Enhancement Of Thermophysical Properties Research Articles

Experimental enhancement study of thermophysical properties of ternary carbonate phase change material with multi-dimensional nanoparticles

Carbonates have great application potential as heat transfer and thermal energy storage media in the development of future phase change materials. This paper gives thermophysical properties enhancement study on ternary carbonates in liquid state by adding aluminum oxide nanoparticles, multi-walled carbon nanotubes, graphene nanosheets, and experimentally evaluate the performance strengthen ability of multi-dimensional nanoparticles. The thermal diffusivities and specific heats of the prepared samples by the water solution method are determined using the laser flash technique and the differential scanning calorimetry at liquid state, respectively. A thermogravimetric analyzer is deployed for evaluate the high-temperature thermal stability of the composite ternary carbonates. Scanning electron microscopy and Fourier transform infrared spectroscopy techniques are utilized to examine the surface morphologies and chemical structures of the samples. The results indicate that there is a cooperative reinforcement impact on the thermophysical properties of ternary carbonate by utilizing zero-dimensional Al2O3 nanoparticles and two-dimensional graphene nanosheets, with a maximum improvement of 56.7 % for thermal conductivity, and 10.3 % for specific heat, which is apparently larger than adding any single nanoparticle. The composites exhibit superior thermal cycling stability after low-high temperature experiment, and samples can maintain thermal stability until 700 °C in the thermogravimetric analysis.

Enhancement of Thermo-Physical Properties of Form-Stable Nano-Enhanced Phase Change Materials: Advancing Maritime Sustainability

This paper explores the application of novel, form-stable eutectic mixtures in thermal energy storage systems for maritime environments. These advanced materials present a significant leap forward, addressing critical challenges faced by conventional phase change materials (PCMs) in marine environments. The stability, eliminating leakage and fluidity issues encountered with liquid PCMs are ensured by incorporating 2-hydroxypropyl ether cellulose (HPEC) as a gelling agent. Additionally, the thermal properties and heat transfer capacities were significantly enhanced, and eventually, overall system efficiency improved by including nano-graphene platelets (NGPs). Notably, NGPs effectively suppress supercooling, minimizing energy losses and guaranteeing consistent performance at elevated temperatures. Further, the eutectic mixture demonstrates exceptional durability through an accelerated thermal reliability test, guaranteeing optimal performance over a projected seventy-year lifespan. This enhanced thermal performance, and enduring stability combination establishes the form-stable eutectic mixture with NGPs as an up-and-coming solution for diverse maritime applications requiring efficient and reliable thermal energy storage. This research provides a compelling case for implementing form-stable eutectic mixtures with NGPs in maritime thermal energy storage systems. Its superior performance and sustainability offer significant advantages for diverse shipboard and offshore applications, contributing to improved energy efficiency, environmental sustainability, and operational resilience within the maritime sector.

Laser additive manufacturing of TiB2-modified Cu15Ni8Sn/GH3230 heterogeneous materials: Processability, interfacial microstructure and mechanical performance

Cu/Ni heterogeneous materials integrate excellent thermal conductivity and high-temperature mechanical properties, enabling them to be widely used in the aerospace domain. Differences in the thermal and physical properties of the Cu and Ni materials, however, make them difficult to be processed using the laser powder bed fusion (LPBF) additive manufacturing process. This study systematically examines the effects of various LPBF process parameters on microstructure, element diffusion, bonding strength and microhardness at the Cu/Ni interface, as well as investigating the mechanisms of defect formation within Cu/Ni heterogeneous materials. The results indicate that a reasonable control of laser energy input (<100 J/mm3) facilitates the Cu/Ni components through strong interfacial metallurgical bonding without pore defect formation. Compared to single-material Cu alloy, the ultimate tensile strength (UTS) of the horizontally bonded Cu/Ni specimen increased by 55.25 %, without significant reductions in elongation. The vertically bonded Cu/Ni tensile specimen fractured in the middle of the Cu region rather than the interfacial region, indicating superb interfacial bonding strength. Another advantage lies in the enhancement of thermophysical properties, with a 109.5 % increase in thermal conductivity achieved in the LPBF-fabricated Cu/Ni heterogeneous materials compared to the single-material Ni alloy. Quasi-static compression experiments indicated that the Cu/Ni lattice structure could absorb more energy when compressed parallel to the build direction (BD), compared to being perpendicular to the BD. This study provides guidance for the design and manufacture of high-performance Cu/Ni heterogeneous components via LPBF.

