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Abstrakt

The void fraction is one of the most important parameters characterizing a multiphase flow. The prediction of the performance of any system operating with more than single phase relies on our knowledge and ability to measure the void fraction. In this work, a validated simulation study was performed in order to predict the void fraction independent of the flow pattern in gas-liquid two-phase flows using a gamma ray 60Co source and just one scintillation detector with the help of an artificial neural network (ANN) model of radial basis function (RBF). Three used inputs of ANN include a registered count under Compton continuum and counts under full energy peaks of 1173 and 1333 keV. The output is a void fraction percentage. Applying this methodology, the percentage of void fraction independent of the flow pattern of a gas-liquid two-phase flow was estimated with a mean relative error less than 1.17%. Although the error obtained in this study is almost close to those obtained in other similar works, only one detector was used, while in the previous studies at least two detectors were employed. Advantages of using fewer detectors are: cost reduction and system simplification.
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Abstrakt

The paper presents the analysis of results of the investigations concerning a vertical pipe submersion coefficient h/L with an air-water mixer of the described type. The investigations were performed on an air lift pump testing stand, constructed in a laboratory on a scale of 1:1. At first, the paper presents the possibilities of application of air lift pumps. The investigations to date have been briefly characterized and a research problem formulated. Then the paper describes the construction and working principle of the air lift pump testing stand, constructed in a laboratory. It presents the methodology of derivation of empirical formulas for calculation of vertical pipe submersion coefficients h/L. The comparative analysis of the values of h/L determined in the measurements with the values of h/L calculated using the derived empirical formulas was carried out. The research scope encompassed the derivation of the aforementioned empirical formulas for five fixed values of air lift pump delivery head H, comparison of the obtained values h/L determined in the measurements with the values of h/L calculated using the derived empirical formulas and the improved analytical Stenning-Martin model. To derive the empirical formulas for calculation of the vertical pipe submersion coefficient h/L, the dimensional analysis and multiple regression was applied. The investigations of the vertical pipe submersion coefficient h/L were carried out for the vertical pipe internal diameter d = 0.04 m and for the fixed delivery heads H: 0.45, 0.90, 1.35, 1.80, 2.25 m. The values calculated using the derived empirical formulas (23), (24), (25), (26), (27) coincide with the values of h/L determined in the measurements for the whole range of the investigated delivery heads H. On the other hand, the values of h/L calculated using the improved analytical Stenning-Martin model do not coincide with the values of h/L determined in the measurements for the delivery heads H equal 0.45 and 0.90 m, whereas they are comparable for H equal 1.35, 1.80, 2.25 m. For the tested air lift pump with the air-water mixer of the described type (Fig. 2), the maximum air pressure should not exceed pp = 145 kPa, because for higher pressures the water flow rate diminishes. In the air lift pump being tested, the water flow rate Qw grows along with the rise in the air flow rate and in the vertical pipe submersion coefficient h/L whereas falls along with the rise in the delivery head H.
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