Heat transfer enhancement of copper-water nanofluids in a lid-driven enclosure (original) (raw)
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Heat Transfer Enhancement of Nanofluids in a Lid-Driven Square Enclosure
Numerical Heat Transfer, Part A: Applications, 2012
In the present study, the behaviour of nanofluids is investigated numerically in a lid-driven triangular enclosure which has a partially heated on bottom side to gain insight into convective recirculation and flow processes induced by a nanofluid. The present model is developed to examine the behaviour of nanofluids taking into account the heater length. Fluid mechanics and conjugate heat transfer, described in terms of continuity, linear momentum and energy equations, were predicted by using the Galerkin finite element method. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Numerical results are obtained for a wide range of parameters such as the Richardson number, and heater length. Copper-water nanofluids is used with Prandtl number, Pr = 6.2. The streamlines, isotherm plots and the variation of the average Nusselt number at the hot surface as well as average fluid temperature in the enclosure is presented and discussed in detailed.
Arabian Journal for Science and Engineering, 2017
The present paper reports a numerical investigation of steady and laminar mixed convection flow within an irregular ventilated enclosure, crossed by Cu-Water nanofluid. The bottom wall is maintained at a constant and uniform temperature, whereas the top and the vertical walls are adiabatic. The inclined wall as well as the nanofluid at the entrance is kept at a lower constant temperature. The governing coupled equations are resolved by the means of the finite volume technique. The computations are performed using a homemade computer code, which was successfully validated, after comparison of our results with pervious numerical and experimental works. Empirical relations to predict the nanofluid's effective thermal conductivity and viscosity were employed. The results are analyzed through dynamic and thermal fields with a particular attention to the Nusselt number evaluated along the active wall. The results reveal that the flow structure is more sensitive to both Richardson and Reynolds numbers variations. Moreover, heat transfer is enhanced by the increase in the nanoparticles volume fraction, Richardson and Reynolds numbers and by the decrease in the nanoparticles diameter. Useful correlations predicting the heat transfer rate as a function of nanoparticles volume fraction and diameter as well as the Richardson number are proposed.
Applied Mathematical Modelling, 2014
In the present work, two-dimensional mixed convection fluid flow and heat transfer of water-(Cu, Ag, Al 2 O 3 and TiO 2 ) nanofluids in a two-sided facing lid-driven cavity partially heated from below have been investigated numerically. Two discrete heat sources are located on the bottom wall of the enclosure; however, the vertical moving walls and the ceiling are cooled at constant temperature. The remaining boundary parts of the bottom wall are kept insulated. The flow is driven by the moving two facing vertical walls in the same direction and the buoyancy force. The governing equations are solved using a second order accurate finite volume approach. The effects of the monitoring parameters in given ranges such as Reynolds ð1 6 Re 6 100Þ and Richardson numbers ð1 6 Ri 6 20Þ, solid volume fraction ð0 6 u 6 0:2Þ, the nanoparticles materials as well as the two heat sources positions are investigated. The conducted benchmark study leads to excellent accordance with previous findings. The present study analyzes and discusses the flow patterns (streamlines structures and isotherms distributions) set up by the competition between the forced flow driven by the moving walls and the buoyancy force effects, and the heat transfer rate quantified by the averaged Nusselt number along the heat source. It was found that significant heat transfer enhancement can be obtained: (i) increasing Ri at high Reynolds number (Re = 100) results in up-to 20% augmentation of heat transfer rate for all Cu volume fractions; (ii) increasing the volume fraction u, a maximum heat transfer rate increase of 47.010% is reached with Cu suspensions for u = 0.2 and Ri = 1, while a minimum increase of 7.059% is observed for TiO 2 -water nanofluid at Ri = 10 and u = 0.05; (iii) a highest heat transfer enhancement occurs when heat sources move toward the two vertical moving walls, while a lower heat transfer is obtained for heat sources located at bottom wall center.
Results in Physics, 2012
This paper focuses on the study of mixed convection heat transfer characteristics in a lid-driven enclosure filled with nanofluids using variable thermal conductivity and variable viscosity. The fluid in the enclosure is a water-based nanofluid containing Al 2 O 3 nanoparticles. The top and bottom horizontal walls are insulated, while the vertical walls are kept at different constant temperatures with the top surface moving at a constant speed. The study has been carried out for the Richardson numbers of 0.01-100, the solid volume fraction of 0-0.06 and the Grashof number of 10 4. Various results for the streamlines and isotherms as well as the local and average Nusselt numbers are presented. The variable viscosity and thermal conductivity of both the Brinkman and the Maxwell-Garnett model were compared. Significant differences are found between the magnitudes of heat transfer enhancement in the enclosure for two employed models.
Heat-Mass Transfer of Nanofluid in Lid-Driven Enclosure under three Convective Modes
GANIT: Journal of Bangladesh Mathematical Society, 2019
Heat is a form of energy which transfers between bodies which are kept under thermal interactions. When a temperature difference occurs between two bodies or a body with its surroundings, heat transfer occurs. Heat transfer occurs in three modes. Three modes of heat transfer are conduction, convection and radiation. Convection is a very important phenomenon in heat transfer applications and it occurs due to two different gradients, such as, temperature and concentration. This paper reports a numerical study on forced-mixed-natural convections within a lid-driven square enclosure, filled with a mixture of water and 2% concentrated Cu nanoparticles. It is assumed that the temperature difference driving the convection comes from the side moving walls, when both horizontal walls are kept insulated. In order to solve general coupled equations, a code based on the Galerkin's finite element method is used. To make clear the effect of using nanofluid on heat and mass transfers inside th...
