Experimental investigation of the effect of cylindrical array structure on heat transfer performance during nucleate boiling

Abstract

Using deionized water as the working fluid, a visualized pool boiling study was carried out on the surface of cylindrical pillar arrays of different sizes and the ordinary smooth surface under atmospheric pressure, and the boiling heat transfer curve and the change of heat transfer coefficient were studied. A high-speed camera is used to quantitatively measure the bubble dynamics, including bubble departure diameter and nucleation sites density. The results show that the onset of nucleate boiling temperature of all cylindrical pillar arrays has been significantly reduced, while the heat transfer coefficient is increased by 23.4%-163.4% compared to that of the smooth surface. The decrease of the pillar spacing helps to improve the performance of boiling heat transfer. The smaller gap optimizes the capillary flow of the liquid to a certain extent, thus facilitating the departure of bubbles, thereby inducing the working fluid to quickly replenish the dry area. The reduction of the diameter of the pillars is beneficial to improve the boiling heat transfer performance. More nucleation sites on the wall promote the bubbles to merge more quickly and reach the bubble departure diameter more easily, thus enhancing the evaporation of the micro-liquid layer and promoting the heat transfer. The correlation expressions as well as the upper and lower limits are obtained by fitting the change of heat transfer coefficient curve. Compared with the data in the literature, the S6 surface with the best performance shows obvious heat transfer advantages.