Numerical Study Of Mixed Convection Research Articles

Magnetic Field Effect and Heat Transfer of Nanofluids within Waveform Microchannel

In this research, a numerical study of mixed convection of non-Newtonian fluid and magnetic field effect along a vertical wavy surface was investigated. A simple coordinate transformation to transform wavy surface to a flat surface is employed. A cubic spline collocation numerical method is employed to analyze transformed equations. The effect of various parameters such as Reynolds number, volume fraction 0-, Hartmann number, and amplitude of wave length was evaluated in improving the performance of a wavy microchannel. According to the presented results, the sinusoidal shape of the microchannel has a direct impact on heat transfer. By increasing the microchannel wave amplitude, the Nusselt number has risen. On the other hand, increasing the heat transfer in the higher wavelength ratio corrugated channel is seen as an effective method of increasing the heat transfer, especially at higher Reynolds numbers. The results showed that with increasing Hartmann numbers, the flow line near the wall becomes more regular and, according to the temperature gradient created, the Nusselt number growth.

Numerical Study Mixed Convection in a Channel with an Open Cavity Involving Rotary Cylinder

A numerical study of mixed convection inside a horizontal channel with an open square cavity that includes an adiabatic rotating cylinder. The bottom wall of the cavity is heated at a constant temperature, and the remaining walls are adiabatic. The flow is incompressible, laminar and steady state. The equations of continuity, momentum and energy are solved numerically using computational fluid dynamics (CFD) with the commercial software package FLUENT 2019 R1. Reynolds number values of 50, 100 and 150, the Richardson number (0.1 ≤ Ri ≤ 10) and the angular velocity (ω) of cylinder is (0.5 ≤ ω ≤ 4) rad/sec with direction counter clockwise. Prandtl number for air flow is (Pr = 0.7). The results are presented in terms of streamlines, isotherms, and the average Nusselt value is given over the heated bottom cavity. The combined effects of natural and forced convection in and out of the cavity were obtained. The results showed that at low Richardson values, Ri = 0.1 the effect of buoyancy force is neglected. The effect of increasing the cylinder speed is clearly noticeable at low Reynolds values, Re = 50. Average Nusselt values increase with increasing rotational speed of the cylinder for all Richardson values.

Numerical study of mixed convection and entropy generation of Water-Ag nanofluid filled semi-elliptic lid-driven cavity

In this study, laminar mixed convection of water/Ag nanofluid with volume fraction of nanoparticles φ = 0, 2, 4, and 6% and Grashof numbers Gr = 50,000, 150,000, 250,000 and 400,000 and Richardson numbers Ri = 0.1, 1, and 10 are simulated using finite volume method. Obtained results indicate that adding a higher volume fraction of nanoparticles at lower Richardson numbers leads to the enhancement of heat transfer and Nusselt number. Streamlines behavior in the cavity is under the influence of two main factors including lid-driven motion (which is the basic factor) and the viscosity of fluid (which transfers the fluid motion to bottom layers and affects the flow domain). Every factor stimulating the flow domain causes uniform temperature distribution in the cavity. The increase of Richardson number leads to the enhancement of lid-driven velocity, temperature penetration and a better mixture of fluid layers, and by increasing Grashof number; this issue can have a great effect on uniform temperature distribution.

Numerical study of mixed convection and buoyancy ratio on MHD fluid flow beyond an inclined sheet

Numerical study of mixed convection and buoyancy ratio on MHD fluid flow beyond an inclined sheet

Experimental and numerical study of mixed convection with surface radiation heat transfer in an air-filled ventilated cavity

The present study deals with the experimental and numerical investigation of steady combined laminar mixed convection and surface radiation heat transfer in the air-filled enclosure subjected to a constant heat flux supplied to the vent side of the cavity. Experimental results are presented for heat inputs, Q = 3.19 W–16.71 W, Reynolds number, Re = 4814–166385, and Richardson number, Ri = 0.1–25. In the present study, the numerical simulation is also performed in the two–dimensional vented cavity to enrich the experimental work for aspect ratio, A = 1–5, and surface emissivity, ε = 0.05–0.85. The momentum and energy equations under Boussinesq approximations are solved using a well-known finite-volume method, and numerical code is developed in Fortan 90 for getting all numerical results. Based on the experimental data, correlations are developed for the Nusselt number and maximum temperature of the heated surface.