3S consideration (Synthesis, Surfactant, and Sonication) for stability and thermophysical properties enhancement of alumina-water nanofluid

Nanofluid (NF), a homogeneous dispersal of nanoparticle (NP)s in a carrying fluid, is used in many thermal applications due to its exceptional thermal characteristics. The goal of the current study is to use two-step technique for development of stable aqua alumina NF. The NF's stability is increased by using cetyltrimethylammonium bromide, a cationic surfactant. Magnetic stirring with heating is used to improve nanoparticles dispersion in the base fluid (BF). Following the development of the NF, the synthesised sample is examined utilising several stability evaluation procedures at various time intervals, including 1 day, 8 days, 15 days, and 30 days. Utilising modern equipments such as KD2Pro analyzer and double gap rotating cylinder type viscometer, thermophysical properties as thermal conductivity (knf) and viscosity (μnf) of NF were evaluated. According to experimental findings, enhancement in the volume fraction of NPs was accompanied by an increase in the nanofluid’s thermophysical properties. At the highest volume concentration, the highest augmentation in knf and μnf was found as 8.52% and 76.21%, respectively.

Stability and thermophysical properties enhancement of Al2O3-water nanofluid using cationic CTAB surfactant

Excellent thermal characteristics of homogeneous dispersion of nano-sized particles in a carrier fluid (nanofluid) make it appealing for use in a variety of thermal applications. The study aims to prepare stable aqua-Al2O3 nanofluid utilizing a two-step method. To increase nanofluid stability, a cationic surfactant called cetyltrimethylammonium bromide (CTAB) is used. The carrier fluid is heated while magnetic stirring is used to increase nanoparticle distribution. Bath sonication with concurrent heating and probe sonication is used to improve long-term stability. The chemical composition of γ-Al2O3 was confirmed by X-ray diffraction (XRD) results, and Scanning Electron Microscopy (SEM) images revealed the shape and mean size of the particles. The stability of the synthesized sample is evaluated utilizing a variety of stability evaluation techniques, including visual examination, UV-vis spectrometry, and Dynamic Light Scattering (DLS), at various time intervals, including 1, 8, 15, and 30 days. After 15 days of manufacture, the stability of the nanofluid without surfactant was low. Due to improved particle suspension, nanofluid with surfactant has demonstrated greater UV-vis light absorption. After a month of synthesis, it was discovered that the mean particle sizes of suspended nanoparticles in carrier fluid were 80 nm and 536 nm for nanofluid with and without surfactant respectively. KD2Pro thermal analyzer and viscometer were used to measure the thermal conductivity and viscosity of nanofluid. As per the experimental results, a nanofluid's thermophysical characteristics were found to be improved with volume concentration of nanofluid. Maximum augmentation in thermal conductivity and dynamic viscosity is 8.5% and 76.2% respectively at 1% nanofluid volume concentration.

Predicting thermophysical properties enhancement of metal-based phase change materials using various machine learning algorithms