Thermal Science, 2016
In this paper, a new approach is used for numerical analysis of the sole effects of nanoparticles volume fraction of Cu-water nanofluid on laminar mixed and natural convection heat transfer in a 2-D cavity. Horizontal walls are insulated and fixed, and vertical walls are maintained at constant temperature. Vertical walls are considered for both fixed and moving conditions. Some researchers have studied flow and heat transfer of nanofluid in a lid-driven cavity, keeping fixed both Richardson and Grashof numbers. They found that by the increase of nanoparticles volume fraction, Nusselt number increases, then from this result they concluded the total heat transfer increases from the walls. It is shown that total heat transfer obtained from the Nusselt number by the mentioned approach results from not only the nanoparticles volume fraction increase but also temperature difference and walls velocity increases. Thus, this approach is not appropriate to study the sole effects of nanoparticles volume fractions on the mixed convection heat transfer. Using the new approach, it is shown that in order to have specific heat transfer rate from the walls, base fluid (water) needs less power for moving the wall than Cu-nanofluid. Therefore, the usage of Cu-water nanofluid is not recommended to increase mixed convection heat transfer in a lid-driven cavity. Moreover, using this new approach, it is shown that the increase of nanoparticles volume fraction reduces natural convection heat transfer, which is contradictory to the previous studies. Thus, its usage is not recommended for this case as well.
Mixed Convection of Water-Based Nanofluids in a Lid-Driven Square Enclosure with a Heat Source
This study is concerned with mixed convection of water-based nanofluids in a lid-driven square enclosure with a constant heat flux heater. The governing equations are solved numerically using the differential quadrature method. The computational results are obtained for the heater lengths of 0.25, 0.50, and 0.75. The Grashof number is kept at a constant value of 10 4 , and the Reynolds number is varied so that the Richardson number will have values in the range of 0.1 to 10. The nanoparticles volume fraction φ is varied as 0%, 5%, and 10% and the value of the ratio of the nanolayer thickness to the original particle radius η is fixed to 0.1. The results show that the presence of nanoparticles in the base fluid causes a significant enhancement of heat transfer. The results also show that the heat transfer rate increases considerably with a decrease in the Richardson number and the length of the heater. * * *
A numerical investigation of mixed convection due to a copper–water nanofluid in an enclosure is presented. The mixed convection is governed by moving the upper lid of the enclosure and imposing a vertical temperature gradient. The transport equations for fluid and heat are modeled by using the Boussinesq approximation. A modified form of the control volume based SIMPLET algorithm is used for the solution of the transport equations. The fluid flow and heat transfer characteristics are studied for a wide range of Reynolds number and Grashof number so as to have the Richardson number greater or less than 1. The nanoparticle volume fraction is considered up to 20%. Heat flow patterns are analyzed through the energy flux vector. The rate of enhancement in heat transfer due to the addition of nanoparticles is analyzed. The entropy generation and Bejan number are evaluated to demonstrate the thermodynamic optimization of the mixed convection. We have obtained the enhancement rate in heat transfer and entropy generation in nanofluid for a wide range of parameter values
Nucleation and Atmospheric Aerosols, 2019
This present numerical simulation of mixed convection heat transfer of nanofluid in a lid-driven porous medium square enclosure with several pairs of heat source-sinks. Two-dimensional Navier-Stokes, energy and volume fraction equations are solved using the finite element method. The top and bottom walls of the enclosure are maintained at cold temperature T c. The left and right walls are kept adiabatic. Both the top and bottom walls move at a uniform liddriven velocity considered. Two square heating and cold blocks inside the enclosure. The fluid inside the enclosure is a water based nanofluid containing type of solid spherical nanoparticles Cu. To investigate the effect of Hartmann number, Darcy number and Richardson number on the fluid flow and heat transfer characteristics inside the enclosure. A set of graphical results are presented in terms of streamlines, isotherms, dimensionless temperature, velocity profiles and average Nusselt numbers. The results reveal that heat transfer rate increases as increasing Darcy number and Richardson number. It is observed that, Hartmann number is a good control parameter for heat transfer in fluid flow through porous medium in enclosure. Moreover, Cu-water nanofluid has greater merit to be used for heat transfer enhancement. The method used is validated against previous published works.
Numerical study of mixed convection flows in a square lid-driven cavity utilizing nanofluid
International Communications in Heat and Mass Transfer, 2010
A numerical investigation of laminar mixed convection flows through a copper-water nanofluid in a square lid-driven cavity has been executed. In the present study, the top and bottom horizontal walls are insulated while the vertical walls are maintained at constant but different temperatures. The study has been carried out for the Rayleigh number 10 4 to 10 6 , Reynolds number 1 to 100 and the solid volume fraction 0 to 0.05. The thermal conductivity and effective viscosity of nanofluid have been calculated by Patel and Brinkman models, respectively. The effects of solid volume fraction of nanofluids on hydrodynamic and thermal characteristics have been investigated and discussed. It is found that at the fixed Reynolds number, the solid concentration affects on the flow pattern and thermal behavior particularly for a higher Rayleigh number. In addition it is observed that the effect of solid concentration decreases by the increase of Reynolds number.