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MXene-based nanofluids are novel trends with improved dispersion stability and thermophysical characteristics over previously established nanofluids. In the present work, the thermohydraulic characteristics of a double pipe heat exchanger (DPHEX) with a Therminol55(TH55)/MXene + Al2O3 nanofluid and various geometrically shaped (triangular, rectangular) ribbed twisted tape (TT) inserts are numerically investigated using the ANSYS Fluent interface. A counter flow arrangement with three different types of inserts (RRTT, TRTT, TT) and TH55/MXene + Al2O3 nanofluid at 0.20 wt% are studied inside the heat exchanger. Adding ribbed inserts to the conventional TT insert enhances the turbulence intensity by creating extra vortices. The thermal boundary layer grows thinner due to increased axial and radial velocity. Due to the substantial flow obstruction, adding ribs increases the overall pressure drop between the inlet and outlet. The maximum increase in Nu is 11.04 % using nanofluid instead of water, whereas the combination of insert and nanofluid exhibited up to 105 % enhancement for rectangular-ribbed TT compared to the plain tube. Nevertheless, the pressure decrease is found to be maximum in rectangular-ribbed TT because of significant flow disruption. This was likewise true with triangular-ribbed TT and TT insert. According to the PEC assessment, the RRTT insert had a maximum PEC value of 1.67 greater than TRTT and traditional TT for both TH55 and nanofluid flowing inside the tube. To summarize, the combination of TH55/MXene + Al2O3 RRTT insert may be a promising choice for improving heat exchanger performance in a new generation efficient thermal system. © 2023 The Authors

The present study numerically investigates the optimization of thermal performance in a dimpled channel using a promising genre of nanofluid which is equipped with the inclusion of two-dimensional (2D) MXene (Ti3C2) nanoparticles to the soybean oil. The stream-wise and span-wise variation of the spherical dimples was kept 3.00 and 3.15 over the flow domain with an elongation of 2.5 mm. The detailed evaluation of both the local and global parameters is carried out for 0.025%, 0.075%, and 0.125% mass concentrations of MXene. The Reynolds number is varied from 1000 to 6000 to understand the effect of both the laminar and turbulent flow characteristics in predicting the thermal performance. The simulations are carried out using finite volume method (FVM) under constant heat flux, assuming the mixture of nanoparticles as homogeneous mixture. The results show that with the increase in the mass concentration of nanoparticles, thermal performances of the nanofluid increase. However, it is also identified that with the increase in Reynolds number, the thermal performance increases under turbulent flow regime. On the contrary, thermal performance was observed to be decreased with the increase in Reynolds number under laminar flow regime. An astounding improvement in 88.9% thermal performance is found for 0.125% mass concentrations of soybean-based MXene nanofluid which exclusively indicates the credibility of MXene nanofluid as a next generation potential candidate for heat exchanger industries.

Brackish water desalination using solar still (SS) is a low-cost sustainable solution to global water scarcity, but this technology suffers from low yield and efficiency. The judicious amalgamation of highly conductive materials with superior solar absorption behavior is one of the most effective approaches to overcome this limitation. In this regard, the present work synthesizes a novel multilayered 2-D MXene from 3-D MAX phase as a coating material for the solar absorber of a SS to improve its performance. Two different loadings of MXene (0.05 and 0.1 wt%) were dispersed in turpentine oil/black paint (1:4) and coated onto the solar absorber of the SS. Higher MXene loading significantly augmented the thermal conductivity and solar absorptivity of the turpentine oil/black paint solution. The 0.1 wt% MXene coated absorber provided a higher heat transfer rate from the absorber to the water, leading to a 6% increase in water temperature and a total water yield of 2.07 kg. The theoretical calculated water yield was identical to the experimental yield with a deviation of ±5%, demonstrating the accuracy of thermal modelling. The average energy efficiency of the SS with 0.1 wt% MXene in the absorber black paint coating was 36.31%. Water quality analysis has shown that the distilled water resulting from the desalination is suitable for drinking. In conclusion, MXene with its excellent thermo-physical properties and solar absorptivity will be beneficial in development of efficient solar desalination units with augmented performance for water purification.

