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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 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]

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]

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]

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]

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]

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]

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]

Octyl laurate phase change material (PCM) was microencapsulated by calcium alginate for eco-friendly low temperature energy storage. The PCM microcapsules were prepared by repeated interfacial coacervation followed by crosslinking method. In order to enhance the antibacterial properties of the as prepared capsules, the calcium alginate shell was functionalized by Ag nanoparticles. Calcium alginate-octyl laurate microcapsules possessed high latent heat of fusion values (130.8 and 128.6 J g−1 on melting and cooling, respectively) which did not significantly change when Ag nanoparticles were entrapped in the shell (127.5 and 125.2 J g−1 for melting and freezing enthalpy changes). Based on these values 71.0 and 69.0% maximal PCM content in the microcapsules were determined by the differential scanning calorimetry method. Both of the Ag-loaded and unloaded calcium alginate-octyl laurate PCM capsules maintained the high heat storing capacity after 250 warming and cooling cycles, which proved they did not suffer from leakage after the accelerated thermal test. [ABSTRACT FROM AUTHOR]

Wood impregnated with a multicomponent mixture of fatty acids as a bio-based phase change material (BPCM) to improve its thermal characteristics was studied. The studied wood/BPCM composites can be used as internal elements in buildings for energy storage. Scots pine and beech sapwood were impregnated with a multicomponent mixture of linoleic acid and coconut oil fatty acids at a ratio of 20:80. Leakage test was conducted and revealed that the maximum leakage for pine and beech were 9 and 8%, respectively. Light microscopy was employed to demonstrate the distribution of the BPCM in the wood structure. Rays in both pine and beech wood served as pathways for impregnation of the BPCM to partly fill the tracheid lumens (pine) and vessels (beech). Thermal characterization of the studied samples employed T-history and DSC methods, concluding that the impregnated wood had significant thermal mass, ability to store excessive energy in terms of latent heat and keep the temperature constant for long time. The specific heat capacity of the impregnated samples was 4–5 J g−1 K−1 i.e., higher than that of the untreated control samples of ca. 2 J g−1 K−1. The thermal conductivity of the samples before and after the impregnation was measured using heat flow meter method and the results showed that the untreated beech wood had higher thermal conductivity compared to pine and the parameter improved when the cell lumens were filled with the BPCM. Scots pine wood with to 80% mass percentage gain (MPG) after impregnation demonstrated an increment in thermal conductivity of 33% while Scots pine and beech with 43 and 38% MPG demonstrated an increase of the conductivity with 8 and 11%, respectively. [ABSTRACT FROM AUTHOR]

A three-dimensional porous activated carbon (HSAC) with high adsorption properties was prepared by using hemp straw as raw material and phosphotungstate as catalyst through low-temperature hydrothermal carbonization combined with KOH high-temperature activation technology. The maximum specific surface area of activated carbon material was 2310.1 m2 g–1, and the maximum adsorption capacity of methylene blue was 2424.2 mg g–1. A series of PEG/HSAC phase change energy storage materials with different mass ratios were prepared by physical blending impregnation by using polyethylene glycol (PEG) as phase change material and porous activated carbon as carrier. Through the study of activated carbon pore structure, energy storage material structure analysis, and DSC comparative analysis, the experimental results showed that PEG and HSAC mass ratio (60/40) was the best. The latent heat of the composite was 51.5 J g–1, and the phase change temperature was 58.5 ℃. No obvious leakage occurred after 20 heat cycles. Composite phase change materials had potential applications in the field of intelligent buildings. [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]

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]

As the energy demand is increasing and conventional energy sources are declining, renewable energy sources are becoming increasingly popular. It is very important to store this energy efficiently. The use of phase change materials (PCMs) as latent heat thermal energy storage (LHTES) technology has utmost importance to researchers due to its high storage density and stable thermal characteristics. During charging and discharging of PCM, correspondingly occurring phase change processes (i.e. melting and solidification/ freezing) have been the crux of discussions in most of the subject-related articles in the recent literature. The objectives of those articles are to analyse and understand the phase change properties of PCM in its natural form, with nano-additives, and with or without metal foams. This manuscript provides a detailed review of energy storage, heat transfer, and melting process characteristics of coconut oil, which is an organic phase change material in its nature. Melting features like the progression of solid–liquid interface, time to complete the melting process, rate of melting, and augmentation in the rate of heat transfer owing to a colloidal suspension of nano-material inside PCM are reviewed and presented. [ABSTRACT FROM AUTHOR]

