Nanofluid Phase Change Material Research Articles

Thermal Energy Storage Using Hybrid Nanofluid Phase Change Material (PCM) Based on Waste Sludge Incorp Rated ZnO/α-Fe2O3.

Renewable solar energy storage facilities are attracting scientists' attention since they can overcome the key issues affecting the shortage of energy. A nanofluid phase change material (PCM) is introduced as a new sort of PCM is settled by suspending small proportions of nanoparticles in melting paraffin. ZnO/α-Fe2O3 nanocrystals were prepared by a simple co-precipitation route and ultrasonically dispersed in the paraffin to be a nanofluid-PCM. The behaviors of the ZnO/α-Fe2O3 nanocrystals were verified by X-ray diffraction (XRD) analysis, and the average particle size and the morphology of the nanoparticles were explored by transmission electron microscopy (TEM). For the object of industrial ecology concept, aluminum-based waste derived from water-works plants alum sludge (AS) is dried and augmented with the ZnO/α-Fe2O3 nanocrystals as a source of multimetals such as aluminum to the composite, and it is named AS-ZnO/α-Fe2O3. The melting and freezing cycles were checked to evaluate the PCM at different weight proportions of AS-ZnO/α-Fe2O3 nanocrystals, which confirmed that their presence enhanced the heat transfer rate of paraffin. The nanofluids with AS-ZnO/α-Fe2O3 nanoparticles revealed good stability in melting paraffin. Additionally, the melting and freezing cycles of nanofluid-PCM (PCM- ZnO/α-Fe2O3 nanoparticles) were significantly superior upon supplementing ZnO/α-Fe2O3 nanoparticles. Nanofluid-PCM contained the AS-ZnO/α-Fe2O3 nanocrystals in the range of 0.25, 0.5, 1.0, and 1.5 wt%. The results showed that 1.0 wt% AS-ZnO/α-Fe2O3 nanocrystals contained in the nanofluid-PCM could enhance the performance with 93% with a heat gained reached 47 kJ.

Experimental thermal performance of deionized water and iron oxide nanofluid for cold thermal storage.

Phase change materials enhance the thermal comfort of buildings by utilizing stored thermal energy. In large air-conditioning systems, ice storage plays a crucial role in managing peak power loads. This experimental study explores the freezing characteristics of deionized water containing suspended iron oxide nanoparticles in spherical containers for cold storage. The synthesized nanofluid phase change material (NFPCM) was investigated for its freezing behavior under surrounding fluid temperatures of - 2°C and - 6°C. The uniformity in charging of NFPCM is the unique feature prevalent in the first quarter of the charging, with 50% mass frozen observed. An increased surface heat flux of 200% was achieved using NFPCM at Tsurr = -6°C. The chiller operational time is optimally reduced by 75% by considering twice the container design's phase change materials. Adding iron oxide nanoparticles and partial charging is suitable for uniform heat transfer for the shorter freezing duration in cooling applications. The novelty of the present study is that the proposed NFPCM nearly nullifies the subcooling effects of deionized water without using nucleating agents. This NFPCM appreciably enhances power competence, yielding large-scale air-conditioning systems' desired economic impact and sustainability. The reported results align with Sustainable Development Goals (7-Affordable and Clean Energy and 13-Climate Action).

Influence of various surfactants on the stability and solidification characteristics of DI water-based CuO NFPCM for cool thermal energy storage system

