Spectral element-Fourier method for unsteady conjugate heat transfer in complex geometry flows

10.2514/3.653 ◽  
1995 ◽  
Vol 9 (2) ◽  
pp. 247-253 ◽  
Author(s):  
Cristina H. Amon
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Complex Geometry ◽  
Fourier Method ◽  
Spectral Element

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.

CFD Analysis of Thermally Stratified Flow and Conjugate Heat Transfer in a PWR Pressurizer Surgeline

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Jong Chull Jo ◽  
Dong Gu Kang
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Thermal Stresses ◽  
Complex Geometry ◽  
Heat Removal ◽  
Heat Transfer Analysis ◽  
Transient Temperature ◽  
Piping System ◽  
Pressurized Water ◽  
Temperature Distributions

Temperature gradients in the thermally stratified fluid flowing through a pipe may cause undesirable excessive thermal stresses at the pipe wall in the axial, circumferential, and radial directions, which can eventually lead to damages such as deformation, support failure, thermal fatigue, cracking, etc., to the piping systems. Several nuclear power plants have so far experienced such unwelcome mechanical damages to the pressurizer surgeline, feedwater nozzle, high pressure safety injection lines, or residual heat removal lines at a pressurized water reactor (PWR). In this regard, determining with accuracy the transient temperature distributions in the wall of a piping system subjected to internally thermal stratification is the essential prerequisite for the assessment of the structural integrity of such a piping system. In this study, to realistically predict the transient temperature distributions in the wall of an actual PWR pressurizer surgeline with a complex geometry of three-dimensionally bent piping, three-dimensional transient computational fluid dynamics (CFD) calculations involving the conjugate heat transfer analysis are performed for the PWR pressurizer surgeline subjected to either out- or in-surge flows using a commercial CFD code. In addition, the wall temperature distributions obtained by taking into account the existence of wall thickness are compared with those by neglecting it to identify some requirements for a realistic and conservative thermal analysis from a safety viewpoint.

Direct Numerical Simulation of Rotating Cavity Flows Using a Spectral Element-Fourier Method

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Diogo B. Pitz ◽  
John W. Chew ◽  
Olaf Marxen ◽  
Nicholas J. Hills
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Fourier Method ◽  
Spectral Element ◽  
Two Dimensions ◽  
High Order ◽  
Experimental Results ◽  
Element Approximation ◽  
Stable Algorithm ◽  
Element Discretization

A high-order numerical method is employed to investigate flow in a rotor/stator cavity without heat transfer and buoyant flow in a rotor/rotor cavity. The numerical tool used employs a spectral element discretization in two dimensions and a Fourier expansion in the remaining direction, which is periodic and corresponds to the azimuthal coordinate in cylindrical coordinates. The spectral element approximation uses a Galerkin method to discretize the governing equations, but employs high-order polynomials within each element to obtain spectral accuracy. A second-order, semi-implicit, stiffly stable algorithm is used for the time discretization. Numerical results obtained for the rotor/stator cavity compare favorably with experimental results for Reynolds numbers up to Re1 = 106 in terms of velocities and Reynolds stresses. The buoyancy-driven flow is simulated using the Boussinesq approximation. Predictions are compared with previous computational and experimental results. Analysis of the present results shows close correspondence to natural convection in a gravitational field and consistency with experimentally observed flow structures in a water-filled rotating annulus. Predicted mean heat transfer levels are higher than the available measurements for an air-filled rotating annulus, but in agreement with correlations for natural convection under gravity.

Thermomechanical Analysis of a Turbocharger Based on Conjugate Heat Transfer

2005 ◽  
Author(s):  
Tom Heuer ◽  
Bertold Engels ◽  
Patrick Wollscheid
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Steady State ◽  
Temperature Distribution ◽  
Conjugate Heat Transfer ◽  
Complex Geometry ◽  
Transfer Coefficients ◽  
Full Load ◽  
Heat Transfer Coefficients ◽  
Turbine Housing

