Comparison of CHF Enhancement on Microstructured Surfaces With a Predictive Model

Effect of surface roughness on pool boiling heat transfer at a heated surface having moderate wettability

“…However, the extent of augmentation demonstrated by the experimental data shows large differences according to the surface type, such as metal surfaces or silicon wafer surfaces. CHF variation with changing roughness on the metal surfaces has been reported to be approximately 10-20% in general [15,18]. In contrast, recent studies on CHF enhancement with silicon wafer surfaces show much larger augmentations with increasing roughness factor r, where roughness factor r is defined as the ratio of the actual contact area to the projected area [7,19,26,27].…”

“…The surface conditions were overlooked for a long time until Ramilison et al [15] reported that they are important and concluded that the wettability effect on CHF is more prominent than the roughness effect. Many other studies related to the effect of surface roughness on the CHF were performed [16][17][18] and their data showed varying augmentation of CHF with increasing surface roughness. However, the extent of the augmentation was no more than ±20%.…”

Effect of nanostructures on heat transfer coefficient of an evaporating meniscus

“…This enhancement in CHF can be attributed to a variety of mechanisms, including increased nucleation site densities [1,5,15], elongated contact line [7,16], enhanced micro-convection around nucleated bubbles [4,17,18], increased bubble departure frequency [19], and enhanced microlayer evaporation via a strong wicking effect [3,9,13,14,[20][21][22]. Among these possible mechanisms, the enhanced microlayer evaporation through wicking has been widely accepted as the dominant mechanism, where correlations [3,21] and theoretical predictions [22] have been established between the CHF and the wicking rate.…”

“…Recent efforts using micro/nanostructured and hierarchical structured surfaces to enhance heat transfer coefficient (HTC) and CHF of boiling experiments have resulted in enhanced CHF on the order of 200-313 W/cm 2 [1,[3][4][5][6][7][8][9][10][11][12][13][14]. This enhancement in CHF can be attributed to a variety of mechanisms, including increased nucleation site densities [1,5,15], elongated contact line [7,16], enhanced micro-convection around nucleated bubbles [4,17,18], increased bubble departure frequency [19], and enhanced microlayer evaporation via a strong wicking effect [3,9,13,14,[20][21][22].…”

Effect of Nanostructured Microporous Surfaces on Pool Boiling Augmentation

“…Among a variety of hypothetical explanations to understand the boiling enhancement, explanations which relate the CHF to the wettability and wickability have been recently presented in the literature [30]- [32]. Wetting is the ability of a liquid to maintain contact with a solid surface, and the degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces which are measured by droplet contact angle.…”