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Pennisetum purpureum is one of the most invasive perennial grasses of the Poaceae family, which are abundant in south-east Asia including Brunei Darussalam. The pyrolysis process at a slow heating rate proved to be highly promising for biochar production. The production and characterization of different Pennisetum purpureum biochars have been investigated at the pyrolysis temperatures of 400 °C, 500 °C and 600 °C with a heating and nitrogen flow rate of 5 °C/min and 0.5 L/min, respectively. The observed higher heating values were 22.18 MJ/kg, 23.02 MJ/kg, 23.75 MJ/kg, and the alkaline pH were 9.10, 9.86, 10.17 for the biochar at 400 °C, 500 °C, 600 °C temperatures, respectively. The water holding capacity was one hundred percent for all biochars and continued to increase for higher pyrolysis temperature. SEM images show that the porosity of the biochars has been enhanced with increased temperatures due to the rearrangement of crystallinity and aromaticity. On the other hand, the yields of biochar have been decreased from 35.13% to 23.02% for the increase of pyrolysis temperature from 400 °C to 600 °C. Energy dispersive X-ray analysis shows that the O/C atomic ratios were 0.15, 0.08 and 0.06 for the biochar of 400, 500 and 600 °C which validates the improvement in heating values. FT-IR analysis revealed that the available functional groups in the biochars were C–O, C=C, and C–H. Thermogravimetric analysis (TGA) under pyrolysis condition showed residue of 46.56%, 51.13% and 55.67% from the biochar at 400, 500, and 600 °C, respectively. The derivative thermogravimetry (DTG) graph indicates that the degradation rate is higher for 400 °C biochar than the 600 °C biochar.

Concentrator photovoltaics (CPV) is of much intrigue among all photovoltaic (PV) technologies because it replaces the expensive PV cell material with cheaper optical concentrators and occupies less land area as compared with conventional PV technology. However, it is challenging to handle the elevated operating temperature of CPV cells, which is reported capable of deteriorating the lifetime and power conversion efficiency of the CPV system. The integration of a CPV system with thermoelectric generators (TEG) provides a state-of-the-art hybrid design for improving energy harnessing from both electrical and thermal outputs, which also implies a better utilization of solar energy. This review article delineates various integration options of the CPV-TEG system and up-to-date developments of different configurations of hybrid CPV-TEG system including CPV-TEG with a spectral beam splitter, CPV/thermal-TEG, and CPV-TEG with phase changing materials. The numerical simulation and experimental studies on various configurations of hybrid CPV-TEG systems are summarized and outlined in this review. It has been found that the integrated CPV-TEG based solar thermal systems have higher electrical and thermal performances than that of non-concentrated PV-TEG systems. Finally, some recommendations are made for the future development of CPV-TEG systems.

Given the excellent thermal properties of MXene, MXene nanomaterials-based nanofluids may have the potential of being used as heat transfer fluids. In this work, we have investigated the dynamic viscosity of MXene-palm oil nanofluid. To prepare the nanofluid, MXene ( $$\hbox {Ti}_{{3}}\hbox {C}_{{2}}$$ ) nanoflakes were first synthesized by the wet chemistry method. Then, nanofluids with 0.01, 0.03, 0.05, 0.08, 0.1, and 0.2 mass% concentrations of MXene nanoflakes were prepared, and their dynamic viscosity values were determined for a wide temperature range of 18–100 $$^\circ \hbox {C}$$ . The dynamic viscosity of the developed nanofluid, for each concentration, was found to be a strong function of temperature and decreased with increasing temperature. The effect of MXene nanoflakes concentration on the dynamic viscosity was found to be more significant at lower temperatures than at higher temperatures. A multilayer perceptron artificial neural network model was also developed in the study. To develop the model, temperature and nanoflakes concentration were given as inputs to the ANN model, whereas dynamic viscosity was the output of the model. The optimum model was found through the trial and error method. Statistical parameters such as mean square error, mean average percentage error, and correlation coefficient (R) were used to evaluate the performance of the developed model. The values of these parameters, for the optimum ANN model, were found to be 4.733E−05, 0.507%, and 0.99975, respectively. 95.67% of the deviations were also found to be in range of ± 2%. The developed model showed good performance, and its predictions were in excellent agreement with the experimental data.

