Conversion Behavior Research Articles

Solar-thermal energy conversion prediction of building envelope using thermochemical sorbent based on established reaction kinetics

In this paper, the dehydration (heat charge) and hydration (discharge) reaction kinetics of thermochemical sorbents synthesised in previous work by the author is established by using the isothermal method, with the aim of understanding their thermochemical conversion behaviour and developing reaction models for numerical simulations. The effects of temperature, reaction advancement, and vapour pressure are fully considered and employed in a thermochemical energy storage model. The derived dehydration reaction activation energies of the LiOH/LiCl@ expanded graphite (LiO2C1@EG and LiO3C1@EG) sorbents are 54.7 and 52.2 kJ/mol, respectively, which are lower than that of pure LiOH·H2O. To achieve the dual-function of space heating and air purification in an efficient manner, a novel solar building envelope combining thermochemical energy storage and photocatalysis is proposed and studied numerically based on the established reaction kinetics. Fresh air can be produced during solar harvesting. The porous wall, which is made of a composite sorbent, absorbs thermal energy to heat air near the wall and thus creates a chimney effect in the channel for continuous space heating. During discharge, the desorbed heat storage wall adsorbs the moist air and the hydration reaction enthalpy can be used again for air heating. The total efficiency including the equivalent formaldehyde degradation efficiency and the thermal efficiency is around 81% when the solar radiation is 600 W/m2. Results indicate that this passive building envelope can achieve a higher heat harvesting and utilisation efficiency in a more compact space compared to previous studies. Moreover, the influence of radiation intensity on air purification and thermal performance is investigated. The present work provides new insights and promotes the integration of passive solar building envelopes and thermochemical energy storage.

Surface Pretreatments of AA5083 Aluminum Alloy with Enhanced Corrosion Protection for Cerium-Based Conversion Coatings Application: Combined Experimental and Computational Analysis.

The effects of surface pretreatments on the cerium-based conversion coating applied on an AA5083 aluminum alloy were investigated using a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), polarization testing, and electrochemical impedance spectroscopy. Two steps of pretreatments containing acidic or alkaline solutions were applied to the surface to study the effects of surface pretreatments. Among the pretreated samples, the sample prepared by the pretreatment of the alkaline solution then acid washing presented higher corrosion protection (~3 orders of magnitude higher than the sample without pretreatment). This pretreatment provided a more active surface for the deposition of the cerium layer and provided a more suitable substrate for film formation, and made a more uniform film. The surface morphology of samples confirmed that the best surface coverage was presented by alkaline solution then acid washing pretreatment. The presence of cerium in the (EDS) analysis demonstrated that pretreatment with the alkaline solution then acid washing resulted in a higher deposition of the cerium layer on the aluminum surface. After selecting the best surface pretreatment, various deposition times of cerium baths were investigated. The best deposition time was achieved at 10 min, and after this critical time, a cracked film formed on the surface that could not be protective. The corrosion resistance of cerium-based conversion coatings obtained by electrochemical tests were used for training three computational techniques (artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine regression (SVMR)) based on Pretreatment-1 (acidic or alkaline cleaning: pH (1)), Pretreatment-2 (acidic or alkaline cleaning: pH (2)), and deposition time in the cerium bath as an input. Various statistical criteria showed that the ANFIS model (R2 = 0.99, MSE = 48.83, and MAE = 3.49) could forecast the corrosion behavior of a cerium-based conversion coating more accurately than other models. Finally, due to the robust performance of ANFIS in modeling, the effect of each parameter was studied.

Listening to Mental Health Crisis Needs at Scale: Using Natural Language Processing to Understand and Evaluate a Mental Health Crisis Text Messaging Service.

The current mental health crisis is a growing public health issue requiring a large-scale response that cannot be met with traditional services alone. Digital support tools are proliferating, yet most are not systematically evaluated, and we know little about their users and their needs. Shout is a free mental health text messaging service run by the charity Mental Health Innovations, which provides support for individuals in the UK experiencing mental or emotional distress and seeking help. Here we study a large data set of anonymised text message conversations and post-conversation surveys compiled through Shout. This data provides an opportunity to hear at scale from those experiencing distress; to better understand mental health needs for people not using traditional mental health services; and to evaluate the impact of a novel form of crisis support. We use natural language processing (NLP) to assess the adherence of volunteers to conversation techniques and formats, and to gain insight into demographic user groups and their behavioural expressions of distress. Our textual analyses achieve accurate classification of conversation stages (weighted accuracy = 88%), behaviours (1-hamming loss = 95%) and texter demographics (weighted accuracy = 96%), exemplifying how the application of NLP to frontline mental health data sets can aid with post-hoc analysis and evaluation of quality of service provision in digital mental health services.

