Influence of size, shape, type of nanoparticles, type and temperature of the base fluid on natural convection MHD of nanofluids

AbstractIn this paper, we have presented MHD natural convection boundary layer flow, heat and mass transfer characteristics of nanofluid through porous media over a vertical cone influenced by different aspects of nanoparticles such as size, shape, type of nanoparticles and type of the base fluid and working temperature of base fluid. To increase the physical significance of the problem, we have taken dynamic viscosity and thermal conductivity as the functions of local volume fraction of nanoparticles. The drift-flux model of nanofluids, Brownian motion, thermophoresis, and enhancement ratio parameters are also considered in the present analysis. The influence of non-dimensional parameters such as magnetic field (M), buoyancy ratio parameter (Nr), conductivity parameter (Nc), viscosity parameter (Nv), Brownian motion parameter (Nb), thermophoresis parameter (Nt), Lewis number (Le) on velocity, temperature and volume fraction of nanoparticles in the boundary layer region is examined in detail. Furthermore the impact of these parameters on local Nusselt number (Nux) and enhancement ratio hnfhbf is also investigated. The results of present study reveal that significant natural convection heat transfer enhancement is noticed as the size of nanoparticles decreases. Moreover, type of the nanoparticles and type of the base fluid also influenced the natural convection heat transfer

Aerodynamics and Heat Transfer over Solid-Deflectors in Transverse, Staggered, Corrugated-Upstream and Corrugated-Downstream Patterns

Computational fluid dynamic simulations were conducted to analysis the influences of two different deflector orientations on turbulent forced-convection flow and skin friction loss of two-dimensional horizontal rectangular cross section channels with upper and lower wall-attached corrugated baffles. The governing flow equations, i.e., continuity, momentum, and energy, were numerically solved by the Finite Volume Method (FVM) using the Semi-Implicit Method for Pressure Linked Equation (SIMPLE) discretization formulation. The help of the CFD code FLUENT was employed to solve the dynamic and thermal behavior of air in the whole domain under investigation. The flow rate in terms of Reynolds number is ranged from 5,000 to 32,000. The obtained results show that augmenting the Reynolds number makes the dynamic thermo energy field redirect in the vicinity of deflector corners, and forces an augmentation in the thermal transfer rate from baffles

Enhancement of the Hydrodynamic Characteristics in Shell-and-Tube Heat Exchangers by Using W-Baffle Vortex Generators

Improving the hydrodynamic characteristics of STHECs (Shell-and-Tube Heat Exchanger Channels) by using BVGs (Baffle-type Vortex Generators) is among the common passive methods due to their proved efficiency. In this computational investigation, the same method is used to enhance the hydrodynamic behavior of STHECs, by inserting W-shaped Baffle-type Vortex Generators. The numerical model represented by the computational FVM (Finite Volume Method) is used to simulate and analyzed the considered physical model. The fluid used is air, its thermal physical properties are constant, turbulent, incompressible, and its temperature is 300 K at the inlet section of the STHEC. The flow velocity ( Uin ) and atmospheric pressure ( Patm ) are considered as boundary conditions at the entrance (x = 0) and exit (x = L) of the channel, respectively. The results showed that the friction coefficients were related to the pressure, velocity, and Reynolds number values. High values of Re yielded an acceleration of the fluid, resulting thus in increased pressure on the solid walls and augmented friction values

The Solar Air Channels: Comparative Analysis, Introduction of Arc-shaped Fins to Improve the Thermal Transfer