The significance of total polyaromatic hydrocarbons (TPAH) determination in assessing the carcinogenicity of environmental samples for measuring the level of environmental pollution cannot be overemphasized. Despite the environmental danger of TPAH, its laboratory quantification is laborious, which consumes appreciable time and other valuable resources. This research work develops a computational intelligence-based model for the first time, which directly estimates and quantifies the level of TPAH of any environmental solid samples using total petroleum hydrocarbons descriptor that can be easily determined experimentally. The hyperparameters of the developed support vector regression (SVR)-based model are optimized using manual search (MS) approach and genetic algorithm (GA) search approach with Gaussian and polynomial kernel functions. Experimental validation of the developed model was carried out using samples obtained from the marine sediments of Arabian Gulf Sea. The future generalization and predictive strength of the developed models were assessed using correlation coefficient (CC), root-mean-square error, mean absolute error and mean absolute percentage deviation (MAPD). GA-SVR-Gaussian performs better than MS-SVR and GA-SVR-poly with performance enhancement of 63.89% and 536.32%, respectively, on the basis of MAPD as a performance-measuring parameter, while MS-SVR model performs better than GA-SVR-poly with performance improvement of 288.25% using MAPD to evaluate the model performance. The estimation accuracy and generalization strength of the developed models indicate the potential of the models in measuring the level of environmental pollution of oil-spilled area without experimental stress, while experimental precision is preserved.

Bi-reforming of methane (BRM) is gaining an increase interest due to the critical requirements to mitigate global warming and provide alternative energy resources. However, there has been a serious challenge to the scale-up of the process to commercial production due to the catalyst deactivation. In the present study, the influence of ZrO2 modifications on the activity and stability of MgO-supported Ni catalyst in the BRM reaction was investigated. The ZrO2-MgO mixed oxide support was prepared by co-precipitation method with variation in the ZrO2 composition and subsequently impregnated with Ni. The characterization of the freshly prepared Ni/MgO and Ni/MgO-ZrO2 catalysts using N2 physisorption analysis, X-Ray Diffraction (XRD), FESEM, XPS, H2-TPR, and CO2-TPD techniques revealed suitable physicochemical properties for the BRM reaction. The Ni/MgO-ZrO2 catalysts showed an improved performance in the BRM reaction in terms of activity and stability compared to the Ni/MgO at 800°C and CH4, H2O, CO2 ratio of 3:2:1, respectively. The best performance was obtained using the Ni/15%ZrO2-MgO for the BRM with CO2 and CH4 conversion of 81.5% and 82.5%, respectively. The characterization of the spent Ni/MgO catalyst using Raman spectroscopy, FESEM, and High Resolution Transmission Electron Microscopy (HRTEM) analysis revealed the formation of amorphous carbon that could be responsible for its fast deactivation.

The heat transfer capacity of any thermal cooling system depends on two factors, i.e., the selection of the coolant and the geometrical pattern of the approach. This article summarizes nanofluids' preparation ranging from 0.01 % to 0.2 % using Graphene nanoplatelets & CNC dispersed in a base fluid. The combination of water with ethylene glycol (EG) is a form of customary heat transmit liquids regularly utilized in numerous energy practices to maintain the water's decent cooling (or heating) capability; thus, 60:40 ratio of EG: W mixture used as the base fluid for thermo-physical properties enhancements. These nanofluids prepared are not used with surfactants as it results in generating bubbles and contaminating the heat transfer channels, influencing the overall performance. XRD & FESEM techniques were used to analyze the surface. The investigated nanofluids remained stable, with no substantial sedimentation for 30 days. The results of GNPs/CNC nanofluids at 0.1% volume concentration has proper stability showing excellent colloidal stability in the base fluid of EG: W at a ratio of 60:40. The present hybrid nanofluid has the ability to switch the traditional heat transfer fluids leading to efficient & compact thermal structures.

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.

