Abstract
The channels employing hydraulic diameters between 200 m and 3 mm are referred to as minichannels 1 . Compared with conventional channels from the view of the heat transfer, narrow and microchannels have significant heat transfer enhancement characteristics 2,3 . With a smooth internal surface and scouring by flowing fluid, the dirt formed on the surface of the channel wall can be easily removed and the fouling problem is not as serious as the deformed channels. Moreover, heat transfer elements can be easily assembled to compact devices. Since the innovative work of Ishibashi et al. 2 , narrow channels have been adopted extensively in engineering applications, e.g., microelectronic cooling 4,5 , advanced nuclear reactor 6,7 , cryogenic, aviation, and space technology. Because the bubble size has approached the dimension of the channel, the size of the flow channel plays a critical role on the flow boiling heat transfer. This results in that the bubble in the narrow channel acts very differently from those in the non-narrow channel.