Numerical Conjugate Heat Transfer Study of a Cooled Compressor Rear Cone

2014 ◽  
Author(s):  
Fabian Bleier ◽  
Max Hufnagel ◽  
Tim Pychynski ◽  
Hans-Jörg Bauer ◽  
Christian Eichler
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Frictional Heating ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Parameter Study ◽  
Operational Parameters ◽  
Transfer Coefficients ◽  
Gap Width ◽  
Transfer Study

The paper presents the setup of a conjugate heat transfer study of an annular conical gap, its validation and a parameter study. The main goal of the work is to identify effects of gap width and swirl ratio on the local and global heat transfer in the annular conical gap. The validation of the numerical model is done by a comparison against experimental data from literature. It is shown that the non-axisymmetric flow in the gap can be well reproduced by a three-dimensional axisymmetric model. To identify influences of geometric and operational parameters on the cooling efficiency, a RANS parameter study of the cooling concept is performed. The parameter study includes variations of the gap width and the pre-swirl of the inlet air. The results are used to evaluate the quality of the cooling concept and to identify the effect of geometry on frictional effects and on heat transfer coefficients. In this respect it is important to separate frictional heating and convective heat transfer effects.

Buoyancy Induced Convection in a Narrow Open-Ended Annulus

1997 ◽  
Vol 119 (3) ◽  
pp. 483-494 ◽  
Author(s):  
K. Vafai ◽  
C. P. Desai ◽  
S. V. Iyer ◽  
M. P. Dyko
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Axial Length ◽  
Numerical Study ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Transfer Coefficients ◽  
State Equations ◽  
Element Analysis ◽  
Gap Width

Results from a combined experimental and numerical investigation of buoyancy driven flow and heat transfer in a narrow annular gap between co-axial, horizontal cylinders are presented in this work. The annulus is open at both ends through which the ambient fluid can interact with the fluid inside the gap. In the experimental study, a constant heat flux was utilized to simulate buoyancy induced convection in an open ended annular cavity with a low gap to inner cylinder radius ratio; local surface temperature measurements were made to determine heat transfer characteristics of the convective flow. The heat transfer results are correlated by Nu = 0.134(Ra*)0.264 for the range of Rayleigh numbers considered (7.09 ×108 ≤ Ra* ≤ 4.76 × 109) in the experiments. In the numerical investigation, solutions to the three-dimensional time-averaged (Reynolds) steady-state equations of fluid motion and heat transfer were obtained using a finite element analysis. Results of the conjugate study including the local temperature distributions, heat transfer coefficients, and the flow field showing the interactions between the ambient and cavity flow fields agree favorably with experimental results. An investigation was also carried out to study the effect of axial length and the gap width of the annulus. A correlation for the average Nusselt number as a function of Rayleigh number, axial length and gap width has been obtained. The present work provides, for the first time, an experimental and numerical study of turbulent buoyancy induced flows in a narrow open-ended annulus.

scholarly journals Axial Heat Conduction in the Context of Developing Flows in Microchannels

2011 ◽  
Author(s):  
Manoj K. Moharana ◽  
Piyush K. Singh ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Three Dimensional ◽  
Constant Heat Flux ◽  
Substrate Thickness ◽  
Transfer Coefficients ◽  
Flow Parameters ◽  
Conjugate Formulation ◽  
Axial Heat ◽  
Square Microchannel

For practical microchannel applications involving convective heat transfer, the flows are usually, not only laminar, they are also simultaneously developing in nature. Moreover, flat plate substrates with microchannels engraved/ machined or etched on them are emerging as one of the most popular flow geometries. Not analyzing such situations as conjugate heat transfer problems with multi-dimensional effects, often leads to erroneous estimation of heat transfer coefficients. In this context, we report three dimensional numerical simulations of simultaneously developing internal convective flow through a square microchannel (side = 400 μm), treating the substrate thickness, flow Reynolds number and the thermal conductivity of the substrate and the fluid, in the conjugate formulation. Constant heat flux is applied at the bottom of the substrate, away from the fluid-solid interface, as in real-time situations. The parametric study reveals that depending on geometry considerations, flow parameters and thermo-physical properties of fluid-solid combination, conjugate heat transfer effects must be accounted for, to correctly estimate the local Nusselt number.

scholarly journals Numerical simulation of variable thermal conductivity on 3D flow of nanofluid over a stretching sheet

2020 ◽  
Vol 9 (1) ◽  
pp. 233-243 ◽  
Author(s):  
Nainaru Tarakaramu ◽  
P.V. Satya Narayana ◽  
Bhumarapu Venkateswarlu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Stretching Sheet ◽  
Three Dimensional ◽  
Variable Thermal Conductivity ◽  
Normal Velocity ◽  
Transfer Coefficients ◽  
Similarity Transformations ◽  
Frictional Coefficients ◽  
The Impact