BackgroundIn this research, five machine learning methods are employed to create the formula and make the model for communication between the melting and solidification processes to find the latent heat and communication between the thermal conductivity and the thermal diffusivity. Paraffin wax was the PCM, while SiO2, ZnO, Fe2O3, and Al2O3 nanoparticles were utilized as additives to enhance the thermal conductivity by considering four concentrations between 2 and 8 wt.%. MethodThe K-Nearest Neighbours (KNN), the decision tree, the stochastic gradient descent (SGD) regressor, the Support Vector Machines (SVM), and the Huber regression are the algorithms that are used in this study. FindingsUsing the Huber regression method, the formula for the latent heat of the solidification-process is created by the melting-process (by latent heat and wt.) with the polynomial form by degree 2, and the R-Squared value is 0.998, and MSE is 0.971172, and by the KNN (K = 3) is made the model with the linear form. The R2 value is 0.999, and MSE is 0.41809, and for the latent heat of the melting-process by the solidification-process (by latent heat and wt.) with the same methods reached to best the R2 for creating the formula and making the model, respectively the R2 values are 0.996 and 0.999, and the MSEs are 1.482458 and 0.608658. Using the Huber regression method, reach the best result for creating the formula in the polynomial form by degree 2 for the thermal conductivity by the thermal diffusivity and wt. and create the formula with the R2 value of 0.998 and MSE is 0.000033, and make the model by the SVM with the R2 value of 0.999 in the linear form, and MSE is 0.000016. The same methods are used for thermal diffusivity by the thermal conductivity and wt.; the R2 values for the formula and the model, respectively, are 0.997 in polynomial form (degree = 2) and 0.999 in linear form. MSEs, respectively, are 0.000020 and 0.000006.

Heat Transfer Enhancement of MHD Natural Convection in a Star-Shaped Enclosure, Using Heated Baffle and MWCNT–Water Nanofluid

Fluids have played and still play a vital role in attaining an optimized output from industrial processes. However, due to technological advancement, fluids with high hydrothermal characteristics are required. In order to overcome these challenges, researchers have developed fluids with dispersed nanoparticles, which are recognized as nanofluids. Various types of nanoparticles can be added to base fluids to produce thermally enhanced liquids. Among these, the addition of multi-walled carbon nanotubes (MWCNTs) is considered the best due to the considerable enhancement of thermophysical properties and the stability of the solution. Thus, in the present investigation, an analysis of the heat transfer characteristics of an MWCNT–water nanofluid included in a star-shaped cavity equipped with a hot rectangular baffle is conducted. In addition, a uniform magnetic field is applied along the x-direction to oppose the convective flow generated by variations in density. Mathematical formulations under assumed boundary conditions and physical assumptions are established in the form of dimensionless PDEs. The finite-element-method-based software “COMSOL” is used to execute the numerical simulations. PARADISO is employed to resolve the developed non-linear system of equations. The effects of the governing parameters on the velocity and temperature fields are presented through streamlines and isotherms. The Nusselt number is evaluated to depict the impact of the addition of nanoparticles (MWCNTs) on the heat transfer enhancement. Changes in the horizontal and vertical components of velocity are also evaluated against the Rayleigh number and nanoparticle volume fraction via cutline representation.

Synthesis, thermophysical characterization and thermal performance analysis of novel Cu-MXene hybrid nanofluids for efficient coolant applications.

Hybrid nanofluids are considered as an alternative for conventional heat transfer fluids and mono nanofluids due to its remarkable enhancement in thermo-physical properties. However, there are some limitations in achieving the better thermo-physical properties due to the stability of nanoparticles in different base fluids at higher concentration. This work aims at synthesizing, thermo-physical characterization and thermal performance estimation of stable Cu-MXene based hybrid nanofluids using various base fluids at very low volume concentration of Cu and MXene nanostructures. Two step method is employed to prepare Cu-MXene hybrid nanofluids by dispersing the low volume concentration of as prepared Cu and MXene nanostructures (ranging from 0.01-0.05 vol%) containing SDS surfactant in various base fluids such as water, methanol, castor oil and silicon oil. Synthesized mono and hybrid nanofluids shows excellent stability against aggregation up to 7 days as evidenced from higher zeta potential values. Wettability studies conducted using contact angle measurement suggests that the castor oil, methanol and silicon oil based hybrid nanofluids exhibits hydrophilic behavior (showing contact angle less than 90°). Hybrid nanofluids display excellent enhancement in thermal conductivity at very low concentration of nanostructures (more than 70% for methanol based Cu-MXene hybrid nanofluid). Viscosity of the silicone oil based hybrid nanofluids show a remarkable enhancement followed by water, methanol and castor oil based hybrid nanofluids. Thermal conductivity and viscosity of hybrid nanofluids are effectively validated with existing theoretical models. Moreover, specific heat and pumping power of the hybrid nanofluids with respect to volume concentration of nanostructures are determined using the existing theoretical equations. Thermal performance of hybrid nanofluids was successfully estimated using Figure of Merit (FOM) analysis and suggested the better heat transfer fluid for improving the heat transfer performance under laminar and turbulent flow conditions for efficient cooling applications.

