Search

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]

The improvement of heat transfer and energy storage are crucial tasks in many renewable energy applications. The thermal and hydrodynamic performances of a nano-encapsulated phase change material (NEPCM) suspension are investigated under a mixed convective heat transfer regime inside a trapezoidal enclosure. As the host fluid and dispersed NEPCM particles circulate in the enclosure, the nanoparticle cores absorb/release heat and undergo a phase transition process, enhancing heat transfer. The governing equations were scaled into a general non-dimensional format and then solved by the finite element method. The influence of nanoparticles fusion temperature and concentration, as well as the wavy wall characteristics and Richardson number, was addressed on heat transfer. A suitable fusion temperature of the nanoparticles can boost the heat transfer rate by 8%. Furthermore, by employing 5% NEPCM particles at a dimensionless fusion temperature of 0.1, the Nusselt number achieved was 9.05. This marks a significant 37% rise when contrasted with a base fluid, which only had a Nusselt number of 5.7. [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]

Novel designs have been proposed for the phase change material (PCM) heat sink of concentrated photovoltaic (CPV) cells to enhance both convective and conductive heat transfer mechanisms. Trapezoid (with two different thickness ratios) and zigzag geometry designs are suggested for the CPV-heat sink. To enhance the performance, two improving treatments have also been presented for the proposed trapezoid phase change material heat sink, (i) using a baffle and (ii) using two small triangle fins. A set of energy, exergy, economics, and environmental analyses has been established by computational fluid dynamics simulation to compare the performance of the proposed heat sinks with the conventional foamed and finned rectangular heat sinks. The results reveal that a trapezoid heat sink with two small triangle fins reduces the average concentrated photovoltaic temperature by 22 °C, the complete melting time of the phase change material by 1800s (50% reduction), and increases the absorbed heat by 3.13 kJ (7.43% increment), the exergy efficiency by 2.22% (23.9% increment), the generated electricity by 10.55%, and CO2 emission reduction by 10.75% compared to the concentrated photovoltaic with the simple rectangular heat sink. These results of the trapezoid heat sink are very similar to the rectangular heat sink with four long fins but with almost 74.3% lower levelized copper cost. [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]

The thermal stability of a shape stable composite phase change material (SSCPCM) has been investigated using a thermogravimetric analyser. X-ray diffraction, Scanning Electron Microscope, Fourier transform infrared, Brunauer–Emmett–Teller, and Differential Scanning Calorimeter analysis are used to characterize the PCM and SSCPCM. The activation energy of PCM and SSCPCM is estimated using multiple value model-free methods, namely, Friedman, Kissinger–Akahira–Sunose, Starink, Ozawa–Flynn–Wall, and Vyazovkin. The SSCPCM exhibits 4.96, 6.95, 6.76, 8.02, and 4% higher activation energy than the pure PCM as determined by the Friedman, KAS, OFW, Vyazovkin, and Starink methods, respectively. The degradation temperature of SSCPCM improved by 12.86, 7.85, and 10.41%, compared to PCM, at a heating rate of 5,10, and 15 °C min−1, respectively. ANFIS modeling is used in this study to predict the degradation of PCM and SSCPCM. The mass loss (%) of PCM and SSCPCM samples is predicted by considering the input parameters as PCM type, temperature, and heating rate of the sample. It is found that the combination of a generalized bell-shaped input and a linear output membership function is best suitable for predicting the mass loss. The developed hybrid ANFIS model very well predicts the experimental mass loss of the SSCPCM with a coefficient of determination (R2) of 0.99. [ABSTRACT FROM AUTHOR]

The aim of this research is optimizing electrical and thermal efficiencies of a photovoltaic (PV) module integrated with phase change materials (PCMs) and Aluminum (AL) wires. Composites of glycerol and beeswax (GLBW) and the mixture of GLBW with paraffin (GLBWP) are presented as new PCMs. PCMs are applied in PV module to regulate its temperature. Aluminum wires are added to GLBWP composite to increase its thermal conductivity. Response surface methodology (RSM) is used to analyze the dependent variables which are the thermal and electrical efficiencies (ηth and ηe) and the optimum condition of the PV/AL-GLBWP system is achieved. The chosen independent factors of the cooling system are glycerol volume fraction in GLBW (A = 0–100% volume), GLBW volume fraction in GLBWP (B = 0–50% volume), and AL mass in GLBWP (C = 0–50g). Cold water is used to decrease the temperature of the PV module through a heat exchanger embedded in the PCM container. The results show that the composite of glycerol, beeswax and paraffin makes the PCM, which put out more thermal and electrical efficiencies than pure paraffin. Results indicate that for the system with no cooling, ηth and ηe are 53.27% and 9.05%, respectively. The addition of AL wire to PCMs noticeably increases the performance of cooling system. The values of thermal and electrical efficiencies are predicted at the highest point, which are 97.67% and 12.98%, respectively, at 75% GLBW, 37.5% GLBWP, and 37.5 g AL wire. [ABSTRACT FROM AUTHOR]