In this research work, novel hybrid graphene-silver (Gr-Ag) nanomaterial has been used for first time with paraffin wax as a phase change material (PCM) to improve its thermo-physical properties. Thermal and electrical energy efficiencies of the novel synthesized nanocomposite (PCM/graphene-silver) has been investigated in solar thermal collector systems (CPV/T). This paper focuses on preparation, characterization, thermo-physical properties and energy efficiency in concentrated photovoltaic/thermal (CPV/T) system of new class of nanocomposites induced with hybrid Gr-Ag nanomaterial in three different concentrations. The specific heat capacity (cp) of hybrid PCM/graphene-silver nanocomposite increased by introducing hybrid Gr-Ag nanomaterial. Electrical and thermal energy performance of the hybrid PCM/graphene-silver is investigated in a CPV/T system using MATLAB 2017b program. The improvement of cp is found to be ~ 40% with 0.3 mass% of hybrid Gr-Ag nanomaterial loaded in PCM. The highest thermal conductivity increment is found to be ~ 11% at 0.3 mass% concentration of hybrid Gr-Ag nanomaterial in PCM. The endothermic enthalpy value of the hybrid PCM/graphene-silver nanocomposite is found to be ~ 75.6 J g−1 at 0.1 mass% loading concentration of hybrid Gr-Ag nanomaterial. Melting point of hybrid PCM/graphene-silver nanocomposite with loading concentration of 0.3 mass% is measured to be 73.2 °C. The highest thermal efficiency using the hybrid graphene-silver nanoparticles reached the value of 39.62% which represents 4.16% increment in comparison with the pure PCM. The equivalent electrical efficiency is improved by 2.8% at the loading concentration of 0.3 mass% of the hybrid Gr-Ag nanomaterial. These new class of nanocomposites represented the capability of enhancement in the performance of the CPV/T system consisting of lower PV temperatures, higher temperature gains across the cooling fluid and higher electrical and thermal efficiencies.

The purpose of this experimental research is to develop a new class of nanofluid as a replacement of conventional water based nanofluid for medium temperature range as PV/T coolant application. For the first time, hybridized Al2O3 + CuO nanoparticles were dispersed into the binary mixture of ionic liquid (IL) and diethylene glycol (DEG) without the addition of any stabilizing agents or surfactants. The formulated Ionanofluid posed excellent dispersion stability together with better thermal stability compared to water-based nanofluid, as evidenced from thermogravimetric analysis. The experimental thermal conductivity assessment showed a maximum of 41.8 % enhancement together with a 31 % penalty in pressure drop at 0.15 wt% concentration. A hybrid PVT system is constructed to numerically examine the effect of Ionanofluid as an active cooling medium under the COMSOL Multiphysics environment. Ionanofluids as coolants in a PVT panel showed a maximum of 69 % thermal efficiency at 0.15 wt% Al2O3 + CuO, higher than 63 % (0.10 wt% Al2O3 + CuO), 58 % (0.05 wt% Al2O3 + CuO), and 56 % (pure IL + DEG). The PV panel temperature was reduced from 65 to 40 °C when IL + DEG was replaced with 0.15 wt% Al2O3 + CuO. At the same concentrations, an electrical efficiency of nearly 12.7 % was observed, representing a 29.91 % improvement over IL + DEG at a flow rate of 4LPM. The formulated Ionanofluid performed thermally better than water but somewhat lower than water-based nanofluids like MWCNT/Water. Nevertheless, Ionanofluid's electrical efficiency was better than MWCNT/Water. Ionanofluid can be a viable alternative to water-based nanofluids for medium-temperature-based coolant applications.

The present study numerically investigates the optimization of thermal performance in a dimpled channel using a promising genre of nanofluid which is equipped with the inclusion of two-dimensional (2D) MXene (Ti3C2) nanoparticles to the soybean oil. The stream-wise and span-wise variation of the spherical dimples was kept 3.00 and 3.15 over the flow domain with an elongation of 2.5 mm. The detailed evaluation of both the local and global parameters is carried out for 0.025%, 0.075%, and 0.125% mass concentrations of MXene. The Reynolds number is varied from 1000 to 6000 to understand the effect of both the laminar and turbulent flow characteristics in predicting the thermal performance. The simulations are carried out using finite volume method (FVM) under constant heat flux, assuming the mixture of nanoparticles as homogeneous mixture. The results show that with the increase in the mass concentration of nanoparticles, thermal performances of the nanofluid increase. However, it is also identified that with the increase in Reynolds number, the thermal performance increases under turbulent flow regime. On the contrary, thermal performance was observed to be decreased with the increase in Reynolds number under laminar flow regime. An astounding improvement in 88.9% thermal performance is found for 0.125% mass concentrations of soybean-based MXene nanofluid which exclusively indicates the credibility of MXene nanofluid as a next generation potential candidate for heat exchanger industries.

