Numerical Investigations on Heat Transfer of Self-Sustained Oscillation of a Turbulent Jet Flow Inside a Cavity

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Farida Iachachene ◽  
Amina Mataoui ◽  
Yacine Halouane
Keyword(s):  
Heat Transfer ◽  
Navier Stokes ◽  
Sustained Oscillation ◽  
Practical Applications ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Wide Range ◽  
Turbulent Jet Flow ◽  
Volume Method ◽  
Plane Jet

Computations of heat transfer and fluid flow of a plane isothermal fully developed turbulent plane jet flowing into a rectangular hot cavity are reported in this paper. Both velocity and temperature distributions are computed by solving the two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations. This approach is based on one-point statistical modeling using the energy-specific dissipation (k-ω) turbulence model. The numerical predictions are achieved by finite volume method. This problem is relevant to a wide range of practical applications including forced convection and the ventilation of mines, enclosure, or corridors. The structural properties of the flow and heat transfer are described for several conditions. An oscillatory regime is evidenced for particular jet location, inducing for each variable a periodic behavior versus time. The jet flapping phenomena are detailed numerically by the instantaneous streamlines contours and the vorticity magnitude contours within one period of oscillation. The heat transfer along the cavity walls is also periodic. Time average of mean Nusselt number is correlated according with some problem parameters.

Characteristics of Fully Developed Flow and Heat Transfer in Channels With Varying Wall Geometry

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Abhishek G. Ramgadia ◽  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Time Dependent ◽  
Navier Stokes ◽  
Fully Developed Flow ◽  
Flow And Heat Transfer ◽  
Collocated Grid ◽  
Wall Profile ◽  
Energy Equations ◽  
Volume Method ◽  
Wall Geometry

Present study focuses on numerical investigation of fully developed flow and heat transfer through three channels having sine-shaped, triangle-shaped, and arc-shaped wall profiles. All computations are performed at Reynolds number of 600. Finite volume method on collocated grid is used to solve the time-dependent Navier–Stokes and energy equations in primitive variable form. For all the geometries considered in the study, the ratios Hmin/Hmax and L/a are kept fixed to 0.4 and 8.0, respectively. The thermal performances of all the three wall configurations are assessed using integral parameters as well as instantaneous, time-averaged and fluctuating flow fields. The geometry with the sinusoidal-shaped wall profile is found to produce the best thermal properties as compared to the triangle-shaped and the arc-shaped profiles though the obtained heat transfer is the highest for the arc-shaped geometry.

scholarly journals Lid-Driven and Inclined Square Cavity Filled With a Nanofluid: Optimum Heat Transfer

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Abdelkader Boutra ◽  
Karim Ragui ◽  
Nabila Labsi ◽  
Youb Khaled Benkahla
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Numerical Study ◽  
Square Enclosure ◽  
Coupled Equations ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Optimum Heat ◽  
Nanoparticles Volume Fraction ◽  
Volume Method

AbstractThis paper reports a numerical study on mixed convection within a square enclosure, filled with a mixture of water and Cu (or Ag) 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 the general coupled equations, a code based on the finite volume method is used and it has been validated after comparison between the present results and those of the literature. To make clear the effect of the main parameters on fluid flow and heat transfer inside the enclosure, a wide range of the Richardson number, taken from 0.01 to 100, the nanoparticles volume fraction (0% to 10%), and the cavity inclination angle (0º to 180º) are investigated. The phenomenon is analyzed through streamlines and isotherm plots, with special attention to the Nusselt number.

Flow and Heat Transfer in an Internally Ribbed Duct With Rotation: An Assessment of LES and URANS

2003 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Density Ratio ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Number Ratio ◽  
Wide Range ◽  
Side Walls ◽  
Subgrid Stresses

