still are discussed. Another aspect of this review article deals with the utilization of wastewater (industrial and non-portable) in solar still and their treatment applicability. It can be concluded from the present review article that the use of phase change materials and nanomaterials improves the heat transfer rate and productivity of solar still and makes it very effective for industrial use. [ABSTRACT FROM AUTHOR]

We investigated the impact of thermally expanded graphite (ExG) on thermal conductivity and charging/discharging time for pristine pentadecane (PD), a potential phase change material for low-temperature thermal energy storage applications. The expanded graphite is prepared using a high-temperature (~ 950 ℃) thermal shock on chemically treated natural graphite flakes and is vacuum impregnated in pentadecane. Four different 5, 10, 15, and 20 mass% expanded graphite and pentadecane (PD-ExG) composite samples are considered for intensive studies of their thermophysical properties using differential scanning calorimeter (DSC), temperature history (T-history), and transient plane source measurements. DSC measurements showed the reduction in latent heat of fusion of pentadecane with increased mass% of ExG, but the melting temperature remained nearly unaffected. Further, thermal conductivity of pentadecane-expanded graphite composites enhanced from ~ 0.18 W m−1 K−1 (for pristine pentadecane) to 1.1 W m−1 K−1, 2.6 W m−1 K−1, 4.7 W m−1 K−1, and 7.1 W m−1 K−1 for 5, 10, 15, and 20 mass% ExG composite samples, respectively. The discharge time for these PD-ExG composites reduced about 42.7 to 67.81% as compared to pristine PD sample. PD-ExG composite with 10% or more ExG also showed the shape stability of PD-ExG composites and thus reduced leakage of PD in liquid state. Thus, PD-ExG form stable phase change material composite with enhanced thermal conductivity and enhanced charge/discharge rate, making it a suitable PCM for low-temperature thermal energy storage system such as space cooling. [ABSTRACT FROM AUTHOR]

In order to solve the phase separation problem of Na2S2O3·5H2O–CH3COONa·3H2O PCM (phase change material), sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), xanthan gum (XG), sodium polyacrylate (PAAS) and polyacrylamide (PAM) were selected as additives. The effects of different proportions of the above thickeners on the supercooling degree, phase separation, phase change temperature and latent heat of Na2S2O3·5H2O–CH3COONa·3H2O system were studied by using the cooling curve and DSC, so as to screen the best thickener for eutectic PCM. The experimental results show that CMC, XG and PAAS can eliminate the phase separation of Na2S2O3·5H2O–CH3COONa·3H2O. Among them, the optimal ratio of CMC, XG and PAAS is 3 mass%, 3 mass% and 1 mass%, respectively. From the perspective of heat storage performance, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O. The phase change temperature is 40.5 °C. The subcooling degree is about 14.7 °C, and the latent heat is about 221 J g−1. The melting time is 15 min. Only PAAS can make Na2S2O3·5H2O–CH3COONa·3H2O eutectic PCM completely exothermic at room temperature, which can not only play the role of thickener to eliminate phase separation, but also is a nucleating agent. After 100 melting-solidification cycles, the change rate of latent heat value was only 5%, and the change rate of phase transition temperature was less than 1%. Considering heat storage performance and cyclic stability, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O PCM. [ABSTRACT FROM AUTHOR]

In this study, a series of phase change nanocomposites using microencapsulated phase change material and graphene nanoplatelet (as an additive material) is synthesized to enhance PCM thermal properties. Paraffin as a PCM is encapsulated by melamine–formaldehyde as a shell material via in situ polymerization method. Graphene nanoplatelet as a heat transfer promoter is added among the microencapsulated phase change materials (MPCMs) in different mass fractions to form phase change nanocomposites. By the applied technique, the defect of leakage and the low thermal conductivity of the phase change material can be overcome simultaneously. The experimental measurements show that the thermal conductivity of the PCNs effectively enhances without a significant influence on their phase change enthalpy. The results indicate that when the amount of the graphene nanoplatelets increases, the thermal diffusivity and thermal conductivity enhance. By using 10 mass % graphene nanoplatelets in the PCN, the PCN's thermal diffusivity and thermal conductivity are raised by 93% and 48%, respectively. The DSC results show that the maximum latent heat of the PCNs is 95.97 J g−1 (PCN with 1 mass % of graphene). However, the maximum difference in the latent heat of PCNs with different graphene percentages is less than 4%. Thermal stability experiments show that the PCNs have a stable structure up to 165 °C without damaging the microcapsule shell. The fabricated PCNs, compared to many previous works, have good thermal properties and low cost which can properly be considered in thermal energy storage and thermal management applications. [ABSTRACT FROM AUTHOR]

The aim of the research work reports the thermal performance of graphene-water-based nanofluid phase change material (NFPCM) with different types of surfactants for a cold thermal storage (CTS) system. The graphene nanoplatelets (GnPs) are dispersed in DI water with the addition of commonly used surfactants, such as cetyltrimethylammonium bromide, sodium dodecylbenzene sulfonate (SDBS), sodium dodecylsulfate (SDS), polysorbate (Tween80), polyvinylpyrrolidone (PVP), and gum arabic (GA). The effect on the stability of different surfactants on the colloidal solution of GnP nanofluids is analyzed by zeta potential and particle size distribution. The average zeta potential values indicate that the SDBS-GnP, SDS-GnP, and GA-GnP combinations have good stability after 72 h. The freezing experiment is performed at − 7 °C cooling bath temperature in a spherical container and reveals that the surfactants have a significant influence on the supercooling rate and freezing time. The maximum reduction of 92.16% and 84.20% is observed for GA-GnP and SDBS-GnP in the supercooling rate, respectively. The prepared NFPCM can be incorporated in the CTS system owing to its enhanced thermal transport properties to increase the energy-saving potential. Also, the reduction of supercooling facilitates the chiller to operate at higher temperatures. [ABSTRACT FROM AUTHOR]

