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\"This book will be beneficial for students, researchers and scientists working in the field of green energy systems. In the last few decades, green energy technologies have gained significant interest. The increase of heat transfer in green energy technologies is one of the most important concerns in energy collection, energy storage, energy utilization, energy conservation, and optimum design. Since nanofluids/nano-enhanced phase change materials are used to increase heat transfer characteristics and thermal properties compared to conventional fluids/phase change materials, the performance of green energy technologies can be improved. These novel strategies are gaining interest to researchers and authors in recent years. This book presents the various applications of nanofluids, hybrid nanofluids, and nano-enhanced phase change materials in green energy technologies such as solar thermal energy storage, photovoltaic/thermal systems, tracking and non-tracking solar collectors, solar thermal power plant, and wind turbine cooling systems. The thermophysical properties of the nanofluids and nano-enhanced phase change materials are also presented. This book also overviews the challenges and opportunities in implementing the nanofluids/nano-enhanced phase change materials application in green energy technologies\"-- Provided by publisher.

Non-Newtonian fluids with nanomaterials are studied to improve industrial efficiency and production by enhancing thermal conductivity. In addition, the titanium dioxide nanoparticles can easily penetrate cells and tissues due to their small size. Its photocatalytic activities can also be utilized to produce reactive oxygen species, which have potential applications in cancer treatment. So, the present investigation intends to analyze the water-based titanium dioxide power-law nanofluid flow over a thin needle. Further, the thermal radiation was incorporated and analyzed as a complete case study for linear, nonlinear, and quadratic radiation. The governing equations are reformed into a dimensionless form using suitable similarity variables. Numerical solutions were found by implementing the Bvp4c technique. The major conclusion drawn from the present investigation reveals that the temperature is enhanced by the radiation, needle size, and titanium dioxide volume fraction. The nonlinear radiation case plays a dominant role compared to the other two radiation cases. In order to provide further insight into the engineering quantities, multiple quadratic regression models are utilized to predict skin friction and thermal transmission rate. The quadratic regression term of radiation and temperature ratio parameters has a negative influence on the heat transmission rate. The outcomes of this investigation may help to get a better theoretical understanding of various scientific research and biomedical applications, especially in the treatment of tumors, sterilization of medical instruments, drug delivery systems, and cancer treatment. Graphical abstract

In the current investigation, a (TiO 2 –Ag/water) hybrid nanofluid (NF), saturated porous medium filled wavy-walled enclosure, and an unstable magneto-mixed convective flow are examined. Heat radiation (Rd) is present with the constant magnetic field (B0), and the cavity, which is partially heated from its bottom wall and cooled from its wavy-left and right walls, contains a square solid block that is solidly surrounded on all sides. The governing PDEs, which are represented in terms of stream function, temperature, and nanoparticle volume percent, are numerically solved using a finite volume technique. It is discovered that as the dimensionless heat source length (B) rises, the streamlines' strength marginally changes while the isotherms in the wavy porous cavity grow increasingly obvious. The results show that increasing the number of undulations and hybrid NF generally produces a higher average Nusselt number when the wave amplitude parameter A  = 0.3 and the volume fractions of (TiO 2 − Ag/water) Hybrid NF = 0.05. Raising the volume percentage of Hybrid NF enhances the average Nusselt number while increasing the Hartmann number observed happened with decreases the average Nusselt number. One of the primary factors contributing to the production of entropy is the irreversibility of the magnetic force, which leads the isentropic lines to diffuse toward the interior of the enclosure as Ha rises. In comparison with previous case studies, the highest Nusselt number is at λ  = 3, and it rises in every case as the wave amplitude parameter and the percentage of hybrid NF volume increase. It was discovered that increasing porosity greatly increased local Nusselt numbers due to improved heat transfer within the enclosure. The lowest local Nusselt number has been determined to be Q  = − 2, which represents the heat generation/absorption factor.

