Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework

2015 ◽  
Author(s):  
Luca Mangani ◽  
David Roos Launchbury ◽  
Ernesto Casartelli ◽  
Giulio Romanelli
Keyword(s):  
Heat Transfer ◽  
Open Source ◽  
Gas Turbines ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Order ◽  
Computational Time

The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine. In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer. The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows. An overview of the development methods is provided, presenting numerical and algorithmic details. The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.

Heat Transfer Enhancement by Turbulent Impinging Jets

2000 ◽  
Author(s):  
M. Kumagai ◽  
R. S. Amano ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.

Flow and Heat Transfer Past a Sudden Contraction With a Porous Insert Using Linear and Non-Linear Turbulence Models

2004 ◽  
Author(s):  
Marcelo Assato ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Porous Insert ◽  
Macroscopic Models ◽  
Flow And Heat Transfer ◽  
Non Linear ◽  
Abrupt Contraction ◽  
Stream Lines

This work presents a numerical investigation for the turbulent flow and heat transfer in an abrupt contraction channel with a porous material placed in a flow passage. The channel has a contraction rate of 3:2. Results for the hybrid medium were obtained using linear and non-linear k-ε macroscopic models. It was used an inlet Reynolds number of Re = 132000 based on the height of the step. Parameters such as porosity, permeability and thickness of the porous insert were varied in order to analyze their effects on the flow pattern. The results of local heat transfer, friction coefficient and stream lines obtained by the two turbulence models were compared for the cases without and with porous insertion of thickness a/H=0.083, 0.166 and 0.250, where H is the step height. Insert porosity of varied between 0.85 and 0.95 with permeability in the range 10−6–10−2 m2.

Numerical Simulation of Local Heat Transfer and Scaling of a Synthetic Impinging Jet in a Canonical Geometry

2011 ◽  
Author(s):  
Luis Silva ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Heated Surface ◽  
Vortex Pair ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Synthetic Jets ◽  
Navier Stokes ◽  
Dependent Flow ◽  
Finite Volume Approach

Synthetic jets are generated by an equivalent inflow and outflow of fluid into a system. Even though such a jet creates no net mass flux, net positive momentum can be produced because the outflow momentum during the first half of the cycle is contained primarily in a vigorous vortex pair created at the orifice edges whereas in the backstroke, the backflow momentum is weaker, despite the fact that mass is conserved. As a consequence of this, the approach can be potentially utilized for the impingement of a cooling fluid over a heated surface. In the present study, a canonical geometry is presented, in order to study the flow and heat transfer of a purely oscillatory jet that is not influenced by the manner in which it is produced. The unsteady Navier-Stokes equations and the convection-diffusion equation were solved using a fully unsteady, two-dimensional finite volume approach in order to capture the complex time dependent flow field. A detailed analysis was performed on the correlation between the complex velocity field and the observed wall heat transfer. A fundamental frequency, in addition to the jet forcing frequency, was found, and was attributed to the coalescence of consecutive vortex pairs. In some instances, this vortex pairing can lead to zones of low heat transfer. Two point correlations showed that the Nusselt number Nu, showed stronger correlation with the vertical velocity v although the spatial-temporal dependencies are not yet fully understood. It was found that the Reynolds number and the Strouhal number, are sufficient to successfully scale the problem at larger dimensions and this is presently being exploited in order to design validation experiments using jets large enough to allow careful local measurements.

Jet Impingement Heat Transfer on a Circular Cylinder by Radial Slot Jets

2005 ◽  
Author(s):  
Neil Zuckerman ◽  
Noam Lior
Keyword(s):  
Heat Transfer ◽  
Numerical Models ◽  
Pressure Rise ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Correlation Equation ◽  
Local Heat ◽  
Wall Jets ◽  
Cylindrical Target

To better understand and facilitate design of an impinging jet device, the heat transfer on a cylindrical target exposed to radial impinging slot jets was investigated using numerical methods. Numerical models were created to test the performance of the Shear Stress Transport (SST), Standard and Realizable k-epsilon, v2f, and Reynolds Stress Model (RSM) turbulence models versus published test data. Based on the validation study the v2f model was ultimately selected for further work. Models were then constructed to simulate a cylinder exposed to a radial array of slot jets. Parametric variations were conducted to produce information about the influence of jet speed, nozzle count, and other independent design variables upon heat transfer. Nozzle count was varied from 2 to 8, jet Reynolds number ranged from 5,000 to 80,000, and target diameter varied from 5 to 10 times the nozzle hydraulic diameter. The interaction of adjacent opposed wall jets caused a static pressure rise and resulted in flow separation on the surface of the cylindrical target. This separation and the fountain flow between the two wall jets greatly influenced the local heat transfer, causing a rise in Nu of an order of magnitude. The resulting average Nu values varied from 19 to 217 and were condensed into a correlation equation incorporating target curvature, number of nozzles, Re, and Pr.