The problem under investigation contains a computational simulation of a specific heat exchanger with complex geometry fins. The problem solved is potentially interesting for researchers and engineers working on solar collectors and aerospace industry. It is known that heat transfer enhancement can be achieved by creating longitudinal vortices in the flow. These vortices can be generated by arc-shaped fins, and a computational analysis of such solar air channels is not a simple task. Therefore, we used a present-day commercial CFD code to solve the problem. The mathematical problem including the main equations and their explanation, as well as the numerical procedure was presented. The impact of arc-fins’ spacings on streamlines and temperature distributions was completely investigated, as well as the heat transfer rate, pressure drop and thermal enhancement factor. The Nusselt number (Nu) and friction loss (f) values of the solar air channel at AR = 1.321 (aspect ratio of channel width-to-height) and S = Pi/2 are found to be around 11.963% and 26.006%; 21.645% and 40.789%; 26.196% and 50.314%; and 30.322% and 58.355% higher than that with S = 3Pi/4, Pi, 5Pi/4 and 3Pi/2, respectively. Importantly, the arc-fins with Re = 12,000 at S = Pi/2 showed higher thermal enhancement performance than the one at S = 3Pi/4, Pi, 5Pi/4 and 3Pi/2 around 2.530%, 6.576%, 6.615% and 6.762%, respectively. This study contains the information which seems to be important for practical engineers

A Review of Solar Energy Collectors: Models and Applications

A current study and discussion in detail about many solar energy collectors of various types, components, classifications and configurations, through the analysis of their performance, is our aim through this review paper. The effects of the geometrical parameters of the solar air collectors as well as the functioning parameters on heat transfer and fluid flow processes were also discussed in detail. The numerical, analytical, and experimental analyses on different models of flat plate solar air collectors with various thermal transfer enhancement strategies were shown in various stages, i.e., modelling, control, measurement, and visualization of airfield, determination of heat transfer, control of friction loss and pressure drop, and evaluation of the thermal performance by the measurement of the augmentation in the temperature of the working fluid at a given solar irradiance and under given flow rate. We concluded this review by identifying the various applications possible for the solar air collectors such as heating and cooling of houses, drying agricultural food materials, and water desalination process

MHD flow of non-Newtonian ferro nanofluid between two vertical porous walls with Cattaneo–Christov heat flux, entropy generation, and time-dependent pressure gradient

This article studies the magnetohydrodynamic flow of non-Newtonian ferro nanofluid subject to time-dependent pressure gradient between two vertical permeable walls with Cattaneo–Christov heat flux and entropy generation. In this study, blood is considered as non-Newtonian fluid (couple stress fluid). Nanoparticles’ shape factor, Joule heating, viscous dissipation, and radiative heat impacts are examined. This investigation is crucial in nanodrug delivery, pharmaceutical processes, microelectronics, biomedicines, and dynamics of physiological fluids. The flow governing partial differential equations are transformed into the system of ordinary differential equations by deploying the perturbation process and then handled with Runge–Kutta 4th-order procedure aided by the shooting approach. Hamilton–Crosser model is employed to analyze the thermal conductivity of different shapes of nanoparticles. The obtained results reveal that intensifying Eckert number leads to a higher temperature, while the reverse is true for increased thermal relaxation parameter. Heat transfer rate escalates for increasing thermal radiation. Entropy dwindles for intensifying thermal relaxation parameter

Free Convection Flow of an Electrically-Conducting Micropolar Fluid between Parallel Porous Vertical Plates Using Differential Transform

In the present study, the effect of temperature-dependent heat sources on the fully developed free convection flow of an electrically conducting micropolar fluid between two parallel porous vertical plates in the presence of a strong cross magnetic field is analyzed. The micropolar fluid fills the space inside the porous plates when the rate of suction at one boundary is equal to the rate of injection at the other boundary. The coupled nonlinear governing differential equations are solved using the differential transform method (DTM). Moreover, the Runge-Kutta shooting method (RKSM), which is a numerical method, is used for the validity of DTM method and an excellent agreement is observed between the solutions of DTM and RKSM. Trusting this validity, the effects of Hartmann number, Reynolds number, micropolar parameter, and applied electric field load parameter are discussed on the velocity, microrotation velocity, and temperature. The skin friction, the couple stress, and Nusselt numbers at the plates are shown in graphs. It is observed that the Hartmann number and the micropolar parameter decreases the skin friction and the couple stress at both plates for suction and injection

