Numerical Analysis Of Mixed Convection Research Articles

Sensitivity study on convective heat transfer in a driven cavity with star-shaped obstacle and hybrid nanofluid using response surface methodology

Sensitivity analysis is significant for understanding and measuring the impact of various parameters and input variables on heat transfer phenomena. The main objective of the current work is to examine the sensitivity of a numerical analysis of mixed convection in a lid-driven square cavity with a magnetic field. The cavity also contains a heated, star-shaped obstacle and is filled with a hybrid nanofluid. The sensitivity analysis was conducted employing the statistical response surface methodology (RSM), while the numerical simulations used the Galerkin weighted residual finite element approach to solve the governing PDEs. The study investigates the impacts of four dimensionless factors: Ri, Re, Ha, and ϕ. The numerical observation was made that there exists an upward trend between the average heat transfer rate with Ri, Re, and ϕ, while there exists a downward trend with Ha. Furthermore, the average heat transfer rate increases by almost half (49.54 %) when ϕ increases from 1 % to 10 % and decreases by 5.97 % when the Ha increases from 0 to 60. Finally, the statistical investigation of the current model and testing techniques imply that R2 values for the response function are high (98.72 %), suggesting that this model is appropriate for estimating Nu.

Numerical analysis of mixed convection and Thomson-Troian slip effects on ternary nanofluid flow and heat transfer over a stretching sheet with porous media: Darcy-Forchheimer model

The present study unveils research that examines the laminar motion of water-infused nanofluid comprised of nanoparticles of TiO2 (titanium dioxide), Ag (silver), and Cu (copper) over a stretching sheet. The flow undergoes a novel slip condition based on Thomson and Troian to model complex fluid behavior near solid walls and incorporate the Darcy-Forchheimer model to comprehensively analyze the influence of a porous medium on flow behavior. Moreover, a heat source/sink and radiation are included to ensure the outcome of the energy equation will resemble most actual-world applications. Partial differential equations (PDEs) of higher order, originally used to describe the system are then reformulated into higher-order non-linear ordinary differential equations (ODEs) by taking symmetry variables that are chosen thoughtfully. The resulting boundary layer equations are then turned into a set of ODEs by implementing relevant similarity transformations, which can be solved using the M ATLAB function bvp4c. Through graphs, the variations in the velocity, Nusselt number, temperature, and skin friction coefficient were displayed. The outcome showed that the incorporation of silver nanoparticles (0.01–0.03) enhanced the skin friction coefficient by ≈ 1.68 % and the Nusselt number reduced up to ≈ 5 %. The Forchheimer number also reported a 6.5% enhancement and 1.5% reduction in the skin friction coefficient and the Nusselt number, respectively. The velocity slip parameter γ1 correlates with an upswing in temperature and skin friction coefficient for the ternary nanofluid while observing a decline in the velocity and Nusselt number.

Fluid-solid interaction of elastic-step type corrugation effects on the mixed convection of nanofluid in a vented cavity with magnetic field

In this study, numerical analysis of mixed convection of CuO-water nanofluid in a cavity with inlet and outlet ports is performed under the effects of inclined magnetic field and step like corrugated elastic walls. The numerical simulation results are obtained by using finite element method. The Arbitrary-Lagrangian–Eulerian method is utilized for the description of the fluid motion with the elastic wall in the fluid-structure interaction model. In the current study, multiple step like corrugation of the wall is considered and it is made elastic which adds additional flexibility for the control of convective heat transfer features of the vented cavity. Effects of various pertinent parameters such as Reynolds number (between 100 and 500), Hartmann number (between 0 and 40), magnetic inclination angle (between 0° and 90°), elastic modulus of the flexible wall (between 5 × 104 and 108), number of step-like corrugation (between 1 and 8) and nanoparticle volume fraction (between 0 and 3%) on the fluid flow and heat transfer characteristics are numerically examined. It is observed that for higher value of Reynolds number, local Nusselt number both deteriorates and enhances in various locations along the hot wall whereas the changes in the local Nusselt number are marginal for lower value of Reynolds number. The multiple vortices in the vented cavity are influenced by the variation of magnetic field parameters and number of step like corrugation of the wall while the effects are not significant for the change of magnetic inclination angle. When the value of Hartmann number augments, the average heat transfer reduces until Hartmann number of 30 and increases for the highest value of Hartmann number. The average Nusselt number increment are in the range of 9-9.5% with the nanoparticle addition at the highest volume fraction in the absence and presence of magnetic field. Even though significant changes in the local Nusselt number are observed when the number of step like corrugation increases, it has a deterioration effect on the average heat transfer generally and 5.5% reduction in the average Nusselt number is obtained when the value is increased from 1 to 8.

