Flows in channels and pipes are often used in the chemical and mechanical engineering applications. In the past, several studies of micro-channels have focused on the mixture characteristics in the C-shaped and the T-shaped with complex flow field of temperature gradient, velocity vector, and pressure change. However, the purpose of this study is to research the flow transport phenomenon by employing different angles to the converging and diverging area in X-shaped micro-channels. As the working fluid, water is injected to micro-channel at different mass flow rate. Over a wide range of flow condition, 0.88 < Re < 661, in X-shaped micro-channels, the mixture performances of numerical simulation, flow visualization, and temperature distribution remain the same. At the same mass flow rate, the bigger the angle, the lower the pressure drops and the slower the low velocity becomes. Therefore, it is the biggest angle that has the best mixture of performance and needs the shortest distance in the mixing area. It is clear that the angle plays an important role in both converging and diverging area in the X-shaped micro-channels.

The phenomenon of nature convection boiling on the outer surface of a heated hemispherical vessel surrounded by a thermal insulation structure was investigated experimentally. The objectives were to observe the behavior of the boiling-induced two-phase motion in the annular gap between the vessel and the insulation structure and to determine the flow effect on the rate of boiling. High-speed photographic records revealed the presence of violent cyclic ejection of the vapor masses generated by boiling on the vessel outer surface which resulted in a buoyancy-driven, upward, concurrent two-phase flow through the channel. When boiling was taking place at high heat flux levels, the flow was found to be three-dimensional with swirl formation. Measurements of the local boiling heat fluxes and the local wall superheats were made under steady-state boiling conditions covering the entire range of nucleate boiling with special emphasis on the high-heat-flux regime.