In this study, the heat transfer performance of [MMI][DMP] ionic liquid solution (20 vol% IL + 80 vol% deionized water) in the presence of Mxene nanoparticle is investigated based on computational fluid dynamics numerical method considering temperature-dependent properties. It should be noted that the thermophysical properties of IoNanofluid were experimentally measured in our previous published study. The modeling results are validated with numerical and experimental works, and the validation results indicate good agreement between them. The effect of adding Mxene nanoparticle to the base liquid was carried out in a horizontal tube with 1–50 range of Reynolds number. The results found that the heat transfer coefficient increased by increasing the Reynolds number and also the nanofluids’ concentration. Moreover, it raises by increasing the fluid inlet temperature while the Nu number decreases. This is because the Nusselt number is in a reverse relationship with the heat transfer coefficient. The maximum heat transfer coefficient observed for 0.2 mass% INf at 308 K fluid inlet temperature and Reynolds number of 50 was 2207.83 W m 2 K −1. However, the maximum Nusselt number detected for pure base fluid at 298.15 K fluid inlet temperature and Reynolds number of 50 was 13.22. Furthermore, the maximum heat transfer enhancement was observed for 0.2 mass% INf at Reynolds number of 50 and 308.15 K fluid inlet temperature (43.6%). Finally, a novel correlation is proposed to estimate the Nusselt number of nanofluids with R 2 = 0.992 and AREP = 2.8%.

In the last decade, nanofluids have set significant milestones as efficient working fluids in the field of solar energy conversion to meet rising energy demand. Research on thermophysical properties, long-term stability, and rheology is progressing to achieve effective practical deployment of nanofluids in renewable solar photo-thermal energy conversion sectors (i.e., solar collectors). Nonetheless, researchers and engineers are having a difficult time coping with nearly infinite culpable variables influencing the output of various types of nanofluids. This paper aims to provide an up-to-date analysis of the developments and challenges of widely used water-based nanofluids, with a focus on formulation methods, main properties (thermophysical, stability, and rheological), and effective implementation in low temperature solar collector systems. Previous experimental and numerical studies on the subject have been compiled and thoroughly scrutinized, providing crucial phenomena, mechanisms, flaws, and responsible parameters for achieving stable and optimized thermal properties that integrate with heat transfer performance. It has been discovered that optimizing the critical factors leads to superior behavior of the nanofluids, which results in improved thermal efficiency of the solar collectors. Finally, emerging concerns are identified, as are potential recommendations to resolve existing problems in the field for future advancement that would mobilize rapid progress and practical engineering use of water based nanofluids on solar collectors. © 2021 Elsevier B.V.

To meet the growing energy demand, double pipe heat exchangers (DPHEX), which are used in a variety of energy and thermal engineering applications, require improved heat transfer performance. In this study, a new class of surfactant-free Ionanofluid is formulated at three different concentrations of 0.01, 0.05 and 0.10 wt% and thermophysical and rheological properties are assessed. Zeta potential analysis is executed to assess the dispersion stability. An optimum concentration has been selected to investigate the hydrothermal performance of an insert fitted DPHEX at varying Re from 400 to 2000. The conventional twisted tape (TT) insert is modified by introducing different types of geometrical (triangular, rectangular, and circular) cuts on its surface. According to the Ionanofluid characterization, 0.10 wt % Ionanofluid has the highest thermal conductivity enhancement of 64% and heat capacity of 16.1% when compared to the base fluid, with a maximum enhancement in Nu of about 116–136% at varying Re. The rectangular-cut TT imparts highest heat transfer enhancement as the additional vortices is more intensive than other cut-inserts. Nevertheless, the value of PEC for the combination of Ionanofluid and RCTT insert, remaining between 1.61 and 1.68 over the entire range of Re, is greater than other combinations.

The objective of the present research work is to investigate a novel high-efficiency nanofluid in a solar dish concentrator by using the numerical model developed. The working fluids examined consisted of soybean oil-based MXene nanofluid of different concentrations (i.e. 0.025, 0.075 and 0.125 wt%) and pure soybean oil. The studied nanofluids yielded excellent thermal properties such as high thermal conductivity and heat capacity, which were two particular factors rendering them excellent candidates for solar thermal applications. The solar dish collector was evaluated for three different cavity receivers including cubical, hemispherical and cylindrical shapes. Then, thermal analysis was performed with a developed numerical model in steady-state conditions, which was validated by using experimental results. Meanwhile, the thermal properties of the oil-based nanofluid were described after the experiments. The analysis was parametric in nature, thereby studying the system performance on a daily basis. According to the analysis, the hemispherical cavity receiver led to maximum thermal efficiency with the nanofluid used. In particular, the daily mean thermal efficiency with nanofluid of 82.66% and the mean equivalent efficiency of 82.46% were achieved, while the mean enhancement was 0.6%. However, the enhancements were higher with the use of other cavities due to the higher thermal losses shown in such cases. Moreover, the equivalent efficiency proved that the increased pumping work due to the use of nanofluid could not overcome the thermal enhancement, thereby improving the overall performance of the solar collector.