The current study goals to investigate the stability and solidification characteristics of deionized water (DI water) based copper oxide (CuO) nanofluid phase change materials (NFPCMs) with a nucleating agent, different types of surfactants (SBDS, CTAB, and GA) and different weight concentration of surfactant for cool thermal energy storage systems (CTES). The stability of NFPCMs was assessed through average particle size distribution, zeta potential, and UV–vis absorbance. Among all NFPCMs, 0.1 wt% SDBS - CuO NFPCM showed prolonged stability with −42.7 mV and 212.6 nm of zeta potential and average particle size value. The heat transfer properties of NFPCMs were studied with differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA) and thermal conductivity measurements. The introduction of 0.05 wt% SDBS to NFPCM resulted in a notable 17.84 % and 7.64 % increase in thermal conductivity in solid and liquid states, with a slight decrease in latent heat by 5.2 % and 6.01 % during melting and crystallization as compared to DI water. The solidification experiments of NFPCMs were investigated in a spherical encapsulation at a surrounding bath temperature of −8 °C and − 10 °C. Comparing various surfactants in NFPCMs, the SDBS–CuO NFPCM was the most efficient in reducing the solidification time by 26.3 % and 28.4 % at −8 °C and − 10 °C respectively, compared to the nucleating agent PCM (NAPCM). Further, the different concentrations of SDBS in NFPCM demonstrated that 0.05 wt% SDBS–CuO NFPCM displayed the greatest reduction in solidification time, achieving 29.4 % and 27.7 % at −10 °C and − 8 °C, respectively, compared to the NAPCM.

Influence of various additives on stability and phase change characteristics of DI water-GnP-based NFPCM for cold thermal energy storage systems.

The present work aims to investigate the effects of various additives on the stability of graphene nanoplatelet (GnP)-based nanofluid phase change material (NFPCM) for cold thermal energy storage (CTES). The NFPCMs are prepared by dispersing six different types of surfactants (anionic, cationic, and non-ionictypes) in deionized (DI) water at a mass ratio of 1:0.5 GnP to surfactant. NFPCMs can be found to be stable with a suitable surfactant even after 30days using zeta-potential distribution, UV-vis absorption, visual inspection, and sedimentation tests at low temperature. The maximum enhancement in thermal conductivity of 8.3% and 48.3% is recorded in both liquid and solid states for the NFPCM with gum arabic (GA) respectively. The viscosity was enhanced by the dispersion of non-ionic surfactants, where the anionic surfactant (sodium dodecylbenzene sulfonate (SDBS)) NFPCM had a 29.9% lower augmentation compared to DI water. Furthermore, differential scanning calorimetry (DSC) results demonstrate that the phase change properties of the NFPCM are significantly affected depending on the surfactant type. The maximum phase change enthalpy is lowered (10.6%) in the Tween 80 NFPCM as compared to the base PCM. The long-term stability with the highest thermal transport property of the NFPCM storage unit integrated with the chiller is capable of achieving environmental pollution remediation by minimising the time it takes to charge the PCM.

Effect of active multi-walled carbon nanotubes (MWCNT) on the energy storage density of DI water for cool thermal storage system.

The present research work aims to investigate the energy saving aspects in cool thermal energy storage system (CTES) by improving the thermophysical properties of deionized (DI) water. The influence of phase change enthalpy, specific heat, thermal conductivity, and cooling rate of the DI water for the dispersion of chemically functionalized multi-walled carbon nanotubes (f-MWCNT) is studied experimentally. The covalent functionalization method is used to modify the surface of the multi-walled carbon nanotubes (MWCNT) with the use of concentrated nitric acid. The nanofluid phase change materials (PCMs) in different mass concentrations (0.25%, 0.50%, and 0.75%) were prepared by dispersions of the f-MWCNT in DI water. The minimum reduction in enthalpy (4.01%) was recorded for the nano-PCM with 0.75% f-MWCNT as compared to the base PCM with 0.5% of sodium dodecyl benzene-sulfonate (10%). The thermal conductivity enhancement of 53.15% and 28.2% was recorded in both states for the nano-PCM (with 0.75%) at the temperature of - 10°C and 5°C respectively. Also, the enhancement of 30% and 23% in cooling rate is recorded for the dispersion of maximum concentration of f-MWCNT at the HTF temperatures of - 8°C and - 6°C, respectively. It is proven from the above findings that the dispersion of f-MWCNT reduces the subcooling and facilitates the running of the CTES system at a higher operating temperature.

