The influence of microgrooves on the dynamics of drop spreading on textured surfaces

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In years of intensive development of electronic and microelectronic equipment, the problem of ensuring the scheduled thermal mode of both individual elements of such equipment and large-sized products, such as data storage databases, has become increasingly acute. Therefore, researchers from many countries are currently making active attempts to develop new systems for ensuring scheduled operating modes of electronic computer elements. One of the options for solving this problem is the drop cooling of surfaces of electronic and microelectronic equipment heated to high temperatures. This technology involves the formation of a cluster on the heat-removal surface of highly loaded computer elements. This allows extreme heat fluxes to be removed through phase change. However, despite a fairly large volume of research on this topic, there are still many unsolved problems in this area of knowledge. For example, the parameters (deposition height, drop feed rate, etc.) of water drop deposition on the surface of substrates used for cooling have not been determined yet. Moreover, the efficiency of drop cooling increases if the surface from which heat is removed is modified (roughness is formed). However, the patterns of spreading and evaporation of coolant drops on rough surfaces have not been sufficiently studied yet. Therefore, the aim of the work was to establish, based on the results of the experiments, the scale of the influence of the fall height of water drops on the characteristics and conditions of their spreading on a textured and polished surface. The paper presents the experimental results of the process of water drop impact on a textured surface. The main characteristics of a liquid drop spreading over a textured surface have been investigated. To establish the characteristics and conditions of spreading (drop spreading speed and time, drop shape stabilization time), typical shapes (in the midsection) of a drop spreading over the surface have been established. It is shown that the characteristic time of formation of the equilibrium state of the “water drop – substrate” system is no more than 0.1 s. This is significantly less than the drop evaporation time, even on high-temperature surfaces. The effect of surface anisotropy on the characteristics and conditions of spreading has been analyzed. It is shown that when water moves across the grooves, drop spreading is higher than along the grooves. A hypothesis has been developed to describe this effect.