Nanofluids have exhibited noteworthy advancement as efficient working fluids in the last decade towards the field of solar energy conversion field to deal with escalating global energy demand. Research developments on thermo-physical, long-term stability and rheology are moving ahead to achieve practical deployment in renewable solar photo-thermal conversion sectors (i.e., solar collectors). Nevertheless, researchers and engineers are encountering many difficulties dealing with nearly infinite culpable variables impacting performance of several categories of NFs. This work attempts to offer an up-to-date review on advances and challenges of oil-based nanofluids focusing on formulation, key properties (stability, thermal conductivity, cp, and viscosity) and effective implementation in concentrating solar collector devices. Previous experimental and numerical studies on the topics are compiled and acutely scrutinized providing essential phenomena, mechanisms, shortcomings, responsible parameters to obtain stable and optimized thermal properties integrating with heat transfer performance. It is observed that optimization of the critical factors leads to superior behavior of the nanofluids, which in turns generates enhanced thermal performance of the solar collectors. Lastly, existing challenges are reported along with recommendations to address the issues for further developments in the field which would mobilize rapid innovation and practical engineering practice of nanofluids.

The counter electrode (CE) containing catalyst layer and transparent conducting oxide (TCO) layer is by far the most expensive components in Dye sensitized solar cells (DSSC) due to use of rare earth element such as Pt. The potential replacement of both the TCO layer and Pt-based catalyst would essentially pave the way to mass commercialization of the technology of DSSC. In this investigation, an attempt has been made to replace both TCO and Pt with a single layer of delaminated 2-D MXene (Ti3C2) being produced by the leaching method which acted as both conducting layer and catalyst. Furthermore, the thickness of Ti3C2 has been optimized for maximum conversion efficiency. The TCO-Pt-free MXene based CEat optimum thickness exhibited a remarkable 8.68% conversion efficiency outperforming the standard TCO-Pt-based CE by 4.03%. The high efficiency is due to high conductivity, high available catalytic cites due to delaminated structure, and good catalytic activity of Ti3C2 towards iodide/triiodide electrolyte. © 2021 Elsevier Ltd and Techna Group S.r.l.

Reasoning of particular mechanism of anomalous thermal transport behaviors is not identified yet for the nanofluids. In this research, the thermal conductivity of maghemite (MH) nanoparticles dispersed deionized water (DW) nanofluids (MH/DW) has been evaluated for the first time using the modified effective medium theories (EMTs). EMTs have been modified with the consideration of static and dynamic effects combinedly for the analysis of anomalous behaviors of thermal conductivity enhancements of the spherical nanoparticles dispersed nanofluids. MH nanoparticles (~20 nm) were synthesized using chemical co-precipitation techniques. MH/DW nanofluids were prepared with the varying MH nanoparticles loading in DW and thermal conductivity was measured using KD2 pro device. The thermal conductivity enhancement (~32 %) was found to be increased linearly with the increasing MH nanoparticle concentration and nonlinearly with the increasing temperature. Existing Maxwell and Maxwell Gantt EMA (MG-EMA) models exhibited awful under-prediction from experimental thermal conductivities of MH/DW nanofluids. Modified model with considering static and dynamic mechanisms of MH nanoparticles combinedly showed reasonably very good agreement with the experimental thermal conductivities of MH/DW nanofluids at elevated temperature. This modified model opens the new windows to analyze the insight of the thermophysical properties of various types of nanofluids by introducing potential parameters.

Back-propagation modeling of viscosity and shear stress of Ionic-MXene nanofluid is carried out in this work. The data for Ionic-MXene nanofluid of 0.05, 0.1, and 0.2 mass concentration (mass%) are collected from the experimental analysis. Shear stress and viscosity as a function of shear rate and mass% of MXene nanoparticles is used as input. Additionally, viscosity as a function of temperature and % of MXene nanoparticles is collected separately. Based on the possible combinations, five back-propagation algorithms are developed. In each algorithm, five models depending upon the number of neurons in the hidden layer are used. The training and testing of all the models in each algorithm are performed. Statistical analysis of the network output is done to evaluate the accuracy of models by finding the losses in terms of mean squared error (MAE), root-mean-squared error, mean absolute error, (MAE), and error deviation. Model 1 is found to have lower accuracy than the remaining models as the number of neurons in its hidden layer is only one. The performance evaluation metrices of the back-propagation model show that the error involved is acceptable. The training and testing of the algorithms are satisfactory as the network output is found to be in comfortably good agreement with the desired experimental output.