One of the most challenging tasks in designing a turbocharger is to guarantee a sufficient lifetime. Turbine housings are critical parts due to their very complex geometry and consequently complicated temperature and stress distributions. Therefore, high thermal loads as well as thermo-mechanical fatigue have to be considered. Calculating the thermal stress distribution in the turbine housing, steady state and transient, can indicate the regions of crack initiation. From this information selective design improvements can be deduced to increase the component lifetime. But the quality of the stress analysis is strongly dependent on a reliable temperature distribution. Taking into account the interdependency of heat transfer between solid walls and fluid, conjugate heat transfer (CHT) calculations can provide temperature data of high accuracy. Since a transient CHT-calculation is still beyond state of the art, a new approach has been developed. Two steady state CHT-calculations serve to determine heat transfer coefficients at engine brake and full load. Beginning with the engine brake temperature distribution, it is assumed that the gas temperature and the mass flow change immediately. Therefore heat transfer coefficients at full load serve as a boundary condition for a subsequent transient solid body calculation simulating the acceleration process. For the deceleration process the full load temperature field is combined with the engine brake heat transfer coefficients. Monitor points give information about the steepest temperature gradients in the material. At discrete time points a steady state stress analysis has to be performed to detect the regions of highest loads. This subsequent step is essential because in a complex geometry like in a spiral housing with a divider and regionally different wall thicknesses, the stress maxima are not necessarily located at the same places as the temperature peaks. For the two steady state CHT-calculations the turbine wheel has been included in order to consider a realistic flow field. Compared to a transient calculation the degree of abstraction is as low as possible because the assumed frozen rotor boundary condition takes into account centrifugal and coriolis forces. This paper demonstrates the calculation procedure considering a twin-entry turbine housing with an integrated manifold designed for a truck application. The computational results are in excellent agreement with thermal shock test data. A second loop with an improved design proves the success of the method.

scholarly journals Polyhedral meshing in numerical analysis of conjugate heat transfer

2018 ◽  
Vol 180 ◽  
pp. 02096 ◽  
Author(s):  
Marcin Sosnowski ◽  
Jaroslaw Krzywanski ◽  
Karolina Grabowska ◽  
Renata Gnatowska
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Complex Geometry ◽  
Detailed Comparison ◽  
Automatic Generation ◽  
Accurate Solution ◽  
Heat Transfer Analysis ◽  
Mesh Quality ◽  
Hexahedral Mesh ◽  
Numerical Diffusion

Computational methods have been widely applied in conjugate heat transfer analysis. The very first and crucial step in such research is the meshing process which consists in dividing the analysed geometry into numerous small control volumes (cells). In Computational Fluid Dynamics (CFD) applications it is desirable to use the hexahedral cells as the resulting mesh is characterized by low numerical diffusion. Unfortunately generating such mesh can be a very time-consuming task and in case of complicated geometry - it may not be possible to generate cells of good quality. Therefore tetrahedral cells have been implemented into commercial pre-processors. Their advantage is the ease of its generation even in case of very complex geometry. On the other hand tetrahedrons cannot be stretched excessively without decreasing the mesh quality factor, so significantly larger number of cells has to be used in comparison to hexahedral mesh in order to achieve a reasonable accuracy. Moreover the numerical diffusion of tetrahedral elements is significantly higher. Therefore the polyhedral cells are proposed within the paper in order to combine the advantages of hexahedrons (low numerical diffusion resulting in accurate solution) and tetrahedrons (rapid semi-automatic generation) as well as to overcome the disadvantages of both the above mentioned mesh types. The major benefit of polyhedral mesh is that each individual cell has many neighbours, so gradients can be well approximated. Polyhedrons are also less sensitive to stretching than tetrahedrons which results in better mesh quality leading to improved numerical stability of the model. In addition, numerical diffusion is reduced due to mass exchange over numerous faces. This leads to a more accurate solution achieved with a lower cell count. Therefore detailed comparison of numerical modelling results concerning conjugate heat transfer using tetrahedral and polyhedral meshes is presented in the paper.

NUMERICAL INVESTIGATION OF CONJUGATE HEAT TRANSFER FROM LAMINAR WALL JET FLOW OVER A SHALLOW CAVITY

2018 ◽  
Vol 49 (12) ◽  
pp. 1151-1170 ◽  
Author(s):  
Maheandera Prabu Paulraj ◽  
Rajesh Kanna Parthasarathy ◽  
Jan Taler ◽  
Dawid Taler ◽  
Pawel Oclon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Conjugate Heat Transfer ◽  
Jet Flow ◽  
Wall Jet ◽  
Shallow Cavity ◽  
Wall Jet Flow
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