Heat transfer enhancement for nucleate boiling via microlayer disruption on micro-pillar arrayed surfaces

Surface modifications have demonstrated significant potential in enhancing heat transfer in nucleate boiling, yet their impact on microlayer evaporation-a key heat transfer mechanism-remains less understood. In this work, we performed isolated bubble nucleate boiling experiments with micro-pillar arrayed surfaces to study the microlayer heat transfer. We initially analyzed the bubble dynamics, including growth dynamics and shape evolution throughout the entire bubble life cycle on these surfaces in detail. The results show that bubble dynamics differ considerably across different surfaces under the same surface superheat, primarily due to differences in microlayer evaporation. We then statistically quantify the bubble growth dynamics to evaluate the microlayer heat transfer performance. Importantly, we found that the experimental results align closely with the inference on the microlayer heat transfer derived from our previous simulation results of initial microlayer morphology on similar surfaces. This alignment allowed us to experimentally confirm the existence of two distinctive microlayer morphologies on micro-pillar arrayed surfaces, as observed in our previous simulations: the disturbed and the disrupted microlayer. We demonstrated that the microlayer morphology governs its heat transfer performance and, consequently, bubble dynamics during the entire bubble life cycle. Notably, our findings suggest the existence of a critical microlayer thickness, which can be achieved through surface modifications, to sustain a high evaporation rate throughout the bubble life cycle. To optimize surface design, we proposed a microlayer morphology concept that links the microlayer morphology with the corresponding heat transfer performance on micro-pillar arrayed surfaces.