MnO2 particles were prepared by a hydrothermal method and characterized via the SEM imaging, XRD and FTIR analyses, showing that the individual particles were spherical and less than 1.0 μm in diameter but were clustered in α type crystal. The particles were then added into the n-octadecane to form a new class of phase-change energy storage composites. After that, the composite powder was wrapped into polyethylene by the suspension polymerization, forming microcapsules with an average size 4.9–5.6 μm in diameter. Eventually the morphology and thermal properties of the microcapsules were analyzed. No forming of chemical bond between the core material and the shell material was found during the microcapsule synthesis process. The latent heat and encapsulation efficiency of the microcapsules with addition of 0.5 mass% MnO2 particles in the n-octadecane were measured at 107.5 ± 1.3 J g−1 and 95.3 ± 1.2%, respectively, which are higher than the microcapsules with pure n-octadecane, measured at 84.9 ± 1.2 J g−1 and 75.3 ± 1.4%, respectively. The thermal conductivity of the n-octadecane microcapsules modified with 0.5 mass% MnO2 was enhanced by about 103.3% at 15.0 °C compared with the microcapsules without MnO2. Thermogravimetric and thermal cycling studies showed that the modified new microcapsules had good thermal stability. Such a modification provided an effective way to prepare phase-change energy storage microcapsules with better thermal properties and higher encapsulation efficiency. [ABSTRACT FROM AUTHOR]

The effect of energy and exergy analysis on the lauric acid and paraffin wax phase change materials (PCMs)-based 0.1% vol. fraction of Al2O3 and CuO nano-additives thermal energy storage (TES) system has been investigated experimentally. The TES system is integrated into the exhaust gas side of the four-stroke diesel engine. Nano-additives in phase change materials improve the charging rate of the TES system (i.e., a decrease in charging time). The temperature profile in radial and axial directions, heat transfer rate, overall heat transfer coefficient, heat transfer rate and the cumulative heat storage in the thermal energy storage system have been analyzed and were compared. Results revealed that 0.1% vol. fraction Al2O3 nano-additives-based lauric acid nano-enhanced phase change material (NEPCM) required 16.13%, 8.06%, 38.71%, 25.81%, and 32.26% less charging period than pure lauric acid PCM, CuO–lauric acid NEPCM, paraffin wax PCM, Al2O3–paraffin wax NEPCM, and CuO–paraffin wax NEPCM, respectively. However, the experimental analysis revealed an optimum thermal performance for the TES system with 0.1% vol. fraction Al2O3 nano-additive-based lauric acid PCM at 7kg engine load with 1500 rpm. Also, 0.1% vol. fraction Al2O3 nano-additives-based lauric acid (NEPCM) TES system along with the heat exchanger was highly effected to obtain the maximum percentages of the energy/exergy charging and energy/exergy saved from the diesel fuel compared to other considered samples. [ABSTRACT FROM AUTHOR]

The present work deals with thermal energy storage behavior of the nano-enhanced phase change materials (NEPCMs) for building space cooling application. The NEPCMs have been prepared using Deionized (DI) water as the base phase change material (PCM) and multi-walled carbon nanotubes (MWCNTs) as nanomaterial with mass concentration of 0.25%, 0.5%, and 0.75%. For better stability of additive materials in the base PCM, sodium dodecyl-benzene sulfonate (SDBS) has been chosen as an additive element. The sub-cooling of the DI water has been completely eliminated for a mass concentration of 0.75% of MWCNT. The differential scanning calorimetry(DSC) analysis has been conducted to measure the phase transition properties of NEPCMs. The enhancements of 12.8% and 14.13% in latent heat values for charging and discharging processes, respectively, were observed for maximum mass concentration. It has also been observed that the onset temperature for charging is reduced from − 12.8 to − 9.7 °C for NEPCM with maximum concentration. The maximum thermal conductivity (k) augmentation of 23% (solid phase) and 11.2% (liquid phase) has been achieved by the NEPCM having a mass concentration of 0.75% MWCNT at − 10 °C and 15 °C, respectively. According to the study results the reductions in total charging times are 28% and 19% with the NEPCM holding a mass concentration of 0.75% MWCNT for − 8 °C and − 6 °C heat transfer fluid (HTF) temperatures, respectively. The environmental pollution remediation can be achieved by the reduction in energy input to the chiller by minimizing the total time taken for the charging the PCM. [ABSTRACT FROM AUTHOR]

Effect of natural convection during the melting process of capric acid-based multi-walled carbon nanotube (MWCNT/CA) thermal energy storage system has been investigated experimentally. The temperature variations of phase change material were measured during the charging process. Effects of Stefan number and Fourier number on Nusselt number, as well as energy and exergy of the storage medium for different vol. fractions of MWCNT/CA-based phase change material, have been analysed and compared during charging process. Furthermore, the present work also extends to evaluate the thermophysical properties, i.e. thermal conductivity and specific heat capacity in liquid and solid phase of MWCNT/CA-based PCM by T-history method. Results revealed that the melting time for 0.02% vol. fraction of MWCNT/CA-based PCM is 66.66% lower compared to pure capric acid PCM. The thermal conductivity and specific heat capacity of 0.02% MWCNT/CA-based PCM obtained higher value than other samples in liquid and solid phases. Rayleigh number justified that natural convection heating process occurred within the TES system. Furthermore, the energy and exergy of 0.02% vol. fraction-based MWCNT/CA storage medium achieved 61.9% and 70.92% maximum values than pure CA phase change material, respectively. Therefore, 0.02% vol. fraction of MWCNT/CA could be suitable nanoenhanced phase change material for thermal energy storage systems. [ABSTRACT FROM AUTHOR]