Research shows that due to enhanced properties IoNanofluids have the potential of being used as heat transfer fluids (HTFs). A significant amount of experimental work has been done to determine the thermophysical and rheological properties of IoNanofluids; however, the number of intelligent models is still limited. In this work, we have experimentally determined the thermal conductivity and viscosity of MXene-doped [MMIM][DMP] ionic liquid. The size of the MXene nanoflakes was determined to be less than 100 nm. The concentration was varied from 0.05 mass% to 0.2 mass%, whereas the temperature varied from 19 °C to 60 °C. The maximum thermal conductivity enhancement of 1.48 was achieved at 0.2 mass% and 30 °C temperature. For viscosity, the maximum relative viscosity of 1.145 was obtained at 0.2 mass% and 23 °C temperature. After the experimental data for thermal conductivity and viscosity were obtained, two multiple linear regression (MLR) models were developed. The MLR models’ performances were found to be poor, which further called for the development of more accurate models. Then two feedforward multilayer perceptron models were developed. The Levenberg–Marquardt algorithm was used to train the models. The optimum models had 4 and 10 neurons for thermal conductivity and viscosity model, respectively. The values of statistical indices showed the models to be well-fit models. Further, relative deviations values were also accessed for training data and testing data, which further showed the models to be well fit.

Since technology progresses, the need to optimize the thermal system’s heat transfer efficiency is continuously confronted by researchers. A primary constraint in the production of heat transfer fluids needed for ultra-high performance was its intrinsic poor heat transfer properties. MXene, a novel 2D nanoparticle possessing fascinating properties has emerged recently as a potential heat dissipative solute in nanofluids. In this research, 2D MXenes (Ti3C2) are synthesized via chemical etching and blended with a binary solution containing Diethylene Glycol (DEG) and ionic liquid (IL) to formulate stable nanofluids at concentrations of 0.1, 0.2, 0.3 and 0.4 wt%. Furthermore, the effect of different temperatures on the studied liquid’s thermophysical characteristics such as thermal conductivity, density, viscosity, specific heat capacity, thermal stability and the rheological property was experimentally conducted. A computational analysis was performed to evaluate the impact of ionic liquid-based 2D MXene nanofluid (Ti3C2/DEG+IL) in hybrid photovoltaic/thermal (PV/T) systems. A 3D numerical model is developed to evaluate the thermal efficiency, electrical efficiency, heat transfer coefficient, pumping power and temperature distribution. The simulations proved that the studied working fluid in the PV/T system results in an enhancement of thermal efficiency, electrical efficiency and heat transfer coefficient by 78.5%, 18.7% and 6%, respectively.

Reasoning of particular mechanism of anomalous thermal transport behaviors is not identified yet for the nanofluids. In this research, the thermal conductivity of maghemite (MH) nanoparticles dispersed deionized water (DW) nanofluids (MH/DW) has been evaluated for the first time using the modified effective medium theories (EMTs). EMTs have been modified with the consideration of static and dynamic effects combinedly for the analysis of anomalous behaviors of thermal conductivity enhancements of the spherical nanoparticles dispersed nanofluids. MH nanoparticles (~20 nm) were synthesized using chemical co-precipitation techniques. MH/DW nanofluids were prepared with the varying MH nanoparticles loading in DW and thermal conductivity was measured using KD2 pro device. The thermal conductivity enhancement (~32 %) was found to be increased linearly with the increasing MH nanoparticle concentration and nonlinearly with the increasing temperature. Existing Maxwell and Maxwell Gantt EMA (MG-EMA) models exhibited awful under-prediction from experimental thermal conductivities of MH/DW nanofluids. Modified model with considering static and dynamic mechanisms of MH nanoparticles combinedly showed reasonably very good agreement with the experimental thermal conductivities of MH/DW nanofluids at elevated temperature. This modified model opens the new windows to analyze the insight of the thermophysical properties of various types of nanofluids by introducing potential parameters.