In today's competitive electric vehicle (EV) market, battery thermal management system (BTMS) designs are aimed toward operating batteries at optimal temperature range during charging and discharging process and meet promised performance and lifespan with zero tolerance on safety. As batteries primary function is to provide electrical power to operate electrical motors, it should possess inbuilt functions such as heating, cooling, insulation and ventilation to survive and emerge among competitors. This literature reviews various methods of cooling battery systems and necessity of thermal management of batteries for electric vehicle. Recent publications were summarized starting with conventional air cooling, liquid cooling and hybrid cooling which includes advanced phase change materials (PCM) and heat pipes. Also, eleven review articles were classified and reviewed in respective cooling strategies. In addition, experimental and numerical studies with flow path and geometrical optimization which enhances battery performance is given priority with key performance metrics or battery state of health (SOH) parameters such as reduction of maximum temperature (Tmax) and temperature difference among individual cells (ΔT) were explained in detail. Research gaps identified have been described in detail which will be eyeopener among research community and industry. Having a primary refrigerated liquid cooling system along with nanofluid-enhanced heat pipes as secondary cooling would be the most efficient way of cooling as both cabin and battery optimal operating temperature requirements fall in same range. [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]

Paraffin- and titania (TiO2)-based nano-encapsulated phase change materials (NePCMs) were synthesized by the sol–gel process to improve thermal as well as phase change performance. Nine different samples of NePCMs were prepared by varying core/shell mass ratios, and their effect was investigated on thermal performance. The paraffin/TiO2 nanocapsules were characterized by Fourier transform infrared spectrophotometer (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and dynamic light scattering (DLS). The characterization techniques confirmed that the paraffin was successfully contained in the TiO2 shell. The maximum effective melting (73.47 Jg−1) and solidification (71.87 Jg−1) latent heat for the NePCMs were found to be at a 52.33% encapsulation ratio. The mean size of the NePCMs was approximately 238 nm measured from DLS. The thermal properties of the same sample stayed almost the same even after 100 thermal cycles validated by the differential scanning calorimetry (DSC) curves, and thermal stability was evaluated by a thermogravimetric analyzer (TGA). [ABSTRACT FROM AUTHOR]

The rapid increase in computing power has facilitated the use of computational fluid dynamics (CFD) as an attractive tool for simulating solar systems. As a result, researchers have conducted numerous experimental and numerical studies on solar technologies, with an increasing emphasis on the utilization of CFD for simulation purposes. Hence, this article is intended to be the first of a two-part assessment of recent improvements in the use of ANSYS-Fluent CFD simulation in solar systems. In this part, the article aims to provide a comprehensive overview of CFD simulations, using ANSYS-Fluent, for different solar systems without concentrators, including solar thermal systems, hybrid photovoltaic/thermal (PV/T) systems, and photovoltaic/phase change material (PV/PCM) systems, while the concentrating solar systems are covered in the second part. Further, this review study includes informative data about the simulations, including the considered assumptions, models, and solution methods that were used with different cooling fluids, PCM materials, absorber designs, and innovative system designs. The present assessment also highlights the results and some remarks that show different important additional information such as the applied radiation and melting/solidification models. Besides, validation techniques and errors between the experimental work and simulations are introduced. In general, the ANSYS-Fluent CFD results were validated and it was possible to optimize many design parameters with minimal effort and expense. Recent research indicated that nanofluids could be a better alternative to conventional fluids to improve the thermal functionality of flat plate and hybrid PV/T systems. Effective cooling mechanisms could reduce PV panel temperature by 15–20%. Besides, integrating PCM with PV systems could enhance efficiency by 33–46% on summer days. Incorporating different nanomaterials and using fined PV/PCM configurations, the PV/PCM system demonstrated improved cost-effectiveness, while a foam layer outside the PCM could extend PV thermal management time by 55%. Many other conclusions about the commonly used physical models, solution methods, and assumptions dealing with different systems are highlighted inside. The article also identifies additional research proposals and challenges that must be addressed to advance the study of this topic. [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]

