Chapter 1 – Measurement techniques for local and global fluid dynamic quantities in two and three phase systems

Publisher Summary This chapter discusses the measurement techniques for local and global fluid dynamic quantities in two and three phase systems. The emphasis is on techniques that can be utilized under conditions of interest in practice, such as high pressure and temperature and large solids holdup. Gas holdup and solids concentration measurement methods can be classified into two categories: those providing an overall or global measurement and those that provide a local or point measurement. The global measuring techniques yield information on the line, area or volume averaged gas or solids holdup. The volume averaged or the overall fractional holdup of a phase is defined as the fraction of the volume of the multiphase dispersion that is occupied by that phase. In general, the measurement of the overall holdup is relatively simple. It provides information regarding what fraction of the system volume is occupied by the phase of interest. Measurement of the phase fraction at a point is in itself not of much use unless the distribution of such point measurements is obtained in space. The knowledge of the volume occupied by the phase of interest as well as the volume of the expanded multiphase dispersion suffices for the needed calculation. For three phase systems no single method can provide both the solids and overall gas holdup. The expansion of solids (when larger solid particles are used) because of the fluidization by either liquid or gas can be measured in a manner similar to the bed expansion method.