Phase change energy storage technology is an important technology to solve the contradiction between energy supply and demand and improve energy efficiency. In the fields of fruit and vegetable preservation, cold chain logistics, chemical industry, medicine and other fields, low-temperature phase change materials below 0 °C have great application space, but many phase change materials have large supercooling, low thermal conductivity, mechanical properties and heat. Poor stability restricts its application in practice. In this study, using the principles of phase balance and phase law and a combination of theory and experiment, an efficient, stable, non-toxic and safe composite phase change material was developed. Using decyl alcohol (DA) and lauryl alcohol (LA) as substrates, adding covalently modified hydroxylated multi-walled carbon nanotubes (MWCNT-OH) with different mass fractions and adding sodium dodecyl benzene sulfonate (SDBS) are used as a dispersant to promote the nanoparticles to be better dispersed in the solution through ultrasonic vibration and to explore the thermal performance and thermal cycle stability of composite phase change materials. The results show that there are no supercooling and no phase separation after DA–LA eutectic. After adding MWCNT-OH and SDBS, the thermal conductivity of the composite phase change material is effectively improved and has little effect on the phase change enthalpy and phase change temperature. DA–LA/MWCNT-OH/SDBS still has good thermal stability after 200 high- and low-temperature cycle. [ABSTRACT FROM AUTHOR]

In this paper, the variation of thermophysical properties such as the thermal conductivity, thermal energy storage capacity, viscosity, and phase change temperature of the novel ternary eutectic phase change material (PCM) with respect to multi-walled carbon nanotubes (MWCNTs) concentration are investigated. The novel ternary eutectic PCM was formed by the permutation of oleic acid, isopropyl palmitate, butyl stearate in a eutectic mole fraction of 0.44–0.33–0.23. The heat transfer analysis of the materials encapsulated in spherical ball was experimentally investigated. The results concluded that the ternary eutectic PCM with 0.10 mass percentage of MWCNT enhances the heat transfer rate by 34.45% with respect to the pure PCM. Furthermore, the thermal conductivity of the MWCNT dispersed ternary eutectic PCM shows an increasing trend and reaches the maximum enhancement of 67.28% for 0.10 mass percentage of MWCNT concentration. The crystallinity decrement of the composite PCM was increased linearly from 0.19 to 3.2% for the increasing MWCNT concentration along with the convergence of melting and solidification enthalpy at the maximum dispersion of MWCNT concentration. New correlations governing the variation of thermal conductivity, viscosity and thermal expandability of the ternary eutectic PCM with respect to MWCNT concentrations have also been developed and presented in this study. The novel ternary eutectic PCM with 0.10 mass percentage of MWCNT with good thermal reliability after 500 thermal cycles and compatibility with the spherical encapsulated high-density polyethylene ball could be an eminent candidate for low-temperature cold storage applications. [ABSTRACT FROM AUTHOR]

In the present investigation, a novel composite of Polyethylene glycol (PEG) with molecular weight 10,000 (10 k) and aluminum oxide nanoparticle were prepared for solar thermal energy storage system. A composite of nanoparticles of Al2O3 in different mass fraction (1%, 2%, 3%, 4%, and 5%) and PEG 10,000 was prepared. The thermal properties of these composites and their chemical stability were studied by DSC and FT-IR analysis. The XRD technique was adopted for analyzing the crystallization of prepared composite materials. The TGA curves was also obtained and utilized to check the thermal stability of nano-enhanced organic phase change materials (NEOPCMs). The chemical and thermal reliability was tested by conducting an aging test on an in-housed designed thermal cycler for 1500 melt/freeze cycles. The results show that the thermal properties of the NEOPCMs do not change considerably after the thermal cycle test. An increment of 52.09% in thermal conductivity was found in the developed composite with 5% incorporation of nanoparticles. On the basis of results obtained, it can be ascertained that the composites possess significant thermal properties and are a good candidate for the latent heat thermal energy storage systems having temperature requirement around 60 °C such as solar water heater, etc. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) can store and release the latent heat associated with a phase transition, so they can be applied in thermal energy management and storage systems. Among them, form-stable (FS) PCMs can consist of two immiscible phases: an active phase, which undergoes the solid–liquid transition, and a matrix, which provides the structural properties and prevents leakage of the active phase when it is liquid. This experimental study focused on the characterization of a metallic FS-PCMs based on an Al–Sn alloy, obtained by powder metallurgy from ball-milled powders, compacted at room temperature and sintered at 200, 250 and 500 °C. The main properties that characterize PCMs are the temperature range over which transition occurs and the associated enthalpy, i.e. the stored energy. Differential scanning calorimetry (DSC) is one of the more suitable characterization techniques to evaluate these properties and so the thermal response of PCMs. To check thermal response and its stability, DSC tests including several thermal cycles were conducted. DSC analyses were performed also before and after several thermal cycles simulating possible operative conditions. Moreover, microstructural analysis, through scanning electron microscopy and X-ray diffraction, allowed to relate the thermal response variations to microstructural and mechanical changes. [ABSTRACT FROM AUTHOR]