Influence of surfactants on the performance enhancement of water-based gamma Al2O3 phase change material for cool thermal energy storage system

The current work investigates the effect of various surfactants on the performance enhancement of water-based gamma Al2O3 PCM (Phase change material) during the solidification process suitable CTES (cool thermal energy storage) system. Two surfactants, one from cationic group (CTAB – cetyl trimethyl ammonium bromide) and other from anionic group (SDBS – sodium dodecylbenzene sulfonate) are selected for this study. Both the nanoparticles and surfactants with 0.1 wt% are dispersed in the base fluid. The freezing experiments were conducted at various surrounding bath temperatures of −6 ℃, −9 ℃ and −12 ℃. The outcomes reveal a reduction in subcooling, advanced onset of solidification and increased heat transfer performance by use of nanofluids. Further it is noted that the performance is also influenced due to the surfactant. The anionic surfactant NFPCM (nanofluid phase change material) displace better performance than cationic surfactant NFPCM during the solidification process. The enhanced performance of NFPCM will pave the way to design an energy efficient CTES system.

Thermal management of lithium-ion batteries with simultaneous use of hybrid nanofluid and nano-enhanced phase change material: A numerical study

In this study, a battery pack consisting of cylindrical cells connected to a solar system is investigated numerically. Using solar energy in an electric car requires storing energy in the battery, and the device that can do this is a charger. In this research, a charge is designed to charge the battery at different rates. Also, the combination of hybrid nanofluid (NF) and nano-enhanced phase change material (PCM) is employed to cool battery cells. The finite element method (FEM) is employed to perform the simulations. The results showed that the simultaneous use of hybrid NF and nano-enhanced PCM entails an increase in the heat transfer rate and a decrease in the time required for complete melting and solidification of PCM. The results also show that the Nu increases before the onset of phase change by increasing the volume ratio of nanoparticles (NPs). On the other hand, it was observed that using a tube with a circular cross section to charge PCM improves the its freezing process up to 10.7%. Moreover, increasing the volume percentage of nanoparticles (VPNPs) reduce the battery temperature by up to 0.5% for the circular tube, while this change is 0.37% for the elliptical tube.

Solidification behavior of water based Al2O3 nanofluids phase change material for energy efficient cool thermal storage system

The present study aims to investigate the solidification behavior of water based Al2O3 nanofluid phase change material encapsulated in a spherical capsule suitable for cool thermal energy storage application. The nanofluid phase change material is prepared by dispersing the Al2O3 nanoparticles mixed with DI water, which is used as a base phase shift material with a volume fraction of 0.1 %. The experiments are conducted with DI water and the Al2O3 nanofluid phase change material at surrounding bath temperatures of -6,-9 and -12 °C respectively. The presence of Al2O3 acts as a nucleating agent that causes an elimination in under cooling. The enhanced thermal properties of the Al2O3 are very useful to dissipate the concealed heat faster and helps to operate the CTES at higher operating temperature for a lesser duration, when compared with PCM where the nucleating agent is absent. So, this act fetches an energy-saving potential.

A neural network approach to estimate non-Newtonian behavior of nanofluid phase change material containing mesoporous silica particles

Neural networks are powerful tools for evaluating the thermophysical characteristics of nanofluids to reduce the cost and time of experiments. Dynamic viscosity is an important property in nanofluids that usually needs to be accurately computed in heat transfer and nanofluid flow problems. In this paper, the rheological properties of nanofluid phase change material containing mesoporous silica nanoparticles are predicted by the artificial neural networks (ANNs) method based on the experimental database reported in literature. Experimental inputs include nanoparticle mass fractions (0-5 wt.%), temperatures (35-55℃), and shear rates (10-200 s-1), and targets include dynamic viscosities and shear stresses. A multilayer perceptron feedforward neural network with Levenberg-Marquardt back-propagation training algorithm is utilized to predict rheological properties. The optimal network architecture consists of 22 neurons in the hidden layer based on the minimum mean square error (MSE). The results showed that the developed ANN has an MSE of 6.67×10-4 and 6.55×10-3 for the training and test dataset, respectively. The predicted dynamic viscosity and shear stress also have the maximum relative error of 6.26% and 0.418%, respectively.

