Heat Transfer Of Cu-water Nanofluid Research Articles

Numerical study on mixed convection heat transfer of copper-water nanofluid in a porous cavity with an isothermal solid block in local thermal non-equilibrium

This manuscript reports a numerical study on mixed convection heat transfer of Cu-water nanofluid in a porous cavity with an isothermal solid block in the state of local thermal non equilibrium. The set of governing equations are solved by finite volume method combined with SIMPLE algorithm. Through streamlines and isothermal contour plots as well as the average Nusselt number, the impact of various parameters like the nanoparticle concentration, Richardson number, Darcy number, and inter phase heat transfer coefficient is highlighted. The main findings indicate that the Local thermal non-equilibrium state (H = 1, 10) produces the maximum heat transfer rate than the local thermal equilibrium state (H = 1000).

Application of lattice Boltzmann method to curved boundaries for simulating nanofluid flow in an L-Shape enclosure

PurposeThis paper aims to use the Lattice Boltzmann method (LBM) to numerically simulate the natural convection heat transfer of Cu-water nanofluid in an L-shaped enclosure with curved boundaries.Design/methodology/approachLBM on three different models of curved L-shape cavity using staircase approach is applied to perform a comparative investigation for the effects of curved boundary on fluid flow and heat transfer. The staircase approximation is a straightforward and efficient approach to simulating curved boundaries in LBM.FindingsThe effect of curved boundary on natural convection in different parameter ranges of Rayleigh number and nanoparticle volume fraction is investigated. The curved L-shape results are also compared to the rectangular L-shape results that were also achieved in this study. The curved boundary LBM simulation is also validated with existing studies, which shows great accuracy in this study. The results show that the top curved boundary in curved L-shape models causes a notable increase in the Nusselt number values.Originality/valueBased on existing literature, there is a lack of comparative studies which would specifically examine the effects of curved boundaries on natural convection in closed cavities. Particularly, the application of curved boundaries to an L-shape cavity has not been examined. In this study, curved boundaries are applied to the sharp corners of the bending section in the L-shape and the results of the curved L-shape models are compared to the simple rectangular L-shape model. Hence, a comparative evaluation is performed for the effect of curved boundaries on fluid flow in the L-shape enclosure.

Mixed convection in sinusoidal lid driven cavity with non-uniform temperature distribution on the wall utilizing nanofluid

Mixed convection heat transfer of Cu-water nanofluid in an arc cavity with non-uniform heating has been numerically studied. The top flat moving wall is isothermally cooled at Tc and moved with a constant velocity. While the heated arc stationary wall of the cavity is maintained at a hot temperature Th. FORTRAN code is used to solve the mass, momentum, and energy equations in dimensionless form with suitable boundary conditions. In this study, the Reynolds number changed from 1 to 2000, and the Rayleigh number changed from 0 to 107. Also, the range of nanoparticles volume fraction extends from ϕ = 0 to 0.07. Stream vorticity method selected for the discretization of flow and energy equations. The present results are compared with the previous results for the validation part, where the results found a good agreement with the others works. The isotherms are regulated near the arc-shape wall causing a steep temperature gradient at these regions and the local and average heat transfer rate increases with increased volume fraction or Reynolds number or Rayleigh number. Finally, Correlation equations of the average Nusselt number from numerical results are presented.

Experimental and numerical study of natural convection of Cu-water nanofluid in a cubic enclosure under constant and alternating magnetic fields

In this paper, experimental and numerical studies of natural convection heat transfer of Cu-water nanofluid in a cubic enclosure under the effects of both the time-unvarying and alternating magnetic fields are presented. The effect of the nanofluid volume fraction on the natural convection heat transfer in the presence of a constant magnetic field is studied for different Grashof numbers. Moreover, the influence of an alternating (in time) magnetic field in the shape of a rectangular wave with different frequencies on the heat transfer rate is investigated. The results show that in the absence of a magnetic field, adding Cu-nanoparticles to water enhances the heat transfer performance. The Nusselt number increases with increasing the volume fraction of the nanofluid. On the other hand, if the enclosure is subjected to a strong enough magnetic field, the negative effect of the elevated electrical conductivity by adding the nanoparticles dominates the effect of the increased thermal performance by using nanofluid. The increased electrical conductivity raises the magnetohydrodynamic effect, which acts against the buoyancy force. As a result, increasing the nanoparticles volume fraction reduces the heat transfer performance if the magnetic field strength is beyond a Hartmann number that is greater than a threshold value.