In this study, beeswax is studied as a phase change material (PCM) to store heat due to its high latent heat. The disadvantages of using beeswax were its low thermal conductivity and high melting point. To enhance the thermal conductivity of beeswax, nanoparticles (of Al2O3, ZnO, and FeO) and other phase change materials are used to decrease its melting point. In the present investigation, the melting point of beeswax was lowered by the addition of other organic PCMs like lauric acid, capric acid, and coconut oil. FeO nanoparticles (3 wt%) were found to give the best result for thermal conductivity enhancement of 112% compared to Al2O3 and ZnO with enhancements of 18.78% and 15.56%, respectively, at 5 mass%. Coconut oil was used to decrease the melting of the beeswax as it was the most stable and easily available one resulting in a melting point of 52 °C. An investigation was performed to study the effect of hot fluid flow rates (1 LPM and 2 LPM) and inlet temperatures (60 °C, 70 °C, and 80 °C) on the charging time of beeswax composite. The study showed that 50:50 mass% of beeswax and coconut oil and its composite with 1 mass% of FeO nanoparticle give us the best result out of all the other composites. The charging time of the material was found to be 15 min less than the composite without nanoparticles. [ABSTRACT FROM AUTHOR]

A novel smart solid-gel phase change materials (PCMs) with the photoluminescence and thermochromic properties were designed and fabricated in a simple way. In this work, luminescent mesoporous alumina (LMAa) was firstly prepared through pomelo peel bio-template method, which showed a better photoluminescence performance under the condition of 254 nm light. Next, LMAa and thermochromic pigment (TP) were evenly dispersed in the gelled capric–myristic–stearic fatty eutectic (CA-MA-SA) using magnetic stirring method, in which hydroxypropyl cellulose served as gelling agent, CA-MA-SA as good thermal storage PCM, LMAa as excellent fluorescent material, and TP as visible temperature change indicator. Some advanced techniques were introduced to characterize physical, chemical, and thermal properties of composite PCMs. Results showed that the CA-MA-SA/LMAa1.0 displays obvious luminescence under 254 nm UV light, excellent thermochromic ability from off-white to red as rising the ambient temperature from 35 to 45 °C, limited fluidity at 60 °C, suitable phase change temperature around 19.11 °C, high latent heat about 114.3 J g−1, and so on. The ideal shape stability, thermal, photoluminescent, and reversible thermochromic properties of composite PCMs had not only great application prospect in the field of thermal energy storage, but also brought convenience in practical application. [ABSTRACT FROM AUTHOR]

Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its practical application. Herein, a series of novel MWCNTs/HPC/PEG PCMs (named as PCMMHP) have been synthesized by hydroxypropyl cellulose grafting onto PEG for the first time and doping multi-walled carbon nanotubes (MWCNTs). The results indicate that the PCMMHP exhibit excellent shape stability and without leakage keeping warm for an hour at 353.2 K. The melting and freezing enthalpy of the PCMM1HP7 is 134.7 J g−1 and 131.2 J g−1, respectively; and corresponding melting point and crystallization temperature are about 324.9 K and 308.8 K, respectively. The PCMMHP show a good reversible thermal stability after 100 heating/cooling cycles. In addition, adding 4 mass% MWCNTs, the PCMM4HP7 possess a higher thermal conductivity of 0.6019 W m−1 K−1, which is 2.1 times that of the PCMHP without MWCNTs (0.2895 W m−1 K−1) and 1.9 times that of pure PEG (0.3228 W m−1 K−1). In a word, the fabricated PCMMHP is a kind of shape-stabilized PCM and has good latent ability. It will have a broad potential application in thermal energy storage applications. [ABSTRACT FROM AUTHOR]

A new shape-stabilized composite phase change material (SSCP) was fabricated by using a promising matter, namely n-octadecane (n-OD) having 200–244.00 kJ kg−1 thermal energy storage capacity. For this aim, one step impregnation method was conducted in order to obtain the composite PCM. Nano-sized gamma alumina (γ-Al2O3) was used as the support material that enhances the thermal properties of the smart composite. The obtained composite materials were investigated by thermal analyse and visualization methods in order to determine its thermal energy storage capacity, phase transition temperature, thermal stability, chemical structure and morphology based on the differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy and polarized optical microscopy analyses, respectively. Based on the DSC results, composite SSCP4 which could be obtained by using a composition of n-OD/γ-Al2O3 of 50:50 (mass/%) has highest thermal energy storage capacity (86.00 J g−1) with the suitable transition temperature (18.95–27.40 °C). Moreover, impregnation ratio of n-OD into the porous framework was found to be 39.58 (mass/%) by TGA. Accordingly, the obtained composite PCM can be a promising candidate for low-temperature (18–30 °C) thermal applications which are required to have the favorable phase change temperature and high energy storage capacity with thanks to its good thermal stability and durability performance. [ABSTRACT FROM AUTHOR]