Role of graphitized mesoporous carbon on solidification and melting characteristics of water for cool thermal storage

Cool thermal energy storage systems (CTES) using phase change materials (PCM) are paramount in the energy management of buildings. This work aims to investigate the role of graphitized mesoporous carbon (GMC) on the thermal storage behavior of water based nanofluid PCM (NFPCM) in a spherical capsule. The NFPCMs exhibit a lower contact angle, indicating a reduction in the nucleation energy barrier. Thermal conductivity of NFPCM shows an enhancement of 36% with the presence of graphitized walls and isotropic nature of GMC. Temperature–time history method is used to evaluate the latent heat of fusion for the NFPCMs and the results are compared with differential scanning calorimetry measurements. Addition of GMC shortens the solidification duration by 6% and reduces the subcooling of NFPCM compared to base PCM. The charging results of NFPCMs demonstrate a cool energy storage of 96% in accelerated mode. The melting rate of NFPCM is expedited at a minimal GMC concentration and melting duration prolongs with further GMC addition. In conclusion, the proposed NFPCMs exhibiting a lower subcooling, improved nucleation behavior and accelerated mode of charging shows great potential for CTES applications.

Enhancement of thermophysical coefficients in nanofluids: A simulation study

Molten salts constitute one kind of PCMs (Phase Change Materials) widely used in concentrating solar power facilities for heat storage and heat transfer. This paper aims to simulate nanofluid PCMs with molecular dynamics method. Concretely, the thermophysical properties of a nanofluid of KNO3 doped with SiO2 nanoparticle are investigated by equilibrium and nonequilibrium molecular dynamics simulations. For the first time, these properties of a nanofluid in the family of PCMs are calculated. The density, thermal expansion coefficient, specific heat capacity, thermal conductivity, and viscosity are characterized as functions of the SiO2 nanoparticle concentration. The effect of the SiO2 nanoparticle size on the nanofluid’s properties is also investigated. The simulation results present an enhancement of the thermophysical properties, especially for the specific heat capacity, in good agreement with the existing experimental results on a representative nanofluid PCM, and open prospects for the understanding of microscopic mechanism leading to such enhancements.

Experimental Study on GNP Based Nanofluid Phase Change Material for Cooling Application

The current study aims to analyze the solidification and melting characteristics of nanofluid phase change material (NFPCM) for building cooling applications. The NFPCM were prepared by using graphene nanoplatelets (GNP) in different concentrations (0.2, 0.4 & 0.6 Wt. %) and DI water as base PCM. The NFPCM was prepared using two step methods and stability of the NFPCM was analyzed using visual sedimentation method. The experimentation was conducted in -12 °C and -9 °C surrounding bath temperatures. The Sub-cooling was eliminated completely for the addition of SDBS and GNP in maximum concentration. The experimental results showed that the 10 % and 8.5 % reduction in solidification time for 0.6 wt. % GNP in base PCM for the surrounding bath temperature of -12 °C and -9 °C respectively. Also, the DSC analysis was conducted for the heating rate of 5 K/min and the reduction of enthalpy during heating and cooling was noticed 14 % and 11 % respectively. It is observed that the reduction of overall solidification time of the NFPCM will have the predominant effect in the chiller operation time.

