Nano-sized calcium carbonate with the diameter between 20 to 30nm was prepared using the rotating packed bed with homocentric ring discs as the filing,and the factors which influence the production of the nano-sized calcium carbonate were investigated.

In this paper,the transition from churn flow to annular flow for upward gas-liquid in vertical concentric annulus is studied and a transition model is developed by considering the structural feature of the concentric annulus and the flow characteristics for churn and annular flows in the concentric annulus.

The transition from slug flow to churn flow for upward gas liquid in vertical concentric annulus is studied and a transition model is developed considering the structural feature of the concentric annulus and the flow characteristics for slug and churn flow in the concentric annulus.

The concentric ring slit flow theory of fluid mechanics ,which is flow rate and pressure difference formula ,is usually used for analysis, research and engineering calculation in hydraulics problems, but the formula origin in general references which is based on the ordinary analysis of parallel plate (plain) pressure flow theory is not refined mathematics analysis .