Thermal analysis of the binary system (Al(NO3)3)–(Cu(NO3)2) of different ratios was performed by using differential scanning calorimetry and thermogravimetric analysis. The eutectic temperature of the binary salt mixture was determined to be 65 °C. Moreover, the degradation temperature, specific heat, latent heat of fusion and thermal stability were reported, respectively. Further, this work focuses on synthesising low-temperature salt mixtures comprised of aluminium nitrate non-hydrate (Al(NO3)3) and copper nitrate hydrate (Cu(NO3)2) of varying compositions (60:40, 50:50, 55:45 and 57.5:42.5), respectively, which are optimised using Design of Expert v13. The performance of the binary salt mixture was determined from the results obtained from thermal stability measurements after the exposure of salt mixture to 120 h at a higher temperature. The results showed that the novel binary molten salt mixtures exhibit decomposition at 215 °C and the latent heat was found to increase from 17.7 to 20.73 J g−1 with the increase in aluminium nitrate composition with excellent repeatability after three sets of experiments. The average specific heat of binary molten salt mixture was observed from 2.73 to 2.13 J g−1 K−1. The optimal molar ratio of binary molten salts is found to be 60:40 (Al/Cu) from the obtained results. Field emission scanning electron microscopy and energy-dispersive X-ray showed a uniform distribution of both the salts in the mixture. The average specific heat of the optimal molar ratio was 21.8% higher compared to other molar ratios, indicating the most promising material to be used in solar applications. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis of the transient performance of the latent heat thermal energy storage unit established on finite difference method. The storage unit consists of a shell and tube arrangement with phase change material (PCM) filled in the shell space and the heat transfer fluid (HTF) flowing in the inner tube. The heat exchange between the HTF, wall and PCM has been investigated by developing a 2-D fully implicit numerical model for the storage module and solving the complete module as a conjugate problem using enthalpy transforming method. A comparative investigation of the total melting time of the PCM has been performed based on natural convection in liquid PCM during the charging process. The novelty of this paper lies in the fact it includes convection in PCM and this investigation includes a detailed parametric study which can be used as a reference to design latent heat storage. The results indicate that natural convection accelerates the melting process by a significant amount of time. In order to optimize the design of the thermal storage unit, parametric study has been accompanied to analyze the influence of various HTF working conditions and geometric dimensions on the total melting time of the PCM. Another important feature considered in this work is the influence of the inner wall of the tube carrying the HTF on the entire melting time of the PCM. An error of around 7.2% is reported when inner wall of the tube is ignored in the analysis. [ABSTRACT FROM AUTHOR]

The thermal energy storage (TES) system is used to store the heat energy for longer periods and retrieve the heat energy as and when required. Experiments were conducted on the TES system with stearic acid (SA) as phase change materials (PCM) with and without iron scrap additives (IS) filled in spherical capsules. The PCM was filled in high-density polyethylene (HDPE) capsules of spherical shape. The process of charging, discharging, and the heat energy retrieved for the aforementioned PCMs were investigated and compared with various heat sources. The TES tank performance was studied with a variable/constant heat source at different flow rates, i.e. 2, 4, and 6 LPM. The results showed that the TES tank is charged to 70 °C in 204 min with 6 LPM flow rate, whereas for 2 LPM flow rate, the TES tank was charged to 70 °C in 254 min for the variable heat source. In the case of a constant heat source, to reach 70 °C, it took 54 min, 43 min, and 33 min for 2 LPM, 4 LPM, and 6 LPM flow rates, respectively. The total heat capacity of the TES tank at 70 °C was around 10,400 kJ. The output hot water at an average of 45 °C was found to be around 164 litres which means that the heat energy recovered from the TES tank was around 32%. The system with IS along PCM filled in spherical capsules was able to give 25% of hot water in extra than the same capacity of the sensible heat storage system. The results obtained reveal that heating and cooling processes were taking place at a faster rate of 13% with the addition of IS particles to the PCM when compared to pure PCM in the spherical capsules. [ABSTRACT FROM AUTHOR]

Performance improvement of a phase change material (PCM) thermal storage system is numerically investigated. A finite volume solver is employed to simulate the melting process of the PCM in different geometrical and boundary conditions. The numerical predictions are initially validated against available experimental data. Afterward, four different scenarios are investigated to improve the thermal characteristics of the phase change process. These scenarios include insertion of radial fins with different radial lengths, insertion of a porous layer on the PCM side of the heat transfer fluid (HTF) tube, doubling the HTF mass flow rate, and also increasing the HTF inlet temperature. The results indicate that all of these scenarios expedite the melting process, but at different rates. The insertion of the porous medium is shown to be more effective than using of radial fins. Moreover, according to the second-law analysis of the thermal storage system, using the porous layer provides a superior exergy efficiency compared to other enhancement scenarios. Overall, the addition of a metallic porous layer around the HTF tube is proven to be the most effective as well as the most efficient approach to improve the thermal characteristics of the energy storage system. [ABSTRACT FROM AUTHOR]