Heat Transfer Coefficient Distributions for the Convective Cooling of Non-Cylindrical Geometries in Crossflow Using Extended Surfaces

1997 ◽  
Author(s):  
Andrew J. Neely ◽  
Peter T. Ireland ◽  
Les R. Harper
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Convective Cooling ◽  
Heat Transfer Coefficients ◽  
Cylindrical Geometries

An experimental investigation of the performance of extended fin surfaces for the forced convective cooling of a range of engine component geometries in crossflow is reported. The experiments were undertaken to measure the surface heat transfer coefficient distributions of external finning around non-cylindrical geometries for use in aviation gas turbines in which the cooling performance/mass ratio must be maximised. The geometries examined were a box (square with rounded corners), a flute (rectangle with circular ends) and a 30° wedge. These models were sized to have equivalent cross sectional area to allow a direct comparison of performance. Perspex models coated with thermochromic liquid crystal were tested at a range of Reynolds numbers in a heat transfer wind tunnel in which a step change in flow temperature was used to measure the transient thermal behaviour of the fins. This technique enables the full surface mapping of local heat transfer coefficients on the surface of the fins. These measurements are compared with those for the equivalent smooth geometries and also with empirical calculations from the literature where available. A comparison with previous cylindrical measurements is also made. Knowledge of the distributions of local heat transfer coefficients enables the optimisation of the geometry through strategies such as baffling of the fins. Some examples of these strategies have been implemented and the results are reported. The finned geometries are seen to outperform the unfinned geometries (by factors greater than 3) though by factors less than simply the increase in area. The enhancement in h results because the increased surface area of the fins more than outweighs the decrease in local h on the fin surface as compared to the smooth geometries.

Local Heat Transfer in Turbine Disk-Cavities: Part II — Rotor Cooling With Radial Location Injection of Coolant

1990 ◽  
Author(s):  
R. S. Bunker ◽  
D. E. Metzger ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Computer Assisted ◽  
Transfer Coefficients ◽  
Disk Radius ◽  
Radial Location ◽  
Heat Transfer Coefficients ◽  
Experimental Apparatus

Detailed radial distributions of rotor heat transfer coefficients are presented for three basic disk-cavity geometries applicable to gas turbines. The experimental apparatus has been designed to obtain local heat transfer data on a number of easily interchangeable rotor surfaces. The method employs thin thermochromic liquid crystal coatings upon the rotor surfaces together with video system data acquisition and computer-assisted image analysis to detect surface color display and to extract heat transfer information. A thermally transient, aerodynamically steady technique is used which attains consistent thermal boundary conditions over the entire disk-cavity. Cooling air is introduced into the disk-cavity via a single circular jet mounted perpendicularly into the stator at one of three radial locations; 0.4, 0.6 or 0.8 times the rotor radius. Rotor heat transfer coefficients have been obtained over a range of parameters including disk rotational Reynolds numbers of 2 to 5 · 105, rotor/stator hub spacing-to-disk radius ratios of .025 to .15, and jet mass flow rates between .10 and .40 times the turbulent pumped flow rate of a free disk. The rotor surfaces include a parallel rotor-stator system, a rotor with 5 percent diverging taper, and a similarly tapered rotor with a rim sealing lip at its extreme radius. Results are presented showing the effects of the parallel rotor, which indicate strong variations in local Nusselt numbers for all but rotational speed. These results are compared to associated hub injection data of Part I of this study, demonstrating that overall rotor heat transfer is optimized by either hub injection or radial location injection of coolant dependent upon the configuration. Results with the use of the tapered rotor show significant local Nusselt number radial variation changes over those of the parallel rotor, while the addition of a rim sealing lip appears to increase the level of the radial distribution.

