Download or read book Characterization of Geometric Effects Induced by 90 Vertical Elbows in Air-water Two-phase Flow written by Shouxu Qiao and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional modeling of two-phase flows is typically based on experimental data acquired in straight flow channels of different flow orientations with no flow restrictions. No model is currently available to dynamically predict the transition between different flow orientations. To bridge this gap, it is important to characterize and model the geometric effects induced by flow restrictions or junctions in air-water two-phase flows. The present work investigates the effects of a 90 vertical-upward to horizontal and a 90 horizontal to vertical-downward elbow on two-phase flow and establishes the interfacial area transport equation (IATE) applicable to air-water two-phase flow influenced by the 90 elbows. A detailed database for the local and global two-phase flow parameters in different flow orientations and across vertical elbows is established with state-of-the-art four-sensor conductivity probes, a pressure transducer, and a high-speed video camera. The elbow effects are characterized by investigating the evolution of void fraction, interfacial area concentration, bubble velocity and two-phase pressure drop across and downstream of elbows. The degree of influence made by the elbow is characterized by the variance of void fraction. The axial development of the flow downstream of the elbow is modeled by an exponential function of the axial length based on the experimental data. Then, the dissipation length of the elbow is determined by characterizing the evolution of the elbow strength parameter. The elbow strength parameter is also used to correlate the void-weighted bubble velocity and covariance terms in the IATE. The two-phase pressure drop across the vertical elbows is modeled with a modified Lockhart-Martinelli correlation that considers the minor loss induced by these elbows. The developed models and correlations are implemented into the IATE to establish a model that is applicable to the region influenced by the elbow. The established IATE is evaluated by the data obtained in different flow orientations and across elbows in bubbly flow. The newly developed IATE can predict the interfacial area concentration with an average percent difference of 6% compared with the experimental data, demonstrating that the models and correlations developed in this work for the two-phase flow parameters in elbow influenced regions are reliable.