Fuel cell produces clean sources of energy and yielding can be improved using emerging material (MXene) in electrocatalysis performance in a fuel cell system. However, MXene in electrocatalysis area for fuel cell is not discovered yet. Therefore, the aim of this study is to enhance the direct methanol fuel cell (DMFC) electrocatalyst performance using combination of bimetallic PtRu and MXene. Optimization is carried out using response surface methodology (RSM). Composition of MXene, Nafion content and methanol concentration are used as factors (input) and current density is used as a response (output) for the optimization analysis. A cyclic voltammetry (CV) is used to measure the current density. RSM generates optimum factors with MXene composition 78.90 wt%, Nafion content 19.71 wt% and methanol concentration of 2.82M. The optimum response is predicted to be 186.59mA/mgPtRu. The validation test is carried out and the result shows that the average current density is 187.05mA/mgPtRu. PtRu/MXene electrocatalyst produces 2.34 times higher current density compared to PtRu/C commercial electrocatalyst. This indicates that MXene has high potential as a nanocatalyst for cleaner energy production through the fuel cell.

In this study, novel nanocomposites containing the pre-defined mass ratio of binary molten salt (NaNO3-KNO3: 60-40 wt. %) dispersed with hexagonal boron nitride (hBN) nanoparticles with nominal size of 70 nm, were prepared through one-phase preparation method. Four different types of samples including pure binary molten salt and binary molten salt-based hBN nanocomposites with loading concentrations of 0.5, 1 and 1.5 wt. % were prepared. The proposed amount of sodium nitrate and potassium nitrate was added to certain amount of DI water, comprising with 0.5, 1 and 1.5 wt. % concentration of hBN nanoparticles. Scanning electronic microscopy (SEM) was conducted to evaluate the uniformity of the synthesized binary molten salt-based hBN nanocomposites. The SEM images revealed uniform dispersion of hexagonal boron nitride nanoparticles and fractal-like structures were observed clearly. Specific heat capacity (cp) and melting temperature measurements were performed using a differential scanning calorimetry (DSC). The experimental achieved data for melting temperature proved that hexagonal boron nitride nanoparticles do not affect the melting temperature of the synthesized nanocomposites. The experimentally achieved data for the average cp values of the binary molten salt in solid and liquid phases were 1.14 and 1.13 J/g K, respectively. While, the average cp values for the binary molten salt-based hBN nanocomposite with the highest loading concentration of nanoparticles (1.5 wt. %) in solid and liquid phases were 2 and 3.17 J/g K, respectively. The measured average cp value in the liquid phase for binary molten salt-based hBN nanocomposite with the highest loading concentration (1.5 wt. %) of nanoparticles revealed enhancement of ~180% in comparison with pure binary molten salt. Thermal stability measurements expressed enhancement of thermal stability in binary molten salt induced with hBN nanoparticles. Binary molten salt-based hBN nanocomposite with loading concentration

Solar thermal collectors have been recognized as promising devices for solar energy harvesting. The absorbing properties of the working fluid are crucial because they can significantly influence the efficiency of the solar thermal collectors. The performance of photovoltaic-thermal (PV/T) systems can be optimized by applying nanofluids as working fluids. MXene is a newly developed 2-D nanomaterial that has proven excellent potential in electrical applications with a lack of research in the thermal and optical applications. The present work extensively studied the optical potential of the water/MXene nanofluids with respect to the variation of MXene concentrations (0.0005–0.05 wt%) and types of surfactant (CTAB or SDBS) used in a hybrid PV/T system. The relationship between the investigated parameters was evaluated through an experimental correlation. The evaluation of the nanofluids in term of the transmittance was conducted through the Rayleigh method. The MXene concentrations and the types of the surfactant play predominant role in the transmittance, absorbance and dispersion stability of the water/MXene nanofluids. The corresponding effects due to these factors become the most noticeable in the wavelengths of 300–1350 nm. Low concentration of the MXene and shorter path lengths lead to higher transmittance. The application of the low concentration of water/MXene nanofluids as the optical filtration in a hybrid PV/T system yields a higher performance compared to a conventional PV/T system. Therefore, this research work provides novelty value in understanding the impacts of using water/MXene nanofluid in the hybrid PV/T solar collectors to harness additional energy.

Solar thermal energy conversion is gaining more attention among researchers due to the recent development in nanofluids and molten salt technology. Among various solar collectors, parabolic trough collector has received significant attention from researchers due to their operating temperature range (150-800 °C) feasible for power generation. Parabolic trough collector is currently having a higher number of installations compared to other concentrated solar power technology around the globe. Most of the conventional heat transfer fluid used in PTC have poor heat transfer and light to heat conversion properties. Therefore, it is advantageous to enhance the thermophysical properties of heat transfer fluid to improve the overall efficiency of the system. Well-engineered nano-enhanced heat transfer fluid is advantageous because a very low mass fraction of nanoparticles brings considerable enhancement in thermophysical properties. This paper focuses on the most recent advancement in heat transfer fluids, their preparation and stability issues when doped with nanoparticles. Various heat transfer fluids currently used in parabolic trough collectors and the nano-enhanced heat transfer fluids having the properties better than conventional heat transfer fluids are compared and their preparation methods and properties are discussed. Enhancement of thermophysical properties of molten salts by doping nanoparticles and their enhancement in thermal stability at high temperature, the possibility of using mono and hybrid nanofluid, ionic liquids, gaseous heat transfer fluid and vegetable oil as the heat transfer fluid in parabolic trough collectors are the key highlights of this review.