Rotating Cylinder Turbulator Effect on The Heat Transfer of a Nanofluid Flow in a Wavy Divergent Channel

Abstract. In this research study, the numerical Galerkin Finite Element Method (GFEM) is used for forced laminar convection heat transfer of Cu-water nanofluid in a divergent wavy channel including a rotating cylinder turbulator. The above boundary of the channel is in low temperatures and the bottom boundary is in hot temperatures as well as the cylinder wall temperature. It is assumed that the cylinder rotates in the cavity and makes vortexes to enhance heat transfers. The dimensionless governing equations including velocity, pressure, and temperature formulation are solved by the Galerkin finite element method. The results are discussed based on the governing factors such as nanoparticle volume fraction, Reynolds number, cylinder diameter and rotating velocity. As a main result, among the all studied parameters (Re, u, φ and r), increasing the Re number has the most effect on heat transfer which has 4.8 and 1.6 Average Nu for the cylinder wall and wavy wall, respectively.

Uniform Magnetic field (UMF) Effect on the Heat Transfer of a Porous Half-Annulus Enclosure Filled by Cu-Water Nanofluid Considering Heat Generation

Background: In this work, the effect of a uniform magnetic field (UMF) on the natural convection heat transfer of Cu-water nanofluid in a porous half-annulus cavity is studied by finite element method, considering heat generation. The effects of four parameters (magnetic field angle (γ), Hartmann number (Ha), nanoparticles volume fraction (φ) and Rayleigh number (Ra)) on the local and average Nusselt numbers of outer wall have been investigated. Methods: Numerical Finite Element Method (FEM) based on FlexPDE commercial code was used to solve the described problems and the validation was also performed by Finite Difference Method (FDM) in previous studies. Results: It was found that by applying external magnetic field with a certain angle with respect to the geometry, the maximum local heat Nusselt number could shift to one side of outer wall and the shift is dependent on the angle of the imposed magnetic field. Conclusion: Our results also confirm that increasing the Hartmann number decreases the Nusselt number due to Lorentz force resulting from the presence of stronger magnetic field which slows down the fluid motion and in turn leads to a decreased heat transfer.

Nanoparticle migration and natural convection heat transfer of Cu-water nanofluid inside a porous undulant-wall enclosure using LTNE and two-phase model

Using Buongiorno's model, the natural convection of Cu-water nanofluid flowing within a wavy wall porous enclosure at the presence of a cylindrical heater was numerically investigated. The problem is considered such that there is no local thermal equilibrium between two phases of porous media. The effects of Rayleigh number (103≤Ra≤106), the Lewis number (1≤Le≤50), Brownian motion parameter (0.1≤Nb≤0.5), the thermophoresis parameter (0.1≤Nt≤0.5), the buoyancy ratio (0.1≤Nr≤0.5), the Darcy number (10−5≤Da≤10−1), porosity (0.1≤ε≤0.9), the ratio of the thermal conductivity of the nanofluid to the solid phase (0.1≤γs≤10), coefficient of heat transfer at the interface (1≤Nhs≤1000) on hydrodynamic and thermal parameter have been studied. Streamlines, distribution of temperature and concentration of nanoparticles are presented and discussed. Increasing in the Rayleigh, the Darcy, the Lewis numbers, the thermal conductivity ratio and the Brownian parameter of the nanoparticle motions homogenizes the nanofluid. Meanwhile, the homogeneity is reduced as thermophoresis is increased. The results show that the thermal equilibrium model for porous media is applicable for the cases with large heat transfer coefficient at the interface between the solid matrix and the nanofluid. Moreover, the average Nusselt number of both porous phases' increases with the Brownian parameter, while the Nusselt number is reduced as the thermophoresis is increased.

