Numerical simulation of fluid flow and heat transfer in microchannels with patterns of hydrophobic/hydrophilic walls

Abstract

The presence of a balance between heat transfer rate and pressure drop is an important issue in designing passages of coolant flows to repel high heat flux. This kind of heat transfer is excessively used in cooling microprocessor chips. Application of microchannels leads to an increase in heat transfer and higher efficiency; however, one main challenge of using these channel kinds is the pressure drop, as well as high power requirement for pumping. One effective way of reducing pressure drop is to substitute some parts of the microchannels surface with hydrophobic surfaces. In the present study, a microchannel, with a rectangular cross-section, was modeled by two kinds of hydrophilic/hydrophobic patterns. Governing equations, including continuity, momentum and energy equations, are solved by the use of computational fluid dynamics. The model under investigation includes two transversal and longitudinal patterns. The fluid flow is three-dimensional and incompressible. In addition, hydrophilic surfaces act as rips of flow and, owing to possessing no-slip condition, have an effect on the resultant heat transfer. Comparisons between longitudinal and transversal models show that in the presence of longitudinal models, the pressure drop decrease is 1.5 times more than transversal ones. According to results, using a longitudinal hydrophobic pattern on one of the walls leads to a 12% decrease of mean velocity in a fully developed region. Also, outcome results indicated that the use of hydrophobic models could reduce the required power fluid pump up to 69% and increases heat flux up to 15%.