Microchannel heat sink (MCHS) is an advanced cooling technique to fulfil the cooling demand for electronic devices installed with high-power integrated circuit packages (microchips). Various microchannel designs have been innovated to improve the heat transfer performance in an MCHS. Specifically, the utilisation of nanotechnology in the form of nanofluid in an MCHS attracted the attention of researchers because of considerable enhancement of thermal conductivity in nanofluid even at a low nanoparticle concentration. However, a high-pressure drop was the main limitation as it controls the MCHS performance resulted from heat transfer augmentation. Therefore, this study aimed to critically summarise the challenges and limitations of both single and hybrid passive methods of MCHS. Furthermore, the performance of nanofluid as a coolant in the MCHS as affected by the type and concentration of nanoparticle and the type of base fluid was reviewed systematically. The review indicated that the hybrid MCHS provides a better cooling performance than MCHS with the single passive method as the former results in a higher heat transfer rate with minimal pressure drop penalty. Besides that, further heat transfer performance can be enhanced by dispersing aluminium dioxide (Al2O3) nanoparticles with a concentration of less than 2.0% (v/v) in the water-based coolant.

Industrial sustainability has gained huge attention in the scientific community owing to the concern of global warming. Establishing sustainability indicators by the application of exergy analysis can guide and motivate industrial sustainability. In this context, an attempt is made to establish sustainability indicators for the industrial sector. Different measures to improve the sustainability of the industrial sector of Bangladesh are also discussed. Based on the energy consumption data from the year 2000–2015, energy, exergy, and sustainability analyses are performed. It is found that the energy efficiency varies from 55.01% to 59.67% and exergy efficiency varies from 53.11% to 56.97%. Exergy efficiency is found to be at lower side due to the accounting of irreversibility. Various sustainability indicators such as sustainability index, depletion number, exergetic renewable share, cumulative exergy loss, and non-renewable exergetic share have been studied as well. It is observed that depletion numbers vary from 43% to 45% and the sustainability index varies from 2.21 to 2.32. Non-renewable exergetic share is as high as 98% and maximum cumulative exergy loss is found to be 217.3 PJ in 2015. Improvement potential shows a continuous increase from 22.75% in 2000 to 101.89% in 2015. Waste heat recovery, energy audit, waste minimization, and adopting renewable energy sources are recommended to increase the efficiency and sustainability of this sector. The outcome of this study reveals that exergy analysis is an effective technique to develop energy conservation policies for this sector.

This study performs a techno-economic analysis of concentrating solar power (CSP) technologies for Malaysia. The solar resource assessment was done by analyzing various rural and regional locations using NASA Surface Meteorology and Solar Energy database. Three different technologies, parabolic trough collector (PTC), solar power tower (SPT) and solar parabolic dish (SPD) were assessed under different economic criterions. Results based on the analysis show that PTC and SPT type plants are particularly suitable for locations at East and Peninsular Malaysia. However, considering simple payback, the net present value (NPV) and internal rate of return (IRR), it is found that PTC type CSP plant will be the most eligible for CSP plant development. Sensitivity analysis is performed to investigate the effect of the levelized cost of electricity (LCOE) on the various project discount rate. Regional renewable energy policy development and regulatory reform in feed-in-tariff (FiT), hybrid technology (PTC with biogas, solar PV and biomass) implementation, project financing under clean development mechanism (CDM) and lesson learned from international experience in local PTC equipment manufacturing are some of the crucial future policy outlooks that need to be applied for CSP technology implementation, as well as long-term sustainable renewable energy system development in the country.

