Boiling Two Phase Flow in Microchannels: a Review

AbstractThe studies in boiling water in microchannel that are shaped along turbine blades has been examined since the 1970s as a means to dissipating large amounts of heat. Later, similar geometries could be found in cooling systems for computers, fusion reactors, rocket nozzles, avionics, hybrid vehicle power electronics, and space systems. This paper addresses: (a) dissipation high heat flux by two phase flow (b) how the geometry of micro channels affects their activity i.e. of circular and non-circular geometry, and (c) means to enhance this performance. It is shown that despite many hundreds of publications attempting to predict the performance of two-phase microchannel heat sinks, there are only a handful of predictive tools that can tackle broad ranges of geometrical and operating parameters or different fluids. There are a lot of complications for the development of these tools because of insufficient databases and also the drastic differences in boiling behavior of different fluids in microchannel. It is shown that cutting-edge heat transfer enhancement techniques, such as the use of nanofluids and carbon nanotube coatings, with proven merits to single-phase macrosystems, may not offer similar ad-vantages to microchannel heat sinks. The boiling flow regimes in microchannels were categorized as the confined bubble, slug flow, and annular flow depending mainly on the length of the bubble. Based on the dominant flow regimes in micro-channels, a steady slug-annular flow model is proposed to predict the pressure drop and heat transfer characteristics. As a correlation method, the homogeneous flow model with empirical correlations was applied to the boiling flow in micro-channels. In addition, this review concludes that boiling flow in microchannel can be an effective way to eliminate heat from the heat sinks