As modern high-efficiency heat exchangers based on microscale fluid flow, microchannel heat sinks (MCHS) have been widely used in many fields given their excellent heat transfer area-to-volume ratios, compact structures, and high heat transfer coefficients.

This paper systematically reviews recent advances in enhanced heat transfer technologies for MCHSs, which are primarily categorized into three major areas: passive enhanced heat transfer technologies, active enhanced heat transfer technologies, and heat transfer enhancement structures. In passive enhanced heat transfer technologies, the application of nanofluids is discussed, and the enhanced heat transfer characteristics of single-component and mixed nanofluids are analyzed in detail. Moreover, an artificial neural network and computational fluid dynamics technology are combined to determine the optimal concentration of nanofluids, thereby reducing the cost and time of experiments. In active enhanced heat transfer techniques, the application of magnetohydrodynamics in microchannels and its enhanced heat transfer mechanism are outlined, showing that gradient magnetic fields enhance heat transfer in magnetic nanofluids more effectively than uniform magnetic fields. For heat transfer enhancement structures, four typical designs—fluid interruption structures, porous structures, concave cavity structures, and nanostructures—are reviewed. The physical mechanisms of heat transfer enhancement, as well as the influence mechanisms of these structures on the boiling process of the flow in microchannels, are analyzed in depth. In addition, this paper outlines the commonly used materials for MCHSs and their practical applications in electronics, chip cooling, and aerospace. Typical microchannel fabrication methods are introduced from the perspectives of subtractive manufacturing and additive manufacturing, and their advantages and disadvantages are summarized.

Although nanoparticle agglomeration substantially enhances the thermal conductivity of nanofluids, it is also prone to generating a fouling layer, leading to fouling formation. This, in turn, triggers problems such as increased pressure drop, channel blockage, and corrosion. At present, the impact of agglomeration patterns on transport properties remains unclear, necessitating systematic research. The size parameters of the heat transfer enhancement structure (especially at the microscale and nanoscale) substantially impact heat transfer performance, and its optimal design must be further explored. For complex microchannels, the difficulty and cost of processing must be considered comprehensively, and more accurate and economical manufacturing processes for complex microchannels must be developed. Alternatively, the synergistic application of various preparative processes must be explored. This paper summarizes the current research status in the field of heat transfer enhancement of MCHSs and provides an outlook on existing challenges and potential future development directions, offering a reference for the development of microchannel enhanced heat transfer.