Large Eddy Simulations (LES) and Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations have been performed for flow and heat transfer in a rotating ribbed duct. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The LES results are based on a higher-order accurate finite difference scheme with a dynamic Smagorinsky model for the subgrid stresses. The URANS procedure utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The URANS computations have been carried out for a wide range of Reynolds number (Re = 12,500–100,000), rotation number (Ro = 0–0.5) and density ratio (Δρ/ρ = 0–0.5), while LES results are reported for a single Reynolds number of 12,500 without and with rotation (Ro = 0.12, Δρ/ρ = 0.13). Comparison is made between the LES and URANS results, and the effects of various parameters on the flow field and surface heat transfer are explored. The LES results clearly reflect the importance of coherent structures in the flow, and the unsteady dynamics associated with these structures. The heat transfer results from both LES and URANS are found to be in reasonable agreement with measurements. LES is found to give higher heat transfer predictions (5–10% higher) than URANS. The Nusselt number ratio (Nu/Nu0) is found to decrease with increasing Reynolds number on all walls, while they increase with the density ratio along the leading and trailing walls. The Nusselt number ratio on the trailing and side walls also increases with rotation. However, the leading wall Nusselt number ratio shows an initial decrease with rotation (till Ro = 0.12) due to the stabilizing effect of rotation on the leading wall. However, beyond Ro = 0.12, the Nusselt number ratio increases with rotation due to the importance of centrifugal-buoyancy at high rotation.

scholarly journals Simulations and Measurements on Impulse Blades for Heat Transfer Prediction in Supersonic Turbine Applications

1998 ◽  
Author(s):  
U. Håll ◽  
J. Larsson ◽  
F. Bario ◽  
P. Kulisa ◽  
J. Slimani ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Leading Edge ◽  
Navier Stokes ◽  
Rocket Engines ◽  
Gas Generator ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Boundary Layer Method ◽  
Fundamental Insight

This paper presents an overview of a research project aimed at improving the currently available methods to predict the flow and heat transfer in uncooled supersonic impulse turbines. These turbines are typically used in rocket engines based on the gas-generator cycle. A fast boundary-layer method, suitable in the design phase, is presented. This method includes effects related to curvature, transition and separation bubbles. For more detailed analysis, Navier-Stokes methods are used. Experiences from using a wide range of two-equation models to predict turbine blade heat transfer are summarized. The experimental work uses a scaled-up, heated, linear blade cascade. The aim is to gain fundamental insight into the phenomena involved in turbine blade heat transfer and to obtain data for validation and development of new numerical methods. Detailed measurements, of both averaged and fluctuating properties of the velocity field, are made in the boundary layers down to a Y+ below 10. The results presented here are focused on the leading edge.

Detached Eddy Simulation of Flow and Heat Transfer in a Stationary Internal Cooling Duct With Skewed Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Detached Eddy Simulation ◽  
Square Duct ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Flow Features

Numerical predictions of a hydrodynamic and thermally developed turbulent flow for a unit period of a stationary duct using Detached Eddy Simulation (DES) and Unsteady Reynolds Averaged Navier-Stokes (URANS) are presented. The domain under consideration is a square duct with 45° ribs on the top and bottom walls arranged in a staggered fashion. Computations are carried out for a bulk Re of 47,000. The rib height to channel hydraulic diameter (e/Dh) is 0.1 and the rib pitch to rib height (P/e) is 10. DES is applied on two grids 80 × 80 × 80 and 128 × 80 × 80 and the initial results are compared with the experimental results and LES computations. Based on this the 128 × 80 × 80 grid is chosen for the comprehensive study. DES and URANS computations are carried out on the grid. The rib geometry introduces a strong secondary flow along the rib. The presence of the secondary flow introduces a spanwise variation in the heat transfer. DES predicts flow features and heat transfer distribution which is consistent with the experimental observations and LES computations. The average friction and the augmentation ratios predicted by DES also concur with the earlier observations.

Effect of Inclination Angle on Three-Dimensional Combined Convective Heat Transfer of Nanofluids in Rectangular Channels

2013 ◽  
Vol 388 ◽  
pp. 176-184
Author(s):  
Hussein A. Mohammed ◽  
Nur Irmawati Om ◽  
Mazlan A. Wahid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Inclination Angle ◽  
Pure Water ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Rectangular Channels ◽  
Energy Equations ◽  
Volume Method

Combined convective nanofluids flow and heat transfer in an inclined rectangular duct is numerically investigated. Three dimensional, laminar Navier-Stokes and energy equations were solved using the finite volume method. Pure water and four types of nanofluids such as Au, CuO, SiO2 and TiO2with volume fractions range of 2% φ 7% are used. This investigation covers the following ranges: 2 × 106 Ra 2 × 107, 100 Re 1000 and 30° Θ 60°. The results revealed that the Nusselt number increased as Rayleigh number increased.SiO2nanofluid has the highest Nusselt number while Au nanofluid has the lowest Nusselt number. An increasing of the duct inclination angle decreases the heat transfer.

