› › Numerical Study Of Jet Impingement Cooling On A Smooth Curve Surface






Heat Transfer Analysis of an Oblique Jet Impingement Cooling on CMC Rough Surface

Author : Karthik Krishna

Publisher :

Page : 140 pages

File Size : 13,98 MB

Release : 2016

Category : Heat

ISBN :

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Book Description

A Ceramic Matrix Composite is high strength and high temperature capability composite, utilized in components like heat shield of space vehicles, flame holders and disc brakes. To be used in both static and dynamic components of a future gas turbine engine and even with high temperature capabilities of these CMC components, convection cooling will still likely be required. The surface of the CMC varies significantly from traditional super-alloy used in a modern engine, with large level of roughness and significant three-dimensional waviness. These complex features will impact the behavior of the near wall flows, and affect the heat transfer rates both internal and external to the blade. Existing design tools should be updated to account for these effects. As a preliminary investigation into these effects, an obliquely impinging circular jet on a CMC surface is studied. Both experimental and numerical methods are employed to find the effect of simulated surface features on heat transfer rates. In this study, oblique angles of 45° and 90°, jet plate distance of 6.5 and 7 jet diameters and three Reynolds numbers, 11,000, 23,000 and 35,000, were selected. The test surface is broken down into segments, and individual segment Nusselt numbers are determined and plotted for the various impingement cases studied. Both experimental and CFD results showed negligible changes in average Nusselt number, while local contours were affected. The computational results were evaluated against literature and experimental results, using v2f turbulence model The computational result showed that the local and average Nusselt number for the smooth surface impingement were estimated very close to experimental values and the error was in the range of 14-17%. In case of impingement over the CMC surface, this model predicted the heat transfer rates close to experimental values in the stagnation region and produced local Nusselt number trends following the experimental results. The impact of the CMC surface feature is negligible compared to the uncertainty in heat transfer coefficient, and therefore traditional design tools can be utilized.



Experimentation, Validation, and Uncertainty Analysis for Engineers

Author : Hugh W. Coleman

Publisher : John Wiley & Sons

Page : 404 pages

File Size : 24,86 MB

Release : 2018-04-09

Category : Technology & Engineering

ISBN : 1119417708

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Book Description

Helps engineers and scientists assess and manage uncertainty at all stages of experimentation and validation of simulations Fully updated from its previous edition, Experimentation, Validation, and Uncertainty Analysis for Engineers, Fourth Edition includes expanded coverage and new examples of applying the Monte Carlo Method (MCM) in performing uncertainty analyses. Presenting the current, internationally accepted methodology from ISO, ANSI, and ASME standards for propagating uncertainties using both the MCM and the Taylor Series Method (TSM), it provides a logical approach to experimentation and validation through the application of uncertainty analysis in the planning, design, construction, debugging, execution, data analysis, and reporting phases of experimental and validation programs. It also illustrates how to use a spreadsheet approach to apply the MCM and the TSM, based on the authors’ experience in applying uncertainty analysis in complex, large-scale testing of real engineering systems. Experimentation, Validation, and Uncertainty Analysis for Engineers, Fourth Edition includes examples throughout, contains end of chapter problems, and is accompanied by the authors’ website www.uncertainty-analysis.com. Guides readers through all aspects of experimentation, validation, and uncertainty analysis Emphasizes the use of the Monte Carlo Method in performing uncertainty analysis Includes complete new examples throughout Features workable problems at the end of chapters Experimentation, Validation, and Uncertainty Analysis for Engineers, Fourth Edition is an ideal text and guide for researchers, engineers, and graduate and senior undergraduate students in engineering and science disciplines. Knowledge of the material in this Fourth Edition is a must for those involved in executing or managing experimental programs or validating models and simulations.





Investigation of Jet Impingement Cooling Using High Prandtl Number Fluids and Ammonia for Military Applications

Author :

Publisher :

Page : 0 pages

File Size : 13,46 MB

Release : 2004

Category :

ISBN :

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Book Description

The objective of this project was to perform a comprehensive numerical study for the prediction of conjugate heat transfer during jet impingement cooling. Calculations were done primarily for two working fluids: MIL-7808 and ammonia. A number of substrate materials were studied. The investigation considered both free and confined jet configurations using circular and slot nozzles. Fifteen different disk or plate thicknesses ranging from 0 to 12 mm and eleven different nozzle heights from 0.4 mm to 12.5 mm were used. A number of heat source patterns were considered to explore the effects of magnitude and location of heat generation. Both steady state heat transfer and the transient start-up of power were investigated. It was found that the magnitude of local heat transfer coefficient or Nusselt number decreased with time at all locations on the disk. A higher heat transfer coefficient at the impingement location was seen at a smaller thickness, whereas a thicker plate provided a more uniform distribution of heat transfer coefficient. Materials with a higher thermal conductivity provided more uniform distribution of interface temperature as well as the heat transfer coefficient. Both local and average heat transfer coefficient increased with Reynolds number. For a given flow rate, a higher heat transfer coefficient was obtained with smaller nozzle diameter. Compared to MIL-7808 and FC-77, ammonia provided smaller solid-fluid interface temperature and higher heat transfer coefficient.



