Boiling heat transfer characteristics of multi-directional dynamic intelligent surfaces based on shape memory alloys

Abstract

Traditional single-modified surfaces lack geometric adaptability during heat transfer processes, relying exclusively on fixed surface properties to accommodate dynamic thermal conditions—a limitation that inherently compromises their boiling heat transfer capacity. Shape memory alloys (SMAs), with their exceptional shape memory effect, offer the potential to achieve enhanced boiling heat transfer across different heat transfer stages. In this study, dynamic surfaces with varying orientations were fabricated using NiTi alloy as the base material, and their boiling performance was investigated. The results indicate that the bent structure of the dynamic surface in the early stage promotes superheat buildup and enhances bubble nucleation, while the upright structure in the later stage facilitates bubble detachment. Additionally, dynamic surfaces with combinations of different bending directions effectively guide bubble detachment and enhance disturbances. These surfaces also provide extra liquid replenishment channels, further improving their heat transfer performance. Among the tested surfaces, the multi-directional dynamic surface (MDS) exhibited the highest critical heat flux (CHF) and heat transfer coefficient (HTC), representing improvements of 71.55 % and 92.85 %, respectively, compared to the plain surface.