Fractal-like branching channels are proposed for a number of microscale applications that include heat sinks, heat exchangers, absorbers, desorbers and micro-mixers. The benefit of fractal-like channel designs includes, based on model predictions, a lower pressure drop than parallel straight channels for a given flow rate, when compared on an equal channel surface area basis, with the terminal channel cross section of the fractal-like network used to define the parallel channel geometry. The fractal-like flow networks are a unique geometry that follows fractal bifurcation patterns, in this case mimicking the flow patterns found in nature. Two-phase flow applications require an understanding of how the geometric constraints impact the flow characteristics during multiphase flow. A combination of one-dimensional modeling predictions with experimental results are used in this study to asses the relative impact of flow network designs on pressure drop and void fraction distributions for adiabatic flow boiling. The characterization of the flow networks includes a specified branching ratio of channel length and channel width (or diameter) and also the number of branching levels, or bifurcations in a given length. The goal of the present study is to identify the adiabatic boiling characteristics within the fractal-like flow network and compare results to straight parallel channels. The model used is a compilation of two-phase flow models presented in the literature. The separated flow model accounts for a local two-phase flow parameter and flow re-development, along with variable property effects. Results are compared with straight channels based on flow boiling conditions, pressure drop and vapor quality distributions for a range of flow rates and subcooling.
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