ABSTRACT
Since the 1980s, a large number of microdevices such as microbiochips, micropumps, micromotors, microfuel cells, and microheat exchangers are used widely. This chapter provides a better understanding of heat transfer and fluid flow for gases in microchannels based on several experimental, analytical, and numerical results of many researches. For the engineering applications and to design microheat exchangers, the predictions of the heat transfer coefficient and the friction factor are important. As the use of microchannels becomes a suitable solution for high flux cooling problem, the fabrication and design technology of microchannels have improved. Many different particle materials are used for nanofluid preparation. Nanofluid is envisioned to describe a fluid in which nanometer-sized particles are suspended in conventional heat transfer basic fluids. A microconvection effect, which is due to the fluid mixing around nanoparticles, is proposed to be important. The high thermal conductivity nanoparticles suspended in the base fluid, which has a low thermal conductivity, remarkably increase thermal conductivity of nanofluids.