Three-Dimensional Attached Viscous Flow

Author : Ernst Heinrich Hirschel

Publisher : Springer Science & Business Media

Page : 396 pages

File Size : 50,92 MB

Release : 2013-10-29

Category : Technology & Engineering

ISBN : 3642413781

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Book Description

Viscous flow is treated usually in the frame of boundary-layer theory and as two-dimensional flow. Books on boundary layers give at most the describing equations for three-dimensional boundary layers, and solutions often only for some special cases. This book provides basic principles and theoretical foundations regarding three-dimensional attached viscous flow. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers. This wider scope is necessary in view of the theoretical and practical problems to be mastered in practice. The topics are weak, strong, and global interaction, the locality principle, properties of three-dimensional viscous flow, thermal surface effects, characteristic properties, wall compatibility conditions, connections between inviscid and viscous flow, flow topology, quasi-one- and two-dimensional flows, laminar-turbulent transition and turbulence. Though the primary flight speed range is that of civil air transport vehicles, flows past other flying vehicles up to hypersonic speeds are also considered. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers, as this wider scope is necessary in view of the theoretical and practical problems that have to be overcome in practice. The specific topics covered include weak, strong, and global interaction; the locality principle; properties of three-dimensional viscous flows; thermal surface effects; characteristic properties; wall compatibility conditions; connections between inviscid and viscous flows; flow topology; quasi-one- and two-dimensional flows; laminar-turbulent transition; and turbulence. Detailed discussions of examples illustrate these topics and the relevant phenomena encountered in three-dimensional viscous flows. The full governing equations, reference-temperature relations for qualitative considerations and estimations of flow properties, and coordinates for fuselages and wings are also provided. Sample problems with solutions allow readers to test their understanding.



Experimental and Numerical Investigation of High Temperature Jet Impingement for Turbine Cooling Applications

Author : Evan L. Martin

Publisher :

Page : pages

File Size : 16,41 MB

Release : 2011

Category :

ISBN :

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Book Description

Modern gas turbine engines commonly operate at temperatures above the melting point of the turbine's blades and vanes. Internal and external cooling of the blades is required for sustained operation and prolonged engine life. Jet impingement, an aggressive form of cooling, is typically used in the airfoil leading edge which is exposed to extreme heat loads. A parametric study is used to experimentally and numerically investigate high temperature jet impingement in the blade leading edge. The effects of jet Reynolds number (Rejet), jet-to-target surface spacing (l/d), jet-to-jet spacing (s/d), jet-to-target surface curvature (D/d), and jet temperature on stagnation Nusselt numbers are evaluated in a high temperature test apparatus. The facility is validated against correlations developed in previous studies. The experimental study is complimented with CFD simulations performed using commercially available software. Nusselt number results show strong dependence on Reynolds number and geometry yet little or no dependence on jet temperature.



Experimental and Numerical Study of Impingement Jet Heat Transfer

Author : Andrew Urban Schroder

Publisher :

Page : 217 pages

File Size : 40,10 MB

Release : 2011

Category :

ISBN :

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Book Description

An experimental test facility has been designed, constructed, and commissioned for studying the convective heat transfer of an array of 55 impingement jets. Spatial variation in time averaged Nusselt number as well as spanwise time averaged Nusselt number are presented for jet Reynolds numbers of 4,000, 8,000, 12,000, and 15,000 for jet to target standoff distances of z/D=3, 4, and 5. For each of these configurations the exit flow configuration has also been varied to include both a single exit and double exit configuration. For each jet standoff distance and exit configuration, time and overall area averaged Nusselt number is presented as a function of jet Reynolds number. Animations of measured unsteady Nusselt number are presented for selected cases. Numerical simulations have been conducted using the Fluent Computational Fluid Dynamics software package. The three dimensional, compressible, Navier Stokes equations are solved. Results for Nusselt number are presented for a grid dependency study of a steady, single impingement jet impacting a target surface at a standoff distance of z/D=3, at jet Reynolds numbers of 4,000 and 15,000. In the single jet grid dependency study flow is exhausted in all directions after impacting the target surface. Grids ranging from 1.2 million to 13.2 million grid points are evaluated. Unsteady simulations were conducted of a single impingement jet at a jet Reynolds number of 4000, a jet to target standoff distance of z/D=3, flow exiting in two directions, and a pair of repeating boundaries in the other two directions. Two cases were studied. The first with a spacing between the two repeating boundaries of y/D=6 and the second with a spacing of y/D=3. For both cases, contour plots of time averaged, as well as animations of unsteady in plane velocity magnitude, normal component of vorticity, and Nusselt number are presented. Unsteady simulations were also conducted of eleven impingement jets at a jet Reynolds number of 4,000, a jet to target standoff distance of z/D=3, and a double exit configuration. Two cases were studied. The first with a spacing between the two repeating boundaries of y/D=4.03 and the second with a spacing of y/D=3. For both cases, contour plots of time averaged in plane velocity magnitude, normal component of vorticity, pressure, temperature, and Nusselt number are presented. Animations of contours of in plane velocity magnitude, normal component of vorticity, and Nusselt number are also presented. Spanwise time average Nusselt number for both eleven jet numerical cases is compared to that of the central row of an experimental case with a double exit configuration. Comparisons are also made between spanwise average Nusselt number for the central jet of an experimental case, a single jet numerical, the single jet numerical cases with the repeating boundaries, as well as the central jet of the eleven jet numerical cases.