Investigation of local heat transfer characteristics and boiling instability mechanisms in trapezoidal ribbed-wall microchannels

With the advancement of microelectronics intensifying heat dissipation challenges in electronic devices, microchannel boiling heat transfer has emerged as a critical solution. This study experimentally investigates the boiling heat transfer characteristics and instability phenomena in trapezoidal ribbed-wall microchannels. The spatial distribution of heat transfer performance across different channels and along the flow path was systematically examined. Results indicate minimal variation in heat transfer characteristics between radial channels, while significant disparities were observed along the channel length. Heat transfer coefficient distribution exhibited strong dependence on flow pattern transitions, with annular flow-dominated convective heat transfer regimes demonstrating superior performance compared to bubble flow-governed nucleate boiling regimes. Downstream regions prone to intensified boiling showed heat transfer deterioration, adversely affecting wall temperature uniformity. Wavelet analysis of time-domain pressure drop signals revealed three coupled instability mechanisms. Among these, the pressure drop-dominated instability exhibited the longest fluctuation period and highest amplitude, demonstrating its predominant role in system instability.