scholarly journals Forced convection of radiating gas over an inclined backward facing step using the blocked-off method

2013 ◽  
Vol 17 (3) ◽  
pp. 773-786 ◽  
Author(s):  
Amir Ansaria ◽  
Nassaba Gandjalikhan
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Gas Flow ◽  
Control Volume ◽  
Research Work ◽  
Temperature Fields ◽  
Discrete Ordinates ◽  
Convection Flow ◽  
Governing Equations ◽  
Backward Facing Step

The present work investigates the laminar forced convection flow of a radiating gas over an inclined backward facing step (BFS) in a horizontal duct. The momentum and energy equations are solved numerically by the CFD techniques to obtain the velocity and temperature fields. Since, the twodimensional Cartesian coordinate system is used to solve the governing equations; the flow over inclined surface is simulated by considering the blocked-off region in regular grid. Discretized forms of the governing equations in the (x,y) plane are obtained by the control volume method and solved using the SIMPLE algorithm. The fluid is treated as a gray, absorbing, emitting and scattering medium. Therefore, all of the convection, conduction and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the radiative heat flux distribution inside the radiating medium. In the numerical results, effects of inclination angle, optical thickness, scattering albedo and the radiation-conduction parameter on the heat transfer behavior of the convection flow are investigated. This research work is a new one in which a combined convection-radiation thermal system with a complex flow geometry is simulate by efficient numerical techniques.

Study of Laminar Forced Convection of Radiating Gas Over an Inclined Backward Facing Step Under Bleeding Condition Using the Blocked-Off Method

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
A. B. Ansari ◽  
S. A. Gandjalikhan Nassab
Keyword(s):  
Forced Convection ◽  
Gas Flow ◽  
Radiation Heat Transfer ◽  
Simple Algorithm ◽  
Temperature Fields ◽  
Convection Flow ◽  
Backward Facing Step ◽  
Cartesian Coordinate ◽  
Volume Method ◽  
Laminar Forced Convection

This paper presents a numerical investigation for laminar forced convection flow of a radiating gas over an inclined backward facing step in a horizontal duct subjected to bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The two-dimensional Cartesian coordinate system is used to simulate flow over inclined surface by considering the blocked-off region in regular grid. The governing differential equations consisting the momentum and energy are solved numerically by the computational fluid dynamics techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, convection, conduction, and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation is solved numerically by the discrete ordinate method to find the radiative heat flux distribution inside the radiating medium. The effects of bleeding coefficient, inclination angle, optical thickness, albedo coefficient, and the radiation-conduction parameter on the flow and temperature distributions are carried out.

Simulation of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a duct under bleeding condition

2012 ◽  
Vol 227 (2) ◽  
pp. 332-345 ◽  
Author(s):  
M Atashafrooz ◽  
SA Gandjalikhan Nassab
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Discrete Ordinates ◽  
Convection Flow ◽  
Backward Facing Step ◽  
Forced Convection Flow ◽  
Laminar Forced Convection

This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.

Combined Mixed Convection and Radiation Heat Transfer in an Obstacle Wall Mounted Lid-driven Cavity

2016 ◽  
Vol 17 (6) ◽  
pp. 277-289 ◽  
Author(s):  
M. Moein Addini ◽  
S. A. Gandjalikhan Nassab
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Gas Flow ◽  
Radiation Heat Transfer ◽  
Simple Algorithm ◽  
Bottom Wall ◽  
Temperature Fields ◽  
Convection Flow ◽  
Driven Cavity ◽  
Laminar Mixed Convection

AbstractThis paper presents a numerical investigation for laminar mixed convection flow of a radiating gas in a lid-driven cavity with a rectangular-shaped obstacle attached on the bottom wall. The vertical walls of the square cavity are assumed to be adiabatic, while other walls of cavity and obstacle are kept at constant temperature. The fluid is treated as a gray, absorbing, emitting and scattering medium. The governing differential equations consisting the continuity, momentum and energy are solved numerically by the computational fluid dynamics techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides convection and conduction, radiative heat transfer also takes place in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation is solved numerically by the discrete ordinate method. The streamline and isotherm plots and the distributions of convective, radiative and total Nusselt numbers along the bottom wall of cavity are presented. The effects of Richardson number, obstacle location, radiation–conduction parameter, optical thickness and albedo coefficient on the flow and temperature distributions are carried out. Comparison between the present numerical results with those obtained by other investigators in the cases of conduction–radiation and pure convection systems shows good consistencies.