The objective of this paper is to develop the influences of channel waviness on the performance of a latent heat storage system during phase change mechanism. The heat exchanger is a vertically oriented double pipe where the heat transfers to/from the PCM in the annulus by moving the water in the inner tube. Various wavelengths, as well as wave amplitudes, are examined at various fluid Re and water temperatures (Tin) to find the effects of channel waviness on different aspects of melting/solidification time, pressure drop, pumping power and exchanged heat rate. Increasing Re, Tin and amplitude of wavy wall improves the system performance during melting and solidification mechanisms. Besides, it is found that there is an optimum dimensionless wavelength of 0.2 for achieving the minimum melting and solidification times as a result of maximum heat exchanged between the water and PCM. Furthermore, the waviness has an almost negligible effect on the pumping power which is reduced for the dimensionless wavelengths higher than 2.0. In the best scenario, the required time to melt and solidify the PCM reduces by almost 28.6% and 57.63%, respectively, using wavy channels compared with the smooth wall case. [ABSTRACT FROM AUTHOR]

Numerical simulations are performed to analyze the thermal characteristics of a latent heat thermal energy storage system with phase change material embedded in highly conductive porous media. A network of finned heat pipes is also employed to enhance the heat transfer within the system. ANSYS-FLUENT 19.0 is used to create a transient multiphase computational model to simulate the thermal behavior of the storage unit. Copper foam is the porous medium used to enhance the heat transfer and is impregnated with the phase change material, potassium nitrate (KNO3). The effects of the porosity of the metal foam and the quantity of heat pipes on the thermal characteristics of storage unit have been investigated. The results indicated that increasing the quantity of the embedded heat pipes leads to drastic acceleration of both charging and discharging process. Impregnating the copper foam with potassium nitrate phase change material significantly affects the total charging and discharging times of the storage unit. It was shown that the porosity of the metal foam plays a key role in the thermal behavior of the system during the charging and discharging processes. [ABSTRACT FROM AUTHOR]

The investigations show that an undeniable part of future smart energy system, which is to be based on 100% clean energies, is energy storage units. Indeed, due to the intermittent inherent of the main source of renewable energies, e.g., wind and solar, energy storage systems will be highly in service in the future. In this regard, investigation of the impacts of combining nanopowders on the thermal behavior of PCM through a thermal energy storage bed in various operational conditions has been an interesting topic of study in the literature. The current article presents entropy generation assessment of a heat storage unit with a water-based nanoparticle-enhanced PCM under the impact of Lorentz forces. In this system, the nanoparticles are dispersed in the pure phase change material (water) to augment the conductive rate, speeding up the solidification (i.e., the discharging) process. For this, the governing equations are derived with impose of Darcy's law for the permeable media and homogeneous model for the CuO–water nanomaterial features. The numerical solution method is Galerkin finite element method using FlexPDE software. The results of the simulations are presented for the entropy generation components (including friction, magnetic and thermal effects) and solid fraction contours for various Rayleigh numbers and flow conditions. [ABSTRACT FROM AUTHOR]

A large portion of world's final energy consumption is employed in thermal form. The proper techniques can be used to improve the efficiencies of thermal energy systems and decrease the energy consumption. Phase change material (PCM) storage modules can be coupled with different thermal systems to improve their thermal efficiency. This paper reviews the real potentials of coupling PCM storage modules to heat pipes and heat pumps in terms of energy saving and thermal energy management. The different systems suggested by researchers are described, and the main findings of the studies are provided. The advantages and disadvantages of these combined systems are discussed, and some suggestions for future studies are provided. The results show that heat pipes show great heat transfer ability and have good efficiency in improving heat transfer within PCMs. Moreover, heat pipes can be incorporated into PCMs to decrease the thermal resistance. The purpose of PCM coupled with heat pipe is to incorporate the large thermal conductivity of heat pipe with the large latent heat capacity of PCM. PCMs have ability to balance the unconformity between supply and demand in heat pumps and decrease the size of storage tank used in a heat pump module. [ABSTRACT FROM AUTHOR]

In this paper, an experimental and numerical study has been performed on melting process of commercial Iranian paraffin wax, with melting temperature of about 60 °C, inside a plate heat exchanger. A 500 × 100 mm plate thermal storage system and 22 mm thick phase change material has been designed. Experimental and numerical results are compared with each other in three different inlet temperatures of heat transfer fluid (HTF), which are 343, 348, and 353 K, and three different volume flow rates, which are 15, 30, are 45 L min−1. The temperature contours of paraffin wax at various time steps are presented to investigate the conduction and convection effects of melting process with respect to time. It has been shown that the melting rate of paraffin wax is higher at the upper part of the system due to the presence of natural convection. Results showed that increasing HTF temperature enhances the amount of heat transfer and reduces the melting time up to 37%. Also, by increasing volume flow rate of HTF, the melting time reduced up to 0.9%. [ABSTRACT FROM AUTHOR]