Kinetic studies and thermal stability become a crucial characteristic for switching in high-temperature regions in nanoscale phase-change materials, which are used as applications for non-volatile next-generation storage class memory. Differential scanning calorimetry has been used for theoretical and experimental studies of the glass transition kinetics, crystallization kinetics and thermal stability of newly synthesized Te(1−x) (GeSe0.5) Scx (x = 0.05, 0.1, 0.15) glasses. Sc has been used as a chemical modifier. The impact of rising Sc amount has been explained by relating the structural relaxation kinematics during glass transition process and devitrification during crystallization process in chalcogenide glasses and their various physicochemical properties. There is observable increase in crystallization rate by Sc incorporation. Te(1−x) (GeSe0.5) Scx material fragility index reveals that the composition is consistent with a potent glass-forming liquid. Heterogeneous nucleation occurs for the composition under study and is then followed by a two- or three-dimensional crystal development phenomena by means of the mean values of kinetic exponent factors. By adding Sc, it has been observed that the average values of the heat of atomization and mean bond energy decrease as the cohesive energy of the samples decreases. Inverse relation has been noticed between thermal stability parameter and enthalpy released while transformation of glass and crystalline phases. [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]

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]

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]

The present study aims to develop and implement data-driven machine learning (ML) models for performance prediction of heat flow and specific heat of sustainable composite phase change materials (SCPCMs). The implementation of ML models is being investigated for the first time, though the usage of PCMs has been studied in many applications. In this work, five ML models, namely decision tree regression (DTR), k-nearest neighbour (k-NN), random forest regression (RFR), extreme gradient boosting regression (XGBR), and cat boost regression (CBR), are considered for predicting the heat flow and specific heat of SCPCMs. A total of 14,303 data points for heat flow and 9059 data points for specific heat are considered. Five input parameters are considered: concentration of PCM, the concentration of biochar, concentration of multi-walled carbon nanotubes (MWCNT), heating rate of the sample, and temperature of the sample. The output parameters are heat flow (mW mg−1) and specific heat (J g−1 °C−1). From the results of performance predictions, the k-NN model exhibited the best coefficient of determination of 0.997 and 0.994 for heat flow and specific heat, respectively, among its peers. A model sensitivity analysis for heat flow prediction is performed and found that the errors between the actual and predicted values are 1.79%, 3.41%, 1.16%, 14.95%, and 1.66% for RFR, DTR, k-NN, XGBR, and CBR, respectively. Similarly, for the specific heat prediction, the error between the actual and predicted values is 0.687%, 0.99%, 0.37%, 10%, and 0.44% for RFR, DTR, k-NN, XGBR, and CBR, respectively. Thus, the developed data-driven machine learning models can be graded as k-NN > CBR > RFR > DTR > XGBR, based on their prediction accuracy and are found to be helpful in the selection of suitable sustainable PCMs for latent heat thermal energy storage systems. [ABSTRACT FROM AUTHOR]

The performance of a photovoltaic (PV) solar system is affected by the elevated module temperature, which is primarily dominated by solar irradiation. This study aims to manage the temperature of PV modules using passive cooling techniques and reports the improvement of comparative Output Power (OP), prospects and limitations. Two different passive cooling techniques have been developed and examined for regulating the PV systems installed in Jeddah. These techniques integrate the copper multi-pipe cooling frames with either phase change material (PCM), or TiO2-doped PCM. The ambient temperature, module surface temperature, solar radiation, wind speed, voltage, current, and maximum power output are recorded during the test. The results show that the module temperatures of PV/PCM and PV/PCM/TiO2 are reduced by 2.78% and 4.37%, respectively, compared to the conventional PV system. As a result, the output power of PV/PCM and PV/PCM/TiO2 exhibited a respective increase of 2.25% and 3.41% compared to the conventional PV system. The utilization of the copper multi-pipe frame filled with TiO2 doped PCM, known for its superior cooling performance, has rendered PV system highly promising in terms of contributing to future energy solution and augmenting the annual energy yield. [ABSTRACT FROM AUTHOR]