As industrial air compressors are the most energy intensive, a comprehensive energy and exergy analysis, reducing energy usage by various energy savings measures are highly important to reduce their energy consumption and emission for the sustainable future growth. A comprehensive analysis on energy performance, exergy efficiency, CO2 emission, sustainability, and the associated economic implications were studied in a typical industrial air compressor system of a TiO2 manufacturing industry, located in Bahia, Brazil. Necessary input data were taken from this industry to analyze energy, exergy, emission, economic, and sustainability performance of the air compressor. The predicted overall exergy efficiency of the compressors varies from to 5.27%–21.94%. Sustainability indicators like Sustainability Index (SI), Depletion Number (DN), Waste Exergy Ratio (WER), & Environmental Effect Factor (EEF) were analyzed and the evaluated sustainability index found to vary from 1.05 to 1.28. Waste exergy ratio is estimated to be 0.95 and environmental effect factor is found to be 17.95 for compressor A. Discharge pressure reduction, power factor improvement, waste heat recoveries are the main areas where improvement have been identified. Reducing discharge pressure can save annually 3515.180 MWh of electricity leading to a reduction of 347.7 ton of CO2 emission per year. It is also noted that the reduced discharge pressure lead to an increased exergetic efficiency. Among various options, reducing discharge pressure came out to be the most cost effective measure with lesser internal rate of return. The industry could save a total of 5634.2 MWh of electricity and reduce CO2 emission by 557 ton per annum with an investment of US$ 570,000. The return on investment for the investment is estimated to be 9 months.

Analytical and numerical solutions were developed to assess the effects of introducing a nanofluid for optical filtration (OF) above the PV module and a layer of a nano-enhanced phase change material (nanoPCM) below the PV panel, on the overall performance of a photovoltaic-thermal solar collector. The analytical study employed six models (M1–M6) with different arrangements of the cooling channel, optical filtration channel, nanoPCM and the number of optical filtration passes. The optical fluid demonstrated an enhancement in the performance by cooling the PV module by convection beside the optical filtration effect. A numerical study was undertaken to distinguish the effects of the optical fluid in enhancing the performance of the photovoltaic-thermal system. The numerical study employed three extra models (N1–N3), which use cooling and optical filtration only. The optical filtration fluid channel and the PV module are separated by an airgap in N-1, while in N-2 the optical filtration channel is directly above the PV module. Optical filtration is not used in N-3. The effect of the channel height, nanoparticle concentration, and mass flow rate on the performance was evaluated. The analytical results show that the use only of a nanoPCM decreases the overall efficiency (thermal + electrical) by about 6.7% (neglecting the storage effects of the nanoPCM). However, the introduction of optical filtration makes the decrease in efficiency very small (

The current study's main objective is to apply energy, exergy, & sustainability analysis and provide suggestions to improve the sustainability of the commercial sector of Bangladesh. Data from 2000 to 2014 is analyzed, and it is found that the estimated energy efficiencies range from 65.42% to 68.5%, while exergy efficiencies range from 10.79% to 11.49%. Depletion number, sustainability index, lack of productivity, relative irreversibility, waste exergy ratio, environmental effect factor, & environmental destruction coefficient are utilized as sustainability indicators. From the study, it is found that sustainability index varies between 1.12 and 1.13, while relative irreversibility varies between 0.44 and 0.53. Lack of productivity is found to be higher for cooking appliances and varies from 3.52 to 4.06. Waste exergy ratio and environmental effect factor are found to be higher for electrical appliances. For electrical appliances, waste exergy ratio varies from 0.42 to 0.50 and environmental effect factor varies from 3.5 to 4.55. Environmental destruction coefficient reaches as high as 9.27. It is determined that Bangladesh's commercial sector is more sustainable compared to Turkey, Japan, Saudi Arabia, and Malaysia but less sustainable than Norway, and Sweden. Utilization of energy efficient lighting, waste energy management, and replacing gas-fired cooking stoves with electrical appliances are provided as recommendations to reduce exergy loss. The study outcome reveals that increasing exergy efficiencies can ensure a sustainable commercial sector.

In the present investigation, a novel ladder polymer, poly(azomethine ester), was prepared via solution polycondensation polymerization between terephthalic acid and the novel monomer. Terephthalic acid was regenerated from PET waste bottles by saponification process, whereas p-phenylenediamine was obtained via Hoffmann rearrangement method. A novel monomer, namely N,N′-bis(2,5-dihydroxy benzylidene)-1,4-diaminobenzene was prepared from the reaction of 2,5-di-hydroxybenzadehyde with p-phenylenediamine in the ratio of 2:1, respectively. For the first time a solution polycondensation method has been employed for the synthesis of a ladder polymer which is otherwise prepared commonly via Diels-Alder cycloaddition reaction. The synthesized ladder polymer was characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR), elemental analysis (CHN), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results revealed that the ladder polymer possess highly regular ladder like framework, and that most of the ester groups have taken part in the side-by-side polymerization reaction.