Present experimental investigation focuses on the performance analysis of metallic foam and phase change material (PCM)-based heat sink at variable heat loads. High porosity (97%) copper and nickel foams are used with PCM (RT-54HC) to enhance the surface area for the heat transfer. Experimental results reveal that metallic foam-based heat sink embedded with PCM can reduce the base temperature of the heat sink efficiently. Copper foam is recognized to be more promising when compared to nickel foam in lowering base temperature for all heat loads (8 W, 16 W and 24 W). It was found that copper foam embedded with 0.8 volume fraction of PCM reduced the base temperature by 26% as compared to that of nickel foam without PCM at 24 W. Furthermore, when the PCM fraction is increased, final temperature of the heat sink gets lessened at the end of charging process while discharging process remains almost intact. So, in this study, copper foam with 0.8 volume fraction is determined to be an optimized configuration. [ABSTRACT FROM AUTHOR]

Phase change materials (PCM) have a potential role in thermal energy storage applications. Recent progress has shown notable work on solid solid phase change materials (SS-PCM) which possess unique advantages of low subcooling, limited volume expansion due to a solid solid phase transition, high thermal stability and also had significant latent heat and thermal conductivity values. This review addresses current research on SS-PCM with the focus on solid solid phase transition mechanisms, properties, thermo-physical property enhancement, and experimental case studies for specific energy storage applications. The mechanism of solid solid phase transition for different classifications of SS-PCM with regards to a phase transition temperature and latent heat has provided in detail. This review also includes information regarding fundamental properties of SS-PCM along with methods for property enhancement, details on binary/ternary mixtures of SS-PCM and hybrid SS-PCMs, which allow altering phase transition temperature and increase thermal conductivity. Finally, the potential use of enhanced SS-PCM are discussed in detail, guiding researchers to select, customize, future scope, and addresses research gap of the SS-PCM for different energy storage applications. [ABSTRACT FROM AUTHOR]

SiC nanowires were prepared by sol–gel sintering at high temperature, then shaped and encapsulated Na2SO4·10H2O-based composite phase change energy storage materials. The properties of these materials, named PCMs-1, PCMs-3, and PCMs-5, were then investigated. The best-shaped phase change energy storage material was prepared when the content of SiC nanowires added reached 3 mass%. By scanning electron microscopy, PCMs-3 showed that SiC nanowires and Na2SO4·10H2O-based phase change materials have good compatibility with the network layer structure formed by SiC nanowires tightly wrapping the Na2SO4·10H2O-based phase change energy storage materials. The layered phenomenon of Na2SO4·10H2O-based phase change energy storage materials can be effectively reduced in this way, with increased additions of SiC nanowires reducing the degree of undercooling from 2.8 to 1, 0.5 and 0.9 °C with 1, 3 and 5 mass% SiC nanowires, respectively. The thermal conductivity of the phase change materials also improved, with conductivities of PCMs, PCMs-1, 3, 5 being 0.7812, 0.9941, 1.001 and 1.016 W m−1 K−1, respectively. By comparing the latent heat values of PCMs, PCMs-1, 3, 5 phase change energy storage materials thermally cycled 500 times, it was determined that PCMs-3 had the lowest phase change latent heat loss, effectively improving the cycle life of the phase change energy storage materials. [ABSTRACT FROM AUTHOR]

Dispersing high-conductivity nanomaterials into phase change materials (PCM) of latent heat thermal energy storage systems (LHTESS) is expected to solve the problem of poor thermal conductivity of PCMs. Accordingly, several metals, metal oxides and non-metals are employed as nanoadditives for PCMs by researchers. Besides thermal conductivity of PCMs, the other thermo-physical properties are also altered by nanoadditives. This paper provides comprehensive information on the effects of nanoadditives on the thermo-physical properties of PCMs through a critical review of related published works. The modified properties ultimately determine the charging and discharging rates of LHTESS. The extent of improvement in the thermal performance and the related issues are addressed. Further, the theoretical/empirical models developed so far for the evaluation of thermo-physical properties are deliberated. [ABSTRACT FROM AUTHOR]

This paper presents numerical investigation of melting N-eicosane as phase change material (PCM). Effect of using innovative tube shape, in which internal fin had been added to HTF tube, in melting process in cylindrical container had been investigated. For understanding the effect of HTF tube shape in melting rate, different number of fin had been added to HTF tube, and also for understanding this effect more clearly, effect of different number of fin had been investigated for two different situations: (1) ratio of A/P which is ratio of HTF perimeter to area that PCM had occupied had been considered fix and (2) outer diameter had been considered fix and by changing the HTF tube shape, does not change. Also, inner tube had been considered as hot tube and outer tube as insulated. Numerical results were shown by increasing the fin to inner tube; rate of melting increases. [ABSTRACT FROM AUTHOR]