As one of the phase change materials (PCMs), paraffin is widely used in solar energy storage and utilization; however, there are limitations to its use due to poor photothermal properties of paraffin with low thermal conductivity and weak spectral absorption. In this present work, an experimental investigation on improving the photothermal properties of PCMs by producing hybrid PCM-based nanofluid with paraffin wax incorporating zinc (Zn) and zinc oxide (ZnO) nanoparticles was carried out. The two-step method was considered for the preparation of the Zn–ZnO/paraffin hybrid nanofluid, and the thermal and optical properties of the hybrid nanofluid were experimentally investigated. The impacts of nanoparticle concentration and solar radiation intensity on the photothermal properties of hybrid nanofluid were also studied. The results show that the addition of Zn and ZnO nanoparticles enhances thermal conductivity and specific heat capacity compared with pure paraffin. On the other hand, the transmission of nanofluid reduces with optical length and nanoparticles concentration increasing. Zn–ZnO/paraffin hybrid nanofluid can promote the photothermal properties in lower concentrations and higher irradiance range, and the maximum photothermal conversion efficiency of Zn–ZnO/paraffin hybrid nanofluids is 42.97%. [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]

As an excellent adsorption material, Expanded graphite (EG) has large surface area and pore volume in micro morphology. Therefore, it is often used as the shape-stabilized material for liquid PCM. In the previous studies, the influence of the density and size of EG on the PCM was less studied. In this paper, the EG with different density and size is selected as the shape-stabilized material of PCM. In the experiment, modified calcium chloride hexahydrate composite PCM and EG with different sizes and densities were used for coupling. The experimental results show that the EG with density of 200 kg m−2 and the size of 50 mesh can better adsorb the PCM. The experiment uses a physical mixing method, and the operation steps are simple and easy to use in practice. The shape-stabilized PCM (ss-PCM) prepared with 50 mesh EG has higher latent heat value (104.21 J g−1) and lower undercooling (1.75 °C). At the end of this paper, the ss-PCM was tested by micro morphology, pore size and infrared spectroscopy. The experimental results showed that the EG and c-PCM were evenly coupled together. ss-PCM still show good stability after 30 thermal cycles and can be used in practical production. [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]

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]

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]

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]

Techniques must be used to improve the thermal conductivity of paraffin phase change materials (PCM) for augmenting the passive thermal management of PV. In this paper, transient three-dimensional numerical simulations of PV-PCM systems with square and circular cross-sectional fins have been carried out to analyse the effect of fins and inclination θ on the performance. Finned PV-PCM systems with multiple fin numbers are considered. The parameters, such as the average temperature and efficiency of the module, are simulated and compared. Results show that the system with square fins gives better thermal regulation over cylindrical ones for all inclinations and fin numbers. The system with 16 square fins at θ = 45 ∘ is found with minimum PV temperature and maximum efficiency. Maximum temperature reductions of 57.56 °C and 56.8 °C and efficiency enhancements of 43.47% and 42.89% are achieved for horizontal systems with 16 square and cylindrical fins, respectively, over PV alone system. The effect of fin length is also simulated, and the maximum PV temperature reductions of 56.8 °C and 45.96 °C are obtained for full-length configurations with inclinations of 0 ∘ and 45 ∘ , respectively. The peak velocity of melted PCM is simulated, and a maximum peak velocity of 4.88 mm s−1 is obtained for the unfinned PV-PCM system with θ = 45 ∘. [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]

