Adiabatic two phase flow distribution and visualization in scaled microchannel heat sinks

The present work investigates the characteristics of adiabatic two-phase flow, and compares the flow distribution in two different multi-channel configurations. One is a standard straight channel design, and the second is similar, except that it has two cross-linked paths located at one-third and two-thirds of the channel length. Each test section consists of 45 rectangular channels with a hydraulic diameter of 1.59 mm and is fabricated out of acrylic to enable flow visualization. The test facility operates with water and air as the working fluids. Gas and water superficial velocities range from 0.03 to 9.93 and 0.04 to 0.83 m/s, respectively, corresponding to a flow quality between 0 and 0.25, whereby the mass flux range is from 41 to 834 kg/m2s. Four channels were selected for flow distribution tracking, and the results showed that the straight and cross-linked designs both have unequal flow distributions. Flow patterns are presented in terms of a fractional time function to gain insight into the flow characteristics. Compared to a single channel flow regime map, the intermittent flow regime was observed 65 to 85% of the times expected, whereas the dispersed flow regime only occurred ∼40% of the times expected for both designs. Further discussion on flow distribution and flow patterns are also documented.

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