Physico-Chemical Study on Heat Transfer Property of Iron Oxide Nanofluid

The analytical characterization of thermophysical properties of metal oxide nanofluid has got significant attention in thermal industries due to their high capability of reducing energy loss and enhancing the efficiency of machinery parts. The fascinating heat transfer characteristics of green modulated iron oxide nanoparticles (IONPs) attain significant importance due to their wide range of diverse applications in different industries. In the current study, IONPs were successfully synthesized using an aqueous extract of Aloe vera (Aloe barbadensis) leaves to evaluate its effective thermophysical properties in base fluid like water. The average particle size of 11nm IONPs with its nanofluid of various volume concentrations 0.01 to 0.05 with a different temperature range of 30°C to 50°C shows an enhancement in thermal conductivity of 34.08% compared to distilled water (base fluid). Different characterization technique like Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, UV-visible spectroscopy, and particle size analyzer has been employed to get characteristic modification and formation of iron oxide nanoparticles. The experimentally measured values of thermal conductivity were compared with existing theoretical models for effective enhancement in thermophysical properties and the same was analyzed with the importance of green technique.

Exploration of radiative heat energy on KKL model micropolar nanofluid past a permeable moving surface

AbstractNanofluid comprises nanoparticles that have varied applications in several industries as well as science and engineering due to their heavier thermal conductivity in comparison to conventional fluids. In such applications the role of transportation is vital. However, biomedical applications such as the flow of blood in the human body, peristaltic pumping, processes, etc. the use of nanofluid are important. Therefore, the present investigation aims at the enhancement of thermophysical properties on the radiative micropolar nanofluid flow past a permeable moving surface. These physical properties are studied incorporating the concept of Koo–Kleinsteuer–Li (KKL) model. The crux of the study is the approximate analytical technique, that is, the Homotopy Perturbation Method (HPM). The illustration of the contributing parameters on the flow phenomena is obtained via graphical as well as tabular form. A comparative study is carried out for the good agreement of the present result with an earlier established result in a particular case. Some important findings of this work are a retardation in the linear velocity profile is observed due to increase in the volume fraction of the particle. Suction slows down the linear velocity profile whereas the impact is counter productive in case of injection. A hike in the angular velocity profile is seen in case of greater suction whereas the opposite effect is observed for injection. An increase in the thermal radiation boosts up the fluid temperature and as a result of this an increase in thermal layer thickness is observed.

Thermophysical Properties Enhancement in Construction Materials Based on Cement and Plaster

Enhancing insulating power of buildings envelope saves energy costs and minimizes associated CO2emissions. The development of materials with good thermal performance is a major challenge. This work shows the effect of incorporating different additions on the thermal properties of composites based on plaster and cement through a series of experiments. The additives used are among the most widespread wastes in Morocco. Dozens of new samples based on cement and plaster have been prepared and experimentally characterized by the box method to develop environmentally friendly and thermally efficient materials. The results show that increasing incorporation rate of additives significantly improves thermophysical properties of based materials. The addition of 4% alfa and 6% of coffee grounds in plaster matrix and the replacement of cement by 50% of ashes in mortar and concrete record the low thermal properties including thermal conductivity, diffusivity, effusivity and specific heat. The good performance of new materials encourages us to integrate them into the building envelope. The results obtained by the annual simulations conducted for a residential building in Meknes have highlighted the economic and environmental benefits of using these new materials. A reduction of 50% in energy and a limitation of 3029.13 kgCO2eq/yr are observed thanks to an effective combination between the developed materials.