Investigation of single particle devolatilization in fluidized bed reactors by X-ray imaging techniques

A non-intrusive X-ray imaging technique has been used to investigate the behaviour of solid feedstock particles in a lab-scale fluidized bed reactor operated at temperatures up to 650 °C. Beech wood and polypropylene particles of different sizes have been chosen to represent the main constituents of typical thermochemical processes feedstock. The experiments were conducted under either oxidizing or inert conditions. The presence of oxygen showed a strong effect on the overall devolatilization time, which was found to be in the range of 30–112 s and 40–174 s for beech wood and polypropylene, respectively. Surprisingly, the oxidizing nature of the fluidizing medium appears to have no influence on the volatiles release within the bed in form of the so-called endogenous bubbles. These volatiles bubbles are responsible for a lift force acting on the feedstock particle itself, which ultimately encourages the segregation towards the bed surface. A one-dimensional physical model has been developed to predict particle axial location over time, taking into account both dynamic and thermal conversion behaviour of a single feedstock particle. A revised version of the model has been proposed due to new knowledge of endogenous bubbles size provided by a novel X-ray imaging approach. Results showed very accurate predictions of the 1D model for biomass particles, which segregate towards the bed surface according to the multiple bubble segregation pattern. However, the model fails in describing plastics behaviour, possibly due to different mechanisms of reactions. The observations reported in this work show the importance of investigation at single particle level and may serve to promote new methods to gain a better understanding of plastics thermal decomposition in fluidized beds, whose mechanism is still uncertain.

Use and E ffect of Google Ads Effect of Google Ads for M arketing S uccess

The present article examines success factors by using and implementing google ads in enterprises. In order to assess the importance of google ads for marketing success, the first step is to classify the importance of google as a search platform. Measured in terms of page views, google was the clear market leader in the search engine market with a market share of 87.66 percent, ahead of Bing and Yahoo. 5.8 billion search queries per day - two trillion search queries per year - also generate opportunities for companies to present themselves and win customers. The results of this research suggest that the keyword for successful online marketing in SEA focuses on relevance. Only if content is created that, in addition to the actual promotion of a product or service, leads to further and for the user target-oriented information, the campaign experiences a quality upgrade, which not only affects the ranking and quality factors, but also the conversion behavior of customers. Based on the execution of a literature review, which has been carried out with emphasis on empirical studies and essays since 2010, four main success factors, such as presentation and content of the website, accordingly keyword marketing, the complementary use of analytics, and ad extension have been evolved.

Melting heat transfer of a magnetized water-based hybrid nanofluid flow past over a stretching/shrinking wedge

This research presents the stagnation point flow with heat transfer of water-based hybrid nanofluid over a stretching/shrinking wedge. Magnetic field is applied normal to the wedge with melting heat transfer effect. The wall of the boundary with slip effect on the surface. Water as base fluid with two different nanoparticles (Al2O3 and Cu) is considered. The Navier-Stokes and heat equation are first simplified through similarity variables to convert the partial differential equations (PDEs) into non-dimensional ordinary differential equations (ODEs). The numerical solutions are obtained with the help of bvp4c technique in MATLAB programming. This study is focused on the impacts of different dimensionless parameters on the velocity field, temperature distribution, skin friction coefficient and Nusselt number. It is seen that the solution of governing ODEs has two branches, first and second branch solutions in some specific range of supervising parameters. It is found that heat transfer rate enhances against melting parameter in the first branch solution and converse behavior can be observed for second branch solution. It is also uncovered that in hybrid nanofluid, the momentum and thermal boundary layer thickness enhances in first solution while reduces in the second solution with the advancement of angle of wedge parameter.

Recent Progress of Sub-Nanometric Materials in Photothermal Energy Conversion.

