Enclosure In Presence Research Articles

Nonhomogeneous model for conjugate mixed convection of nanofluid and entropy generation in an enclosure in presence of inclined magnetic field with Joule heating

PurposeThis study aims to numerically analyse the impact of an inclined magnetic field and Joule heating on the conjugate heat transfer because of the mixed convection of an Al2O3–water nanofluid in a thick wall enclosure.Design/methodology/approachA horizontal temperature gradient together with the shear-driven Flow creates the mixed convection inside the enclosure. The nonhomogeneous model, in which the nanoparticles have a slip velocity because of thermophoresis and Brownian diffusion, is adopted in the present study. The thermal performance is evaluated by determining the entropy generation, which includes the contribution because of magnetic field. A control volume method over a staggered grid arrangement is adopted to compute the governing equations.FindingsThe Lorentz force created by the applied magnetic field has an adverse effect on the flow and thermal field, and consequently, the heat transfer and entropy generation attenuate because of the presence of magnetic force. The Joule heating enhances the fluid temperature but attenuates the heat transfer. The impact of the magnetic field diminishes as the angle of inclination of the magnetic field is increased, and it manifests as the volume fraction of nanoparticles is increased. Addition of nanoparticles enhances both the heat transfer and entropy generation compared to the clear fluid with enhancement in entropy generation higher than the rate by which the heat transfer augments. The average Bejan number and mixing-cup temperature are evaluated to analyse the thermodynamic characteristics of the nanofluid.Originality/valueThis literature survey suggests that the impact of an inclined magnetic field and Joule heating on conjugate heat transfer based on a two-phase model has not been addressed before. The impact of the relative slip velocity of nanoparticles diminishes as the magnetic field becomes stronger.

Numerical simulation for impact of Coulomb force on nanofluid heat transfer in a porous enclosure in presence of thermal radiation

Influence of thermal radiation and external electric field on Fe3O4-Ethylene glycol nanofluid hydrothermal treatment is presented in this article. The lid driven cavity is porous media and the bottom wall is selected as positive electrode. Influence of supplied voltage on viscosity of nanofluid is taken into account. Control Volume based Finite Element Method is utilized to estimate the roles of radiation parameter (Rd), Darcy number (Da), Reynolds number (Re), nanofluid volume fraction (ϕ) and supplied voltage (Δφ). Results indicate that shape of nanoparticles can change the flow style and maximum rate of heat transfer is obtained by selecting platelet shape nanoparticles. The convective heat transfer improves with augment of permeability and Coulomb force.

Nanofluid heat transfer in a permeable enclosure in presence of variable magnetic field by means of CVFEM

This research is about modeling the influence of Lorentz forces on Fe3O4–water nanofluid heat transfer enhancement in a permeable cavity. Shape factor influence on thermal conductivity of nanofluid is taken into consideration. Vorticity stream function formulation is utilized. The solutions of final equations are obtained by Control Volume based Finite Element Method. Graphs are shown for different values of radiation parameter (Rd), Darcy number (Da), nanofluid volume fraction (ϕ), Rayleigh number (Ra) and Hartmann number (Ha). Results indicate that heat transfer rate enhances with augment of Hartmann number. Selecting Platelet shaped nanoparticles leads to greatest heat transfer rate.

Finite element analysis of double-diffusive natural convection in a porous triangular enclosure filled with Al2O3 -water nanofluid in presence of heat generation.

The problem of double-diffusive natural convection of Al2O3-water nanofluid in a porous triangular enclosure in presence of heat generation has been studied numerically in this paper. The bottom wall of the cavity is heated isothermally, the left inclined wall is non-isothermal and the right inclined wall is considered to be cold. The concentration is higher at bottom wall, lower at right inclined wall and non-isoconcentration at left inclined wall of the cavity. The governing equations are transformed to the dimensionless form and solved numerically using Galerkin weighted residual technique of finite element method. The results are obtained in terms of streamlines, isotherms, isoconcentrations, average Nueeslt number (Nu) and average Sherwood number (Sh) for the parameters thermal Rayleigh number (RaT), dimensionless heat generation parameter (λ), solid volume fraction (ϕ) and Lewis number (Le) while Prandtl number (Pr), Buoyancy ratio (N) and Darcy number (Da) are considered to be fixed. It is observed that flow pattern, temperature fields and concentration fields are affected by the variation of above considered parameters.

