Unified two-component interfacial area concentration model for narrow channel two-phase flow

Abstract

The conventional interfacial area concentration (IAC) models do not distinguish narrow and wide side interfaces when applied in narrow channels, which hinders accurate modeling of interfacial transfer mechanisms at different interfaces. In order to overcome such deficiency, void fraction data obtained in narrow-channel air-water flow with the flexible printed circuit (FPC) wire-mesh sensor (WMS) is analyzed to establish a two-component IAC model which consists of two essential parameters, i.e. the projected interfacial area concentration (PIAC) and projected interfacial length concentration (PILC). Based on the refined and sharpened void fraction distribution, the postprocessing algorithm is developed to obtain the PIAC and PILC for different flow patterns. Analysis of experimental data indicates that the PIAC is approximately proportional to void fraction, while variation of the PILC with void fraction is complicated. The ratio of PILC to PIAC, which characterizes topology of interfaces, shows distinct value in bubbly flow compared with other flow patterns. Such difference is attributed to the existence of large bubbles, typically with spanwise length over 70% of the channel width, in flow patterns other than bubbly flow. Hence, bubbles are separated into two groups with the critical ratio of bubble width to channel width in the model derivation. The semi-empirical PIAC and PILC models are derived for each bubble group. Based on volume fraction of two bubble groups, the unified PIAC and PILC models are obtained to realize the accurate prediction in all the flow patterns. The unified two-component IAC model and other IAC models are evaluated with the present IAC experimental data and the experimental data of Shen et al. (2012). The evaluation shows the superiority of the unified two-component IAC model and that the proposed unified two-component model can be applied in the narrow-channel air-water two-phase flow patterns with α¯≤0.9.