Experimental study on boiling heat transfer of liquid film on micro-channel surfaces

Boiling heat transfer performance is strongly influenced by the structure and wettability of the liquid film on the heating surface. However, the fabrication processes for high-performance heat transfer surfaces are often complex, limiting their practical application in high-power devices that require efficient heat dissipation. To address this issue, this study fabricated channelled surfaces with different geometries using simplified wire-cutting. Boiling heat transfer experiments were then conducted using a liquid-level reduction method on smooth surfaces, micro-channel surfaces under high-heat-flux conditions. The variations in heat transfer coefficient (HTC) and critical heat flux (CHF) with liquid level (L) showed that micro-channel surfaces exhibited superior boiling heat transfer performance compared with smooth surfaces under the same liquid-level conditions. Increasing the geometric dimensions of the microstructures enlarged the effective heat transfer area and activated more bubble nucleation sites. In contrast to parallel-channel surfaces with fixed channel widths and spacing, staggered micro-channel surfaces provided a more complex channel structure, allowing the working fluid to contact a larger heat transfer area while offering additional liquid re-supply pathways to accelerate liquid return. When the liquid level decreased to the critical range between 1.0 and 0.4 cm, the HTC and CHF of both parallel micro-channel and staggered micro-channel showed a non-monotonic correlation with liquid level. At a liquid level of 0.6 cm, the staggered micro-channel surface achieved the best heat transfer performance, with a CHF of 440.67 W/cm² at a wall superheat of 8.7 K, which was 3.9 times higher than that of the smooth surface under the same liquid-level condition. The corresponding HTC reached 50.67 W/(cm²·K), which was 12.7 times higher than that of the smooth surface. These results clarify the boiling heat transfer mechanisms of different microstructured surfaces and provide guidance for the design of high-efficiency heat transfer devices.