AbstractThe present investigation deals with the steady three-dimensional flow and heat transfer of nanofluids due to stretching sheet in the presence of magnetic field and heat source. Three types of water based nanoparticles namely, copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are considered in this study. The temperature dependent variable thermal conductivity and thermal radiation has been introduced in the energy equation. Using suitable similarity transformations the dimensional non-linear expressions are converted into dimensionless system and are then solved numerically by Runge-Kutta-Fehlberg scheme along with well-known shooting technique. The impact of various flow parameters on axial and transverse velocities, temperature, surface frictional coefficients and rate of heat transfer coefficients are visualized both in qualitative and quantitative manners in the vicinity of stretching sheet. The results reviled that the temperature and velocity of the fluid rise with increasing values of variable thermal conductivity parameter. Also, the temperature and normal velocity of the fluid in case of Cu-water nanoparticles is more than that of Al2O3- water nanofluid. On the other hand, the axial velocity of the fluid in case of Al2O3- water nanofluid is more than that of TiO2nanoparticles. In addition, the current outcomes are matched with the previously published consequences and initiate to be a good contract as a limiting sense.

Flow Past a Spinning Sphere With Surface Blowing and Heat Transfer

2005 ◽  
Vol 127 (1) ◽  
pp. 163-171 ◽  
Author(s):  
H. Niazmand ◽  
M. Renksizbulut
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Solid Sphere ◽  
Temporal Variations ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Particle Spin ◽  
Flow Past ◽  
Angular Velocities

Computations are performed to determine the transient three-dimensional heat transfer rates and fluid forces acting on a stream-wise spinning sphere for Reynolds numbers in the range 10⩽Re⩽300 and angular velocities Ωx⩽2. In this Re range, classical flow past a solid sphere develops four different flow regimes, and the effects of particle spin are studied in each regime. Furthermore, the combined effects of particle spin and surface blowing are examined. Sphere spin increases drag in all flow regimes, while lift shows a nonmonotonic behavior. Heat transfer rates are not influenced by spin up to a certain Ωx but increase monotonically thereafter. An interesting feature associated with sphere spin is the development of a special wake regime such that the wake simply spins without temporal variations in its shape. For this flow condition, the magnitudes of the lift, drag, and heat transfer coefficients remain constant in time. Correlations are provided for drag and heat transfer.

Comparison of a Conventional Thermal Analysis of a Turbine Cascade to a Full Conjugate Heat Transfer Computation

2008 ◽  
Author(s):  
Christoph Starke ◽  
Erik Janke ◽  
Toma´sˇ Hofer ◽  
Davide Lengani
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Conjugate Heat Transfer ◽  
Complex Geometry ◽  
Thermal Analyses ◽  
Turbine Cascade ◽  
Transfer Coefficients ◽  
Commercial Code ◽  
Blade Tip ◽  
Transfer Method

Recent development in commercial CFD codes offers possibilities to include the solid body in order to perform conjugate heat transfer computations for complex geometries. The current paper aims to analyse the differences between a conjugate heat transfer computation and conventional uncoupled approaches where a heat transfer coefficient is first derived from a flow solution and then taken as boundary condition for a thermal conduction analysis of the solid part. Whereas the thermal analyses are done with a Rolls-Royce in-house finite element code, the CFD as well as the conjugate heat transfer computation are done using the new version 8 of the commercial code Fine Turbo from Numeca International. The analysed geometry is a turbine cascade that was tested by VKI in Brussels within the European FP6 project AITEB 2. First, the paper presents the aerodynamic results. The pure flow solutions are validated against pressure measurements of the cascade test. Then, the heat transfer from flow computations with wall temperature boundary conditions is compared to the measured heat transfer. Once validated, the heat transfer coefficients are used as boundary condition for three uncoupled thermal analyses of the blade to predict its surface temperatures in a steady state. The results are then compared to a conjugate heat transfer method. Therefore, a mesh of the solid blade was added to the validated flow computation. The paper will present and compare the results of conventional uncoupled thermal analyses with different strategies for the wall boundary condition to results of a conjugate heat transfer computation. As it turns out, the global results are similar but especially the over-tip region with its complex geometry and flow structure and where effective cooling is crucial shows remarkable differences because the conjugate heat transfer solution predicts lower blade tip temperatures. This will be explained by the missing coupling between the fluid and the solid domain.