Numerical study of mixed convection of nanofluid inside an inlet/outlet inclined cavity under the effect of Brownian motion using Lattice Boltzmann Method (LBM)

In the present numerical study, the mixed convection of Cu-water and CuO-water nanofluids is modeled inside an inclined square-shaped cavity by utilizing the thermal model of the Lattice Boltzmann Method (LBM). A cold fluid flow enters into the cavity at the upper side of the left wall and, after being heated by the hot obstacle, exits from the lowest right side of the cavity The effective thermal conductivity and viscosity of nanofluids are computed by the KKL (Koo-Kleinstreuer-Li) equation. The results are presented in the constant Rayleigh number of 104 and the Richardson numbers of 0.1,1 and 10. Obtained results reveal that by incrementing Ri because of the augmentation of inlet fluid velocity from the left side, the gradient of isothermal lines decreases, and temperature distribution becomes more uniform, leading to Nusselt number reduction on hot wall. Although the Nuavg enhances considerably in Ri of 0.1, in Ri = 1 and 10, there is no sensible change. In the angle of 0o, by augmenting Ri, Nuavg decreases, but in the angle of 60o, by increasing Ri from 0.1 to 1, Nuavg increments up to 22%. This augmentation is due to the change of angle of the collision of flow with the hot obstacle. Furthermore, when the hot obstacle is located in the flow path, heat transfer improves. Application of such studies shows its importance in the design of electronic components cooling systems, solar energy storage, heat exchangers, and lubrication systems.

A numerical study of mixed convection in a two‐sided lid‐driven tall cavity containing a heated triangular block for non‐Newtonian power‐law fluids

AbstractThe study of hydrodynamics and thermal characteristics inside a lid‐driven cavity has been one of the most captivating problems in computational fluid dynamics. In this numerical work, the mixed convection phenomenon inside a two‐dimensional, tall lid‐driven cavity with top and bottom lids moving in opposite directions, +x and –x, respectively, has been explored for non‐Newtonian power‐law fluids. The cavity contains a uniformly heated equilateral triangular obstacle at its geometric center. Numerical experimentation is performed for a range of flow governing parameters, such as aspect ratio (0.25, 0.5, and 0.75), Prandtl number (1, 50, and 100) Richardson number (0.1, 1, and 10), power‐law index (0.6–1.4) and Grashof number of 104. The physical perceptions of the cavity are explained by using streamline and isotherm contours. The fluid movement is limited adjacent to the moving wall concerning the Richardson number at the lower Prandtl number. With a rise in the aspect ratio of the cavity, the flow‐pattern becomes more dispersed inside the cavity. Heat transfer enhancement is observed at a lower aspect ratio equal to 0.25.

Three-dimensional numerical study of mixed convection within a ventilated cavity (Shape ‘ L ‘) crossed by a nanofluid under the effect of a magnetic field

The present work is dedicated to the three-dimensional numerical study of mixed convection heat transfer, taking place within a ventilated cavity (of shape L) crossed by Cu-water nanofluid. The enclosure is subjected to the action of a magnetic field. The ventilation is assured by two openings of the same size. The cold flow enters by an opening practiced at the top of the left wall, and exits by another opening practiced at the bottom of the right vertical wall. All the cavity walls are maintained at the same temperature, superior to that of the entering flow, except the side walls which are considered as adiabatic. The control parameters are: the Reynolds number and the Hartmann number as well as the nanoparticles volume fraction.

Convection Heat Transfer Analysis in a Channel with an Open Trapezoidal Cavity: Heat Source Locations effect

In this work, a numerical study of mixed convection inside a horizontal channel with an open trapezoidal enclosure subjected to a discrete heat source in different locations is carried out. The heat source with the length of ε = 0.75, is maintained at a constant temperature. The air flow with a fixed velocity and a cold temperature enters the channel horizontally. The other walls of the enclosure and the channel are adiabatic. The results are presented in the form of the contours of velocity, isotherms and Nusselt numbers profiles for various heat source locations, Prandtl number (Pr = 0.71) and Reynolds number (Re = 100) respectively. The distribution of the isotherms depends significantly on the position of the heat source. We noted that the best heat transfer is detected where the heat source is placed in the top of the left .

Numerical study of mixed convection in a ventilated square enclosure with the lattice Boltzmann method

In this article, numerical study of heat transfer by convection in a square cavity was investigated. The vertical walls of the cavity are differentially heated and the horizontal walls are considered adiabatic. A ventilation jet is created by a fan placed in the cavity. A lattice Boltzmann model for incompressible flow equation is used to simulate the problem. A parametric study was performed presenting the influence of Reynolds number (20 ≤ Re ≤ 500), Rayleigh number (10≤Ra ≤ 10+6), and fan position (0.2 ≤ LF≤0.8). It has been observed that heat transfer rate increases with the Reynolds number increasing and it is maximal for the LF=0.2.