K2CO3–Li2CO3 molten carbonate mixtures and their nanofluids for thermal energy storage: An overview of the literature

The research and development of new thermal energy storage materials with high working temperatures are key topics to increase the efficiency of thermal energy to electricity conversion. The use of molten salt combinations with a wide range of operating temperatures is one of the ways to fulfil this purpose, and among them, molten carbonates present several advantages, such as high thermal stability, moderate cost, and less corrosiveness, compared to other molten salt mixtures. The present work contains a state-of-the-art review of the most important thermophysical properties for the thermal energy storage capacity of binary mixtures of potassium and lithium carbonates (K2CO3–Li2CO3). The available literature on the properties that play a key role in the heat transfer rate (viscosity and thermal conductivity) and volumetric storage capacity (melting point, density, latent heat of fusion and specific heat) is reviewed and presented. This includes the works that deal with nanofluids based on these binary mixtures of molten carbonates by analysing the influence of nanoparticles on thermophysical properties. Special attention is paid to specific heat as abnormal increases are registered in molten salts when introducing nanoparticles. Although future research is necessary about the thermophysical properties enhancement of these materials, the advanced capacities they offer for high-temperature thermal energy storage are promising, and this work aims to compile the available data on them until the present day.

Thermophysical properties enhancement and characterization of CuO nanoparticles enhanced HITEC molten salt for concentrated solar power applications

Molten salts are utilized in concentrated solar power (CSP) as a working fluid to store and transfer solar thermal energy. In this study, we attempted to enhance the thermal energy storage (TES) characteristics of the ternary nitrate molten salt of KNO3, NaNO2, and NaNO3, also known as HITEC molten salt, using cupric oxide (CuO) as additives for CSP applications. HITEC was doped with 0.1, 1, 3, and 5 wt% of CuO nanoparticles using the two-step wet method. Differential scanning calorimeter (DSC) was utilized to evaluate the specific heat capacity, melting point, and latent heat of the prepared material. Thermal stability was measured by thermogravimetric analysis (TGA) while the characterization analysis was performed using Fourier-Transform Infrared (FT-IR) spectroscopy, Field Emission Scanning Electron Microscope (FESEM), and Energy Dispersive X-ray Spectroscopy (EDS). The results showed that 0.1 wt% CuO nanoparticles is the optimum CuO nanoparticles concentration which resulted in a specific heat capacity enhancement of 5.6%, a 30% improvement of latent heat, and 9% enhancement of thermal stability. The morphological analysis revealed the formation of bright chain-like nanostructure due to nanoparticle dispersion, which may the possible reason for the thermophysical property enhancement.

Study of thermophysical properties of chloride salts doped with CuO nanoparticles for solar thermal energy storage

As heat storage and heat transfer medium, molten salt plays a vital role in achieving high heat transfer efficiency in concentrating solar power (CSP) plants. In this study, ternary chloride salts (NaCl–KCl–MgCl 2 ) is considered as the base salt and the nanocomposites doped with different mass fractions of CuO are synthesized using the solution evaporation method. The thermophysical properties of the nanocomposites, including melting temperature, phase change enthalpy, specific heat, thermal diffusivity, and thermal conductivity are investigated. The experimental results indicated the melting temperature of the nanocomposites is very close to that of the base salt. The specific heat of the nanocomposite in the liquid phase region is 10.51% higher than that of the base salt when the mass fraction of CuO was 0.7%. The addition of CuO nanoparticles significantly increase the thermal diffusivity and thermal conductivity of the base salt. The thermal diffusivity and thermal conductivity of the nanocomposites are increased by 10.95–37.23% and 15.85–39.55% compared to the base salt, respectively. The nanocomposites doped with CuO nanoparticles exhibit good application prospects and excellent thermal energy storage performance for high-temperature CSP systems. To improve the heat transfer characteristics of chloride salts, nanocomposites doped with 0.2, 0.7, and 2.0 wt% CuO nanoparticles were synthesized. The nanocomposites showed excellent TES performance for high-temperature CSP systems. • Nanocomposites doped with CuO exhibited excellent thermal energy storage performance. • Specific heat in liquid phase region had an enhancement of 10.51% by doping 0.7 wt% CuO nanoparticles. • Thermal diffusivity of nanocomposites increased with increasing temperature. • Thermal diffusivity and thermal conductivity of base salt can be increased by adding CuO nanoparticles. • The mechanism of the enhancement of thermophysical properties of nanocomposites was investigated.