Numerical analysis of mixed convection of different nanofluids in concentric annulus

Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

Numerical analysis of mixed convection of two-phase non-Newtonian nanofluid flow inside a partially porous square enclosure with a rotating cylinder

In this study, mixed convection heat transfer of the non-Newtonian power-law nanofluid including CuO nanoparticles, inside a partially porous square enclosure with a concentric rotating cylinder and a hot side wall is numerically investigated. Two-phase mixture model is utilized for nanofluid flow simulation and the mixture viscosity and thermal conductivity are computed by Corcione’s correlation. The effect of different angular velocity (− 4000 ≤ Ω ≤ 4000) for various Rayleigh (104 ≤ Ra ≤ 106), Darcy (10−4 ≤ Da ≤ 10−1), power-law index (0.8 ≤ n ≥ 1.2) and effective to base fluid thermal conductivity ratio (keff/kf= 16, 4) are studied on heat transfer. Results are presented and compared in terms of the average Nusselt number, and streamline and isotherm contours. Outcomes show that for different kinds of fluid, depending on the value of Ra, Da, keff/kf and the amount and direction of angular velocity, heat transfer can be improved by augmenting heat convection and also can be deteriorated by increasing viscosity. Consequently, optimal values of Ra, Da, keff/kf and Ω exist in order to maximize the average Nu number.

Numerical analysis of mixed convection at various walls speed ratios in two-sided lid-driven cavity partially heated and filled with nanofluid

In this study, the problem of laminar mixed convection in a two-sided lid-driven square cavity partially heated and filled with Cu/water nanofluid, is analyzed using a numerical procedure based on the finite volume method with the help of a full multigrid solver. Two heat sources of dimensionless length B maintained at high temperature (TH) are embedded in the center of the two side walls of the cavity. The top and bottom walls of the enclosure are considered with low temperature (TC), while the remaining boundary parts of the enclosure are thermally insulated. The top and bottom walls of the cavity can slide in the same or opposite direction with various speed ratios named λ. A parametric study is conducted and a set of graphical results is presented and discussed to illustrate the effects of λ (−2≤λ≤2), the Richardson number Ri (0.01≤Ri≤100) and the solid volume fraction ϕ (0≤ϕ≤0.1) on the flow and heat transfer characteristics. The results show that varying the speed ratio has significant effects on both the flow structure and the heat transfer. It is found that heat transfer enhancement can be provided by the presence of nanoparticles and that this is accentuated by decreasing the Richardson number. Special attention has been given to predict a characteristic Richardson number of equilibrium, namely Rie, leading to an equal heat transfer rate balance between the two opposite sources. Finally, multiple correlations in terms of Richardson number and volume fraction nanoparticles have been established at various speed ratios.

Numerical analysis of mixed convection in pulsating flow for a horizontal channel with a cavity heated from below

In this study, a channel with a cavity heated from below is numerically investigated for the mixed convection case in pulsating flow for a range of Richardson numbers (Ri=0.1, 1, 10, 100) at Reynolds number of 50 in the laminar flow regime. At the inlet of the channel, pulsating velocity is imposed for Strouhal numbers between 0.1 to 1 and velocity amplitude ratio between 0.3 to 0.9. The effect of the pulsation frequency, amplitude and Richardson number on the heat transfer enhancement is numerically analyzed. The results are presented in terms of streamlines, isotherm plots and averaged Nusselt number plots. FFT plots for the Nusselt number response to single sinusoidal velocity forcing at the inlet and nonlinearity in the response is also provided.

