Análise numérica sobre a influência de variações da seção transversal de microcanais no escoamento laminar

Abstract

In recent years, the reduction of electronic devices in several application fields, such as biomedicine, chemistry and computer technology has been providing high efficiency related to the space in equipment. At the same time, this reduction in physical space is counterweighted by the high performance required at the refrigeration systems in such equipment. Therefore, the thermal control is one of the most critical areas for the development of modern microelectronic devices. A lot of experimental and numerical studies have been done by several researchers, in the last decades, seeking to investigate the hydrodynamic and heat transfer in microscale. However, the results show divergences among them. In general, these related diversions can be viewed through the Poiseuille and Nusselt numbers, when compared to the predicted results through conventional theory. Usually, the reported divergences related to the measurements in microscale are associated to the microchannel geometric factors, such as channel aspect ratio, channel hydraulic diameter and surface roughness. Some deviations related to the friction factor were attributed to cross-section variations of the microchannels. The aim of this work was verify numerically how the hydrodynamic and heat transfer characteristics can be influenced by cross-section variations of the microchannels. The results obtained for the single-phase laminar flow of water in microchannels with deformities at the cross-section were compared to the perfect ones, through Poiseuille and local Nusselt numbers. Deviations at Poiseuille and local Nusselt numbers, through imperfections and variations of the cross-section of microchannels, were verified. Some deviations at Poiseuille number were dependent on Reynolds number. However, some results obtained for the local Nusselt number showed that it is more sensitive to the shape of the cross-section of the microchannel than Poiseuille number. Such results were obtained through mass conservation, Navier-Stokes and energy equations, by computational fluid dynamics (CFD).