Purpose The purpose of this study is to theoretically analyze the laminar free convection heat transfer of nanofluids in a square cavity. The sidewalls of the cavity are subject to temperature difference, whereas the bottom and top are insulated. Based on the available experimental results in the literature, two new non-dimensional parameters, namely, the thermal conductivity parameter (Nc) and dynamic viscosity parameter (Nv) are introduced. These parameters indicate the augmentation of the thermal conductivity and dynamic viscosity of the nanofluid by dispersing nanoparticles. Design/methodology/approach The governing equations are transformed into non-dimensional form using the thermo-physical properties of the base fluid. The obtained governing equations are solved numerically using the finite element method. The results are reported for the general non-dimensional form of the problem as well as case studies in the form of isotherms, streamlines and the graphs of the average Nusselt number. Using the concept of Nc and Nv, some criteria for convective enhancement of nanofluids are proposed. As practical cases, the effect of the size of nanoparticles, the shape of nanoparticles, the type of nanoparticles, the type of base fluids and working temperature on the enhancement of heat transfer are analyzed. Findings The results show that the increase of the magnitude of the Rayleigh number increases of the efficiency of using nanofluids. The type of nanoparticles and the type of the base fluid significantly affects the enhancement of using nanofluids. Some practical cases are found, in which utilizing nanoparticles in the base fluid results in deterioration of the heat transfer. The working temperature of the nanofluid is very crucial issue. The increase of the working temperature of the nanofluid decreases the convective heat transfer, which limits the capability of nanofluids in decreasing the size of the thermal systems. Originality/value In the present study, a separation line based on two non-dimensional parameters (i.e. Nc and Nv) are introduced. The separation line demonstrates a boundary between augmentation and deterioration of heat transfer by using nanoparticles. Indeed, by utilizing the separation lines, the convective enhancement of using nanofluid with a specified Nc and Nv can be simply estimated.

We examine thermal management in the heat exchange of compact density nanoentities in crude base liquids. It demands the study of the heat and flow problem with non-uniform physical properties. This study was conceived to analyze magnetohydrodynamic Eyring–Powell nanofluid transformations due to slender sheets with varying thicknesses. Temperature-dependent thermal conductivity and viscosity prevail. Bioconvection due to motivated and dynamic microorganisms for Eyring–Powell fluid flow is a novel aspect herein. The governing PDEs are transmuted into a nonlinear differential structure of coupled ODEs using a series of viable similarity transformations. An efficient code for the Runge–Kutta method is developed in MATLAB script to attain numeric solutions. These findings are also compared to previous research to ensure that current findings are accurate. Computational activities were carried out with a variation in pertinent parameters to perceive physical insights on the quantities of interest. Representative outcomes for velocity, temperature, nanoparticles concentration, and bioconvection distributions as well as the local thermal transport for different inputs of parameters are portrayed in both graphical and tabular forms. The results show that the fluid’s velocity increases with mixed convection parameters due to growing buoyancy effects and the fluid’s temperature also increased with higher Brownian motion Nb and thermophoretic Nt. The numerical findings might be used to create efficient heat exchangers for increasingly challenging thermo-technical activities in manufacturing, construction, and transportation.