Experimental investigation on reducing the solidification time of NFPCM by reducing sub cooling for different heat transfer fluid temperature for cooling applications

This study aims to investigate the solidification characteristics of water based nanofluid NFPCM (Nanofluid phase change material) with an aim to form an efficient CTES (Cool Thermal Energy Storage) system. Here we have taken base PCM as deionized water and Graphene is taken as nanoparticle because of its property of high thermal conductivity. The PCM was prepared by adding surfactant (0.2wt%) which is used to reduce the surface tension of the solution and then various concentration of graphene nanoparticle are added i.e. 0.2wt% and 0.4wt%, and the effect in solidification time and reduction of sub cooling is seen and studied. The enhanced heat transfer rate of NFPCM without sub cooling is advantageous for many CTES applications. So, finally it is constructed from experimental results that by embedding this technology with chiller systems which is used to cool large spaces can help us to conquer our motive to save energy and provide effective and efficient cooling.

Dynamic tuning of magnetic phase change composites for solar-thermal conversion and energy storage

Photo-thermal conversion and energy storage using phase change materials are now being applied in industrial processes and technologies, particularly for electronics and thermal systems. This method relies on adding high thermal conductivity fillers, such as nanoparticles, to enhance the phase change process. In the long term, dynamic tuning heat transfer provides a superior means of tuning control the heat transfer efficiency and speed. In this study, a nanofluid phase change material was prepared by adding magnetic nanoparticles, effectively combining the properties of high thermal conductivity and magnetism, in an attempt to develop a magnetically enhanced approach for dynamic tuning of photo-thermal conversion charging. Our results showed that the phase change efficiency of magnetic phase change material can be improved by magnetic field application. With the increasing magnetic strength, the photo-thermal storage efficiency was enhanced, and storage capacity was improved by more than 48%. Meanwhile the steady temperature of the magnetic phase change material increased, enhancing the open-circuit voltage in photo-thermoelectricity experiments. Thus, the proposed method demonstrated in this study achieved superior phase change heat transfer characteristics within a photo-thermal conversion process by dynamically controlling the magnetic field distribution, which should be especially useful for direct solar energy utilisation.

Preparation of a low-temperature nanofluid phase change material: MgCl2–H2O eutectic salt solution system with multi-walled carbon nanotubes (MWCNTs)

Abstract With the rapid development of cold chain logistics, there is a growing demand for refrigerated transportation equipment for low-temperature products, such as fresh products, chemical supplies and medical vaccines. For some products with low transport temperatures, phase change materials (PCMs) from −10 C to −40 °C are still to be developed. This paper focuses on the development of a low phase transition temperature nanofluid phase change materials (NFPCMs) with excellent thermodynamic properties, simple preparation method and low cost. 23 wt% MgCl2 eutectic solution was used as phase change material in the NFPCMs, in which Multi-walled carbon nanotubes (MWCNTs) and nucleating agents play a supportive role to reduce supercooling degree. At that, the addition of MWCNTs increases the thermal conductivity and thickener xanthan gum (XG) can prevent phase separation and agglomeration. The NFPCM with 1 wt% MWCNTs has a phase transition temperature of −34.54 °C, a phase transition enthalpy of 146.9 kJ kg−1, and thermal conductivity of 0.5344 W (m k)−1. Also, under the synergistic action of MWCNTs with CaCl2 and Ca(OH)2, the supercooling degree of NFPCM decreased to 1.82 °C, which was 89% lower than that of the pure eutectic salt solution. Furthermore, the NFPCMs still showed excellent stability after 400 thermal cycles. The results show that the NFPCMs has high latent heat, higher thermal conductivity, low supercooling degree and excellent thermal stability, which makes it have practical application value and broad development prospects in the field of the cold chain.

Experimental models to estimate supercooling behavior of ZrO2 nanofluid phase change materials

The present research experimentally introduces novel corrective models to facilitate comparison and evaluation of the supercooling degree and critical nucleation radius of nanofluid phase change materials with surfactant. A dimensionless number (C parameter) is applied in the predictive models considering the essential thermophysical properties effective on solidification behavior (i.e., thermal conductivity, kinematic viscosity and surface tension). Based on theoretical analysis, the C parameter is defined and finally validated with experimental data. It is found that the models are capable of precise estimation. It is also observed that the C parameter is an effective factor on ratios of solidification characteristics, such as ratios of supercooling degree and critical nucleation radius, which can be extended to other characteristics.