Investigation of natural convection heat transfer performance of the QFN-PCB electronic module by using nanofluid for power electronics cooling applications

Natural convection heat transfer of Cu-water nanofluid in a 3 × 3 array of a typical isothermal quad flat non-lead (QFN) embedded printed circuit board (PCB) module which can be bounded with respect to the sealed non-Darcy porous enclosure is numerically investigated. The Darcy-Brinkman-Forchheimer model is adopted to model the fluid flow in the porous medium under the presence of an external magnetic field. The transport governing equations are solved by the finite volume method based on the SIMPLE algorithm and the power law scheme. Main efforts focus on the effects of the parameters such as a nanoparticle volume fraction, Hartmann number, Darcy number and the enclosure side aspect ratio on the fluid flow and heat transfer characteristics inside the enclosure. The obtained results indicate that the influence of nanofluid of the overall Nusselt number increases with increasing the Darcy number, but decreases with increasing the Hartmann number. The overall Nusselt number attains its maximum value in the range of enclosure side aspect ratio from 1.5 to 3 with respect to the Darcy number. Moreover, the proposed correlations improve the efficiency, reliability and stability of the electronic device encountered in various applications in electronic industries.

Magnetohydrodynamics flow and heat transfer of Cu-water nanofluid through a partially porous wavy channel

In this paper, the lattice Boltzmann method is applied to investigate the effects of uniform vertical magnetic field on thermo-hydrodynamics of nanofluid in a partially porous channel. Cu-water nanofluid with constant pressure gradient is forced to flow into the channel while the top wall is heated by constant heat flux and bottom wavy wall of the channel is insulated against heat. The porous media is modeled using the Brinkman–Forchheimer model. Good agreements with the previous results verify that the selected numerical method is a capable method for simulating magnetic fluids in a porous media. The effects of active parameters, i.e. solid volume fraction of nanoparticles, pressure gradient, magnetic field and permeability of the porous layer, on thermo-hydrodynamics of flow are examined. The results reveal that the Nusselt number is an increasing function of nanoparticle volume fraction, Hartmann number, pressure gradient and Darcy number, although the effect of Darcy numbers and pressure gradient on the temperature profile are more noticeable than others.

Effects of radiation on convection heat transfer of Cu-water nanofluid past a moving wedge

Heat transfer characteristics of a two-dimensional steady hydrodynamic flow of water-based copper(Cu) nanofluid over a moving wedge, taking into account the effects of thermal radiation, have been investigated numerically. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations and solved numerically by using the fourth-order Runge-kutta method with shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The existence of unique and dual solutions for self-similar equations of the flow and heat transfer are analyzed numerically. The results indicate that there is strong dependence of the thermal gradient at the surface of the wedge on both velocity ratio parameter and thermal radiation.

Lattice Boltzmann Simulation of MHD Natural Convection Heat Transfer of Cu-Water Nanofluid in a Linearly/Sinusoidally Heated Cavity

Lattice Boltzmann Simulation of MHD Natural Convection Heat Transfer of Cu-Water Nanofluid in a Linearly/Sinusoidally Heated Cavity

Flow and Heat Transfer of Cu‐Water Nanofluid between a Stretching Sheet and a Porous Surface in a Rotating System

The aim of the present paper is to study the flow of nanofluid and heat transfer characteristics between two horizontal plates in a rotating system. The lower plate is a stretching sheet and the upper one is a solid porous plate. Copper (Cu) as nanoparticle and water as its base fluid have been considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved analytically using the homotopy analysis method (HAM). Comparison between HAM and numerical solutions results showed an excellent agreement. The results for the flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction/injection parameter, rotation parameter, and Reynolds number. It is shown that the inclusion of a nanoparticle into the base fluid of this problem is capable of causing change in the flow pattern. It is found that for both suction and injection, the heat transfer rate at the surface increases with increasing the nanoparticle volume fraction, Reynolds number, and injection/suction parameter and it decreases with power of rotation parameter.