The current study demonstrates the simplistic approach for the synthesis of SrTiO3 nanocubes incorporated polyaniline flakes (PANI-SrTiO3) by facile in-situ oxidative polymerisation route. The synthesised nanocomposites were characterised by various spectroscopic and surface analysis techniques viz. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller analysis (BET). The electrochemical performance of the prepared nanocomposites for energy storage application was evaluated by electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) in 1 M of KOH as an electrolyte. The electrochemical investigations demonstrate that the performance of the PANI-SrTiO3 nanocomposite in terms of rate capability was significantly higher as compared to the polyaniline flakes and SrTiO3 nanocubes. Supercapattery was fabricated by combining activated carbon and PANI-SrTiO3-250 as negative and positive electrodes respectively in order to evaluate complete device performance. It is found that fabricated supercapattery gave an energy density of 13.2 W h/kg at a power density of 299 W/kg. Additionally, the fabricated supercapattery also offered excellent stability cycle with 114% capacity retention after 4000 cycles. Moreover, the performance of PANI-SrTiO3-250 was found to be better than the other compositions.

© 2019 The Author(s). Background: Microalgae have been experimented as a potential feedstock for biofuel generation in current era owing to its' rich energy content, inflated growth rate, inexpensive culture approaches, the notable capacity of CO2 fixation, and O2 addition to the environment. Currently, research is ongoing towards the advancement of microalgal-biofuel technologies. The nano-additive application has been appeared as a prominent innovation to meet this phenomenon. Main text: The main objective of this study was to delineate the synergistic impact of microalgal biofuel integrated with nano-additive applications. Numerous nano-additives such as nano-fibres, nano-particles, nano-tubes, nano-sheets, nano-droplets, and other nano-structures' applications have been reviewed in this study to facilitate microalgae growth to biofuel utilization. The present paper was intended to comprehensively review the nano-particles preparing techniques for microalgae cultivation and harvesting, biofuel extraction, and application of microalgae-biofuel nano-particles blends. Prospects of solid nano-additives and nano-fluid applications in the future on microalgae production, microalgae biomass conversion to biofuels as well as enhancement of biofuel combustion for revolutionary advancement in biofuel technology have been demonstrated elaborately by this review. This study also highlighted the potential biofuels from microalgae, numerous technologies, and conversion processes. Along with that, the study recounted suitability of potential microalgae candidates with an integrated design generating value-added co-products besides biofuel production. Conclusions: Nano-additive applications at different stages from microalgae culture to end-product utilization presented strong possibility in mercantile approach as well as positive impact on the environment along with valuable co-products generation into the near future.

1D hematite (alpha-Fe2O3) nanorods were synthesized in the presence of rice starch solution. The size of the nanorods was about 250 nm and 50 nm in length and diameter, respectively. The synthesized nanorods possessed a single alpha-Fe2O3 phase without any impurities and crystal defects. The obtained hematite nanorods were employed as an adsorbent for lead (II) removal. The isotherms and kinetic studies indicated that our material would be a potential candidate for heavy metal adsorption and removal.

The main objective of this work is to comprehensively investigate R450A behavior in refrigeration systems and subsequently optimize the main operating variables for the first time to reach the maximum performance. For this purpose, a hybrid multi-objective optimization model coupling response surface method and non-dominated sorted genetic algorithm II is established. The regression analysis results reveal a good agreement of experimental data samples with the quadratic polynomial models with a coefficient of determination exceeding 0.97. The optimum results for the first scenario indicate that the reduction in the motor-compressor electrical power consumption and discharge temperature is 18.39% and 53.51%, respectively, and percentage of growth in the refrigerant mass flow rate is 215.57% when the middle evaporator temperature, middle condenser temperature, superheating degree, and subcooling degree change from −14.95 °C to 8.71°C, 31.28 °C to 24.50°C, 13.12 K to 10.49 K, and 15.65 K to 15.66 K, respectively.