scholarly journals The response of skin friction, wall heat transfer and pressure drop to wall waviness in the presence of buoyancy

1982 ◽  
Vol 5 (3) ◽  
pp. 585-594 ◽  
Author(s):  
C. N. B. Rao ◽  
K. S. Sastri
Keyword(s):  
Heat Transfer ◽  
Viscous Incompressible Fluid ◽  
Temperature Fields ◽  
Wave Number ◽  
Convection Flow ◽  
Governing Equations ◽  
Natural Convection Flow ◽  
Flow And Heat Transfer ◽  
Fluid Properties ◽  
Laminar Natural Convection

Laminar natural convection flow and heat transfer of a viscous incompressible fluid confined between two long vertical wavy walls has been analysed taking the fluid properties constant and variable. In particular, attention is restricted to estimate the effects of viscous dissipation and wall waviness on the flow and heat transfer characteristics. Use has been made of a linearization technique to simplify the governing equations and of Galerkin's method in the solution. The solutions obtained for the velocity and the temperature-fields hold good for all values of the Grashof number and wave number of the wavy walls.

scholarly journals Magnetohydrodynamic mixed convection in a nanofluid filled tubular enclosure

2020 ◽  
Vol 4 (1) ◽  
pp. 19-24
Author(s):  
Mohammad Mokaddes Ali
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Temperature Fields ◽  
Convection Flow ◽  
Governing Equations ◽  
Convection Regime ◽  
Special Cases ◽  
Flow Domain

Mixed convection flow in a tubular enclosure filled with nanofluid in the presence of a magnetic field is numerically investigated in the present study. The bottom and top curved wall of the enclosure are respectively kept isothermally hot and cool while the remaining walls are insulated. The governing equations are formulated based on Boussinesq assumptions and solved with finite element method. The computation is carried out for mixed convection regime (0.1 ≤ Ri ≤ 10) and also natural convection regime (10 < Ri ≤ 100) with fixed values of remaining parameters. A detailed parametric discussion is presented for the physical properties of flow and temperature distributions in terms of streamlines, isotherms, average heat transfer rate within the flow domain. The results show that the flow and temperature fields affected by varying of pertinent parameters. Moreover, heat transfer rate is increased by 139.50% with the increase in Richardson number from 0.1 to 100. The increasing rate of heat transfer due to Ri is respectively decreased by 58.11% with varying of Ha from 0 to 60 and increased by 23.97% with the addition of nanoparticles up to 3%. Comparison is performed against the previously published results on the basis of special cases and found to be in excellent agreement.

scholarly journals Numerical Simulation of Secondary Flow in Gas Turbine Disc Cavities, Including Conjugate Heat Transfer

1996 ◽  
Author(s):  
Y.-H. Ho ◽  
M. M. Athavale ◽  
J. M. Forry ◽  
R. C. Hendricks ◽  
B. M. Steinetz
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Conjugate Heat Transfer ◽  
Gas Flow ◽  
Numerical Study ◽  
Labyrinth Seal ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Flow Rates ◽  
Turbine Disc

A numerical study of the flow and heat transfer in secondary flow elements of the entire inner portion of the turbine section of the Allison T-56/501D engine is presented. The flow simulation included the interstage cavities, rim seals and associated main path flows, while the energy equation also included the solid parts of the turbine disc, rotor supports, and stator supports. Solutions of the energy equations in these problems usually face the difficulty in specifications of wall thermal boundary conditions. By solving the entire turbine section this difficulty is thus removed, and realistic thermal conditions are realized on all internal walls. The simulation was performed using SCISEAL, an advanced 2D/3D CFD code for predictions of fluid flows and forces in turbomachinery seals and secondary flow elements. The mass flow rates and gas temperatures at various seal locations were compared with the design data from Allison. Computed gas flow rates and temperatures in the rim and labyrinth seal show a fair 10 good comparison with the design calculations. The conjugate heat transfer analysis indicates temperature gradients in the stationary intercavity walls, as well as the rotating turbine discs. The thermal strains in the stationary wall may lead to altered interstage labyrinth seal clearances and affect the disc cavity flows. The temperature, fields in the turbine discs also may lead to distortions that can alter the rim seal clearances. Such details of the flow and temperature fields are important in designs of the turbine sections to account for possible thermal distortions and their effects on the performance. The simulation shows that the present day CFD codes can provide the means to understand the complex flow field and thereby aid the design process.