Recent advances in thermophysical properties enhancement of phase change materials for thermal energy storage

Phase change materials (PCM) are promising technology to store thermal energy at a constant temperature. A large amount of energy can be stored or released in latent heat form during the transition of material from one phase to another. Despite the great benefits, most PCMs have their own limitations i.e., low phase change enthalpy, poor specific heat and thermal conductivity, supercooling, volume change, phase segregation, etc. Consequently, efficient thermal energy storage requires improving the thermophysical properties of PCMs. The present study is a comprehensive review of existing techniques for PCMs thermophysical properties enhancement. The research progresses on adding zero, one, two, and three-dimensionally structured additives to PCM is assessed to improve the thermal transport by enhancing the PCM effective thermal conductivity. The enhancement of latent heat of fusion and specific heat using various additives is also discussed. Further, the latest techniques on supercooling and phase segregation reduction are also presented. Last, the modelling of the novel composite materials formed by combining a PCM with other materials is presented. Despite the fact that the majority of these methods are still in the research and development stage, some of them have the potential to be commercialized in the near future. Reliable and efficient PCMs are exceptionally useful for storing solar energy and industrial waste heat, especially for constant temperature applications.

Thermophysical properties enhancement of octadecane using reduced graphene oxide and graphene oxide nanoplatelets

The main aim of this study is to investigate the impact of various graphite derivatives on thermophysical properties (melting enthalpy, melting point, specific heat capacity, total heat storage thermal stability, and heat capacity) of octadecane (OD) organic paraffin as a base material for the Composite Phase Change Material (CPCM) for Thermal Energy Storage (TES). Three types of graphite derivatives additives of Reduced Graphene Oxide (RGO), Graphene Oxide Nanoplatelets (GONPs), and Expanded Graphite (EG) were mixed with the base material with four weight fractions. These ratios were 0.1, 0.3, 0.5 and 0.75 wt.% for GONPs and RGO while were 5, 10, 15, and 20 wt.% for EG. The results obtained revealed that the graphite derivatives had a significant effect on the thermophysical properties of the OD particularly the specific heat capacity (Cp). It was proved that RGO, the two-dimensional (2D) sheet structure, was the champion additive to improve the thermophysical properties of the OD. RGO increased Cp by 385% and 491% in the solid and liquid regions, respectively in comparison with the pristine base material and it was found that the total thermal energy storage (TES) capacity enhanced by 274%. Moreover, GONPs (2D) improved the Cp by 377% and 385% in the solid and liquid regions, respectively. On the other hand, the EG reduced the Cp of the OD by 31% and 71% in the liquid and solid regions, respectively.

Recent Progress on Stability and Thermo-Physical Properties of Mono and Hybrid towards Green Nanofluids.

Many studies have shown the remarkable enhancement of thermo-physical properties with the addition of a small quantity of nanoparticles into conventional fluids. However, the long-term stability of the nanofluids, which plays a significant role in enhancing these properties, is hard to achieve, thus limiting the performance of the heat transfer fluids in practical applications. The present paper attempts to highlight various approaches used by researchers in improving and evaluating the stability of thermal fluids and thoroughly explores various factors that contribute to the enhancement of the thermo-physical properties of mono, hybrid, and green nanofluids. There are various methods to maintain the stability of nanofluids, but this paper particularly focuses on the sonication process, pH modification, and the use of surfactant. In addition, the common techniques to evaluate the stability of nanofluids are undertaken by using visual observation, TEM, FESEM, XRD, zeta potential analysis, and UV-Vis spectroscopy. Prior investigations revealed that the type of nanoparticle, particle volume concentration, size and shape of particles, temperature, and base fluids highly influence the thermo-physical properties of nanofluids. In conclusion, this paper summarized the findings and strategies to enhance the stability and factors affecting the thermal conductivity and dynamic viscosity of mono and hybrid of nanofluids towards green nanofluids.