Heat Transfer and Entropy Generation in a Porous Square Enclosure in Presence of an Adiabatic Block

The present work investigates the thermal aspects of a differentially heated porous square enclosure in the presence of an adiabatic block of different block sizes utilizing Darcy–Rayleigh number in the range of 1–10,000 with Darcy number $$10^{-2}$$ – $$10^{-6}$$ . Heatlines and Nusselt number, streamlines, and entropy generation are used for the analysis of heat transfer, flow circulation, and irreversibility production in the enclosure. The study reveals that the presence of an adiabatic block affects the heat transfer process severely, and three different zones of heat transfer are identified. These are namely the zone of heat transfer augmentation, the zone of heat transfer augmentation along with entropy generation reduction, and the zone of both heat transfer and entropy generation reduction. It is also found that the presence of an adiabatic block can enhance heat transfer up to a certain critical block size; thereafter, further increasing in block size reduces the heat transfer rate. An optimal block size where the heat transfer enhancement is maximum is observed to be smaller than the critical block size. The study demonstrates the analyses of heat transfer and entropy generation for a better thermal design of a system. This study is also extended for higher Prandtl number fluids.

Effect of buoyancy ratio on unsteady thermosolutal combined convection in a lid driven trapezoidal enclosure in the presence of magnetic field

In this paper we concentrate to investigate the double diffusive unsteady mixed convection flow in a trapezoidal enclosure in presence of magnetic field. The bottom wall of the enclosure is heated and concentrated uniformly (case-I) and non-uniformly (case-II) while the top wall is cooled and moved uniformly with a constant velocity. Both side walls are adiabatic and impermeable. The coupled governing equations for this phenomenon is solved numerically using weighted residual based Galerkin technique of finite element method (FEM) for Richardson’s number (Ri=0.1–100) and Buoyancy ratio (Br=−10 to 10) at time τ=1.0. Reynolds number, Prandtl number and Lewis number are fixed at 100, 0.71 and 10 respectively. Streamlines, isotherm lines and iso-concentration lines are used to show the result graphically for velocity, temperature and mass distribution respectively. Nusselt and Sherwood number values are presented graphically to show the heat and mass transfer rate from the bottom surface of the cavity.

Heat flux boundary condition for nanofluid filled enclosure in presence of magnetic field

In this paper, effect of magnetic field on free convection heat transfer in an enclosure filled with nanofluid is studied. KKL (Koo-Kleinstreuer-Li) correlation is used for simulating effective thermal conductivity and viscosity of nanofluid. The inner cylinder is maintained at uniform heat flux and the outer cylinder has constant temperature. The governing equations are solved via Control Volume based Finite Element Method. The heat transfer between cold and hot regions of the enclosure cannot be well understood by using isotherm patterns so heatline visualization technique is used to find the direction and intensity of heat transfer in a domain. Effect of Hartmann number, volume fraction of nanoparticle, Rayleigh number and aspect ratio on streamline, isotherm and heatline are examined. The results show that as Hartmann number increases Nusselt number decreases while opposite trend is observed as nanoparticles volume fraction, Rayleigh number and aspect ratio increase. Domination of conduction mechanism causes heat transfer enhancement to increase. So enhancement in heat transfer increases with increase of Hartmann number and aspect ratio while it decreases with augment of Rayleigh number.

Transient Mixed Convection Coupled with Surface Radiation inside a Square Cavity with Different Configurations - A Critical Study

The conjugate heat transfer within differentially heated enclosure in presence of surface radiation is a complex phenomenon, which has become a research topic because of its practical relevance. The flow and heat transfer depends on the orientation of source of buoyancy and shear force. Buoyancy driven flow depends on the terminal temperature difference between the walls and its orientation. Similarly, the shear driven flow depends on the wall movement and its direction. The interaction between the shear induced flow with the buoyancy induced flow caused due to different orientation of differential heating of walls in presence of surface radiation is studied in the present article. The governing equations of mass, momentum and energy are solved using modified MAC method. The unsteady flow and heat transfer characteristics significantly vary with the magnitude of velocity and the direction of wall movement. The relative importance of different influencing parameters such as Rayleigh number (Ra), emissivity (ε) and Richardson number (Ri) has been analyzed in the present study. It is noticed that direction of wall movement and Rayleigh number affect both steady and unsteady flow patterns and heat transport processes in the cavity. Presence of surface radiation significantly changes the flow structures in case of vertical wall movement compared to horizontal wall movement for bottom heated cavity. Period of transience for shear dominated regimes (Ri << 1) is less compared to buoyancy dominated regimes (Ri >> 1). This study finds its application in industrial convection ovens and uninterrupted-flow in bakery systems, in food processing industries.