Materials Science and Engineering Commons^™

Wall Thickness Optimization Of A Transpiration-Cooled Sharp Leading Edge At Atmospheric Re-Entry, Christian Dittert

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The purpose of this paper is to find the necessary cooling mass flow for a defined wall thickness distribution, which allows a selective cooling for an acceptable temperature range of the sharp leading edge of an atmospheric re-entry vehicle. Due to the angle of attack during the re-entry flight the pressure at the top side is lower than the pressure at the bottom side. However, the highest heat load occurs at the stagnation point at which also the maximum pressure is effective. The efficiency of a transpiration cooling depends on the mass flow rate of the coolant. The cooling mass …

Comparison Of Volume-Average Simulation And Pore-Scale Simulation Of Thermal Radiation And Natural Convection In High Temperature Packed Beds, Le Zhang, Ruina Xu, Peixue Jiang

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The phenomenon of natural convection and thermal radiation heat transfer in fluid-saturated high temperature packed beds has been widely studied due to its various applications ranging from solar collectors to high temperature gas cooled reactor. With the local thermal non-equilibrium model, the majority of the numerical simulation studies on natural convection and radiation heat transfer in fluid-saturated porous media have limits. In these studies the internal heat transfer coefficients have always been calculated as the existing formulas, which were obtained by the experiments of forced convection in porous media [1-2]. However, natural convection heat transfer in porous media is dominated …

Three Dimensional Heat And Mass Transfer In Capillary Evaporator, Laetitia Mottet, Typhaine Coquard, Marc Prat

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Heat and mass transfer inside the porous wick of a capillary evaporator is studied using a mixed porenetwork model. The impact of the thermal conductivity of the wick on the overheating limit (defined as the difference between the maximum temperature at the top of the metallic casing and the saturated temperature), breakthrough (which occurs when the vapor reaches the wick inlet) and the parasitic heat flux lost by conduction at the entrance of the wick (which decreases the efficiency of the evaporator) is investigated. The study suggests a bilayer wick as a possible better design to optimize the performance of …

Onset Of Double Diffusive Reaction-Convection In An Anisotropic Porous Layer With Internal Heat Source, S.N. Gaikwad, M. Dhanraj

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The effect of internal heat source on the onset of double diffusive reaction-convection in an anisotropic porous layer subjected to chemical equilibrium on the boundaries is investigated analytically using linear stability analyses. The linear analysis is based on the usual normal mode method. The Darcy model is employed for the momentum equation. The effect of internal Rayleigh number, Damkohler number, mechanical anisotropy parameter and thermal anisotropy parameter on the stationary and oscillatory convection is shown graphically. It is found that the effect of internal Rayleigh number and mechanical anisotropy parameter have destabilizing effect, while the thermal anisotropy parameter has stabilizing …

Evaluating Deformation Behavior Of A Tbc-System During Thermal Gradient Mechanical Fatigue By Means Of High Energy X-Ray Diffraction, M. Bartsch, J. Wischek, C. Meid, K. Knipe, A. Manero, S. Raghavan, A. M. Karlsson, J. Okasinski, J. Almer

Thermal Barrier Coatings IV

No abstract provided.

Manufacture Of Silicide Coatings For The Protection Of Niobium Alloys Against High Temperature Oxidation, M. Vilasi, S. Matheieu, S. Knittel, L. Portebois, T. Katrina, C. Rapin, C. Petitjean, P. J. Panteix, S. Drawin

Thermal Barrier Coatings IV

At the moment, silicide coatings provide the best protection against high temperature oxidation for niobium alloys. These are envisaged for replacing nickel base alloys currently used in the hot section of turbo-engines. Silicides confer higher protectiveness to Nb base system when compared to the environmental resistance presented by Nb alloys coated with aluminides. One major advantage of silicides is probably the great number of possibilities for modifying their composition as well as their crystallographic structure. Thus, many elemental substitutions were performed over the past 20 years in order to optimize their performances in terms of oxidation resistance. The works performed …

Lifetime Of Environmental/Thermal Barrier Coatings Deposited On An Nb/Nb5si3- Based Alloy With Feb-Modified M7si6-Based Bond Coat, Reinhold Braun, Annika Lange, Uwe Schulz, Leo Portebois, Stephane Mathieu, Michael Vilasi, Stefan Drawin

Thermal Barrier Coatings IV

To enhance the performance of aircraft engines, high temperature materials are required being capable to operate at temperatures significantly higher than the temperature limit of about 1150°C approached for Ni-based superalloys currently employed. Nb/Nb5Si3-based composites are promising candidates for turbine engine applications at temperatures up to 1300°C, exhibiting balanced mechanical properties and reduced density compared to Ni-based superalloys [1]. To use these composites in gas turbine combustion atmosphere, environmental/thermal barrier coatings (E/TBCs) are required to protect them against heat, degradation in flowing water vapour and chemical attack of calcium-magnesium-alumino-silicate (CMAS).

Simulations Of Fracture In Coatings With Complex Microstructures, Mathew R. Begley, William Pro, Rone Kwei Lim, Linda Petzold

Thermal Barrier Coatings IV

No abstract provided.

Lifetime Assessment Tools For Thermal Barrier Systems, Jean Louis Chaboche, Frederic Feyel, Martine Poulain, Noemie Rakotamalala, Arjen Roos, Jean Roch Vaunois, Arnaud Longuet, Pascale Kanaoute

Thermal Barrier Coatings IV

No abstract provided.

