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Laser speckle photography for heat transfer
128 Abstracts for The 3rd World Conference
Thermography: Fundamentals and Applications Telmo Nobre
Instituto de Soldadura e Qualidade Thermography Department Lisboa, Portugal Thermography is an infrared scanning method that has been very developed in the last few years, with the advent of new, powerful integrated chips as well as high-level digital systems. Thermography is very easy to use and a powerful tool that can provide us with an accurate thermal image of an object or surface. With these thermal images, it is possible to measure the temperature distribution of a surface, as well as to find the location of specific temperatures, that can characterize the process under observation.
Experimental Techniques for Thermal Contact Resistance Measurements L. S. Fletcher
Department of Mechanical Engineering Texas A & M University College Station, Texas A number of different experimental techniques have been used to determine the thermal resistance of materials in contact, depending upon specific test requirements. These techniques and associated experimental facilities are reviewed, including the traditional cut-bar vertical-column test facilities and more specialized facilities and techniques for measurement of the thermal contact resistance of such configurations or contacts as bolted joints, periodically contacting surfaces, full and partial scale component models, and analog techniques. Experimental thermal contact resistance data are presented and compared for selected categories of materials in contact, including similar metallic junctions, junctions with interstitial fluids or fillers, and metallic junctions with metallic and nonmetallic surface coatings. These experimental results demonstrate that the characteristics of thermal contact resistance may be used to thermally enhance a junction between materials, or thermally isolate a junction, depending upon thermal design requirements.
Laser Speckle Photography for Heat Transfer Zeng-Yuan Guo Yao-Zu Song
Department of Engineering Mechanics Tsinghua University Beijing, China Laser speckle photography, a technique making use of the displacement of optical speckle by refraction as information carrier, was recently used to measure fluid density, temperature, and heat transfer. The concept of laser speckle photography and the measuring principle of the temperature gradient field are described briefly. The concepts cover the formation of laser speckle and its displacement, six kinds of recording systems, and two reconstruction methods of specklegram. Maor advantages of the
laser speckle photography method for heat transfer study over interferometric methods are listed and discussed. Finally, many applications of laser speckle photography in heat transfer study are given, including natural convection along a vertical plate; measurements of axisymmetric temperature field of a flame; heat transfer in channel natural convection and verification of thermal drag phenomena; and heat transfer of small-scale objects.
Use of Probes in Combustion Systems Henry A. Becker
Centre for Advanced Gas Combustion Technology Department of Chemical Engineering Queen's University Kingston, Ontario, Canada Although use of optical techniques has become common in combustion research, physical probes still have many useful, and in some cases unique, applications. In industry particularly, optical techniques are often ill-suited to the situation, and moreover, physical probes offer compelling cost advantages. Effective exploitation of these probes, as with any sensor, requires a sound knowledge of response characteristics and of the principles of optimum design and use. The behavior in respect to spatiotemporal resolution and effects of turbulence, for example, should be adequately recognized. The present paper covers simple pitot probes, differential pitot probes, static pressure probes, five-hole probes, and gas sampling probes.
Aerothermodynamics of Vibrationally Nonequilibrium Gases J. William Rich Sergey O. Macheret
Department of Mechanical Engineering The Ohio State Unh3ersity Columbus, Ohio Theory and experiments of diatomic molecular gas and plasma flows with vibrational disequilibrium are reviewed. We discuss some recent developments in electric discharges, expanding and shock gas dynamic flows, and optically pumped cells.