Sub‐nanometric materials (SNMs) are an attractive scope in recent years due to their atomic‐level size and unique properties. Among various performances of SNMs, photothermal energy conversion is one of the most important ones because it can efficiently utilize the light energy. Herein, the SNMs with photothermal energy conversion behaviors and their applications are reviewed. First, a hydrothermal/solvothermal method for the synthesis of SNMs is systematically discussed, including the LaMer pathway and the cluster–nuclei coassembly pathway. Based on this synthetic strategy, many kinds of SNMs with different morphologies are successfully prepared, such as nanorings, nanowires, nanosheets, and nanobelts. These SNMs exhibit excellent photothermal performance under the laser or solar irradiation according to their different light absorption ranges. These enhanced absorption performances of SNMs are induced by the mechanism of plasmonic localized heating or nonradiative relaxation. Finally, the applications of the photothermal SNMs are illustrated. The SNMs with photothermal behaviors can be widely applied in the fields of solar vapor generation, biomedicine, and light‐responsive composites construction. It is hoped that this review can provide new viewpoints and profound understanding to the SNMs in photothermal energy conversion.

Weather, cropland expansion, and deforestation in Ethiopia

We use high-resolution weather data and rich Ethiopian household- and plot-level data in 2011/12, 2013/14, and 2015/16 growing seasons to investigate the impact of weather shocks on agricultural producers' cropland expansion and land conversion behaviors. We find that weather above 32 °C is harmful to crop growth. Household-level analysis shows that each additional average harmful growing degree day (defined as temperature above 32 °C) leads to a 17.2%, 20.1%, and 20.0% increase in total land holdings, cropland, and cropland allocated to cereal production, respectively. Each additional average harmful growing degree day reduces households' forest by 24.7% for households with some forest in the baseline growing season. Further analysis shows that farmers' cropland expansion substitutes migration and off-farm employment. The significant impacts of weather shocks on cropland expansion are only significant for households with relatively fewer assets but not for households with more assets, which suggests that only households without enough resources would expand cropland. These findings highlight the need to identify and facilitate coping strategies that are sustainable in the long run.

Effects of variable thermal conductivity and electrical conductivity on flow of Williamson nanofluid between two parallel disks

The variable nature of the thermal conductivity of nanofluid with respect to temperature plays an important role in many engineering and industrial applications including solar collectors and thermoelectricity. Thus, the foremost motivation of this article is to investigate the effects of thermal conductivity and electric conductivity due to variable temperature on the flow of Williamson nanofluid. The flow is considered between two stretchable rotating disks. The mathematical modeling and analysis have been made in the presence of magnetohydrodynamic and thermal radiation. The governing differential equations of the problem are transformed into non-dimensional differential equations by using similarity transformations. The transformed differential equations are thus solved by a finite difference method. The behaviors of velocity, temperature and concentration profiles due to various parameters are discussed. For magnetic parameter, the radial and tangential velocities have showed decreasing behavior, while converse behavior is observed for axial velocity. The temperature profile shows increasing behavior due to an increase in the Weissenberg number, heat generation parameter and Eckert number, while it declines by increasing electric conductivity parameter. The nanoparticle concentration profile declines due to an increase in the Lewis number and Reynolds number.

Performance Assessment of Thermoelectric Generators with Application on Aerodynamic Heat Recovery.

Based on thermoelectric generators (TEGs), an aerodynamic heat energy recovery system for vehicle is proposed. A mathematical model describing the energy conversion law of the system is established, and the integrated calculation method which combined aerodynamic heating and thermoelectric (TE) conversion is given. Furthermore, the influences of the typical flight Mach number, flight altitudes and the length of TE legs on the energy conversion behavior of energy recovery systems are investigated. The performance of the energy recovery system is analyzed and evaluated. The results show that, the decrease of flight altitude and the increase of Mach number will obviously improve the performance of the heat energy recovery system with TEGs. The increase of leg length will increase the temperature of the hot end of TEGs and reduce the heat absorbed at the hot end. When the external load, Mach number and flight altitude is fixed, there exists an optimal length of legs corresponding to the maximum output power and maximum conversion efficiency of the system. The results will have significant positive impact on thermal protection and management of supersonic/hypersonic vehicles.

Engineering metal-sulfides with cations-tunable metal-oxides electrocatalysts with promoted catalytic conversion for robust ions-storage capability