In this research, a new class of nanofluid is successfully formulated from Soybean oil and MXene (Ti3C2) particles to implement as working fluid on a hybrid photovoltaic-thermal (PV/T) solar collector for performance optimization. This study emphasizes on the preparation of the Soybean oil/MXene (SO/Ti3C2) nanofluid, optical and thermal characterization of the nanofluid including suspension stability. The SO/Ti3C2 nanofluid samples are formulated suspending two-dimensional (2D) MXene particles at 0.025–0.125 wt% concentrations into pure Soybean oil. SEM, UV–vis, FTIR and TGA analysis are performed for morphology, optical and thermal stability characterization respectively. Achieved thermal conductivity results of SO/Ti3C2 nanofluid for 0.125 wt% of Ti3C2 exhibited 60.82% enhancement at 55 °C compared to pure Soybean oil. The specific heat capacity (cp) of formulated nanofluids is measured employing a differential scanning calorimeter (DSC). Maximum cp augmentation is found to be 24.49% at 0.125 wt% loading of Ti3C2 in the base oil. Numerical implementation of the prepared SO/Ti3C2 nanofluids on PV/T is performed using COMSOL Multiphysics software resulted noteworthy improvement compared to conventional water, Alumina/water and MXene/palm oil nanofluids as working fluid. Overall thermal effectiveness of the PV/T system is achieved 84.25% using SO/Ti3C2 nanofluids at 0.07 kg/s mass flow rate. Furthermore, employing the nanofluids electrical output of the PV/T is improved by 15.44% in comparison with water/alumina nanofluids at an irradiance of 1000 W/m2 and mass flow rate of 0.07 kg/s. The stated findings indicate overall effectiveness of the Soybean oil based MXene nanofluids over conventional fluids used for cooling purpose in the PV/T collector.

The system efficiency of concentrated solar power (CSP) was determined by using the working temperature of heat transfer fluid (HTF). Initially, organic HTFs were used for this purpose, which had a maximum operating temperature of 400 °C. However, it exhibits poor thermal storage property. The use of inorganic salts which are stable at high temperature (500~600 °C) can significantly increase the system efficiency. These salts can be used as energy storage material as well. In this paper, nanocomposite comprising of ternary nitrate eutectic molten salt having pre-defined mass dispersed with Al2O3 nanoparticles of 0.1, 0.3, 0.5, and 1 wt.% was tested. The enthalpy and melting point measurements were performed using differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was conducted to study the thermal stability of the eutectic salt and mass loss measurement at a temperature higher than 600 ⁰C. The homogeneity and microstructure of synthesized molten salt were examined using scanning electron microscopy (SEM) imaging. The results showed that the melting point of eutectic salt was reduced by 23% with the addition of 1 wt.% of Al2O3 nanoparticles. By increasing the doping of Al2O3, the enthalpy of the mixture increased, indicating that the eutectic mixture could be used for thermal energy storage. SEM imaging analysis revealed the uniform dispersion of Al2O3 nanoparticles in the pure eutectic mixture. Based on the DSC and TGA results, both enthalpy and thermal stability of the molten salt have increased by the addition of Al2O3 nanoparticle, making it a potential candidate salt for CSP applications.

The addition of ionic liquids with MXene nanofluid has a substantial impact on the solar thermal collectors’ working fluid’s optical properties that effectively absorb and distribute solar radiation. Increased solar radiation absorption potential ensures that heats are transported more rapidly and effectively. This research endeavors to investigate the concept of accumulating solar energy via the usage of ionic liquid-based 2D MXene nanofluid (Ionanofluids) for solar applications. In this study, the optical potential of Diethylene Glycol/MXene nanofluid incorporated with 1-ethyl-3-methyl imidazolium octyl sulfate ([Emim][OSO4 ]) ionic liquid was extensively investigated with respect to MXene concentration (0.1 to 0.4 wt%) and time (first day and seventh day) through UV-Vis Spectroscopy. A two-step approach was employed to synthesize the proposed ionanofluids with nanoparticle concentrations from 0.1 to 0.4 wt%. In wavelengths between 240 to 790 nm, the effect of ionic liquids, MXene concentration, and dispersion stability played a significant part in enhancing the absorbance capacity of the formulated MXene based Ionanofluid. Furthermore, the increase in the concentration of MXene nanoparticles resulted in more absorbance peaks facilitating high light absorption. Finally, the electrical conductivity of the ionanofluids is also analyzed as MXene renders them promising for solar cell applications. The utmost electrical conductivity of the formulated fluids of 571 µS/cm (micro siemens per centimeter) was achieved at 0.4 wt% concentration.