The need of the hour in present world scenario is to reduce the emission of greenhouse gases and environmental pollution whilst satisfying the world energy demands. The most promising and readily available source of energy over the whole world is solar energy. One of the ways of taping this energy into useful energy is using Concentrated Photovoltaic Thermal systems. The paper presents the advanced comprehensive review on the design components of Concentrated Photovoltaic Thermal, heat transfer medium, recent application area such as Tissue Dyeing, domestic hot water, Organic Rankine Cycle, and the economic aspect of the Concentrated Photovoltaic Thermal system. Furthermore, the review paper simplifies the classification into two systems namely thermally coupled and thermally decoupled systems. Concentrated Photovoltaic Thermal shows potential to deliver better gains compared to Concentrated Photovoltaic, Photovoltaic and Photovoltaic Thermal. But matching the different components like the heat transfer component and the medium for specific use is an area that requires research. Therefore, this review concentrates more on the advantages and limitations of using different heat transfer components and heat transfer medium. The benefits of this paper would be the understanding of the components of the heat transport system like fins, microchannel, storage tank and underground heat exchangers and the fluid used in the Concentrated Photovoltaic Thermal integrated system like water, air, nanofluids, Phase Change Materials. It is found that the heat transfer device performance is limited due to its large area, thermal losses, mirror effect on the thermal and electrical efficiencies, and the temperature difference between the sink and device. Likewise, the performance of the heat transfer fluid is dependent on the mass flow rate, thermal mass, viscosity, density, time and the required temperature. Finally, for economic feasibility of the Concentrated Photovoltaic Thermal system requires the need for a grid connected system with properly sized system with feed-in-tariff and carbon incentives. Furthermore, the recommendation for heat transfer device, medium and economic aspect is also presented. However, more experimental research is required to further understand the compatibility of each components with Concentrating Photovoltaic Thermal System as presented in way forward.

In the quest for alternatives for fossil fuels, phase change materials (PCMs) have attracted considerable attention due to their ability to store renewable thermal energy. Compared to other storage systems, PCM systems are of low cost and capable of the storage of a high density of energy. However, few drawbacks hinder their practical application at an industrial scale. Among the drawbacks, supercooling problem affecting all types of PCMs is crucial. Supercooling as a shortcoming in PCM applications limits their practical applications. However, a comprehensive discussion or review articles have not been published. A PCM can exists in the liquid form below the phase change temperature or its freezing point, without fully freezing, due to supercooling. Thus, practical applications are limited by major problems such as the temperature variations and the increase of energy consumption. In this paper, most of the reported supercooling mitigation techniques for various types of PCMs and nanofluids are reviewed. These techniques are based mainly on adding nucleating agents (such as carbon nanotubes, fine salt particles, and nanoaditives), thickeners (such as carboxy methyl cellulose), and macroporous structures. The mitigation of phase separation and thermal cycling effects on supercooling are also discussed. The mitigation of supercooling in encapsulated organic PCMs, which is an important issue that is not very well understood, too is briefly addressed. Recommendations and future challenges to enhance the application of PCMs are discussed.

Owing to the improvements in thermophysical properties, nanofluids are considered advantageous over pure fluids in heat transfer applications. However, these improvements may be regarded as meaningful for applications provided that optimum dispersion of nanoparticles is ensured throughout the process, which mostly depend on preparation technique. In this study, alumina (Al2O3)–water nanofluids of 0.5 vol% were prepared using ultrasonication (up to 5 h) and stored at stationary condition until 30 days. We have evaluated stability as temporal volume fraction by measuring density. Further, thermal conductivity and viscosity were measured, and heat transfer performance was analyzed for the case of fully developed laminar flow inside a tube. All the measurements were conducted at 25 °C temperature. Results revealed that longer ultrasonication reduces sedimentation of nanoparticles and hence, increases stability of nanofluids. Thermal conductivity increased, while viscosity decreased with increasing sonication time. Moreover, these thermophysical properties decreased with storage periods. It was observed, until 30 days of storage that ultrasonication process for different durations induced significant changes in viscosity, although those in thermal conductivity was not as pronounced. All the prepared samples were determined beneficial as heat transfer fluids over water, even after 30 days from preparation.

