Research on Flow Boling Heat Transfer Characteristics of Two-Phase Flow in Micro-Channels

To explore the mechanism of flow boiling bubble dynamics in micro-channel, a set experiment platform was established with width of 0.5mm, 1.0mm, 1.5mm, 2.0mm, focusing on heat transfer characteristics, pressure loss and two-phase flow pattern identification. Bubble flow, restricted bubble flow and dry area were observed in all four channels. The appearance of flow pattern was related to flow rate and channel width. Under the condition of the same channel width, the initial heat flux of subcooled boiling gradually increased with the increasing of flow rate, and this change trend was close to the linear trend. Under the same flow rate, the initial heat flux of subcooled boiling increased with the decreasing of channel width, which was due to the faster flow rate of working medium in the narrow channel, resulting in the shortening of heating time. The increasing of bubble generation frequency directly led to the increase of wall heat transfer coefficient and the decrease of bubble separation diameter. With mathematical analysis, it could be seen that under the condition of small flow, the reduction of channel size led to the reduction of total wall heat transfer coefficient. In this condition, the reduction of channel size could not enhance heat transfer.With the increasing volume flow rate, the range of hydrodynamic control area became larger and the index became smaller. When the flow rate was large enough, the total heat transfer coefficient increased greatly with the decreasing of channel size. The theoretical values were in good agreement with the experimental data