Thermal energy storage systems provide efficiency in order to have better utilization of energy sources while protecting the environment. Thermal energy storage can be classified as sensible and latent heat storage. The storage of latent heat allows a greater density of energy storage with a narrow temperature range during phase change. Phase change materials (PCMs) are important novel materials, which are used as the storage of thermal energy as latent heat, and can provide utilization of waste heat energy. In this study, the capric acid and oleic acid mixture containing hexadecane were encapsulated as the core with styrene–divinylbenzene copolymer shell by emulsion polymerization technique. Thermal properties of fatty acid microcapsules were characterized by differential scanning calorimetry and thermogravimetric analysis and also their morphology and structure were examined by scanning electron microscopy, polarized optical microscopy and Fourier transform infrared spectroscopy (FT-IR), respectively. The heat storage property of microencapsulated PCM was tested in a horizontal air flow channel system equipped with a flat heating plate, air fan and air flow sensors. The microencapsulated PCM was prepared successfully, and results of the analysis presented that this material is promising candidate for potential heating and cooling system applications. [ABSTRACT FROM AUTHOR]

In this study, tetradecanol–palmitic acid/expanded perlite composites containing carbon fiber (TD-PA/EP-CF CPCMs) were prepared by a vacuum impregnation method. Binary eutectic mixtures of PA and TD were utilized as thermal energy storage material in the composites, where EP behaved as supporting material. X-ray diffraction demonstrated that crystal structures of PA, TD, EP, and CF remained unchanged, confirming no chemical interactions among raw materials besides physical combinations. The microstructures indicated that TD-PA was sufficiently absorbed into EP porous structure, forming no leakage even in molten state. Differential scanning calorimetry estimated the melting temperature of TD-PA/EP-CF CPCM to 33.6 °C, with high phase change latent heat (PCLH) of 138.3 kJ kg−1. Also, the freezing temperature was estimated at 29.7 °C, with PCLH of 137.5 kJ kg−1. The thermal cycling measurements showed that PCM composite had adequate stability even after 200 melting/freezing cycles. Moreover, the thermal conductivity enhanced from 0.48 to 1.081 W m−1 K−1 in the presence of CF. Overall, the proposed CPCMs look promising materials for future applications due to their appropriate phase change temperature, elevated PCLH, and better thermal stability. [ABSTRACT FROM AUTHOR]

In order to obtain a low-cost, high latent heat and thermostable phase change material with a phase change temperature between 18 and 25 °C as a room temperature phase change material, a novel solid-liquid calcium-based composite named as PCM-Ca of 44.6% CaCl2, 6.9% Ca(NO3)2, 1.2% SrCl2 and 47.3% H2O with a phase change temperature of 21.8 °C and latent heat of 155.5 J g−1 was developed. The determination of thermal performances of PCM-Ca indicated that the thermal conductivities in liquid and solid state are of 0.6429 and 0.8256 W m−1 K−1, and the thermal conductivity in the phase change point is 1.2401 W m−1 K−1; the specific heat capacities at the temperature range of 5.5-26.5 °C and 31.5-38.5 °C were fitted as y = 0.0001x4 − 0.0042x3 + 0.0707x2 − 0.4151x + 3.9526 (r = 0.9999) and y = −0.0001x4 + 0.0208x3 − 1.1155x2 + 26.477x + 231.57 (r = 0.9984), respectively. The stability analysis demonstrated that PCM-Ca is stable at the temperatures less than 130 °C, and no phase separation and the obvious supercooling phenomenon were presented after thirty times cycle use. This material PCM-Ca has a potential for energy storage application. [ABSTRACT FROM AUTHOR]

Sugar alcohols are food grade, low cost and have very high latent heat capacities. They are therefore an attractive candidate for energy storage applications. However, to be able to utilize their potential, thermal conductivity is an important constraint. Laser flash analysis (LFA 447) was used for the measurement of thermal diffusivity. Influence of sample thickness, measurement time, voltage, pulse width and choice of curve fitting model on the measured thermal diffusivity values is studied. These parameters are then carefully chosen to ensure repeatability in the diffusivity measurement of sugar alcohols. Diffusivity results obtained using these criteria for several sugar alcohols are found to be in good agreement with consecutive measurements. [ABSTRACT FROM AUTHOR]

The effective and facile microencapsulation of paraffin with poly(styrene) was conducted using emulsion polymerization. The optimal independent variables using response surface methodology were paraffin wax/styrene mass ratio of 0.39, SDS/styrene mass ratio of 0.032 and the stirring rate of 1500 rpm which are different from those of in the previous works. The thermal characterization of the optimal sample was carried out using TG and DSC analysis. Microcapsules produced using this method show less mass loss during the heating process. The microencapsulation ratio ( ER) reached to 87.8 ± 0.2% under the optimal conditions. The morphology of the optimal microcapsules was considered by SEM analysis. The results showed that the obtained microparticles were smaller, smoother and have greater microencapsulation ratios than was the case for those produced in previous studies. Thus, the optimal encapsulated paraffin with the maximum ratio and good stability can be considered to have good potential for energy storage. [ABSTRACT FROM AUTHOR]