The critical review presented here exclusively covers the studies on battery thermal management systems (BTMSs), which utilize heat pipes of different structural designs and operating parameters as a cooling medium. The review paper is divided into five major parts, and each part addresses the role of heat pipes in BTMS categorically. Experimental studies, numerical analyses, combined experimental and numerical investigations, optimum utilization of a phase-change material (PCM) with a heat pipe (HP), oscillating heat pipe (OHP), and micro heat pipes combined with PCM for Li-ion BTMS using heat pipes are presented. The usage of HP's and PCM can keep the temperature of the battery system in the desirable limit for a longer duration compared to other traditional and passive methods. More emphasis is made on how one can achieve a suitable cooling system design and structure, which may tend to enhance the energy density of the batteries, improve thermal performance at maximum and minimum temperature range. Arrangement of battery cells in a pack or module, type of cooling fluid used, heat pipe configuration, type of PCM used, working fluid in a heat pipe, and surrounding environmental conditions are reviewed. According to the study, the battery's effectiveness is significantly influenced by temperature. The usage of flat HPs and heat sink proves to be the best cooling method for keeping the battery working temperature below 50 °C and reduces the heat sink thermal resistance by 30%. With an intake temperature of 25 °C and a discharge rate of 1 L per minute, an HP that uses water as a coolant is also effective at regulating battery cell temperature and maintaining it below the permissible 55 °C range. Using beeswax as a PCM in HPs reduces the temperature of BTMS by up to 26.62 °C, while the usage of RT44 in HPs reduces the temperature of BTMS by 33.42 °C. The use of fins along with copper spreaders drastically decreases the temperature capability of HPTMS by 11 °C. MHPA shows excellent performance in controlling the battery temperature within 40 °C. The effective thermal management can be done by incorporating heat pipe alone or by coupling with liquid cooling or metal plate. However, extensive and extended research is required to improve thermal management to safely and effectively use the battery for day-to-day applications. [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 utilization of phase change materials (PCMs) in buildings leads to the reduction of energy consumption and maintaining the indoor temperature within the comfort range. The PCM performance strongly depends on the climatic conditions, causing a major challenge. To overcome this issue, the employment of a double-layer PCM system is introduced. The energy and economic assessments of various double PCM systems in the building located in different climatic conditions of Iran have been conducted for the first time. In this study, two PCM wallboards with different enthalpy and melting temperatures were embedded in the external walls of a residential building located in various climatic regions of Iran. The performance of the double-layer PCM system in five cities of Iran including Tehran, Isfahan, Shiraz, Tabriz, and Bandar Abbas during hot and cold months of the year was evaluated from energy and economic viewpoints. It was inferred that embedding a double-layer PCM system reduces the heating/cooling energy consumption compared to single-layer ones. It was concluded that the RT18/RT28 double PCM system was the best candidate to be employed in the external walls of the building located in Tehran and Shiraz, which reduced the total energy consumption of the building up to 6.26% and 5.17%. The RT18/RT22 double PCM system was the most efficient system for the building placed in Tabriz and Isfahan reducing the total energy consumption up to 4.41% and 3.87%, and the RT22/RT28 double PCM system had the best performance in the building located in Bandar Abbas, which could save 6.58% of total energy. Moreover, it was concluded that the use of a double PCM system reduced temperature fluctuations in the external walls. In addition, the economic analysis was performed using the dynamic payback period and the results revealed that the employment of a double-layer PCM system reduced the investment return period by up to 50%. [ABSTRACT FROM AUTHOR]

Heat transfer in a duct, between air and a battery pack numerically and using Comsol software, is the subject of this article. The duct has two separate air inlets and a battery pack in the middle. All batteries are made of lithium-ion and are placed in a PCM housing in a circular shape. The (Re) of air in the duct varied between 100 and 400, and the time of transient study was 200 min. Simultaneously, a cool environment is used to resemble a domestic building. Using Design Builder software, the thermal energy (TLEY) needed for this structure was determined yearly in various seasons. The TLEY produced in the batteries is used to heat the house, and then, it is calculated what percentage of the energy required by the house can be supplied by the battery. The results of this paper clearly indicate that the maximum and average battery temperature (T-Bt) cells in the duct increase at the beginning of the process and then decrease. After this period, depending on the amount of (Re) of air in the duct, no variations in the T-Bt are detected after a specific duration. The fixed duration of the battery temperature grew as the (Re) level increased, while the T-Bt decreased. The outlet air temperature and the average PCM fraction of the melt also remain constant after the initial decrease, after a certain time. Increasing the (Re) rate reduces the quantity of exhaust air temperature and the PCM fraction of the melt. Thus, ideally, 13.83% of the required TLEY can be supplied from the batteries in the required seasons. [ABSTRACT FROM AUTHOR]

Efficient heat management is a serious challenge of integrating and miniaturizing high-power electronic devices. Fin heat sink based on phase change material (PCM) is an efficient passive cooling technology for electronic devices with alternative high-power density. It is developed to cool down electronic parts in transient applications. The efficiency of PCM-based heat sink is acceptable only below the melting point so that afterward, the temperature of electronic parts increases notably. The present study, in addition to using an aluminum heat sink with PCM for passive thermal management, forced airflow (2.5 ms−1 and 4.5 ms−1) was employed to examine the effects on the system performance. In addition, two PCM materials (n-Eicosane and paraffin) with two different layouts were used at power levels 10 W (8.3 kW m−2) and 15W (12.5 kW m−2). The results indicated that with paraffin in the middle and airflow velocity of 2.5 ms−1 and 4.5 ms−1 the maximum temperature of the heat sink decreased by 45% and 58%, respectively, compared to the design without forced convection. The layout of PCM in multi-PCM design had a notable impact on the performance in forced convection condition in particular. The increment rate at 100 mW mode and airflow of 4.5 ms−1 with paraffin in the middle was 150% higher than that of the alternate layout. [ABSTRACT FROM AUTHOR]