Numerical study of mixed convection for different concentrations of a parabolic trough collector and experimental determination of temperatures (case study for winter climatic conditions)

ABSTRACT In this paper, a numerical study has been performed using FLUENT to investigate the thermal behaviour of a parabolic trough solar receiver with different concentrations. In order to confirm the viability of our study, the model has been validated with experimental data. The obtained results show that the concentration of C = 70 gives the best heat exchange between the receiver’s wall and the heat transfer fluid at the bottom of the receiver, while the concentration of C = 17 gives the best heat exchange at the top of the receiver. On the other side, the experimental study has been done under real climatic conditions of Ghardaia (South of Algeria) in order to study the variations of different temperatures in the solar receiver of the concentrator with the best concentration.

Numerical study of mixed convection inside a three-dimensional ventilated cavity in the presence of an isothermal heating block

Numerical study of mixed convection inside a three-dimensional ventilated cavity in the presence of an isothermal heating block

Numerical study of mixed convection in a horizontal no parallel-plates channel with an unheated moving plate

PurposeThe purpose of this paper is to analyze the thermal and fluid dynamic behaviors of mixed convection in air because of the interaction between a buoyancy flow and a moving plate induced flow in a horizontal no parallel-plates channel to investigate the effects of the minimum channel spacing, wall heat flux, moving plate velocity and converging angle.Design/methodology/approachThe horizontal channel is made up of an upper inclined plate heated at uniform wall heat flux and a lower adiabatic moving surface (belt). The belt moves from the minimum channel spacing section to the maximum channel spacing section at a constant velocity so that its effect interferes with the buoyancy effect. The numerical analysis is accomplished by means of the finite volume method, using the commercial code Fluent.FindingsResults in terms of heated upper plate and moving lower plate temperatures and stream function fields are presented. The paper underlines the thermal and fluid dynamic differences when natural convection or mixed convection takes place, varying minimum channel spacing, wall heat flux, moving plate velocity and converging angle.Research limitations/implicationsThe hypotheses on which the present analysis is based are two-dimensional, laminar and steady state flow and constant thermo physical properties with the Boussinesq approximation. The minimum distance between the upper heated plate of the channel and its lower adiabatic moving plate is 10 and 20 mm. The moving plate velocity varies in the range 0-1 m/s; the belt moves from the right reservoir to the left one. Three values of the uniform wall heat flux are considered, 30, 60 and 120 W/m2, whereas the inclination angle of the upper plate θ is 2° and 10°.Practical implicationsMixed convection because of moving surfaces in channels is present in many industrial applications; examples of processes include continuous casting, extrusion of plastics and other polymeric materials, bonding, annealing and tempering, cooling and/or drying of paper and textiles, chemical catalytic reactors, nuclear waste repositories, petroleum reservoirs, composite materials manufacturing and many others. The investigated configuration is used in applications such as re-heating of billets in furnaces for hot rolling process, continuous extrusion of materials and chemical vapor deposition, and it could also be used in thermal control of electronic systems.Originality/valueThis paper evaluates the thermal and velocity fields to detect the maximum temperature location and the presence of fluid recirculation. The paper is useful to thermal designers.

Numerical study of mixed convection and flow pattern in various across-shape concave enclosures

Numerical study of mixed convection and flow pattern in various across-shape concave enclosures

Analysis of mixed convection of nanofluid in a 3D lid-driven trapezoidal cavity with flexible side surfaces and inner cylinder

Numerical study of mixed convection in a lid-driven 3D flexible walled trapezoidal cavity with nanofluids was performed by using Galerkin weighted residual finite element method. Effects of various pertinent parameters such as Richardson number (between 0.05 and 50), elastic modulus of the side surfaces (between 1000 and 105), side wall inclination angle (between 0° and 20°) and solid particle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer characteristics in a 3D lid-driven-trapezoidal cavity were numerically examined. It was observed that these characteristics are influenced when the pertinent parameters change. Flexible side surface can be used as control element for heat transfer rate. Increment and reduction in the space which are provided by the flexible side walls result in heat transfer enhancement and deterioration for side wall inclination angle of 0° and 10°. Average Nusselt number enhances by about 9.80% when the value of the elastic modulus is increased from 1000 to 105 for side wall inclination angles of θ=0°. Adding nanoparticles to the base fluid results in linear increment of heat transfer and at the highest volume fraction, 25.30% of heat transfer enhancement is obtained. A polynomial type correlation for the average Nusselt number along the hot wall was proposed and it has a fourth order polynomial dependence upon the Richardson number and first order dependence upon the solid particle volume fraction.

Mixed convection in a partially heated triangular cavity filled with nanofluid having a partially flexible wall and internal heat generation

Abstract Numerical study of mixed convection in a partially heated nanofluid-filled lid driven cavity with internal heat generation and having a partial flexible wall was performed. The bottom wall of the triangular enclosure is moving with constant speed and left vertical wall is partially heated. The inclined wall of the cavity is cooled and partially flexible. The governing equations are solved with Galerkin weighted residual finite element method. The effects of Richardson number (between 0.05 and 50), internal Rayleigh number (between 10 4 and 10 8 ), size and elastic modulus of the partial flexible wall and nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer were numerically investigated. It was observed that the local and averaged heat transfer reduce as the value of the Richardson number and internal Rayleigh number increase. As the value of the elastic modulus of the inclined wall and nanoparticle volume fraction increase, local and average heat transfer enhance. The discrepancy between the averaged Nusselt number increase for different sizes for the lower values of elastic modulus of the flexible wall. When heat transfer process is effective adding nanoparticles to the base fluid is advantageous.

