Pool boiling heat transfer enhancement induced by capillary wicking from radial gradient structures: A lattice boltzmann study

Abstract

With the aid of a three-dimensional lattice Boltzmann model built in the lab, the boiling state on the surface with gradient groove structure is investigated. The emphasize is placed on the impact brought by the wicking capability from the gradient structure on boiling performance. Besides the roles of distribution, number, width and depth of the grooves in the boiling process discussed in detail, the effects of wall superheat and wettability on boiling heat transfer are also explored. The results show that the wicking force generated by the gradient grooves can improve the boiling performance to an extent. Adjusting the geometry of grooves can enhance heat flux by up to 27.46% compared to a flat competitor. However, there exists a limit for the gradient defined in this study. Pursuing larger gradient values can extend the pit region at the center of surface. Upon TPCL being trapped within the pit region, it causes a negative effect on the boiling performance. The wicking capability has a positive relationship with surface wettability at a given groove number and size. In regards to the parametric effects of groove, the heat flux first increases but then declines with increasing the groove width at a fixed Jacob number. Despite the enhanced boiling performance with increasing the groove number and depth, the enhancement has an upper limit. But, the groove distribution has a minor effect on the boiling performance if TPCL is outside the pit region. This study provides quantitative evidence for the fact that wicking can promote boiling from the numerical view.