On the Kinematics of the Quasi-Coherent Vortical Structure in Near-Wall Turbulence Nobuhide Kasagi Yasushi Sumitani Yuji Suzuki Oaki Iida
Department of Mechanical Engineering The University of Tokyo Bunkyo-ku, Tokyo, Japan Near-wall turbulence structures in a direct numerical simulation database of turbulent channel flow were investigated by using a 3-D computer graphics software tool. Several candidate methods to detect near-wall vortical structures were tested. They were based on instantaneous flow properties such as pressure, vorticity, enstrophy, dissi-
Thermography: Fundamentals and Applications Telmo Nobre
Instituto de Soldadura e Qualidade Thermography Department Lisboa, Portugal Thermography is an infrared scanning method that has been very developed in the last few years, with the advent of new, powerful integrated chips as well as high-level digital systems. Thermography is very easy to use and a powerful tool that can provide us with an accurate thermal image of an object or surface. With these thermal images, it is possible to measure the temperature distribution of a surface, as well as to find the location of specific temperatures, that can characterize the process under observation.
Experimental Techniques for Thermal Contact Resistance Measurements L. S. Fletcher
Department of Mechanical Engineering Texas A & M University College Station, Texas A number of different experimental techniques have been used to determine the thermal resistance of materials in contact, depending upon specific test requirements. These techniques and associated experimental facilities are reviewed, including the traditional cut-bar vertical-column test facilities and more specialized facilities and techniques for measurement of the thermal contact resistance of such configurations or contacts as bolted joints, periodically contacting surfaces, full and partial scale component models, and analog techniques. Experimental thermal contact resistance data are presented and compared for selected categories of materials in contact, including similar metallic junctions, junctions with interstitial fluids or fillers, and metallic junctions with metallic and nonmetallic surface coatings. These experimental results demonstrate that the characteristics of thermal contact resistance may be used to thermally enhance a junction between materials, or thermally isolate a junction, depending upon thermal design requirements.
Laser Speckle Photography for Heat Transfer Zeng-Yuan Guo Yao-Zu Song
Department of Engineering Mechanics Tsinghua University Beijing, China Laser speckle photography, a technique making use of the displacement of optical speckle by refraction as information carrier, was recently used to measure fluid density, temperature, and heat transfer. The concept of laser speckle photography and the measuring principle of the temperature gradient field are described briefly. The concepts cover the formation of laser speckle and its displacement, six kinds of recording systems, and two reconstruction methods of specklegram. Maor advantages of the
laser speckle photography method for heat transfer study over interferometric methods are listed and discussed. Finally, many applications of laser speckle photography in heat transfer study are given, including natural convection along a vertical plate; measurements of axisymmetric temperature field of a flame; heat transfer in channel natural convection and verification of thermal drag phenomena; and heat transfer of small-scale objects.
Use of Probes in Combustion Systems Henry A. Becker
Centre for Advanced Gas Combustion Technology Department of Chemical Engineering Queen's University Kingston, Ontario, Canada Although use of optical techniques has become common in combustion research, physical probes still have many useful, and in some cases unique, applications. In industry particularly, optical techniques are often ill-suited to the situation, and moreover, physical probes offer compelling cost advantages. Effective exploitation of these probes, as with any sensor, requires a sound knowledge of response characteristics and of the principles of optimum design and use. The behavior in respect to spatiotemporal resolution and effects of turbulence, for example, should be adequately recognized. The present paper covers simple pitot probes, differential pitot probes, static pressure probes, five-hole probes, and gas sampling probes.
Aerothermodynamics of Vibrationally Nonequilibrium Gases J. William Rich Sergey O. Macheret
Department of Mechanical Engineering The Ohio State Unh3ersity Columbus, Ohio Theory and experiments of diatomic molecular gas and plasma flows with vibrational disequilibrium are reviewed. We discuss some recent developments in electric discharges, expanding and shock gas dynamic flows, and optically pumped cells.
On the Kinematics of the Quasi-Coherent Vortical Structure in Near-Wall Turbulence Nobuhide Kasagi Yasushi Sumitani Yuji Suzuki Oaki Iida
Department of Mechanical Engineering The University of Tokyo Bunkyo-ku, Tokyo, Japan Near-wall turbulence structures in a direct numerical simulation database of turbulent channel flow were investigated by using a 3-D computer graphics software tool. Several candidate methods to detect near-wall vortical structures were tested. They were based on instantaneous flow properties such as pressure, vorticity, enstrophy, dissi-