Numerical Simulation of Turbulent Impingement Cooling

2001 ◽  
Author(s):  
Andreas Abdon ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Transition Process ◽  
Local Heat ◽  
Boundary Layer Transition ◽  
Wall Jet ◽  
Layer Transition ◽  
Stagnation Region

Simulations of turbulent impinging jet heat transfer for different nozzle configurations using Reynolds averaged governing equations and two-equation turbulence models have been conducted. The considered nozzle configurations are a square-edged orifice and a pipe exit. The results for a jet Reynolds number of 10000 and dimensionless nozzle-to-plate distance of 2 show that the heat transfer is well predicted for the pipe configuration but underpredicted for the orifice. The disagreement may be partly explained by underprediction of turbulence in the stagnation region and inaccurate treatment of the wall jet boundary layer transition. An investigation of the local heat transfer distribution for the orifice reveals two local maxima. These are related to an accelerating laminar boundary layer and the transition process of the wall jet, respectively, for the calculations. The application of a realizability constraint on the models leads to reduced turbulence levels, not only in the stagnation region, but also in the throttled flow of the orifice configuration. This improves the prediction of heat transfer and nozzle exit turbulence levels significantly.

scholarly journals Local Heat Transfer in Turbine Disk-Cavities: Part I — Rotor and Stator Cooling With Hub Injection of Coolant

1990 ◽  
Author(s):  
R. S. Bunker ◽  
D. E. Metzger ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Computer Assisted ◽  
Disk Radius ◽  
Wide Range

Results are presented from an experimental study designed to obtain detailed radial heat transfer coefficient distributions applicable to the cooling of disk-cavity regions of gas turbines. An experimental apparatus has been designed to obtain local heat transfer data on both the rotating and stationary surfaces of a parallel geometry disk-cavity system. The method employed utilizes thin thermochromic liquid crystal coatings together with video system data acquisition and computer-assisted image analysis to extract heat transfer information. The color display of the liquid crystal coatings is detected through the analysis of standard video chromanance signals. The experimental technique used is an aerodynamically steady but thermally transient one which provides consistent disk-cavity thermal boundary conditions while yet being inexpensive and highly versatile. A single circular jet is used to introduce fluid from the stator into the disk-cavity by impingement normal to the rotor surface. The present study investigates hub injection of coolant over a wide range of parameters including disk rotational Reynolds numbers of 2 to 5 · 105, rotor/stator spacing-to-disk radius ratios of .025 to .15, and jet mass flow rates between .10 and .40 times the turbulent pumped flow rate of a free disk. The results are presented as radial distributions of local Nusselt numbers. Rotor heat transfer exhibits regions of impingement and rotational domination with a transition region between, while stator heat transfer shows flow reattachment and convection regions with evidence of an inner recirculation zone. The local effects of rotation, spacing, and mass flow rate are all displayed. The significant magnitude of stator heat transfer in many cases indicates the importance of proper stator modeling to rotor and disk-cavity heat transfer results.

Transient Data Processing of Flow Boiling Local Heat Transfer in a Multi-Microchannel Evaporator Under a Heat Flux Disturbance

2017 ◽  
Vol 139 (1) ◽  
Author(s):  
Houxue Huang ◽  
Nicolas Lamaison ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Data Reduction ◽  
Transient Flow ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Fluid ◽  
Computational Time ◽  
Ir Camera

Multi-microchannel evaporators are often used to cool down electronic devices subjected to continuous heat load variations. However, so far, rare studies have addressed the transient flow boiling local heat transfer data occurring in such applications. The present paper introduces and compares two different data reduction methods for transient flow boiling data in a multi-microchannel evaporator. A transient test of heat disturbance from 20 to 30 W cm−2 was conducted in a multi-microchannel evaporator using R236fa as the test fluid. The test section was 1 × 1 cm2 in size and had 67 channels, each having a cross-sectional area of 100 × 100 μm2. The micro-evaporator backside temperature was obtained with a fine-resolution infrared (IR) camera. The first data reduction method (referred to three-dimensional (3D)-TDMA) consists in solving a transient 3D inverse heat conduction problem by using a tridiagonal matrix algorithm (TDMA), a Newton–Raphson iteration, and a local energy balance method. The second method (referred to two-dimensional (2D)-controlled) considers only 2D conduction in the substrate of the micro-evaporator and solves at each time step the well-posed 2D conduction problem using a semi-implicit solver. It is shown that the first method is more accurate, while the second one reduces significantly the computational time but led to an approximated solution. This is mainly due to the 2D assumption used in the second method without considering heat conduction in the widthwise direction of the micro-evaporator.

scholarly journals CFD Calculation of Internal Natural Convection in the Annulus Between Horizontal Concentric Cylinders

2003 ◽  
Author(s):  
Stephen W. Webb ◽  
Nicholas D. Francis ◽  
Michael T. Itamura ◽  
Darryl L. James
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Wall Functions ◽  
Thermally Induced ◽  
Concentric Cylinders ◽  
Commercial Code

Thermally-induced natural convection heat transfer in the annulus between horizontal concentric cylinders has been studied using the commercial code Fluent. The boundary layers are meshed all the way to the wall because forced convection wall functions are not appropriate. Various oneand two-equation turbulence models have been considered. Overall and local heat transfer rates are compared with existing experimental data.

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