Numerical simulation of nitrogen vapor condensation on microstructure surface

Abstract

• A three-dimensional model of condensation on micro fin is established. • Micro fin surface area exhibits different functionalities. • Micro fin curvature radius affects the driving force of liquid film movement. • An optimal micro fin structure for best performance is proposed. The mechanism of the condensation heat transfer enhancement on the microstructure surface has not been deeply explored, which restricts the full play of microstructure strengthening ability. In this study, a three-dimensional numerical simulation of the condensation on the micro fin surface revealed the liquid film flow behavior and the heat transfer performance, and the model is in good agreement with the experimental and theoretical results. The internal flow field on the curved surface shows that the liquid film is redistributed, and it proves that the surface tension plays a leading role in promoting the transverse movement of the liquid film. The micro fin surface area exhibits different functionalities, the excellent mass transfer region is located at the fin top, and its local heat transfer coefficient can reach 25 k W · m - 2 · K - 1 , which is one order of magnitude higher than Nusselt's theoretical value. The fin bottom is the condensate collection area, where the condensate discharge velocity is increased by 2–3 times. The simulation results of the different micro fins indicate that the curvature radius of the micro fin could affect the condensate flow process, and the aspect ratio of the micro fin determines the local heat transfer enhancement degree and the strengthening area ratio. This study finally pointed out that the high-efficiency micro structure should have a large area of the fin top for enhancing heat transfer, as well as a large volume of the fin bottom for the liquid drainage.