This research demonstrates the performance of a novel parabolic trough collector (PTC) that uses a naturally circulated open loop, and it is evaluated experimentally for several classes of solar radiation data. A concentric absorber tube packed with phase change material (PCM) is used in the development of an indoor PTC system. A comparative study has been performed for both bare and PCM-based receiver tubes for various classes of solar radiation data. According to the findings, the overall thermal efficiency of the naturally circulated PTC system in bare receiver tubes is 0.66, 0.57, 0.63, 0.64, 0.66, and 0.63, respectively, at classes 2, 3, 5, 6, 8, 9, and 10. Meanwhile, the overall thermal efficiency of PCM-based receiver tubes is 0.70, 0.62, 0.69, 0.65, 0.68, and 0.66, respectively. However, the instantaneous thermal efficiency of the developed system at various classes of solar radiation can be predicted by using different machine learning (ML) models. These models include linear regression (LR), polynomial regression (PR), decision tree (DT), random forest (RF), artificial neural network (ANN), KNN regression, and Gaussian process regression (GPR). Among all of these, the GPR model is showing higher prediction performance (i.e. RMSE = 0.0049, R2 = 0.9977) than that of the remaining developed ML models. [ABSTRACT FROM AUTHOR]

A prototype data center was created as part of this project. Lauric acid (LA), stearic acid (SA), and undecanoic acid (UA) were blended at a mass of 16%, 10%, and 32%, respectively, to be placed in the system. LA, SA, and UA thermophysical characteristics were examined. The melting temperatures and latent heat values of LA, SA, and UA were determined by differential scanning calorimetry to be 17.13 °C, 71.9 °C, 26.82 °C, and 24.49 °C, respectively, and 190 J g−1, 235 J g−1, 178 J g−1, and 150 J g−1. Thermal conductivities measured with the KD2 Pro were 0.288 W mK−1 for LA, 0.143 W mK−1 for SA, 0.201 W mK−1 for UA, and 0.245 W mK−1 for LA–SA–UA. The heat capacity values for LA, SA, UA, and LA–SA–UA were found to be 22.15 J g−1, 18.82 J g−1, 17.20 J g−1, and 20.49 J g−1, respectively. The findings demonstrate the utility of the LA–SA–UA mixture in energy storage. Thermocouples are deployed in the system at predetermined locations to compare the conditions when the data center is empty and with PCM. At four different speeds (5 m s−1, 4.45 m s−1, 4.25 m s−1, and 2.5 m s−1), empty and PCM cases were compared. 5 m s−1, 4.45 m s−1, 4.25 m s−1, and 2.5 m s−1 PCM system timings were 7800–16440 s, 6960–14,200 s, 5880–11900 s, 4440 s, and 9360 s, respectively. The presence of LA–SA–UA energy storage in the data center is demonstrated in this study. [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]

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]

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]

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]

The focus of this research was on the thermal conductivity and rheological properties of poly(ethylene glycol) with a molecular mass of 200 g mol−1 (i.e., PEG200) loaded with four different types of multi-walled carbon nanotubes (MWCNTs) in a wide concentration range up to 10 mass%. MWCNTs used differ in size (both diameter and length) and the content of COOH (oxidized) functional groups on their surface. It was found that the use of oxidized, shorter and wider MWCNTs in PEG200 results in highest enhancement in thermal conductivity by 133% for 10 mass% MWCNTs-PEG200 nanofluids. Investigation of the shear rate dependence of dynamic viscosity (η) showed that the use of MWCNTs in concentrations greater than 0.1 mass% changes the Newtonian behavior of PEG200 and results in the shear-thinning behavior. This behavior is strongly influenced by the MWCNT concentration in the nanofluid. When comparing the same nanofluid concentration, the highest degree of MWCNT agglomeration in PEG200 nanofluids was observed when long, thin and pristine MWCNTs were used. The thermal conductivity results were correlated with the most commonly used theoretical models: Maxwell, Hamilton-Crosser, Xue, and Murshed. Dynamic viscosity results were correlated with Einstein, Brinkman, and Brenner-Condiff theoretical models. The best agreement with the experimental results was obtained by the Maxwell and Einstein models, indicating the formation of sphere-like MWCNT agglomerates in each PEG200 nanofluid studied. [ABSTRACT FROM AUTHOR]