Reliable Measurement Of Mechanical Tbc Properties For Quality Control And Life Prediction, Peter Wittig, Stefan Lampenscherf, Uwe Rettig, Matthias Oechsner

Thermal Barrier Coatings IV

No abstract provided.

High Temperature Environmental Resistance Of Mo-Si-B Alloys And Coatings, John H. Perepezko

Thermal Barrier Coatings IV

No abstract provided.

Mechanical Stability Limits Of Bi-Layer Thermal Barrier Coatings, Mario Rudolphi, Mathias Galetz, Michael Schutze, Martin Frommherz, Alfred Scholz, Mathias Oechsner, Emine Bakan, Robert Vassen, Werner Stamn

Thermal Barrier Coatings IV

Thermal barrier coatings based on yttria stabilized zirconia (YSZ) have reached a state in development, where a further increase in lifetime and/or maximum operating temperature has become more and more difficult. Nevertheless, the demand for even higher operating temperatures is persisting, and it is pushing the YSZ-based thermal barrier coatings to and beyond their limit. Especially phase instabilities of YSZ at temperatures above 1200°C lead to a fast deterioration of the ceramic top coating. Consequently, the search for new materials with low thermal conductivity, relatively low coefficient of thermal expansion and phase stability at temperatures well above 1200°C was started, …

Specific Failure Modes Of Ni-Base Superalloys And Tbcs Under A Simulated Combustion Gas Atmosphere, Mazaku Okazaki, Satoshi Yamagishi, Y. Hayashi

Thermal Barrier Coatings IV

No abstract provided.

Nasa’S Advanced Environmental Barrier Coatings Development For Sic/Sic Ceramic Matrix Composites: Understanding Cmas Degradations And Resistance, Dongming Zhu

Thermal Barrier Coatings IV

No abstract provided.

Ceramic Matrix Composite Environmental Protection Strategies, Bradley Richards, Hengbei Zhao, Haydn Wadley

Thermal Barrier Coatings IV

No abstract provided.

Keynote Talk – Novel Convective Heat Transfer Enhancement In Channels And Tubes Filled With Nanofluid-Saturated Metal Foams, Fumika Sakai, Wenhao Li, Akira Nakayama

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

A local thermal non-equilibrium theory was exploited to investigate heat transfer in nanofluid saturated porous media, in view of possible heat transfer applications of metal foams filled with nanofluids as high performance heat exchangers. The resulting set of the macroscopic equations based on the modified Buongiorno model proposed by Yan et al. for convective heat transfer in nanofluids were used to obtain the analytical solutions for laminar fully developed forced convection in channels and tubes filled with nanofluid saturated metal foams. The analytical and numerical solutions were obtained for laminar fully developed forced convection in channels and tubes filled with …

Development Of A Mobile High Shear Colloidal Grout Pump For The Construction Industry, John Kijak, David Kennedy

Conference Papers

The aim of this project was to design and develop a group pump and solve associated technical issues for a construction company in Ireland. The design is based on a high shear colloidal group mixing and pumping rig. The initial machine has failed in terms of bearing and seal performance, has high manufacturing costs and is poorly designed.

To account for these issues, extensive research of the design features of grout mixing units from various competitors and suppliers was carried out by research and field studies at trade fairs. Using the information gathered, and incorporating improvements into the existing design, …

Effect Of Variable Porosity On Composite Heat Transfer In A Boundary Layer Flow, Puttabasavsetty Nagaraju

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The effects of variable porosity and variable thermal conductivity of the medium and also the emission, absorption and scattering of radiation are studied in this paper. The comparative study has been made for three different situations, namely a) variable porosity b) constant porosity and c) absence of porous medium.In carrying out the solution, the momentum and energy equations are coupled and they are solved simultaneously by Runge-Kutta Gill method in conjunction with Newton-Raphson iterative scheme. The results of the analyses show that, in the cases of variable porosity and absence of porous medium the velocity profiles possess very small curvature …

Mri Evidence Of Nanoparticles Migration In Drying Porous Media, Emmanuel Keita, Pamela Faure, Stephane Rodts, Phillippe Coussot

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Due to the migration of elements they induce imbibition-drying cycles are known to play a major role in the colloid-facilitated transport in many industrials process, for instance for pollutants migration in soils or pores clogging in building materials. We study the drying of a colloidal suspension in a porous media. The critical physical phenomenon at work here is the displacement and redistribution of colloidal particles induced by evaporation of the liquid phase from the porous medium. This can be clearly seen by filling a bead packing with coffee. Indeed after full drying the sample has shaded tones with darker regions …

Phase Change With Local Thermal Non-Equilibrium In A Two-Phase Mixture Model, Franz Lindner, Michael Pfitzner, Christian Mundt

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

CFD solutions of multi-phase, single-component flow through a vertical channel, filled with a porous medium, heated from one side, are shown. Steady-state solutions are presented for Darcian flow through capillary porous media. Local thermal non- equilibrium is used with a two-phase mixture. The effects of variation of Peclet-number and dimensionless heat input are shown. The displacement effect of the super-heated vapor reduces the free cross-section of flow of the liquid fluid and accelerates the liquid fluid flowing past the evaporation front. The temperatures, liquid saturations, liquid and vapor heat transfer coefficients are shown for cases with super-heated vapor.