Host: The Japan Society of Mechanical Engineers
Name : The 30th International Conference on Nuclear Engineering (ICONE30)
Date : May 21, 2023 - May 26, 2023
Condensation heat transfer enhancement has received increased attention in nuclear engineering in the past few years. Coalescence-induced droplet jumping is a spontaneous dewetting phenomenon, which may promote dropwise condensation. It not only further enhances condensation heat transfer, but also is consistent with passive characteristic of nuclear design without extra heat exchange area. In this paper, a stepped-structure surface was designed, with five different heights (0mm, 0.4mm, 0.8mm, 1.2mm, 1.6mm). We experimentally studied coalescence and departure process of two water droplets with fixed droplet size (R=0.8mm). Stepped-structure surface exhibited excellent performance with strong horizontal droplet transport ability and high energy efficiency, whose jumping direction is ranging from ~6.2° to ~90°, maximum non-dimension velocity v* = 0.65 and maximum energy efficiency η = 34.9%. By disassembling η into three sub-efficiencies, one correlates to step height and two correlate to duration of merge stage and contact stage, we analyzed mechanism of jumping enhancement. Results showed that largely changed duration of merge stage and contact stage is the main reason of high energy efficiency, while step height had little influence on it. Stepped-structure surface provides a new solution for breaking the condensation limit.
