Basic Flow Patterns

The analysis of tubular contactors for heat transfer with phase changes in fluid-fluid systems was shown to be heavily dependent on a proper understanding of two-phase hydrodynamics. It was shown that three basic flow patterns exist within a tube, each with a different heat-transfer mechanism. The formulation of the proper mass and energy models pinpointed three key... 

A selection of ammonia reactors is illustrated in Figures 17.21 and 17.22. These vessels incorporate particularly elaborate means for temperature regulation. The basic flow pattern is indicated in... 

In the present La Porte reactor (Figure 2) the basic flow pattern is an upflow at the center and downflow at the walls. This type of a flow pattern mixes the product with the reactants at the bottom of the reactor and causes poorer production of products. 

In practice, flow is either mass flow, or it is not. Describing the basic flow pattern as either mass flow or non-mass flow removes all grounds for confusion. It is proposed that these should be preferred expressions in the description of pattern of flow behaviour in storage containers. 

One of the problems in studying and reporting liquid-liquid flow patterns is the lack of coherence in the terminology used by various investigators for the different flow regimes. The basic flow patterns that someone can identify in microchannels with internal diameter from 0.1 to 10 mm are the following ... 

On trays with controlled vapor and liquid flow (reflux), the basic flow pattern is cross flow. In columns without controlled liquid guidance, the flow pattern is counterflow. 

There are seven basic flow patterns in horizontal flow. These are shown on the map in Fig. 10.4.5 and discussed below. 

A flow model implies certain knowledge of the basic flow pattern in the reactor. It assigns some detailed mixing characteristics to the particular RTD. For example, sketches in Figure 7 are three different flow models describing an exponential RTD in more detail. The parameters of the models are either obtained based on physical considerations or are estimated by matching model predictions with experimentally observed tracer... 

A schematic diagram of a 1-2 S T exchanger is shown in Figure 15.12. It can be seen that the basic flow patterns of the shell and tube fluids are not countercurrent. Indeed, the flow patterns of the two fluids are very complicated. However, for 1-2 S T exchangers a reasonable assunption is that the shell-side fluid flows cocurrently with the tube-side fluid in one direction and counter-currently in the other direction. Using this idealized model of the fluid flow, an analytical expression may be conputed for the F factor... 

The basic flow patterns in a heat exchanger are countercurrent How, co-cunent (parallel) flow, and cross flow, see Figure 2, For oountercuiient flow pattern, two flow streams are flowing in opposite direction to each other. For co-current flow pattern, two flow streams are flowing in the same direction. For cross flow pattern, two flow streams are flowing at an angle to each other. 

Figure 2 Basic flow patterns in heat exchangers and the corresponding beating/oooling curves.

Figure 10.5a illustrates basic flow patterns in a circular drum partway filled with a mixture of particles and rotated at intermediate speeds. The majority of particles move in solid-like rotation with the drum walls, and a thin free-surface layer flows in laminar-like shear flow over the top surface. Segregation occurs in this thin layer and, as in shaken systems, large particles typically rise to the top. 

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