scholarly journals The Influence of Combined Turbulators on the Hydraulic-Thermal Performance and Exergy Efficiency of MWCNT-Cu/Water Nanofluid in a Parabolic Solar Collector: A Numerical Approach

2021 ◽  
Vol 9 ◽  
Author(s):  
Yacine Khetib ◽  
Ammar Melaibari ◽  
Radi Alsulami
Keyword(s):  
Solar Collector ◽  
Volume Fraction ◽  
Numerical Approach ◽  
Exergy Efficiency ◽  
Multiphase Model ◽  
Two Phase ◽  
Simpler Algorithm ◽  
Fluent Software ◽  
Parabolic Geometries ◽  
Volume Method

The present research benefits from the finite volume method in investigating the influence of combined turbulators on the thermal and hydraulic exergy of a parabolic solar collector with two-phase hybrid MWCNT-Cu/water nanofluid. All parabolic geometries are produced using DesignModeler software. Furthermore, FLUENT software, equipped with a SIMPLER algorithm, is applied for analyzing the performance of thermal and hydraulic, and exergy efficiency. The Eulerian–Eulerian multiphase model and k-ε were opted for simulating the two-phase hybrid MWCNT-Cu/water nanofluid and turbulence model in the collector. The research was analyzed in torsion ratios from 1 to 4, Re numbers from 6,000 to 18,000 (turbulent flow), and the nanofluid volume fraction of 3%. The numerical outcomes confirm that the heat transfer and lowest pressure drop are relevant to the Re number of 18,000, nanofluid volume fraction of 3%, and torsion ratio of 4. Furthermore, in all torsion ratios, rising Re numbers and volume fraction lead to more exergy efficiency. The maximum value of 26.32% in the exergy efficiency was obtained at a volume fraction of 3% and a torsion ratio of 3, as the Re number goes from 60,000 to 18,000.

Numerical Study of Natural Convection in Vertical Cylindrical Annular Enclosure Filled with Cu-Water Nanofluid under Magnetic Fields

2019 ◽  
Vol 392 ◽  
pp. 123-137 ◽  
Author(s):  
Mohamed A. Medebber ◽  
Abderrahmane Aissa ◽  
Mohamed El Amine Slimani ◽  
Noureddine Retiel
Keyword(s):  
Natural Convection ◽  
Magnetic Fields ◽  
Volume Fraction ◽  
Numerical Study ◽  
Physical Parameters ◽  
Cold Temperatures ◽  
Simpler Algorithm ◽  
Wide Range ◽  
Nanoparticles Volume Fraction ◽  
Volume Method

The two dimensional study of natural convection in vertical cylindrical annular enclosure filled with Cu-water nanofluid under magnetic fields is numerically analyzed. The vertical walls are maintained at different uniform hot and cold temperatures, THand TC, respectively. The top and bottom walls of the enclosure are thermally insulated. The governing equations are solved numerically by using a finite volume method. The coupling between the continuity and momentum equations is effected using the SIMPLER algorithm. Numerical analysis has been carried out for a wide range of Rayleigh number (103≤Ra≤106), Hartmann number (1 ≤Ha≤100) and nanoparticles volume fraction (0 ≤φ≤0.08). The influence of theses physical parameters on the streamlines, isotherms and average Nusselt has been numerically investigated.

Numerical Simulation of Liquid-Solid Two-Phase Flow Reflux in Particle Impact Drilling System

2011 ◽  
Vol 402 ◽  
pp. 824-827
Author(s):  
Hao Yu Sun ◽  
Yang Zhang ◽  
Bin Bin Wang
Keyword(s):  
Flow Rate ◽  
Critical Flow ◽  
Particle Impact ◽  
Multiphase Model ◽  
Two Phase ◽  
Economic Reason ◽  
Critical Flow Rate ◽  
Annular Gap ◽  
Fluent Software ◽  
Drilling System

In particle impact drilling system, the steel particles would be recycled for economic reason. Thus, whether particles can return to the ground under certain conditions is an important problem. In this paper, the relationship between critical flow rate and annular gap is numerically studied using the Eulerian multiphase model in FLUENT software. Both the numerical and the experiment results show that the critical flow rate decreases with the increasing annular gap, and the simulation results correspond well with experimental results.

Numerical Analysis of Erosive Wear on the Guide Vanes of a Francis Turbine

2015 ◽  
Vol 741 ◽  
pp. 531-535
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Numerical Analysis ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Erosive Wear ◽  
Francis Turbine ◽  
Two Phase ◽  
Guide Vanes ◽  
Flow Equations ◽  
Sand Erosion ◽  
Volume Method

The paper presents the numerical analysis of erosive wear on the guide vanes of a Francis turbine using CFD code. The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the volume fraction of sand at the top of the guide vanes is higher than others and the maximum of volume fraction of sand is at same location with the maximum of sand erosion rate density. The erosive wear is more serious at the top of the guide vanes.