Numerical Analysis on Nanofluid Forced Convection in Ducts With Triangular Cross Sections

2011 ◽  
Author(s):  
O. Manca ◽  
S. Nardini ◽  
D. Ricci ◽  
S. Tamburrino
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Forced Convection ◽  
Cross Sections ◽  
Fluid Dynamic ◽  
Pure Water ◽  
Convection Flow ◽  
Uniform Heat Flux ◽  
Surface Shear Stress ◽  
Surface Shear

Heat transfer of fluids is very important to many industrial heating or cooling equipments. Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions or by enhancing the thermal conductivity of the working fluids. An innovative way of improving the fluid thermal conductivity is to introduce suspended small solid nanoparticles in the base fluids. In this paper a numerical investigation on laminar forced convection flow of a water–Al2O3 nanofluid in a duct having an equilateral triangular cross section is performed. The hydraulic diameter is set equal to 1.0×10−2 m. A constant and uniform heat flux on the external surfaces has been applied and the single-phase model approach has been employed. The analysis has been run in steady state regime for a nanoparticle size equal to 38 nm, considering different volume particle concentrations. The CFD code Fluent has been employed in order to solve the tri-dimensional numerical model. Results are presented in terms of temperature and velocity distributions, surface shear stress and heat transfer convective coefficient, Nusselt number and required pumping power profiles. Comparison with results related to the fluid dynamic and thermal behaviors in pure water are carried out in order to evaluate the enhancement due to the presence of nanoparticles in terms of volumetric concentration.

scholarly journals Analysis Of Field Synergy In Bottom Heated Lid Driven Cubical Cavity

2019 ◽  
Vol 128 ◽  
pp. 07007
Author(s):  
H.P. Rani ◽  
V. Narayana ◽  
Y. Rameshwar
Keyword(s):  
Forced Convection ◽  
Computational Cost ◽  
Convection Flow ◽  
Field Synergy ◽  
Governing Equations ◽  
Field Synergy Principle ◽  
Stream Functions ◽  
Forced Convective Flow ◽  
Volume Method ◽  
Cubical Cavity

This study presents an innovative visualization tool for the analysis of the mixed convection in a lid-driven air filled cubical cavity heated from below. The total energy of the flow in the cavity isvisualized based on the energy stream functions or energy streamlines. Also the heat transfer enhancement in the cavity is presented with an analogy between conduction and convection, namely, the field synergy principle. Flow is assumed to be driven by the vertical temperature gradient and by the top lid of the cavity, which is assumed to slide on its own plane at a uniform speed. The top and bottom walls are assumed to be isothermal and all other walls are thermally insulated. Non dimensional governing equations of this problem are solved by using the finite volume method. Established open source CFD package OpenFOAM is utilized to investigate the flow with respect to the control parameters arising in the system. The nonlinear terms arising in the governing equations are discretized with the NVD schemes. The convection differencing schemes namely, UPWIND, QUICK, SUPERBEE and SFCD discussed and are used to simulate the flow using MPI code. It is observed that the computational cost for all the differencing schemes get reduced tremendously when the MPI code is implemented. Also SFCD scheme gave the Nuseelt number values close to those available in the literature. Extensive numerical flow visualization is conducted for the Reynolds number (Re = 100, 400, 1000) and the Richardson number (Ri = 0.001, 1, 10), which categorize the free and forced convective flow, respectively. It is observed that for a fixed value of Re, as Ri increases, the average Nusselt number (Nu¯), decreases. This shows that the natural convection starts to prevail with an increasing of Ri. But, for a fixed Ri, as Re increases (Nu¯) increases and the forced convection mode becomes dominant, leading to a chaotic flow. Plots demonstrating the influences of Re and Ri in termsof the contours of the fluid streamlines, isotherms, vortex corelines, and field synergy principle. The synergy angle of buoyant-aiding flow is high while the buoyant-opposing flow is significantly less than that of forced convection flow.

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