There is a growing body of work in the field of nanofluids and several investigations have been conducted on their thermal conductivities. While the experimental works require considerable investments to provide a highly equipped laboratory and proper instruments, the predictive models are useful to promote understanding nanofluids under different operational conditions. However, the restrictions on the traditional predictive models require scholars to develop reliable models that are capable of simulating the thermophysical properties of nanofluids. Data-driven models have attracted huge attention and been widely applied in various fields. There is no specific review on application of data-driven models in thermal conductivity of nanofluids till now and thus this is the first review paper which gives a state of the art review of research progress in this field of study. It was identified that the effective thermal conductivity of nanofluids is reflected well by the new predictive models. The authors believe that the data-driven models are fast, reliable, simple-to-use, and practical. This may open a new door for the scientists, engineers, and researchers in the field of nanofluid for calculating the effective thermal conductivity with excellent precision. This investigation leads to the recognition of the main problems and the opportunities in the research area for the future works.

Increasing population combined with pollution of water bodies makes human being on this earth fully dependent on purified or desalinated water Keeping in mind the end goal to take care of the demand for consumable water, desalination systems of different kind have been proposed by many industrial establishments and research groups. Among the known water purification system Humidification Dehumidification (HDH) has become popular due to its simple operation, economic viability, absence of skilled labor and dependence on green and low grade energy to power the system. The theoretical analysis has been carried out using a simulation code in ‘C’ language to study the performance and quantity of output at various operating conditions. Results demonstrate that with increment in the mass flow rate of water and air, the effect of productivity on desalinated water increases and decreases respectively. In addition, the freshwater output increases with decrease in the heat input which is favorable for the enhancement of desalination efficiency.

Electric motors and boilers lead the industrial components which consume the largest portion of energy in an industry. This study explores the energy audit data of the condiment industry in India. The study mainly focuses on the estimation of the load factor, energy use, energy savings and annual bill savings with payback period of the electric motors of the plant. During the audit, it was found that there were several motors running under loaded conditions despite non-availability of variable speed drives installed in the plant. Therefore, variable speed drives are recommended to be installed to save energy by reducing the motors speed by up to 60%. According to the estimation, about 276 MWh, 551 MWh and 827 MWh electrical energy can be saved for 20%, 40% and 60% speed reduction of the motors using variable speed drives, respectively, where in most of the cases the payback period remains below 1 year. Furthermore, some suggestions are made to improve the poor power factor of running motors by using capacitor banks to save the reactive power. Besides, an estimation of energy saving is performed with a 2-ton capacity boiler. Since, there was no heat recovery system in the boiler; an air-preheater is suggested to be installed at the end of flue gas exhausting path of the boiler with the purpose of saving 68 tons of fuel per annum and having a payback period of 12 months. Moreover, a digital monitoring system, namely, “The Smart Joules” has been proposed to be installed in the plant aiming at saving about 3–5% of total energy per annum and having a payback period of 19 months. Finally, a summarization is made concluding in the fact that about 90 MWh energy and 95 tons of fuel can be saved (excluding motor energy savings) per annum by implementing proposed measures with a payback period of 15 months.