Numerical Simulation of Nanofluid-Cooling Enhancement of Three Fins Mounted in a Horizontal Channel

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Moussa Khentoul ◽  
Rachid Bessaïh
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Horizontal Channel ◽  
Thermal Fields ◽  
Nusselt Numbers ◽  
Simpler Algorithm ◽  
Laminar Mixed Convection ◽  
Cooling Enhancement ◽  
Volume Method

This article presents a numerical study of two-dimensional laminar mixed convection in a horizontal channel. The upper horizontal wall of the channel is insulated. The governing equations were solved by using the finite volume method based on the simpler algorithm. Comparisons with previous results were performed and found to be in excellent agreement. The results were presented in terms of streamlines, isotherms, local and average Nusselt numbers for the Richardson number (0 ≤ Ri ≤ 10), Reynolds number (5 ≤ Re ≤ 100), solid volume fraction of nanoparticles (0 ≤ ϕ ≤ 0.10), and the type of nanofluids (Cu, Ag, Al2O3, and TiO2). The results show that the previous parameters have considerable effects on the flow and thermal fields. It was found that the heat transfer increases with increasing of Ra, Re, and ϕ.

Exergy Analysis of a Flat Plate Solar Collector With Grooved Absorber Tube Configuration Using Aqueous ZnO–Ethylene Glycol

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Yash Kashyap ◽  
Apurva Singh ◽  
Y. Raja Sekhar
Keyword(s):  
Ethylene Glycol ◽  
Flat Plate ◽  
Solar Collector ◽  
Volume Fraction ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Plain Tube ◽  
Collector Temperature ◽  
Grooved Tube ◽  
Flat Plate Solar Collector

In this study, the exergetic performance of a flat plate solar collector (FPSC) setup with ZnO-based ethylene glycol (EG)/water nanofluid as a working fluid has been evaluated against that of EG/water. As a passive means to augment the rate of heat transfer, internally grooved tubes of two different pitches (e = 0.43 and e = 0.44) have been examined and compared against the performance of plain tube. The mass flow rate was fixed at 0.015 kg/s and the volume fraction of ZnO nanoparticles is ф = 0.02% v/v. The results indicate an enhancement in exergy efficiency of 44.61% when using the grooved tube (e = 0.44) against plain tube without the nanofluid and 39.17% when nanofluid is used. Using the nanofluid enhanced the exergy efficiency of the FPSC by a maximum of 73.81%. Maximum exergy efficiency obtained was 5.95% for grooved tube (e = 0.44) with nanofluid as working fluid and is in good agreement with previous literature. Exergy destruction/irreversibility due to temperature differences and heat flow within the system has been reported. Sun-collector temperature difference accounts for nearly 86–94% of the irreversibility. The results for thermal efficiency of this experimental setup have been published and summarized in this study for reference.

Determining the Optimum Arrangement of Micromixers in a Microchannel Filled with CuO-Water Nanofluid via Minimizing Entropy Generation

2017 ◽  
Vol 378 ◽  
pp. 39-58 ◽  
Author(s):  
Ahmad Ababaei ◽  
Mahmoud Abbaszadeh ◽  
Ali Akbar Abbasian Arani
Keyword(s):  
Boundary Conditions ◽  
Parallel Plate ◽  
Slip Velocity ◽  
Temperature Jump ◽  
Volume Fraction ◽  
Reynolds Numbers ◽  
Governing Equations ◽  
Simpler Algorithm ◽  
Optimum Arrangement ◽  
Volume Method

In this study, the flow of CuO-water nanofluid in a parallel-plate microchannel in the presence of several micromixers is examined to find optimum arrangements of the micromixers. The governing equations, which are accompanied with the slip velocity and temperature jump boundary conditions, are solved by the Finite Volume Method and SIMPLER algorithm. The study is conducted for the Reynolds numbers in the range of 10 ≤ Re ≤ 100, Knudsen numbers ranging of 0 ≤ Kn ≤ 0.1 and volume fraction of nanoparticles ranging of 0 ≤ ϕ ≤ 4%. The results show that the optimum arrangements of the micromixers belong to cases in which the heights of micromixers are smaller, the distance between them is lower, and their numbers are more.