Metal rich-sulfides, with remarkable theoretical capacity, still suffer from the disolving of polysulfides and sluggish kinetics. Electrocatalysts, as the vital meditors, have been applied in Li-S systems with notable improvements, but scarcely explored for ions-storage battery. Herein, for introducting cation-tunable MOx (M=Mn/Fe/Co/Ni) as electrocatalysts, various MoS2@MOx are designed through chemical-precipitation and thermal-treatment manners. Benefitting from the high affinity of MoS2 and MOx, the interfacial chemical bonds Mo-S-M are established, boosting the improvement of ions/electrons transferring and structural integrality. Owing to the evolution of outer orbitals and ionic radius, the capturing and conversion of Li2S8 are tailored in order of Fe2O3>MnO>CoO>NiO. Supported by unique 3d-orbital/ion-radiu and Mo-S-Fe bonds, the ultra-fast ability of MoS2@Fe2O3 remains ∼612 mAh g−1 after 3,000 loops even at 5.0 A g−1, meanwhile delivering ∼800 mAh g−1 at 0.5 A g−1 in full-cell. Assisted by detailed kinetic behaviors and theoretical calculations, the redox reaction mechisms are clearly proposed, whilst the reduced Gibbs free energy (-1.25 of Fe2O3) serves crucial roles in the reaction (Li2S8 → Li2S6). This work is expected to shed light on the in-depth understanding of fourth-periods MOx electrocatalysts, and offers more possibilities for designing advanced metal-sulfides electrodes.MoS2 nanosheets uniformly anchored with MOx (M=Mn, Fe, Co, Ni) were rationally engineered, accompanied by the establishment of Mo-S-M interfacial chemical bonds. The electrocatalytic abilities of introduced MOx were successfully tailored by the evolution of cationic outer orbitals and ionic radius, inducing the fascinated catalytic conversion behaviors.

Quasi-solid-state self-assembly of 1D-branched ZnSe/ZnS quantum rods into parallel monorail-like continuous films for solar devices

Translating the extraordinary optoelectric properties of colloidal quantum rods (QRs) into functional devices requires multiscale structural control to preserve the nanoscale attributes as well as to introduce micro- and macroscale interactions between the building blocks. Self-assembly of anisotropic QRs into ordered nanostructures can tailor the photoelectric properties of the QRs, such as in light absorption, and charge separation and transfer. However, it remains a challenge to assemble anisotropic nanomaterial into centimeter-sized, multilayered continuous films that retain nanoscale properties in the fabricated macroscopic devices. We have developed a quasi-solid-state self-assembly of randomly oriented nanostructures for overcoming this challenge, demonstrated by the re-assembly of randomly packed ZnSe/ZnS QRs into aligned and ordered parallel monorails (PMs). These ZnSe/ZnS PMs show significant enhancement in photo-excited charge transport, boosting photocatalytic oxygen evolution rates and the enhancement of photoelectrochemical activities, with a photocurrent density of 18 μA/cm 2 , 5 times higher than the parent random packing of ZnSe/ZnS QRs. The ZnSe/ZnS PMs enrich the p-n heterojunctions, which can modulate charge carrier separation and transport at the interfaces. The new method has applicability for re-assembling randomly packed films of anisotropic nanoparticles into ordered nanostructures. Importantly, the extraordinary photoelectro-energy conversion behavior of the Type-I core/shell quantum materials illuminates the pathways for novel designed materials by tailoring the hierarchical structures at all scales. • The quasi-solid-state self-assembly of randomly oriented 1-D nanostructures to close packed paralleled monorail alignment. • A general fabrication strategy for designing macroscopic solar devices at all scales. • A ‘electron-leaky’ Type-I core/shell quantum rods with significantly enhanced photoelectrochemical activities.

Tailoring the Pore Size, Basicity, and Binding Energy of Mesoporous C3 N5 for CO2 Capture and Conversion.

We investigated the CO2 adsorption and electrochemical conversion behavior of triazole-based C3 N5 nanorods as a single matrix for consecutive CO2 capture and conversion. The pore size, basicity, and binding energy were tailored to identify critical factors for consecutive CO2 capture and conversion over carbon nitrides. Temperature-programmed desorption (TPD) analysis of CO2 demonstrates that triazole-based C3 N5 shows higher basicity and stronger CO2 binding energy than g-C3 N4 . Triazole-based C3 N5 nanorods with 6.1 nm mesopore channels exhibit better CO2 adsorption than nanorods with 3.5 and 5.4 nm mesopore channels. C3 N5 nanorods with wider mesopore channels are effective in increasing the current density as an electrocatalyst during the CO2 reduction reaction. Triazole-based C3 N5 nanorods with tailored pore sizes exhibit CO2 adsorption abilities of 5.6-9.1 mmol/g at 0 °C and 30 bar. Their Faraday efficiencies for reducing CO2 to CO are 14-38% at a potential of -0.8 V vs. RHE.