Analysis of Fluid Dynamics and Heat Transfer in a Rectangular Duct with Staggered Baffles

This computational fluid dynamic analysis attempts to simulate the incompressible steady fluid flow and heat transfer in a solar air channel with wall-mounted baffles. Two ꞌSꞌ-shaped baffles, having different orientations, i.e., ꞌSꞌ-upstream and ꞌSꞌ-downstream, were inserted into the channel and fixed to the top and bottom walls of the channel in a periodically staggered manner to develop vortices to improve the mixing and consequently the heat transfer. The analyses are conducted with the Commercial CFD software FLUENT using the finite volume method for Reynolds number varying from 12,000 to 32,000. The numerical results are presented in terms of streamlines, velocity-magnitude, x-velocity, y-velocity, dynamic pressure coefficient, turbulent kinetic energy, turbulent viscosity, turbulent intensity, temperature field, coefficient and factor of normalized skin friction, local and average numbers of normalized Nusselt, and thermal performance factor. The insertion of the S-shaped baffles in the channel not only causes a much high friction loss, f/f0 = 3.319 - 32.336, but also provides a considerable augmentation in the thermal transfer rate in the channel, Nu/Nu0 = 1.939 - 4.582, depending on the S-baffle orientations and the Reynolds number. The S-upstream baffle provides higher friction loss and heat transfer rate than the S-Downstream around 56.443 %, 55.700 %, 54.972 %, 54.289 % and 53.660 %; and 25.011 %, 23.455 %, 21.977 %, 20.626 %, and 19.414 % for Re = 12,000, 17,000, 22,000, 27,000, and 32,000, respectively. In addition, the result analysis shows that the optimum thermal performance factor is around 1.513 at the highest Reynolds number and S-downstream

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

Thermo-fluidic Transport Process in a Novel M-shaped Cavity Packed with Non-Darcian Porous Medium and Hybrid Nanofluid: Application of Artificial Neural Network (ANN)

In this work, an attempt has been made to explore numerically the thermo-fluidic transport process in a novel M-shaped enclosure filled with permeable material along with Al2O3-Cu hybrid nanoparticles suspended in water under the influence of a horizontal magnetizing field. To exercise the influence of geometric parameters, a classical trapezoidal cavity is modified with an inverted triangle at the top to construct an M-shaped cavity. The cavity is heated isothermally from the bottom and cooled from the top, whereas the inclined sidewalls are insulated. The role of geometric parameters on the thermal performance is scrutinized thoroughly by changing the sidewall inclination, number, and height of the top inverted triangular undulation under similar boundary conditions. The governing equations transformed into dimensionless form are solved by using a computing code written in the finite volume approach. The analysis is conducted by considering a wide range of parametric influences like sidewall angles (γ), number (n), and height (δ) of the top triangular undulations, modified Rayleigh number (Ram), Darcy number (Da), Hartmann number (Ha), and hybrid nanoparticle concentrations (φ). Furthermore, the artificial neural network (ANN) technique is implemented and tested to predict the overall thermal behavior of the novel cavity to predict new cases. The results revealed that the design of sidewall inclination (γ) is an important parameter for modulating the thermo-flow physics. The M-shaped cavity (compared to trapezoidal) reveals either a rise or drop in the fluid circulation strength depending upon the magnitude of δ, but the heat transfer rate always increases due to an increase in the cooling length. The heat transfer increment is ∼61.01% as δ increases. Single undulation with higher depth is the optimum choice for achieving improved heat transfer (which may go up to ∼355.75% for δ = 0.5 and γ  = 45°). A decrease in Da or Ha causes a drop in the flow strength, which consequently leads to a drop in the heat transfer rate. Furthermore, the concepts of ANN will help researchers predict the behavior for such complicated cavity shapes with a multiphysics approach. This will save efforts as well as computing time for exploring the thermal behavior of any range of a dataset