Augmentation of pool boiling heat transfer using the laser treatment technology

Abstract

The paper discusses applying the laser technique to modify the copper heater surface. The interaction of the laser beam with the base material leads to its melting, and various shapes can be obtained during the process. The study is focused on the boiling heat transfer analyses of the specimen in the form of a disc with longitudinal microfins of a height of 0.5 mm. The optical microscope was used to determine the morphology of the surface. The laser beam generated significant roughness, which benefitted the overall thermal performance. Considerable heat transfer augmentation was recorded for the laser–made surface in relation to the untreated sample, which served as a reference. The heat flux was several times higher, while the laser–treated sample's boiling curves were shifted to the area of smaller temperature differences. Two boiling models proved unsuccessful in predicting the heat exchange process occurring during pool boiling of distilled water and ethyl alcohol. According to the Smirnov, Xin and Chao models, the average differences between the experimental data and calculation results were ca. 93 kW/m2 and 116 kW/m2 for water, 78 kW/m2 and 68 kW/m2 for ethanol.