Computational Insights Into Air-Side Flow and Heat Transfer in Compact Heat Exchangers

2005 ◽  
Author(s):  
D. K. Tafti
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Computer Experiments ◽  
Transfer Coefficients ◽  
Substantial Impact ◽  
Compact Heat Exchangers ◽  
Thermal Phenomena ◽  
Side Flow

The paper describes two- and three-dimensional computer simulations which are used to study fundamental flow and thermal phenomena in multilouvered fins used for air-side heat transfer enhancement in compact heat exchangers. Results pertaining to flow transition, thermal wake interference, and fintube junction effects are presented. It is shown that a Reynolds number based on flow path rather than louver pitch is more appropriate in defining the onset of transition, and characteristic frequencies in the louver bank scale better with a global length scale such as fin pitch than with louver pitch or thickness. With the aid of computer experiments, the effect of thermal wakes is quantified on the heat capacity of the fin as well as the heat transfer coefficient, and it is established that experiments which neglect accounting for thermal wakes can introduce large errors in the measurement of heat transfer coefficients. Further, it is shown that the geometry of the louver in the vicinity of the tube surface has a large effect on tube heat transfer and can have a substantial impact on the overall heat capacity.

Full 3D Conjugate Heat Transfer Simulation and Heat Transfer Coefficient Prediction for the Effusion-Cooled Wall of a Gas Turbine Combustor

2008 ◽  
Author(s):  
Andreas Jeromin ◽  
Christian Eichler ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Gas Turbine ◽  
Conjugate Heat Transfer ◽  
Solid Wall ◽  
Heat Fluxes ◽  
Computational Domain ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Numerical Predictions

Numerical predictions of conjugate heat transfer on an effusion cooled flat plate were performed and compared to detailed experimental data. The commercial package CFX® is used as flow solver. The effusion holes in the referenced experiment had an inclination angle of 17 degrees and were distributed in a staggered array of 7 rows. The geometry and boundary conditions in the experiments were derived from modern gas turbine combustors. The computational domain contains a plenum chamber for coolant supply, a solid wall and the main flow duct. Conjugate heat transfer conditions are applied in order to couple the heat fluxes between the fluid region and the solid wall. The fluid domain contains 2.4 million nodes, the solid domain 300,000 nodes. Turbulence modeling is provided by the SST turbulence model which allows the resolution of the laminar sublayer without wall functions. The numerical predictions of velocity and temperature distributions at certain locations show significant differences to the experimental data in velocity and temperature profiles. It is assumed that this behavior is due to inappropriate modeling of turbulence especially in the effusion hole. Nonetheless, the numerically predicted heat transfer coefficients are in good agreement with the experimental data at low blowing ratios.

scholarly journals Significance of Nonsimilar Numerical Simulations in Forced Convection from Stretching Cylinder Subjected to External Magnetized Flow of Sisko Fluid

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jifeng Cui ◽  
Umer Farooq ◽  
Ahmed Jan ◽  
Murtada K. Elbashir ◽  
Waseem Asghar Khan ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Frictional Heating ◽  
Fluid Velocity ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Axial Direction ◽  
High Viscosity ◽  
Heat Equations ◽  
Dimensionless Numbers ◽  
Sisko Fluid

The practice of flowing effort is participating in various industries especially in nutrition productions all around the world. These fluids practices are utilized extensively in nutrition handling productions by making use of sticky liquids to produce valuable food manufactured goods in bulk. Nevertheless, such productions ought to guarantee that involved equipment such as pipelines are maintained clean as well as are cleared out for the efficient movement of fluids. The nonsimilar characteristics of involuntary convection from circular cylinder stretching in the axial direction subjected to an external flow of Sisko fluid characterized by the freely growing boundary layers (BL) are presented in this research. A circular cylinder is submerged in a stationary fluid. The axial stretching of the cylinder causes external fluid flow. The magnetic force of strength ″ B 0 ″ is enforced in the transverse direction. Because of the fluid's high viscosity, frictional heating due to viscous dissipation is quite significant. The flow is three dimensional but with no circumferential variations. The governing equations for axisymmetric flow that include the mass balance, x -momentum, and heat equation are modeled through conservation laws. The dimensionless system is developed by employing appropriate nonsimilar transformations. The numerical analyses are presented by adapting local nonsimilarity via finite-difference (FDM)-based MATLAB algorithm bvp4c. The characteristics of dimensionless numbers are determined by graphs that are plotted on momentum and heat equations. The nonsimilar simulations have been compared with the existing local similar solutions. Fluid velocity is increased as the material and curvature parameters are increased, resulting in improved heat transfer. The deviation in skin friction and local Nusselt number against the various dimensionless numbers is also analyzed.

Clocking Effects of Inlet Non-Uniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and high-pressure vanes are then investigated considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first one where hot spot and swirl core are aligned with passage and the second one where they are aligned with the leading edge. Comparisons between metal temperature distributions obtained from conjugate heat transfer simulations are performed evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The leading edge aligned configuration is resulted to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage aligned case. A strong sensitivity of both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

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