Experimental investigation of surface finishing technique impact on subcooled flow boiling heat transfer enhancement: sandpapering and sandblasting

Despite surface characteristics being perceived as a prominent factor in boiling, the effect of surface roughness has not been consistently understood. Evidence of this is the diverse representations of the surface characteristics in widely used correlations. The surface's microscopic profile is a determinant factor since the minuscule peaks and valleys serve as potential bubble generation sites. To understand the effect of finishing on surface characteristics and boiling, eight sample surfaces generated via two techniques, namely sandpapering and sandblasting, are investigated and later put under subcooled flow boiling tests of water in this study. The experiments are conducted in atmospheric pressure with flow rates ranging from 2.5 to 7.5 L/min and subcooling of 5.6 and 9.6 °C. The results obtained from profilometry show that cavities' geometry and distribution are characteristically different when comparing the two finishing techniques. Increasing the average roughness ( S_a ) from 0.017 to 7.325 µm is shown to generally enhance subcooled flow boiling heat transfer coefficient up to 100