Experimental and Numerical Approach to Enlargement and Determination of Performance of Primary Sedimentation Basin

2007 ◽  
Author(s):  
A. M. Razmi ◽  
B. Firoozabadi
Keyword(s):  
Numerical Scheme ◽  
Fluid Model ◽  
Settling Tank ◽  
Numerical Approach ◽  
Acoustic Doppler Velocimeter ◽  
Two Phase ◽  
Optimum Position ◽  
Volume Of Fluid Model ◽  
Volume Method

In the present study, the presence of a baffle and its effect on the hydrodynamics of the flow in a primary settling tank has been investigated experimentally by ADV (Acoustic Doppler Velocimeter). On the other hand, the characteristics of this flow field were simulated by an unsteady two-phase finite volume method, and VOF (Volume of Fluid) model; and results were evaluated by the experimental data. The numerical calculation performed by using k–ε RNG model agrees well with experiments. It depicts the ability of this method in predicting the velocity profile and flow structure. In addition, the optimum position of the baffle to achieve the best performance of the tank was determined by applying the above mentioned numerical scheme.

Numerical Simulation of Steady and Unsteady Compressible Multiphase Flows

2012 ◽  
Author(s):  
Huiying Li ◽  
Sergio A. Vasquez
Keyword(s):  
Experimental Data ◽  
Multiphase Flows ◽  
Volume Fraction ◽  
Numerical Approach ◽  
Absolute Pressure ◽  
Multiphase Model ◽  
Phase Volume ◽  
Phase Volume Fraction ◽  
Wide Range ◽  
Liquid Flows

The present work concerns the development of an advanced numerical approach to simulate steady and unsteady compressible multiphase flows in the CFD solver FLUENT. Compressible multiphase flows can be simulated under the framework of either the multiphase Mixture/VOF or the Eulerian multifluid model. The governing equations solved are the mixture (Mixture or VOF model) or phase (Eulerian multifluid model) momentum, energy, species transport equations and phase volume fraction equations. Turbulence effects are accounted for using a range of multiphase turbulence models. For the compressible multiphase model, it assumes that only one phase is a compressible gas/gaseous mixture with multiple species. In gas-liquid flows, all the liquid phases can be compressible /incompressible liquid, while in gas-solid flows the solid phase can be treated as a granular flow. To ensure numerical stability and obtain physical solutions, the absolute pressure is limited in a way to satisfy the constraints for both incompressible and compressible flows that may exist in different regions. The compressible effects are taken into account by adding extra terms related to sound speed and phase volume fractions in both the phase volume fraction and the pressure-correction equations. For flow conditions at inlets and exits, only pressure and mass-flow-rate boundaries are applicable. The mixture Mach numbers are defined and used to determine the subsonic or supersonic flows and thermal boundary conditions. The compressible multiphase model have been successfully used to simulate steady and unsteady, sub- and super-sonic compressible multiphase flows in a wide range of 2D and 3D multiphase systems. The examples presented in the paper include: (1). Gas-liquid separation in a vertical cylindrical container; (2). Transient pressure variations in compressible liquid and gas-liquid flows of water hammers; (3). Sub- and super-sonic gas-liquid two-phase flows in a nozzle; (4). Cavitating and ventilated super-cavitating flows; and (5). 3D gas-liquid flows in a three-stream injector. The solver robustness and convergence performance will be discussed. The solutions will be compared with available experimental data or numerical solutions. Emphasis will be focused on the solver performances on simulations of compressible multiphase flows. Overall, the results obtained from the present compressible multiphase model are in line with analytical/CFD solutions or available experimental data. The numerical approach is reasonably fast and robust, and suitable for practical compressible multiphase applications.

Heat Transfer Enhancement Using Cu-Water Nanofluid in an Enclosure with Moving Cold Sidewalls

2012 ◽  
Vol 326-328 ◽  
pp. 440-445
Author(s):  
Ghanbar Ali Sheikhzadeh ◽  
M. Tavakoli ◽  
H. Alizadeh
Keyword(s):  
Heat Source ◽  
Richardson Number ◽  
Volume Fraction ◽  
Maximum Temperature ◽  
Source Surface ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Square Cavity ◽  
Simpler Algorithm ◽  
Volume Method

Mixed convection of Cu-water nanofluid in a lid-driven square cavity with a heat source embedded in the bottom wall is studied numerically. The governing equations together with the respective boundary conditions are solved numerically using the finite volume method and the SIMPLER algorithm. The computations are performed for various Richardson numbers (), heat source length () and volume fraction of the nanoparticles (). It is observed from the results that the average Nusselt number is increased by increasing the Richardson number and the volume fraction of the nanoparticles. Moreover, the maximum temperature at the heat source surface decreases by increasing the Richardson number and the volume fraction of the nanoparticles.

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