Solar thermal conversion and thermal energy storage of CuO/Paraffin phase change composites

A nanofluid phase change material (PCM) is prepared by adding a small amount of CuO nanopowders to paraffin, for use in solar thermal conversion, thermal storage, and thermoelectric applications. Results show that adding CuO nanopowders to paraffin can greatly improve the solar thermal conversion capacity by enhancing the light absorption ability of PCMs. The steady temperature increased with increasing mass fraction of CuO NPs at low mass concentrations (0–0.1%). The largest increase was about 2.3 times that of the pure paraffin with comparable latent heat. In the solar thermoelectricity experiments, the open-circuit voltage improved (1.35 V) with the CuO/Paraffin composite (fm = 0.1%) under the same conditions, and was almost 1.8 times that of the pure paraffin. More importantly, a unique feature of the CuO/Paraffin composite PCM is the extension of thermal release, which enables the continuation of the voltage output when the solar simulator is switched off. The introduction of a very low mass concentration of CuO nanopowders can endow the composite PCMs with strong solar absorption ability, and contribute to realizing efficient solar thermal and solar thermoelectric energy conversion and storage. This provides a new prospect for solar radiation usage efficiency and direct solar energy conversion and utilization.

Investigation of specific heat and latent heat enhancement in hydrate salt based TiO2 nanofluid phase change material

In this study, the enhancements of specific heat and latent heat of inorganic hydrate salt based nanofluid phase change material were reported. The samples were prepared by incorporating TiO2 nanoparticles with different mass fractions (0.1, 0.3, and 0.5wt%) into the eutectic hydrate salt (EHS). The phase change enthalpy and specific heat capacity were measured by differential scanning calorimeter (DSC). The results showed that the loading of 0.3wt% TiO2 nanoparticles can increase specific heat by up to 83.5% and latent heat up to 6.4%. Moreover, the optical microscopy on crystal configuration confirmed the increase of solid specific heat and the corresponding mechanism. The interaction between EHS and TiO2 nanoparticles, which was responsible for elevation of phase change temperature, was revealed by Raman spectra. The chemical thermodynamics gave an explanation for latent heat improvement. These findings suggested that hydrate salt based TiO2 nanofluid offered a promising route for the achievement of high heat energy storage targets of hydrate salt phase change materials.

Solidification characteristics of water based graphene nanofluid PCM in a spherical capsule for cool thermal energy storage applications

This study aimed to investigate the solidification behavior of water dispersed with graphene nanoplatelets (GNPs) in a spherical container during solidification. The nanofluid phase change materials (NFPCMs) with GNP mass concentrations of 0.3%, 0.6%, 0.9% and 1.2% were prepared and their corresponding thermal conductivity was measured both in liquid and solid states. The thermal conductivity data showed the linear and nonlinear enhancement in liquid and solid state, respectively. The addition of GNPs resulted to an appreciable reduction in the subcooling of water from −7 °C to −2.5 °C along with reduction of 25% in solidification time owing to its high thermal conductivity and larger specific surface area. The onset of solidification got advanced in the case of NFPCM due to higher cooling rate in the subcooling region for any given driving potential. The accelerated mode of energy charging occurred during 78% of total solidification time.

Nanofluids: An innovative phase change material for cold storage systems?

An analytical approach is used to solve a contact melting problem where an alumina-water nanofluid is used as the phase change material. The mathematical model describing the process is reduced to three ordinary differential equations which are solved by means of the Heat Balance Integral Method. The melt front separating the solid and liquid constituents that possess different thermophysical problems (dependent on nanoparticle volume fraction) is tracked. The liquid height, solid height, total melt and melt rates are determined, as well as times to the onset of melting and melt completion. The results for both base fluid and nanofluid are compared, showing that the nanofluid phase change material may not be more efficient at releasing energy and that the efficiency is dependent on system size.