Flow Patterns and Operating Regimes

For batch systems a stirred vessel or loop reactor with an in-line mixer is used. Where plug flow is required, for long residence times a cascade of stirred vessels or loop reactors is commonly used, and for short residence times the choice will often be a static mixer or ejectors. For continuous flow systems requiring an approach to backmixed flow, stirred vessels or loop reactors are indicated. 

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Flows that develop a state that depends only on the local flow quantities, such as the local value of the mean velocity and the flow resistance, are said to be self-similar or self-preserving. This state of flow is present in the turbulent flow regime when sufficiently high Reynolds numbers are achieved. A majority of industrial combustion systems operate in this flow regime. When the scale model and prototype are both operating in the selfsimilar flow regime, they will manifest the same flow patterns and pressure drop coefficient despite different absolute local flow quantities. 

As shown in Fig. 8.6, several typical flow patterns can be found in the monolith channels, depending on gas-liquid ratio, flow rates, viscosity, surface tension, and channel diameter. All of these flow patterns show a very low static hold-up, but only two are regular and allow stable operation the so-called Taylor-flow and the film-flow regime. 

Pumping changes the underground pressure regime, and fluids begin to move in new directions. Thus information that was not collected at the very beginning of a well operation is lost and may not be obtained later. The hydrologic evolution of flow patterns induced by human activity in exploited water systems can be established by frequent comparisons to the initial situation (section 7.5). 

The flow regimes in capillaries have been investigated extensively, and the reported results provide a good basis for imderstanding the hydrodynamics of multiphase operation of monoliths. Figure 11 shows the well-known two-phase flow patterns observed in tubes (16,17). 

The primary glow discharge reactor in this configuration could be used for plasma coating in a low-pressure regime, in principle however, in consideration of flow pattern in such a multiple shelves reactor and electrical field in multiple electrodes, it is difficult to achieve uniform coatings in such a mode of operation. 

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