Introduction Chronic lung disease is a major cause of morbidity in African children with HIV infection; however, the microbial determinants of HIV-associated chronic lung disease (HCLD) remain poorly understood. We conducted a case–control study to investigate the prevalence and densities of respiratory microbes among pneumococcal conjugate vaccine (PCV)-naive children with (HCLD +) and without HCLD (HCLD-) established on antiretroviral treatment (ART). Methods Nasopharyngeal swabs collected from HCLD + (defined as forced-expiratory-volume/second < -1.0 without reversibility postbronchodilation) and age-, site-, and duration-of-ART-matched HCLD- participants aged between 6–19 years enrolled in Zimbabwe and Malawi (BREATHE trial-NCT02426112) were tested for 94 pneumococcal serotypes together with twelve bacteria, including Streptococcus pneumoniae (SP), Staphylococcus aureus (SA), Haemophilus influenzae (HI), Moraxella catarrhalis (MC), and eight viruses, including human rhinovirus (HRV), respiratory syncytial virus A or B, and human metapneumovirus, using nanofluidic qPCR (Standard BioTools formerly known as Fluidigm). Fisher's exact test and logistic regression analysis were used for between-group comparisons and risk factors associated with common respiratory microbes, respectively. Results A total of 345 participants (287 HCLD + , 58 HCLD-; median age, 15.5 years [IQR = 12.8–18], females, 52%) were included in the final analysis. The prevalence of SP (40%[116/287] vs. 21%[12/58], p  = 0.005) and HRV (7%[21/287] vs. 0%[0/58], p  = 0.032) were higher in HCLD + participants compared to HCLD- participants. Of the participants positive for SP (116 HCLD + & 12 HCLD-), 66% [85/128] had non-PCV-13 serotypes detected. Overall, PCV-13 serotypes (4, 19A, 19F: 16% [7/43] each) and NVT 13 and 21 (9% [8/85] each) predominated. The densities of HI (2 × 10 4 genomic equivalents [GE/ml] vs. 3 × 10 2 GE/ml, p  = 0.006) and MC (1 × 10 4 GE/ml vs. 1 × 10 3 GE/ml , p  = 0.031) were higher in HCLD + compared to HCLD-. Bacterial codetection (≥ any 2 bacteria) was higher in the HCLD + group (36% [114/287] vs. (19% [11/58]), ( p  = 0.014), with SP and HI codetection (HCLD + : 30% [86/287] vs. HCLD-: 12% [7/58], p  = 0.005) predominating. Viruses (predominantly HRV) were detected only in HCLD + participants. Lastly, participants with a history of previous tuberculosis treatment were more likely to carry SP (adjusted odds ratio (aOR): 1.9 [1.1 -3.2], p  = 0.021) or HI (aOR: 2.0 [1.2 – 3.3], p  = 0.011), while those who used ART for ≥ 2 years were less likely to carry HI (aOR: 0.3 [0.1 – 0.8], p  = 0.005) and MC (aOR: 0.4 [0.1 – 0.9], p  = 0.039). Conclusion Children with HCLD + were more likely to be colonized by SP and HRV and had higher HI and MC bacterial loads in their nasopharynx. The role of SP, HI, and HRV in the pathogenesis of CLD, including how they influence the risk of acute exacerbations, should be studied further. Trial registration The BREATHE trial (ClinicalTrials.gov Identifier: NCT02426112 , registered date: 24 April 2015).

Multiple tools have been used to determine the sensitivity of phosphates from the early Archaean Barberton greenstone belt to transformation. The assessment of the degree of transformation is crucial for verifying data about the parameters of the paleo-environment. From the obtained results, three generations of phosphates can be distinguished. Group A is observed in cherts and banded iron formation BIF early-generation fluor-hydroxyapatite that precipitated from seawater. It is characterized by flat rare earth element (REE) patterns with a positive Eu anomaly and high Y/Ho ratio in the range of 54–70. Apatites in this group lack any visible indicators of secondary alterations at the micro- and nanoscales. Fourier transform infrared spectra indicate that these apatites are relatively rich in water, and, due to cationic substitution, their OH-stretching regions exhibit complex ordering and numerous component bands. The characteristics observed in the cherts and silicified felsic volcaniclastics of group B imply advanced metasomatic alteration. They exhibit light and heavy REE depletion and an absence of water in the halogen site. Nanoscale investigations reveal cracks, pores, nanofluid inclusions and nanochannel-like structures, as well as inclusions. Group C is represented by igneous-derived apatites that partially reflect their igneous origin. The phosphates are predominantly fluorapatite with typical magmatic apatite REE distribution patterns. Imaging at the micro- and nanoscales indicates that they partially preserve the signature of igneous origin. It seems that some of the analyzed apatite partially preserved their primordial features; therefore, they might be used for the reconstruction of Archaean abiotic systems.

