An experimental investigation on the effect of surface roughness and finishing on subcooled flow boiling

Flow boiling heat transfer has been extensively used as an effective means to remove large amounts of heat from various thermal equipments. Several factors have been reported by the researchers as influential on the boiling phenomenon, among which surface characteristics is not clearly understood yet. The effect of surface roughness and finishing is additionally important since several heat transfer enhancement techniques rely on surface manipulation. In this paper, a range of surface treatment methods have been studied in terms of subcooled flow boiling performance. With average roughness ranging from 0.017 to 7.325 ʽm, these sample surfaces showed different trends in terms of initiation of boiling and heat transfer coefficient. The obtained results showed a 22% improvement in heat transfer coefficient in the considered range of average roughness. The experimental output also shows that standard roughness parameters are inadequate representatives of the surface topology and that relative closeness of microscopic peaks and valleys also affects the boiling performance.

Keywords:

Subcooled flow boiling , Surface roughness , Surface finish , Surface treatment