In-plane anisotropic 2D CrPS4 for promising polarization-sensitive photodetection

Polarized photodetectors have been widely used in military and civilian applications. The investigation of promising two-dimensional materials with low symmetry structures will be of great significance for the development of polarized integrated nanodevices. In this work, chromium thiophosphate (CrPS4), a ternary layered semiconductor with low symmetry puckered structures and unique linear dichroism (LD) conversion behavior is introduced to act as a polarization-sensitive photodetector. Angle-resolved polarized Raman spectra (ARPRS), polarization-resolved photoluminescence (PL) spectra, polarization-resolved absorption spectroscopy (PRAS), and electrical transport measurement systematically indicate intriguing anisotropic optical and electrical properties in 2D (two-dimensional) CrPS4. The photodetector of CrPS4 shows a linear anisotropy ratio of ≈1.33 with 405 nm illumination. This pioneering research not only stimulates interest in the development of novel anisotropic 2D materials but also enriches the family of polarization-sensitive photodetectors.

Highly Electrocatalytic Conversion and Separation of Organometallic Ions to Vapor on an Au-Modified Nickel Foam Cathode: A Classic Application for Mercury Speciation Analysis at the μg/L Level

A simple, accurate, and sustainable electrocatalytic conversion strategy has been used for the speciation analysis of trace mercury. An Au- or Ag-modified nickel foam electrode (Au/NFE or Ag/NFE) prepared by cyclic voltammetry was used first as a cathode for the gaseous conversion of organomercury. The mechanism of improving the electrochemical inertness of methylmercury is considered to be the migration of charge centers and the weakening of C–Hg bonds caused by the formation of Au–Hg amalgam. A large specific surface area, high catalytic activity, and low transport resistance allow an effective conversion of 0.1 μg L–1 level organomercury on the Au/NFE surface. The difference of gaseous conversion behavior under current control also provides a green way for the analysis of mercury speciation. A lower limit of detection (4.9 pg g –1 for Hg2+ and 5.5 pg g –1 for CH3Hg+), stronger anti-interference ability, more than 180 sample analysis capacities, and less than 8% signal fluctuation, importantly, confirmed that the electrocatalytic conversion technology based on the gold/silver-modified NFE is very suitable for the analysis of ultratrace methylmercury in complex matrix samples, such as animal and plant samples.

A metamaterial ultrasound mode convertor for complete transformation of Lamb waves into shear horizontal waves

This article reports a new mechanism involving a non-perforated resonant elastic metamaterial to achieve the complete conversion of Lamb waves (A0 and S0) into the fundamental shear horizontal (SH0) wave. The proposed metamaterial ultrasound mode convertor is studied via the observation of the special resonant shear motion of its unit cells, initiating with a conventional additive stub design. Thereafter, such a stubbed structure is further modified to fully couple the Lamb modes with the shear horizontal stub motion. By investigating the band structure of the metamaterial unit cell through modal analysis and tuning the shear resonant motions, a complete SH0 mode generation band within the simultaneous Lamb modes bandgap can be established in a wide frequency range. Such a special bandgap situation enables the complete mode conversion from Lamb waves into shear horizontal waves. The transformation capability of the proposed ultrasound mode convertor is further substantiated via the harmonic analysis of metamaterial chain model, showcasing the frequency spectrum of the transmitted wave modes. The optimal configuration is determined by conducting a parametric study to identify the most effective mode conversion performance. Finally, a coupled-field transient finite element simulation is carried out to acquire the dynamic response of the structure. The frequency-wavenumber analysis of the transmitted wave field illuminates the successful realization of the mode conversion behavior. Experimental demonstrations are presented to validate the numerical predictions. The proposed complete mode conversion capability may possess great potential for wave control and manipulation.

Ultrawideband and high-efficient polarization conversion metasurface based on multi-resonant element and interference theory.

In this work, an ultrawideband and high-efficient polarization conversion metasurface (PCM) is proposed, which can efficiently convert linearly polarized waves into cross-polarized waves in an ultra-wide frequency range. The unit cell of the proposed PCM is composed of two pairs of L-shaped metallic patches covered by a dielectric superstrate and an air-based substrate attached with a metallic ground. The PCM has an operating band from 3.37 to 22.07 GHz with the polarization conversion ratio (PCR) over 90% under the normal incidence, which the ratio bandwidth (fH/fL) is 6.5:1. The PCR can achieve 100% at seven resonant frequencies. The equivalent circuit model is analyzed to explain the fundamental cause of the PCM's multi-resonance and polarization conversion behaviors. In addition, all possible near-field interactions among the resonator, the superstrate, and the ground sheet can be accurately calculated using interference theory, which reveals the underlying physical mechanisms of the multi-resonance metasurface. The theoretical calculated, numerically simulated, and measured results are in good agreement. Compared to other PCMs, the proposed PCM has a simple geometry structure but an ultrawideband and high PCR property.