The addition of carbon nanofillers to phase change materials (PCMs) has received much attentions recently. The shape effects of carbon nanofillers on the thermal properties of paraffin were investigated in this work. Four types of nanocomposite PCMs were prepared by mixing paraffin with multi-wall carbon nanotubes (MWCNTs), graphitized MWCNTs, nanographene with different layer numbers (GNP-B, GNP-C). It shows that phase change enthalpy of nanocomposite PCM decreases gradually with the increasing of the loading of carbon nanofillers. Due to the nucleating action of carbon nanofillers, the supercooling degree of nanocomposite PCM slightly decreases. The microstructure of the nanofillers plays an important role in enhancing the thermal conductivity of paraffin. It is the flaky structure of GNP shows a more significant effect on enhancing the thermal conductivity of paraffin than the tubular structure of CNTs, which is confirmed by comparing the melting/freezing time of PCM. In the four kinds of carbon nanofillers, GNP-C shows the greatest thermal conductivity enhancement up to 52.4 % at the loading of 3 mass%. [ABSTRACT FROM AUTHOR]

Stearic acid/diatomite composite form-stable phase change materials (PCMs) have been prepared by using a direct impregnation method without vacuum treatment. The surface morphology, chemical compatibility, thermal properties and thermal stability were characterized by scanning electron microscopy, Fourier transform infrared spectrometer and X-ray diffraction (XRD), differential scanning calorimeter and thermogravimetric analysis (TG), respectively. The results show that there are only physical interactions between stearic acid and diatomite in composite PCM. XRD analysis reveals that crystal type is not affected by composite technology of SA/diatomite composite form-stable PCM with decrease in crystal size due to the limited pores in diatomite. The melting and freezing temperatures of stearic acid/diatomite composite, respectively, are 52.3 and 48.4 °C. The latent heat of SA/diatomite composite reaches 57.1 J g, potential to be used in a practical application. TG result indicates that the decomposition of SA/diatomite composite starts at 192 °C, implying that the SA/diatomite has a good thermal stability. [ABSTRACT FROM AUTHOR]

This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n-octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g) and crystallization (94.8 J g) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/ n-octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n-octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential. [ABSTRACT FROM AUTHOR]

This investigation deals with thermodynamic analysis, which offers an alternative approach to evaluate the performance of solar dryers and thin-layer drying characteristics of garlic cloves in a developed system. The garlic cloves were dried from a moisture content of 55.5 % (w.b.) to 6.5 % (w.b.) for 8 h. The drying data obtained were fitted to five different drying kinetics models. Of these, the model suggested by Midilli et al. [] had the best fit with the drying behavior of garlic cloves. The energy efficiency without and with recirculation of the air exiting the drying chamber during the study varied from 43.06 to 83.73 %, and 3.98 to 14.95 %, respectively, while the exergy efficiency corresponding to the energy efficiency of the drying process ranged from 5.01 to 55.30 % and 67.06 to 88.24 %, respectively. [ABSTRACT FROM AUTHOR]

This communication presents the comparative study of two different types of thermal management systems for room's heating applications using calcium chloride hexahydrate as the thermal energy storage material encapsulated in panels and balls. During the daytime, TMS was outside the test room to store the solar heat in TMS. The solar heat made available to charge the PCM from solid to liquid and to warm the test room throughout the observation period during night time. As the room temperature drops significantly during the night time, so as the level of comfort. Both the thermal management systems have been used to heat the test room during night time and the temperature of the test room has been maintained at thermal comfort level without any conventional source of energy, i.e. using passive system. Also the experimental values were compared with those of the theoretical values and are found in good agreement with each other. Thus, it can be concluded that the experimental study carried out for both the thermal management systems have been validated by theoretical approach or vice versa and hence found to be satisfactory towards the successful operation of these systems. [ABSTRACT FROM AUTHOR]

In this paper, organic phase change materials (PCM)/Ag nanoparticles composite materials were prepared and characterized for the first time. The effect of Ag nanoparticles on the thermal conductivity of PCM was investigated. 1-tetradecanol (TD) was selected as a PCM. A series of nano-Ag-TD composite materials in aqueous solution were in-situ synthesized and characterized by means of thermal conductivity evaluation method, TG-DSC, IR, XRD and TEM. The results showed that the thermal conductivity of the composite material was enhanced as the loading of Ag nanoparticles increased. The composite materials still had relatively large phase change enthalpy. Their phase change enthalpy could be correlated linearly with the loading of TD, but their phase change temperature was a little bite lower than that of pure TD. The thermal stability of the composite materials was close to that of pure TD. It appeared that there was no strong interaction between the Ag nanoparticles and the TD. Furthermore, the experiment results indicated that the Ag nanoparticles dispersed uniformly in the materials, occurred in the forms of pure metal. [ABSTRACT FROM AUTHOR]