Experimental study on flow boiling of two rectangular expanding microchannel heat sinks in series connection and flow patterns analysis

Addressing the cooling challenges posed by multi-heat sources with high heat flux in densely integrated electronic devices remains a pressing concern. A study was conducted to explore the performance of two distinct microchannel heat sinks, with featuring grooves or not, in a series connection. This investigative series connection mode exhibited notable enhancements in performance. Bubble behavior flow patterns within microchannels were observed utilizing a high-speed camera, followed by an analysis of the associated heat transfer mechanisms. The study encompassed the acquisition and detailed analysis of three key parameters, wall temperature, heat transfer coefficient (HTC), and pressure drop, of both heat sinks across diverse series connection configurations. Flow patterns were varied and including bubble flow, elongated bubble formations, and the presence of thin liquid films with steam channels in different positional heat sinks. Remarkably, the series connection exerted a substantial influence on postposition heat sinks compared to their preposition counterparts. Among the investigated series connection modes, with featuring grooves ones, exhibited the most favorable impact on heat sink performance. Notably, the postposition heat sink in this configuration demonstrated a maximum HTC increase of 12.77 kW/(m²K). The distinctive heat transfer mechanisms led to higher HTC and lower wall temperature in postposition heat sinks compared to their preposition counterparts. Findings in this study offer crucial insights into addressing cooling challenges associated with multi-heat sources featuring high heat flux, serving as valuable groundwork for potential solutions in this critical domain.