In situatomic-scale observation of the conversion behavior in a Cu-Zn alloy for twinnability enhancement

Cu-Zn based alloys have been widely used in various applications due to their outstanding properties, such as high electrical conductivity and increased hardness over pure Cu. The thermal effect during electrical conduction leads to the requirement of excellent thermal stability for maintaining performance, which is strongly related to the microstructural transformation and kinetics. However, the atomic-scale microstructural evolution of Cu-Zn systems has scarcely been discussed. In this study, the reaction process of Cu-Zn systems was observed via in situ high-resolution transmission electron microscopy (in situ HRTEM). The Zn/Cu thin films were converted to β-CuZn at 180 ℃ and exhibited an epitaxial relationship with Cu, which was described as (01 1¯)β-CuZn // (1¯11)Cu and [100]β-CuZn // [110]Cu. Subsequently, the Cu-rich solid solution (α phase) was formed at 300 ℃ to decrease the Gibbs free energy, where layer-by-layer diffusion took place on the (1¯1¯ 1) plane. Based on the improved twinnability of the α phase with decreasing stacking fault energy (SFE), nanotwins grew along with the α phase. The twin boundaries effectively retard atomic migration, which is expected to optimize the mechanical properties. The fundamental science described in this study provides novel insights into Cu-Zn alloys, which could be explored in a wide range of alloy systems.

Improvement of a phase change heat storage system by Blossom-Shaped Fins: Energy analysis

The present paper introduces a novel latent heat storage system applicable to hot water systems equipped with a Phase Change Material (PCM) and a Novel set of Blossom-Shaped Fins (BSFs). The water supplied by the collector is injected into the heat exchanger as a Heat Transfer Fluid (HTF). The PCM is charged during the daytime and will be reused as a primary system to supply the building's heating load at nighttime. The system's performance is investigated for various geometrical parameters, including the fin-number, fin's degree of compactness, fin-height, and the combined-fin heights/pin. Moreover, thermodynamic optimization through exergy analysis is applied to give better insights into the system's performance and efficiency. Results imply that both the variations of the fin-number and the fin's degree of compactness improve the charging time by 17% and 2%, respectively. Moreover, the fin-number variations positively affect the exergy efficiency by 6%, while compactness of fins shows a converse behavior with an 8% reduction in the exergy efficiency. On the other hand, the fin height/pin parameter variations improve the melting performance by 15% while having fewer exergy efficiencies. In addition, reducing the fin-height parameter improves the exergy efficiency of the case with the least melting time by 25% while associated with the most prolonged melting duration. Hence, considering the different impacts of geometric parameters on the exergy efficiency and the storage time, one should pay attention to the designer's view and climate conditions to choose the suitable heat exchanger based on the desired application. If the storage time is limited, the combined fin height/pin is preferred. Otherwise, the fin-height might be a better candidate to achieve higher exergy efficiencies and system performance.

Exploring the photo-thermal conversion behavior and extinction coefficient of activated carbon nanofluids for direct absorption solar collector applications.

This work aims to explore the optical and thermal conversion characteristics of activated carbon-solar glycol nanofluids with various volume fractions namely 0.2, 0.4, and 0.6%, respectively. Kigelia africana leaves were synthesized into porous activated carbon nanomaterials by using the high-temperature sintering process and the pyrolysis process in a muffle furnace. The experimental investigation was carried out with different nanofluid concentrations by using the solar simulator. Nanofluids were heated with the assistance of a solar simulator test system and the convection/conduction heat loss was decreased by using the glass as an insulating material around the test section. Prepared nanofluid with 0.6 vol% activated carbon augmented the thermal conductivity by 14.36% at 60°C. The maximum temperature difference of 10°C was attained at 0.6% volume concentrations of nanofluid as compared with base fluid (solar glycol). In addition, maximum receiver efficiency of 94.51% was attained at 0.6% volume fractions of activated carbon-based nanofluid compared with solar glycol thru a light radiation time of 600 s. Moreover, activated carbon-based nanofluid exhibited significantly higher absorption efficiency as the majority of the radiation was absorbed by the nanofluid. It is concluded that activated carbon-based nanofluids could be a suitable low-cost highly stable material for developing working fluid for direct absorbance solar collector-based applications.