Temperature-dependent wicking dynamics and its effects on critical heat flux on micropillar structures in pool boiling heat transfer

Boiling heat transfer is a vital process that needs to be incorporated into next-generation cooling systems due to its high heat transfer performance. The critical heat flux (CHF), which defines boiling performance, needs to be enhanced to expand the operating limits of heat transfer applications. The crucial factor enhancing CHF is wicking performance, i.e., liquid-supply capacity during the boiling process. This study investigated the relationship between wicking performance and CHF enhancement using micropillar structures of various roughness (diameter: 4–20 um and gap: 10–40 um). To measure wicking performance near the boiling condition, we increased the surface temperature from 20 °C to 95 °C. At the highest temperature (95 °C), the D04 G10 sample (i.e., highly-roughness) showed an enhanced wicking coefficient (6.8 mm/s^0.5), 48% higher than the value measured at room temperature. For the boiling tests, the D04 G10 sample (∼164 W/cm²) showed a notable CHF enhancement of 85%, compared to the plain surface (∼89 W/cm²), owing to the strong liquid flow induced by wicking, which delayed vapor film formation. Based on these results, we proposed a new CHF correlation that accounts for the wicking performance near the boiling condition, which is accurate within an error of 9% with experimental results.