scholarly journals Computations of Flow and Heat Transfer in a Channel With Rows of Hemispherical Cavities

1999 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I-P. Shih ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Wall Functions ◽  
Time Stepping ◽  
Flow And Heat Transfer ◽  
A Cell ◽  
Volume Method

Computations were performed to investigate the three-dimensional flow and heat transfer in a high aspect ratio channel in which one or two wall are lined with four rows of hemispherical cavities arranged in a staggered fashion with two Reynolds numbers (23,000 and 46,000). The focus is on understanding the flow induced by cavities and how that flow affects surface heat transfer. Computed results were compared with available experimental data. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by the low Reynolds number shear-stress transport k-ω turbulence model (wall functions were not used). Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.

scholarly journals The Influence of Different Types of Nanofluid on Thermal and Fluid Flow Performance of Liquid Cold Plate

2018 ◽  
Vol 7 (4.35) ◽  
pp. 148 ◽  
Author(s):  
Nur Irmawati Om ◽  
Rozli Zulkifli ◽  
P. Gunnasegaran
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Cold Plate ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Different Types ◽  
Volume Method

The influence of utilizing different nanofluids types on the liquid cold plate (LCP) is numerically investigated. The thermal and fluid flow performance of LCP is examined by using pure ethylene glycol (EG), Al2O3-EG and CuO-EG. The volume fraction of the nanoparticle for both nanofluid is 2%. The finite volume method (FVM) has been used to solved 3-D steady state, laminar flow and heat transfer governing equations. The presented results indicate that Al2O3-EG able to provide the lowest surface temperature of the heater block followed by CuO-EG and EG, respectively. It is also found that the pressure drop and friction factor are higher for Al2O3-EG and CuO-EG compared to the pure EG.

Effects of Guide Vanes on the Tip Heat Transfer Enhancement of a Turbine Blade

2011 ◽  
Author(s):  
Gongnan Xie ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Enhancement ◽  
Turbine Blade ◽  
Pressure Loss ◽  
Transfer Enhancement ◽  
Guide Vanes ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Blade Tip

Gas turbine blade tips encounter large heat load as they are exposed to the high temperature gas. A common way to cool the blade and its tip is to design serpentine passages with 180-deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip life time. This paper presents numerical predictions of turbulent fluid flow and heat transfer through two-pass channels with and without guide vanes placed in the turn regions using RANS turbulence modeling. The effects of adding guide vanes on the tip-wall heat transfer enhancement and the channel pressure loss were analyzed. The guide vanes have a height identical to that of the channel. The inlet Reynolds numbers are ranging from 100,000 to 600,000. The detailed three-dimensional fluid flow and heat transfer over the tip-walls are presented. The overall performances of several two-pass channels are also evaluated and compared. It is found that the tip heat transfer coefficients of the channels with guide vanes are 10∼60% higher than that of a channel without guide vanes, while the pressure loss might be reduced when the guide vanes are properly designed and located, otherwise the pressure loss is expected to be increased severely. It is suggested that the usage of proper guide vanes is a suitable way to augment the blade tip heat transfer and improve the flow structure, but is not the most effective way compared to the augmentation by surface modifications imposed on the tip-wall directly.

Passive Heat Transfer in Porous Enclosures Using a Two-Energy Equation Model

2012 ◽  
Author(s):  
Marcelo J. S. deLemos ◽  
Paulo H. S. Carvalho
Keyword(s):  
Heat Transfer ◽  
Energy Equation ◽  
Equation Model ◽  
Thermal Conductivity Ratio ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Energy Models ◽  
Different Temperatures ◽  
Volume Method ◽  
Generalized Coordinate

This paper presents computations for natural convection within a porous cavity filled with a fluid saturated permeable medium. The finite volume method in a generalized coordinate system is applied. The walls are maintained at constant but different temperatures, while the horizontal walls are kept insulated. Governing equations are written in terms of primitive variables and are recast into a general form. Flow and heat transfer characteristics are investigated for two energy models and distinct solid-to-fluid thermal conductivity ratio.

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