时 间：2014年10月23日 13:30-15:30
Multiphase systems are ubiquitous in industrial applications aimed at the generation of products either by chemical/biological reaction or physical separation based on density, electrical charge or surface properties such as hydrophobicity. The physical processing of these multiphase systems is carried out at all scales of operation and within an endless variety of vessel shapes and ancillary devices. Underpinning each process is a complex interaction between phases involving hydrodynamic, heat and mass transport. These phenomena are in turn governed largely by the nature of the flow, and in particular whether laminar of turbulent conditions prevail. In large-scale industrial processes the flows are almost always turbulent, whilst for micro-scale operations the flow will be laminar. Each condition provides its own challenge in being able to predict (and optimise) performance in terms of operational stability and efficiency of energy utilisation.
Turbulent systems are particularly difficult to optimise, where the efficiency of utilisation of turbulent energy to enhance the transport phenomena is poor, usually less than 5 percent. The major loss of efficiency can be attributed to the non-optimal distribution of turbulent energy dissipation rate and the length scale of energetic flow structures. The length scale of turbulence and spatial distribution of energy dissipation rate, especially in the region of the interface between the phases, must be tailored to the desired application in order to achieve higher efficiency. This might sound easy but tailoring energy dissipation to the operational requirements is very difficult to achieve in practice.