Computation of Mixed Convection and Volumetric Radiation in Vertical Channel Based on Hybrid Thermal Lattice Boltzmann Method

The present paper presents a numerical study of mixed convection coupled with volumetric radiation in a vertical channel. The geometry of the physical model consists of two isothermal plates. The governing equations of the problem are solved using a hybrid scheme of the lattice Boltzmann method (LBM) and finite-difference method (FDM). The main objective of this study is to evaluate the influence of the Richardson number (Ri) and the emissivity of the walls (εi) on the heat transfer, on the flow, and on the temperature distribution. Results show that Richardson number and emissivity have a significant effect on heat transfer and air flow.

Combined convective heat and airborne pollutant removals in a slot vented enclosure under different flow schemes: Parametric investigations and non unique flow solutions

This paper reports a numerical study of mixed convection on a heated and polluted strip within a slot ventilated enclosure in which the displacement and mixing flow schemes are considered. Contours of streamfunction, heatfunction, and massfunction are presented to clearly scrutinize the mechanism of heat and airborne pollutant transports. For the displacement flow scheme, thermal Nusselt and pollutant Sherwood numbers under different Reynolds numbers remain almost constant as the value of Gr/Re2 decreases down to the regime of forced convection dominated. However, as Ar increases up to the regime of natural convection dominated, both Nu and Sh increase sharply with Ar (Gr/Re2). Similar trends could be observed for the situation of mixing ventilated flow scheme. In the mixing scheme, non unique steady flow solutions could be observed for the range of transitional flow regime. Upward solutions, downward solutions and rest solutions have been exemplified with varying Gr/Re2. Dual solution branches could be sustained at the range of 39.0 ≤ Gr/Re2 ≤ 6.0 × 103, while the rest solutions obtained from rest states were completely coinciding with former continuous solutions. The present work could be significant for the natural optimization and passive control of heat and pollutant removals from the electronic boxes or building enclosures.

Numerical study of mixed convection heat transfer in a lid-driven cavity filled with a nanofluid

This paper reports a numerical study of mixed convection in a square enclosure, filled with a mixture of water and different types of nanoparticles. The upper and the bottom walls of the cavity are thermally insulated, while the remaining walls are mobile and differentially heated. In order to solve the general coupled equations, a computer code based on the finite volume method is used and it has been validated after a comparison between the present results and those of the literature. To make clear the effects of the governing parameters on the fluid flow and heat transfer inside the square, a wide range of the Richardson number, taken as 0.01 to 100, and the nanoparticles volume fraction, taken from 0 to 10%, is investigated. The phenomenon is analyzed through streamlines and isotherm plots with a special attention to the Nusselt number. The obtained results show that the mean Nusselt number is an increasing function of the decrease Richardson number, and increases with increasing values of the nanoparticles volume fraction, and far from the natural convection mode, higher heat transfer is noted with Ag-water nanofluid. At the end, useful correlations predicting heat transfer rate as a function of the solid volume fraction are proposed for each value of the Richardson number, which predict the numerical results within ±0.02%.

Numerical Investigation of Double Diffusive Mixed Convection Laminar Flow in Two Sided Lid Driven Porous Cavity

This paper presents the numerical study of mixed convection in a two‐sided lid driven porous cavity due to temperature and concentration gradients. The top and bottom walls are stationary and insulated. The left and right walls are moving at an equal velocity (Vo) in the same direction. The temperature and concentration are kept high at the right wall and low at the left wall. The governing equations are discretized using finite volume method. The pressure–velocity coupling is performed by the SIMPLE algorithm. A third order differed QUICK scheme is applied at the inner nodes and a second order central difference scheme is used at the boundary nodes. The flow behavior and heat transfer are analyzed for different nondimensional numbers, such as, 1 × 10−4 ≤ Ri ≤ 10, 1 × 10−4 ≤ Da ≤ 0.1 and 0.7 < Pr < 10. The present numerical results are compared with the literature and are in good agreement. For the above selected nondimensional numbers, the heat and fluid flow behavior is investigated using local and average Nusselt (Nu) and Sherwood (Sh) numbers. Results show that the convection flow is significant up to Da = 0.1, beyond that the effect of porosity is negligible. The effect of Prandtl number (Pr) on average Nu is found to increase significantly.