An experimental investigation of flow boiling characteristics in silicon-based groove-wall microchannels with different structural parameters

摘要

The groove-wall microchannel possesses high performance for flow boiling heat transfer. However, the structural parameters of grooves have not been studied comprehensively. This paper presents an experimental study of the effects of groove-wall microchannel aspect ratio, groove spacing ratio and groove depth on the flow boiling. The silicon-based channel aspect ratios of 1, 2.5 and 4 with the same channel height of 200 μm, groove spacing ratios of 2, 5 and 8, and groove depths of 15, 30 and 45 μm, are investigated. Experiments are performed using deionized water as the working fluid with mass fluxes of 446-963 kg/m~2·s and heat fluxes of 36.3-502.8 W/cm~2. As a comparison, flow boiling experiments of plain-wall microchannels are conducted. A high-speed camera is used to record the flow patterns in microchannels, providing an in-depth understanding of the heat transfer. The average heat transfer coefficient is found to vary significantly with the channel aspect ratio, while it varies moderately with different spacing ratios or groove depths. At the aspect ratio of 2.5, the groove-wall channel achieves the best improvement of heat transfer. The critical heat flux is easily triggered at the aspect ratio of 4 and it becomes significantly high at the aspect ratio of 1 in both channels. Encouragingly, reduced pressure drops are achieved over most test cases. The high aspect ratio groove-wall channel is found with the ability to reduce more pressure drop. Similar pressure drops are observed for channels with different groove spacing ratios or different groove depths. This work provides a guidance for the optimal design of the groove-wall microchannels to enhance flow boiling.