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Nanotechnology applications in green energy systems
\"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.
BOOK
Influence of base fluid, temperature, and concentration on the thermophysical properties of hybrid nanofluids of alumina–ferrofluid: experimental data, modeling through enhanced ANN, ANFIS, and curve fitting
Recently, the suspension of hybrid nanoparticles in conventional fluids has been investigated as a technique for improving the thermophysical properties of nanofluids. The dearth of documentation on the trio influence of volume concentration, base fluid, and temperature on the electrical conductivity and viscosity of hybrid alumina–ferrofluids [Al2O3–Fe2O3 (25:75 mass%)] has led to this study. The effective viscosity and electrical conductivity of the deionized water (DW)-based and ethylene glycol (EG)–DW-based (50:50 vol%) hybrid alumina–ferrofluids were measured at temperatures of 20–50 °C and volume concentrations of 0.05–0.75%. Based on the importance of soft computing methods to engineers, adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) were used for predicting the relative viscosity and electrical conductivity of the two types of hybrid ferrofluids. The measured data for viscosity and electrical conductivity were used in the modeling. Model performances were evaluated using the root mean squared error index. Viscosity was enhanced by 3.23–43.64% and 2.79–49.38%, while electrical conductivity was increased by 163.37–1692.16% and 717.14–7618.89% for the DW- and EG–DIW-based hybrid ferrofluids, respectively, compared with the respective base fluids. Increasing volume concentration augmented the viscosity and electrical conductivity of all the hybrid alumina–ferrofluids, whereas a rise in temperature enhanced their electrical conductivity and detracted the viscosity. DW-based hybrid alumina–ferrofluid was observed to have a lower viscosity and higher electrical conductivity than the EG–DW-based counterpart. The results showed that the optimum ANN and ANFIS models have a maximum error of less than 4.5% and 3.9% for relative viscosity and electrical conductivity, respectively, which were lower than those proposed using regression analysis. With the hybrid alumina–ferrofluids possessing a lower viscosity relative to single-particle ferrofluids, they are recommended for engineering application.
Journal Article
Comparative study of some non-Newtonian nanofluid models across stretching sheet: a case of linear radiation and activation energy effects
The use of renewable energy sources is leading the charge to solve the world’s energy problems, and non-Newtonian nanofluid dynamics play a significant role in applications such as expanding solar sheets, which are examined in this paper, along with the impacts of activation energy and solar radiation. We solve physical flow issues using partial differential equations and models like Casson, Williamson, and Prandtl. To get numerical solutions, we first apply a transformation to make these equations ordinary differential equations, and then we use the MATLAB-integrated bvp4c methodology. Through the examination of dimensionless velocity, concentration, and temperature functions under varied parameters, our work explores the physical properties of nanofluids. In addition to numerical and tabular studies of the skin friction coefficient, Sherwood number, and local Nusselt number, important components of the flow field are graphically shown and analyzed. Consistent with previous research, this work adds important new information to the continuing conversation in this area. Through the examination of dimensionless velocity, concentration, and temperature functions under varied parameters, our work explores the physical properties of nanofluids. Comparing the Casson nanofluid to the Williamson and Prandtl nanofluids, it is found that the former has a lower velocity. Compared to Casson and Williamson nanofluid, Prandtl nanofluid advanced in heat flux more quickly. The transfer of heat rates are
25.87
%
,
33.61
%
and
40.52
%
at
R
d
=
0.5
,
R
d
=
1.0
, and
R
d
=
1.5
, respectively. The heat transfer rate is increased by
6.91
%
as the value of
Rd
rises from 1.0 to 1.5. This study is further strengthened by a comparative analysis with previous research, which is complemented by an extensive table of comparisons for a full evaluation.
