Contradictory Behavior of Superhydrophobic Surfaces: Investigation of Hydrodynamic Behavior

Abstract

Nowadays, considering the enhanced power density of electronic devices and energy systems, increasing the efficiency of heat transfer is inevitable. Recent studies have shown that microchannels could be effective for heat transfer enhancement; however, the dominance of surface forces in microchannels increases the power consumption of such systems, which is not desirable and economical. Therefore, finding an efficient and economical solution to solve this problem paved the way for the study of superhydrophobic surfaces, inspired by nature. Despite the peculiar properties of superhydrophobic surfaces, so far, no comprehensive and accurate study has investigated superhydrophobic surfaces and their effects on hydrodynamic performance in a three-dimensional flow field numerically. Thus, the present study aims to propose a new approach toward the acting mechanism of superhydrophobic surfaces and determinant factors affecting their performance and efficiency. For this purpose, for a conventional microchannel the hydrodynamic performance is assessed numerically, in two different cases: (a) with smooth walls and (b) with superhydrophobic surfaces, at different flow rates. Despite previous arguments, the comparative analysis reveals that superhydrophobic surfaces in the three-dimensional flow field slightly increase the pressure drop (about 0.08% - 1.049%). The results indicate that several factors such as; the vortices inside the air cavities, the periodicity of the cavities, the pressure difference between the flowing fluid over the cavity and the air inside the cavity determine the overall acting mechanism of superhydrophobic surfaces in microchannels. Therefore, applying the superhydrophobic surfaces with the aim of mitigating the pressure drop and frictional resistance requires the consideration of various factors, and special measurements which will result in better system design and optimization.Thus, the ultimate goal of this study is to address the challenges revolving around the ability of superhydrophobic surfaces in reducing the skin friction drag and pressure drop and the gap between current achievements and required performance which will provide a good starting point for further research into the potential of superhydrophobic surfaces.