Thermal Effects on Fluid Flow in Mini/Micro Channel (Keynote)

The present work discusses the characteristics of the thermal effects at microscale. The thermal effects are divided into two types, steady and unsteady. The unsteady thermal effect focuses on the thermal response of object during heating. It relies on the object thermal inertia. Thermal response phenomena have seldom application of practical uses in devises at conventional scale. However, the miniaturization in device size due to the development of the state-of-the-art technology makes it possible to utilize thermal responses due to its significantly reduced thermal inertia. The swift thermal response can be utilized in the designs of micro dual-layered metal membrane pumps, phase change pumps, polymerase chain reaction (PRC). For steady type the thermal effect in microchennels varies with the boundary conditions and flow parameters. The relative importance of different forces changes with the scale going down. The viscous dissipation and the work due to expansion may not be neglected for the convection inside a microchannel; the conduction in the wall has to be considered in the calculation of the Nusselt number for microchannel. The relative importance of different heat transfer mode also varies with size. The natural convection presides over the heat transport inside a microchamber and the heat through an air gap by thermal radiation may exceed that by conduction at nanoscale. All the above mentioned variations make the heat transfer at microscale different from that at conventional scale.