Progrès récents en métrologie diphasique

Abstract

Click to increase image sizeClick to decrease image sizeThis review of recent progress in two-phase metrology is by no means exhaustive, having deliberately been limited to the description of a few methods and techniques developed in France during the last few years. Some of these have already been presented at Author's Seminary on Two-Phase Metrology (see special issue of La Houille Blanche No. 5, 1978). In this report, recent developments are discussed under the following headings : I. Measurement of interface areas and material transfer coefficients by a chemical method This method was developed and first applied by Charpentier, Laurent and Prost at the 'Ecole Nationale des Industries Chimiques' in Nancy. It is a global method for determining interface area and material transfer coefficients. A gas-liquid absorption process can take place without a chemical reaction (diffusion) or with one. Transfer coefficients can be determined from the former process, interface area from one with reaction. II. Measurement of two-phase flow boundary friction by an electro-chemical method This method was designed and tested by Cognet, Lebouche and Souhar at the 'Laboratoire d'Energétique et de Mécanique Théorique et Appliquée' in Nancy. It is an instantaneous, local measurement method based on the principle of the mass transfer equivalent of heat transfer applied in anemometry. The limit of electrolytic current produced by contact of two electrodes embedded in a pipe wall is a simple function of the local velocity gradient at the boundary. By using two electrodes, the direction of flow can be determined. III. Determination of the phase-indicating function in finely-dispersed two phase flow by an optical refraction method This method was developed by Danel in the 'Assistance Industrielle Dauphinoise' Company's laboratory. It is an extension of an earlier method designed by Danel and Delahaye (C.E.N.G.), using more efficient, miniaturized 40 µ diameter probes (20 µ at the sensitive tip) with a 1/10th microsecond response. IV. Determination of air-bubble or water droplet size by an optical diffusion method This method was designed and developed by Avellan and Resch at the 'Institut de Mécanique Statistique de la Turbulence' of Aix-Marseilles University. The prototype was produced by the A.I.D. Company. This is a local measurement method of the dimensions of bubbles or droplets passing through the measurement space. The flux diffused by each bubble or droplet in a perpendicular direction to the incident ray depends solely on the bubble or droplet diameter. The particle diameter detection range is from a few microns up to approximately a millimetre. V. Numerical processing of a hot-film anemometer output signal in cavity flow This study was carried out by Abel and Resch at Toronto University under a joint French-Canadian cooperation scheme. The method is a numerical method whereby gas and liquid phases in cavity flow (or mixed flow with bubbles and cavities) can be identified by processing the output signal from a hot-film anemometer in the flow.