Numerical analysis of mixed convection in partially open cavities heated from below

Mixed and natural convection in cavities are extensively investigated subjects in the field of heat transfer, due to the wide range of situations where this configuration appears in technological applications and natural phenomena. Although the flow behavior is rather complex, most of the numerical studies found in the literature apply simplified two-dimensional stationary models to investigate the influence of the governing parameters. In the study reported herein, the main characteristics of mixed convection in partially open cavities with internal heat sources are investigated using a transient three-dimensional model. An inlet condition occupying half of the entire right wall and an opposite opening in the left wall were included to allow the fluid inlet and outlet. The model also comprises an external region adjacent to the opening, since recirculations can appear at the opening and generate backflow. The heat sources are placed at the bottom wall of the cavity, which is also maintained at a high temperature, while the upper part of the cavity is cooled as a result of the presence of cold walls. These conditions are similar to those found in common Rayleigh–Bénard systems, therefore, the emergence of thermal convective cells occurs when a sufficiently high temperature difference is reached. Different values for the Rayleigh numbers associated with the internal heat source intensity and with the temperature difference between the hot and cold walls were evaluated, allowing the determination of the modifications in the flow field as the buoyancy forces become dominant. The results show that the buoyancy forces are dominant for low Re and high R or Rae values, and in this case the flow field correspond to two recirculations rotating in opposite directions. As the relative intensity of the shear flow increases, the recirculations become distorted and the size of the recirculation close to the inlet increases. For higher Re values, when the inertial forces induced by the inlet velocity are stronger than the buoyancy forces, recirculation zones in the upper part of the cavity can also appear due to the influence of the horizontal flow. For intermediate values, the competition between the buoyancy and inertial forces generates a complex dynamic behavior, with periodic and quasiperiodic regimes found for some set of the governing parameters. Furthermore, the importance of a fully three-dimensional model is demonstrated by the analysis of the flow field and energy distribution along the three directions.

Numerical analysis of mixed convection over horizontal moving porous flat plate by the method of one parameter continuous group theory

PurposeThe paper aims to consider non‐viscous, laminar mixed convection boundary‐layer flow over a horizontal moving porous flat plate, with chemical reaction.Design/methodology/approachThe governing equations are expressed in non‐dimensional form and the series solutions of coupled system of equations are constructed for velocity, temperature and concentration functions using numerical method.FindingsThe investigated parameters are: buoyancy parameter, chemical reaction parameter, order of chemical reaction, Prandtl number and Schmidt number.Originality/valueThe partial differential equations are transformed to ordinary differential equations. The method of one parameter continuous group theory is used for this transformation.

Numerical analysis of mixed convection in three‐dimensional rectangular channel with flush‐mounted heat sources based on field synergy principle

AbstractIn this paper the fluid flow and heat transfer characteristics of mixed convection in three‐dimensional rectangular channel with four heat sources are investigated numerically. The SIMPLEC algorithm is applied to deal with the coupling between pressure and velocity, and a new high‐order stability‐guaranteed second‐order difference (SGSD) scheme is adopted to discretize the convection term. The influence of four parameters is studied: Richardson number, heat source distribution, channel height and inclination angle. The numerical results are analysed from the viewpoint of the field synergy principle, which says that the enhanced convective heat transfer is related not only to the velocity field and temperature field, but also to the synergy between them. It is found that the effects of the four parameters on the thermal performance can all be explained with the field synergy principle. To obtain better electronic cooling, the synergy between the velocity and temperature gradient should be increased when other conditions are unchanged. Copyright © 2006 John Wiley & Sons, Ltd.

Numerical analysis of mixed convection at the entrance region of a rectangular duct heated from below

An entrance region of a rectangular duct is examined numerically for a thermally-developing flow between a cooled top and a heated bottom boundary. Based on the results, which agree well with previous experimental results, equations for the entrance lengths, L 1 for the onset and L 2 for the full development of mixed convection are proposed. L 1 approximately corresponds to the location where the Nusselt number takes a minimum before is increases as the buoyancy-induced flow becomes dominant. Results on the effects of the sidewall thermal condition as well as the inlet gas temperature are also discussed in relation to thermal transport.

Numerical analysis of mixed convection from horizontal cylinders

Mixed convective heat transfer from horizontal cylinders was investigated using numerical procedures. Elliptic partial differential equations were transformed into finite difference equations and numerical results were computed using a non-uniform grid. A method to reliably verify the procedure is given, along with a comparison between results from this study and prior work. The results of this analysis agree to within 5% with published experimental work. Increasing flow rate over the object will not necessarily increase heat transfer by mixed convection, because of flow separation effects. The results of this study may be applied in the post-harvest cooling of agricultural produce of relevant shape.