EXPERIMENTAL AND THEORETICAL CHARACTERIZATION OF TWO-PHASE FLOW DISTRIBUTION IN UNBALANCED FLOW NETWORKS

This study investigates two-phase flow distribution of R-1234yf into two-branched channels. Especially, the effect of unbalanced pressure drop and tube diameter on the flow distribution was characterized and modeled. The experiments were conducted for a mass flux ranging from 393 to 1179 kg/m2s and the inlet quality was fixed at 0.2. The flow distribution was mainly governed by the pressure drop ratio between two branched channels. The mal-distribution under the unbalanced pressure drop condition was mitigated by increasing mass flux, whereas sustained mal-distribution was observed under unbalanced tube diameter conditions. Correspondingly, a theoretical representation of the phenomenon, based on the principle of minimum entropy production, was developed and adopted to predict two-phase flow distribution in an unbalanced flow network. The characteristics of the experimental data were clearly and quantitatively reflected in the prediction results. Under the unbalanced pressure drop condition, the predictions agreed well with the experimental data maintaining the maximum deviation within ±30%, whereas it exceeded ± 30% under the unbalanced tube diameter condition. The analysis of such theoretical formulation suggested the necessity of appropriate pressure drop models of flow impact, contraction, and merging at the outlet channel, that are compatible with the extremization of entropy production for further improving the prediction accuracy without compromising its generality.