Journal Article
Conjugate natural convection flow of Ag–MgO/water hybrid nanofluid in a square cavity
The conjugate natural convection of a new type of hybrid nanofluid (Ag–MgO/water hybrid nanofluid) inside a square cavity is addressed. A thick layer of conductive solid is considered over the hot wall. The governing partial differential equations (PDEs) representing the physical model of the natural convection of the hybrid nanofluid along with the boundary conditions are reported. The thermophysical properties of the nanofluid are directly calculated using experimental data. The governing PDEs are transformed into a dimensionless form and solved by the finite element method. The effect of the variation of key parameters, such as the volume fraction of nanoparticles, Rayleigh number, and the ratio between the thermal conductivity of the wall and the thermal conductivity of the hybrid nanofluid (Rk), is studied. Furthermore, the effects of the key parameters are investigated on the temperature distribution, local Nusselt number, and average Nusselt number. The results of this study show that the heat transfer rate increases by adding hybrid nanoparticles for a conduction-dominant regime (low Rayleigh number). The heat transfer rate is an increasing function of both the Rayleigh number and the thermal conductivity ratio (Rk). In the case of a convective-dominant flow (high Rayleigh number flow) and an excellent thermally conductive wall, the local Nusselt number at the surface of the conjugate wall decreases substantially by moving from the bottom of the cavity toward the top.
Journal Article
Numerical simulation of hydrothermal features of Cu–H2O nanofluid natural convection within a porous annulus considering diverse configurations of heater
The purpose of the current study is to numerically investigate the effects of shape factors of nanoparticles on natural convection in a fluid-saturated porous annulus developed between the elliptical cylinder and square enclosure. A numerical method called the control volume-based finite element method is implemented for solving the governing equations. The modified flow and thermal structures and corresponding heat transfer features are investigated. Numerical outcomes reveal very good grid independency and excellent agreement with the existing studies. The obtained results convey that at a certain aspect ratio, an increment in Rayleigh and Darcy numbers significantly augments the heat transfer and average Nusselt number. Further, enhancement of Rayleigh number increases the velocity of nanofluid, while that of aspect ratio of the elliptical cylinder shows the opposite trend.
Journal Article
Mixed convection flow caused by an oscillating cylinder in a square cavity filled with Cu–Al2O3/water hybrid nanofluid
The aim of this paper is to examine the effects of Cu–Al
2
O
3
/water hybrid nanofluid and Al
2
O
3
/water nanofluid on the mixed convection inside a square cavity caused by a hot oscillating cylinder. The governing equations are first transformed into dimensionless form and then discretized over a non-uniform unstructured moving grid with triangular elements. The effects of several parameters, such as the nanoparticle volume fraction, the Rayleigh number, the amplitude of the oscillation, and the period of the oscillation of the cylinder are investigated numerically. The results indicate that the motion of the oscillating cylinder toward the top and bottom walls increases the average Nusselt number when the Rayleigh number is low. Furthermore, the presence of Al
2
O
3
and Cu–Al
2
O
3
nanoparticles leads to an increase in the values of the average Nusselt number
Nu
avg
for cases of low values of the Rayleigh number. It is found that the natural convection heat transfer rate of a simple Al
2
O
3
/water nanofluid is better than that of Cu–Al
2
O
3
/water hybrid nanofluid.
Journal Article
Entropy analysis of Powell–Eyring hybrid nanofluid including effect of linear thermal radiation and viscous dissipation
Hybrid nanofluids are introduced as heat transfer fluids with greater surface stability, diffusion and dispersion capabilities compared to traditional nanofluids. In this work, flow, convective heat transport and volumetric entropy generation in Powell–Eyring hybrid nanofluid are investigated. Hybrid nanofluid occupies the space over the uniform horizontal porous stretching surface with velocity slip at the interface. Effect of viscous dissipation and linear thermal radiation are also included in the simplified model. Mathematical equations for conservation of mass, momentum, energy and entropy are simplified under assumptions of boundary layer flow of Powell–Eyring hybrid nanofluid. Similarity solutions are obtained by transformation of governing partial differential equations to ordinary differential equations, using similarity variables. Keller box finite difference scheme is then adopted to find the approximate solutions of reduced ordinary differential equations. Numerical computations are performed for alumina–copper water ( Al2O3 – Cu/H2O ) hybrid nanofluid and conventional copper water ( Cu – H2O ) nanofluid. Graphs are produced for velocity, temperature and entropy profiles to study the effect of governing parameters. Skin friction factor and the local Nusselt number are also calculated at the boundary. The notable findings indicate that the hybrid Powell–Eyring nanofluid is better thermal conductor when compared with the conventional nanofluid. The rate of heat transfer at the boundary is greatest for smallest value of the shape factor parameter. The increase in Reynolds number and Brinkman number increases the overall entropy of the system.
Journal Article