Analysis of Single Phase Convective Heat Transfer in Microchannels With Variable Thermal Conductivity and Viscosity

The need for maximizing the performance of micro-mechanical systems and electronic components has resulted in a trend of minimization. Minimized sizes and dimensions have come along with a complex heat transfer and fluid problem within these devices and components. For a variety of fields in which these devices are used, such as; biomedicine, micro fabrication, and optics, fluid flow and heat transfer at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making some extensions to the conventional theories by including the scaling effects that become important for microscale. Studies performed in the last decade have shown that, some of the effects that are thought to become significant for a microscale gas flow are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, the temperature variable thermal conductivity and viscosity may become important in microscale gas flow due to the high temperature gradients that may exist in the fluid. Therefore, effects of variable thermal conductivity and viscosity in microscale gas flow and convection heat transfer are investigated in this study. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in a micro gap between parallel plates is numerically analyzed. In the analyses, scaling effects such as rarefaction, viscous dissipation, and axial conduction are taken into account in addition to the temperature variable thermal conductivity and viscosity.