Enhancement of Thermo-Physical Properties of Expanded Vermiculite-Based Organic Composite Phase Change Materials for Improving the Thermal Energy Storage Efficiency.

In this work, expanded vermiculite (EVM) was modified by acid leaching with different concentrations (0.01, 0.05, and 0.1 mol/L) of HCl solution to obtain three kinds of acid-modified EVM (AEVM-1, AEVM-2, and AEVM-3, respectively). In the composite, polyethylene glycol (PEG) was served as a phase change material (PCM), while EVM and AEVM were served as supporting matrixes. Then, graphite was served as an additive to enhance thermal conductivity, and a series of shape-stabilized composite PCMs (PEG/EVM, PEG/AEVM-1, PEG/AEVM-2, PEG/AEVM-3, and PEG-C/AEVM-3 ss-CPCMs) were prepared by physical impregnation. The latent heats of PEG/AEVM-3 and PEG-C/AEVM-3 in the melting process were 154.8 and 144.7 J/g, respectively, which increased by 22.7 and 14.7%, respectively, compared with that of PEG/EVM, indicating that acid modification effectively enhanced the heat storage capacity. The thermal conductivity of PEG-C/AEVM-3 was 0.43 W/mK, which was 65.4 and 48.3% higher than that of PEG and PEG/EVM, respectively. The results of Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and the thermal cycle test indicated that PEG-C/AEVM-3 reflected favorable chemical stability, thermal stability, and thermal reliability. Therefore, the prepared PEG-C/AEVM-3 with high latent heat and acceptable thermal conductivity was a promising composite PCM in the field of building energy storage.

Covalent Functionalization of Graphene for the Enhancement of Thermophysical Properties in Nanofluids

AbstractCovalent functionalization of graphene nanoparticles by autoclave, reflux‐condensation, and microwave‐assisted methods was performed. Nanofluids prepared by acidic functionalized graphene exhibit a higher dispersion stability than raw graphene. The thermal conductivity of nanofluids obtained by the microwave‐assisted method was higher than with other functionalization methods, and a signifcant maximum thermal conductivity enhancement compared to deionized water was achieved. Microwave‐assisted thermochemical synthesis is a highly effective energy‐saving method over other conventional approaches.

Nitrate based nanocomposite thermal storage materials: Understanding the enhancement of thermophysical properties in thermal energy storage

Molten salt is considered to be a significant medium of thermal energy storage (TES) used for concentrating solar power (CSP). Reasonably improving its thermophysical properties can realize the efficient utilization of solar energy. To investigate the effect of nanoparticle-doped molten salt, adding two size nano-alumina (NA, NA1 and NA2) with different content to solar salt (SS, with 60:40 ratio) by high temperature melting method. The using temperature zone had been broadened. For the same system, the specific heat (cp) of the solid was higher than that of the liquid. The maximum cp values in liquid of both systems appeared at the NA content of 0.5 wt%, corresponding to 1.71 J g−1K−1 and 1.84 J g−1K−1, respectively, which increased by 9.62% and 17.95% compared with the pure SS. Due to the high specific surface areas of NA1 and NA2, which were 151.3 m2 g−1 and 177.04 m2 g−1, respectively. And the higher surface tension (γ) of NA2-SS, which had a higher surface energy to improve the cp nanocomposites. The thermal conductivity (λ) increased with the content of NAs, increasing by 2.27% and 4.28%, respectively when the content of two NAs was 0.5 wt%. The content of NAs had little effect on viscosity (η). As a nitrate-based nanocomposite thermal storage material, it has great application prospects in TES, owing to its high cp and λ, widened operating temperature range and reliability.