Common phase change materials (PCMs) possess very low thermal conductivity whilst hybrid PCM with graphene filler could be produced to achieve increased thermal conductivity. This research focuses on the effects of graphene flakes on the thermal conductivity of a PCM (paraffin wax). Three experimental parameters at different levels of average lateral sizes of graphene flakes (4.5, 5 and 7µm), mass fractions (0.1, 0.2 and 0.25 wt.%), and rising temperatures (25-75°C) are considered. For the first time in the literature, the impact of various parameters on the thermal conductivity performance of the nanoPCM-based graphene nano-composites is investigated extensively by adopting response surface methodology supported by central composite design. Thermal conductivity prediction is proposed by a new general correlation and a promising value of the coefficient of determination (R2) higher than 0.88. Amongst the investigated various variables in terms of impact on thermal conductivity, the temperature is identified as the most influential parameter on response variables. According to the implemented optimization technique, for the composite with the average graphene flake size of 4.5 µm, the optimum value of the thermal conductivity is found 0.275 W/m K at the mass fraction of 0.186 wt.% and temperature of 69.73°C.

In this research work, MXene with a chemical formula of Ti3C2 is used for the first time with silicone oil to improve thermo-physical properties of MXene based silicone oil. This paper focuses on preparation, characterization, thermal properties, thermal stability and performance investigation of new class of silicone oil nanofluids induced with MXene in three different concentrations for a Concentrated Solar Photovoltaic Thermal (CPVT) collector. The thermal conductivity of the silicone oil-based MXene nanofluids is measured using a Transient Hot Bridge (THB) 500. Viscosity is measured using a Rheometer at various temperatures including 25, 50, 75, 100, and 125 degrees C. PerkinElmer Lambda 750 is used to measure optical absorbance. The highest thermal conductivity enhancement is found to be 64% for 0.1 wt% concentration of silicone oil-MXene nanofluid compared to pure silicone oil at 150 degrees C. The viscosity of MXene with silicone oil nanofluids is found to be independent of addition of MXene nanoparticles in the silicone oil base fluid. Viscosity is reduced by 37% when temperature is raised from 25 degrees C to 50 degrees C for different concentrations of MXene with silicone oil. Silicone oil-based MXene nanofluid with 0.1 wt% concentration is thermally stable up to similar to 380 degrees C. Introducing more MXene nanoparticles into silicone oil improves electrical efficiency of PV module due to better cooling of MXene based nanofluids. Higher solar concentration is resulted in higher average temperature of the PV module. This consequently raises thermal energy gain which is useful for different applications.

In this study, nanocomposites containing a pre-defined mass ratio of solar salt (NaNO3-KNO3: 60-40 wt.%) dispersed with magnesium oxide (MgO) nanoparticles with nominal sizes of 100 nm were prepared in solid and liquid states. The proposed amounts of sodium nitrate and potassium nitrate were added to certain amounts of ultrapure deionized (DI) water comprising a 5 wt.% concentration of MgO nanoparticles. Afterward, the prepared mixture was placed in a dry oven to mix in a liquid state to obtain well-dispersed nanocomposites. Scanning electronic microscopy (SEM) was conducted to evaluate the uniformity of synthesized, molten salt–based magnesium oxide–nanoparticles, revealing a uniform dispersion. Enthalpy and melting point measurements were performed using differential scanning calorimetry. The experimental results of solar salt–based MgO indicated decreases in melting point and enthalpy by 7% and 12.4%, respectively. The reduction of enthalpy indicated that, with the addition of magnesium oxide to solar salt, the final nanocomposite tends to have more exothermic reactions and enhanced thermal conductivity performance at the melting point. Lower melting points constitute one of the major concerns regarding molten salt–based nanofluids. MgO nanoparticles with a concentration of 5 wt.% have a melting point decreased by 7%. Mass loss and thermal stability measurements were conducted using thermogravimetric analysis (TGA). The experimentally acquired results revealed an increment of decomposition temperature from 734.29°C to 750.73°C, demonstrating the enhancement of thermal stability at high temperatures.