Void fraction measurements in gas-liquid flows using capacitance sensors

72 ANNUAL LITERATURE SURVEY 1996 merits of liquid nitrogen and water enables us to understand the transition from the motion being heat transfer dominant to that being liquid inertia dominant. Oxidation of iron powder in a fluidized bed reactor Bodas M.G., Dash D.R. & Sivaramakrishnan C.S., Materials and Design, 1996, 17/3 (167-172). In English. The potential and technological viability of oxidation of iron powder for the production of higher purity ferric oxide for soft ferrites have been discussed. Results of cold model studies have been incorporated. It has been shown that the conversion of iron powder to ferric oxide is a function of particle size, time and temperature of fluidization. Non-uniform hydrogen attack cavitation and the role of interaction with creep Van der Burg M.W.D. & Van der Giessen E., Materials Science and Engineering A, 1996, A220/1-2 (200-214). In English. Hydrogen attack (HA) is the development of grain-boundary porosity by cavities filled with high-pressure methane that originates from the reaction of carbides with hydrogen at high temperatures. The cavities grow by grain-boundary diffusion and by creep of the adjacent grain material till they coalesce with neighbouring cavities to form a microcrack. Here, non-uniform cavitation properties on the grain-size scale are assumed in a polycrystalline aggregate, and unit cell analyses are performed to investigate the influence of the adjacent grains on the development of the grain-boundary HA. The numerical results are explained in terms of two simplified models which highlight the key parameters governing the grain deformation-grain boundary cavitation interaction process. Microstrncture, permeability and mechanical behaviour of ceramic foams Lopes R.A. & Scgadaes A.M., Materials Science and Engineering A, 1996, A209/1-2 (149-155). In English. This work is part of a model study aimed at upgrading the technique of creating porosity via the incorporation of organic particles used in traditional ceramics, exploring at the same time colloidal processing from coagulated slurries. The method described in another work, based on the manipulation of short-range repulsive (lubricating) hydration force and long-range attractive van der Waals force, was used to pack to a high density a bimodal mixture ofsubmicron ceramic particles (matrix) and much larger organic particles (inclusions) during consolidation by pressure filtration of dispersed suspensions coagulated by added electrolyte. Investigations carried out to produce strong porous ceramic bodies, with a tailored pore structure, are described. Notched behaviour of a silicon carbide particulate reinforced aluminium alloy matrix composite Z¢ Weng Huang, McColl I.R. & Harris S.J., Materials Science and Engineering A, 1996, A215/1-2 (67-72). In English. The notched fatigue behaviour of a fine particulate reinforced Al-Cu-Mg (2124) matrix composite is compared with that of an equivalent monolithic alloy (2024), both in the T4 condition. The difference in response of the materials for tensile and fatigue loading is pronounced. Under tensile loading the composite exhibits 'notch weakening' and an almost brittle fracture, while the monolithic alloy shows a degree of'notch strengthening'. In contrast, under fatigue loading the composite exhibits a much smaller notch sensitivity than that of the monolithic alloy. The notched tensile behaviour of the composite is interpreted in terms of its reduced ductility and susceptibility to cavitation. Conventional notch theory is able to account for the notch sensitivity of the monolithic alloy in fatigue, but not the composite. Void fraction measurements in gas-liquid flows using capacitance sensors Elkow K.J. & Rezkallah K.S., Measurement Science and Technology, 1996, 7/8 (1153-1163). In English. Void fraction measurements for vertical flow in a small diameter tube (9.53 mm) were taken using two nonintrusive capacitive void fraction sensors. The sensors were needed to measure the void fraction of water-air two-phase flow under normal gravity and mierogravity conditions. Void fraction data were collected with: 1) a sensor having helical wound electrodes that was used to collect data under normal gravity and microgravity conditions, 2) a sensor having concave plate electrodes, used to collect data at normal gravity. This paper covers the calibration results for both sensors and some of the problems associated with the helical wound design. Nonlinearity in the helical sensor is addressed, with improvements shown in the concave plate sensor. Comparisons are made between the capacitive sensors, quick-closing valves and a gamma densitometer. Particle image velocimetry: simultaneous two-phase flow measurements Jakobsen M.L., Easson W.J., Greated C.A. & Glass D.H., Measurement Science and Technology, 1996, 7/9 (1270-1280). In English. A method using particle image velocimetry to study pneumatic conveyance of a solid phase is presented. The technology enables simultaneous velocitymeasurements of both phases by isolatingthe measurements of each phase. The image processing which implements the phase separation issimple, but has limitations.The method isrestrictedto low soliddensitiesto avoid a quality drop in the measurements, and cross-talkbetween measurements of the two phases. Study optimizes gas lift in Gulf of Suez field Abdel-Waly A.A., Darwish T.A., Salama A.O. & EI-Naggar M., OilandGas Journal, 1996, 94/26 (38,40-44). In English. Studies of pressure-volume-temperaturE (PVT) data combined with fluid and multiphase flow correlations were used to optimise gas lift in oil wells on the Ramadan Field. This article describes this study, production optimisation, and results in detail. PVT data was used to determine the best fluid properties and multiphase flow correlations for calculating pressure losses. This was applied to calculate production tubing pressure losses in each well. Expected production rates were then determined for injected gas rates at various points of injection