The MXenes are a novel family of 2-D materials with promising biomedical activity, however, their anticancer potential is still largely unexplored. In this study, a comparative cytotoxicity investigation of Ti3C2 MXenes with polypropylene glycol (PPG), and polyethylene glycol (PEG) surface-modified 2-D Ti3C2 MXene flakes has been conducted towards normal and cancerous human cell lines. The wet chemical etching method was used to synthesize MXene followed by a simple chemical mixing method for surface modification of Ti3C2 MXene with PPG and PEG molecules. SEM and XRD analyses were performed to examine surface morphology and elemental composition, respectively. FTIR and UV-vis spectroscopy were used to confirm surface modification and light absorption, respectively. The cell lines used to study the cytotoxicity of MXene and surface-modified MXenes in this study were normal (HaCaT and MCF-10A) and cancerous (MCF-7 and A375) cells. These cell lines were also used as controls (without exposure to study material and irradiation) to measure their baseline cell viability under the same lab environment. The surface-modified MXenes exhibited a sharp reduction in cell viability towards both normal (HaCaT and MCF-10A) and cancerous (MCF-7 and A375) cells but cytotoxicity was more pronounced towards cancerous cell lines. This may be due to the difference in cell metabolism and the occurrence of high pre-existing levels of reactive oxygen species (ROS) within cancerous cells. The highest toxicity towards both normal and cancerous cell lines was observed with PEGylated MXenes followed by PPGylated and bare MXenes. The normal cell’s viability was barely above 70% threshold with 250 mg/L PEGylated MXene concentration whereas PPGylated and bare MXene were less toxic towards normal cells, even at 500 mg/L concentration. Moreover, the toxicity was found to be directly related to the type of cell lines. In general, the HaCaT cell line exhibited the lowest toxicity while toxicity was highest in the case of the A375 cell line. The photothermal studies revealed high photo response for PEGylated MXene followed by PPGylated and bare MXenes. However, the PPGylated MXene’s lower cytotoxicity towards normal cells while comparable toxicity towards malignant cells as compared to PEGylated MXenes makes the former a relatively safe and effective anticancer agent.

Refrigeration systems have experienced massive technological changes in the past 50 years. Nanotechnology can lead to a promising technological leap in the refrigeration industry. Nano-refrigerant still remains unknown because of the complexity of the phase change process of the mixture including refrigerant, lubricant, and nanoparticle. In this study, the stability of Al2O3 nanofluid and the performance of a nano-refrigerant-based domestic refrigerator have been experimentally investigated, with the focus on the thermodynamic and energy approaches. It was found that by increasing the nanoparticle concentration, the stability of nano-lubricant was decreased and evaporator temperature gradient was increased. The average of the temperature gradient increment in the evaporator was 20.2% in case of using 0.1%-Al2O3. The results showed that the energy consumption of the refrigerator reduced around 2.69% when 0.1%-Al2O3 nanoparticle was added to the system.

This study deals with the preparation of activated carbon (CDSP) from date seed powder (DSP) by chemical activation to eliminate polyaromatic hydrocarbon—PAHs (naphthalene—C10H8) from synthetic wastewater. The chemical activation process was carried out using a weak Lewis acid of zinc acetate dihydrate salt (Zn(CH3CO2)2·2H2O). The equilibrium isotherm and kinetics analysis was carried out using DSP and CDSP samples, and their performances were compared for the removal of a volatile organic compound—naphthalene (C10H8)—from synthetic aqueous effluents or wastewater. The equilibrium isotherm data was analyzed using the linear regression model of the Langmuir, Freundlich and Temkin equations. The R2 values for the Langmuir isotherm were 0.93 and 0.99 for naphthalene (C10H8) adsorption using DSP and CDSP, respectively. CDSP showed a higher equilibrium sorption capacity (qe) of 379.64 µg/g. DSP had an equilibrium sorption capacity of 369.06 µg/g for C10H8. The rate of reaction was estimated for C10H8 adsorption using a pseudo-first order, pseudo-second order and Elovich kinetic equation. The reaction mechanism for both the sorbents (CDSP and DSP) was studied using the intraparticle diffusion model. The equilibrium data was well-fitted with the pseudo-second order kinetics model showing the chemisorption nature of the equilibrium system. CDSP showed a higher sorption performance than DSP due to its higher BET surface area and carbon content. Physiochemical characterizations of the DSP and CDSP samples were carried out using the BET surface area analysis, Fourier-scanning microscopic analysis (FSEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform spectroscopic analysis (FTIR). A thermogravimetric and ultimate analysis was also carried out to determine the carbon content in both the sorbents (DSP and CDSP) here. This study confirms the potential of DSP and CDSP to remove C10H8 from lab-scale synthetic wastewater.

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.