The Effects of Cross Links on Adiabatic Two-Phase Flow Characteristics in Scaled Microchannel Heat Sinks

The effects of cross-links, introduced in the channel core of an array of parallel scaled microchannels, were investigated by comparison of the flow distribution in six different multichannel configurations. A standard straight channel test section and five other test sections, which incorporated cross-links were used. One case includes two cross-links located at 1/3 and 2/3’s of the channel length, with their width varied by one, two, and three times the channel width. Whereas, four and six cross-links were used for the other case. All test sections had 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm, and were fabricated from clear acrylic to enhance flow visualization. The flow distribution was monitored at four select channels. The working mixture was air and water with superficial velocities ranging from 0.03 to 9.93 m/s, and 0.04 to 0.83 m/s, respectively. This corresponds to an observed range of flow quality between 0 and 0.25, whereby the mass flux range is from 42 kg/m²s to 834 kg/m²s. The cross-linked designs permit fluid communication between channels, and the results showed that there is a significant impact on flow distribution when compared to the straight channel design. This is due to flow sharing between neighboring channels. Flow patterns were presented in terms of fractional time function, and provided further insight to flow characteristics. Comparing with a single channel flow regime map, the expected intermittent flow regime was observed 84% to 90% of the time for the cross-linked designs, whereas 65% to 80% of that for the straight channel design.