This study aims to develop a multi-objective version of the search group algorithm (SGA) called the multi-objective search group algorithm (MOSGA) to help determine thermo-economic optimization of flat-plate solar collector (FPSC) systems. Search mechanisms of the SGA were modified to determine non-dominated solutions through mutation, generation, and selection stages. Authors also mined the Pareto archive with a selection mechanism to maintain and intensify convergence and distribution of solutions. The study tested the proposed MOSGA with well-known multi-objective benchmark problems. Results were compared with outcomes from conventional algorithms using the same performance metrics to validate the capability and performance of the MOSGA. Afterward, MOSGA was applied to find the best design parameters to simultaneously optimize thermal efficiency and the total annual cost of FPSC systems. Four case studies were conducted with four different working fluids (pure water, SiO 2 , Al 2 O 3, and CuO nanofluids). Optimization results obtained by the MOSGA were analyzed and compared with solutions provided by other algorithms. The findings revealed relative improvement in thermal efficiency and reduced annual cost for all nanofluids compared to pure water. Thermal efficiency was improved by 2.2748%, 2.4298%, and 2.7948% for SiO 2 , Al 2 O 3, and CuO case studies, respectively, compared to pure water. Meanwhile, TAC rates were increased by 2.4111%, 2.3403%, and 2.9133% for these case studies, respectively. Comparative results also demonstrated that MOGSA was robustly effective and superior in the selection of appropriate design parameters of FPSC systems.

In this study, we conducted numerical simulations to investigate a novel approach for revolutionizing agricultural methods. The focus was on combining sun-powered tractors with Magnetohydrodynamics (MHD) in the flow of a tetra hybrid nanofluid (TETHNF). The TETHNF consists of Magnetite (Fe3O4), Silver (Ag), carbon nanotubes (CNT) nanoparticles suspended in Ethylene Glycol (EG). The utilization of TETHNF increases thermal transport properties, leading to intensified energy efficiency in agricultural equipment. Solar thermal radiation, entropy generation, heat generation, porous medium phenomena are adapted in analyzing the flow problem. Appropriate technique for nondimensionalization is employed to simplify the governing flow equations into a system of nonlinear ordinary differential equations (ODEs). To solve the modeled equations, the Galerkin approach is utilized. The results indicate that the fluid temperature rises as the radiation factor and thermal Biot number increase.

Highly concentrated triple-junction solar cells (HCTJSCs) are cells that have diverse applications for power generation. Their electrical efficiency is almost 45%, which may be increased to 50% by the end of the year 2030. Despite their overwhelming ability to generate power, their efficiency is lower when utilized in a concentrated manner, which introduces a high-temperature surge, leading to a sudden drop in output power. In this study, the efficiency of a 10 mm × 10 mm multijunction solar cell (MJSC) was increased to almost 42% under the climatic conditions in Lahore, Pakistan. Active cooling was selected, where SiO2–water- and Al2O3–water-based nanofluids with varying volume fractions, ranging from 5% to 15% by volume, were used with a 0.001 kg/s mass flow rate. In addition, two- and three-layer microchannel heat sinks (MCHSs) with squared microchannels were designed to perform thermal management. Regarding the concentration ratio, 1500 suns were considered for 15 August at noon, with 805 W/m2 and 110 W/m2 direct and indirect radiation, respectively. A complete model including a triple-junction solar cell and allied assemblies was modeled in Solidworks software, followed by temperature profile generation in steady-state thermal analyses (SSTA). Thereafter, a coupling of SSTA and Ansys Fluent was made, in combination with the thermal management of the entire model, where the temperature of the TJSC was found to be 991 °C without active cooling, resulting in a decrease in electrical output. At 0.001 kg/s, the optimum average surface temperature (44.5 °C), electrical efficiency (41.97%), and temperature uniformity (16.47 °C) were achieved in the of MJSC with SiO2–water nanofluid with three layers of MCHS at a 15% volume fraction. Furthermore, the average outlet temperature of the Al2O3–water nanofluid at all volume fractions was high, between 29.53 °C and 31.83 °C, using the two-layer configuration. For the three-layer arrangement, the input and output temperatures of the working fluid were found to be the same at 25 °C.