Information-flow diagram

The lines and arrows connecting the blocks show the flow of information from one subprogram to the next. An information flow diagram is a form of directed graph (a diagraph). 

The calculation topology defined by the information diagram is transformed into a numerical form suitable for input into the computer, usually as a matrix. 

Note (1) Modules have been added to represent mixing and separation tees. 

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If the number of equations is equal to the number of unknowns, the model is complete and a solution can be obtained. The easiest way to demonstrate this is via an information flow diagram as shown in Fig. 1.4. 

Figure 1.4. Information flow diagram for the complex reaction model equations.

It is seen that all the variables, required for the solution of any one equation block are obtained as results from other blocks. The information flow diagram thus emphasises the complex interrelationship of this very simple problem. 

VI. For additional insight with complex problems, construct an information flow diagram... 

Information flow diagrams can be useful in understanding complex interactions (Franks, 1967). They help to identify missing relationships and provide a graphical aid to a full understanding of system interaction. An example of such a diagram is shown in Fig. 1.4. 

Energy balances are needed whenever temperature changes are important, as caused by reaction heating effects or by cooling and heating for temperature control. For example, such a balance is needed when the heat of reaction causes a change in reactor temperature. This is seen in the information flow diagram for a non-isothermal continuous reactor as shown in Fig. 1.19. 

Figure 1.19. Information flow diagram for modelling a non-isothermal, chemical reactor, with simultaneous mass and energy balances.

The information flow diagram, for a non-isothermal, continuous-flow reactor, in Fig. 1.19, shown previously in Sec. 1.2.5, illustrates the close interlinking and highly interactive nature of the total mass balance, component mass balance, energy balance, rate equation, Arrhenius equation and flow effects F. This close interrelationship often brings about highly complex dynamic behaviour in chemical reactors. 

The implicit loop nature of the calculation is illustrated, by the information flow diagram, shown in Fig. 3.6. In this, Tj is needed in order to calculate Pj,... 

Since the steam in the jacket is saturated, the temperature-density relationship, of course, follows a unique form. This direct method of calculation is illustrated by the information flow diagram of Fig. 3.7. 

Fig. 3.19 represents an information flow diagram for the above control scheme. 

The information flow diagram. Fig. 3.31, for this system shows the two component mass balance relations to be linked by the equilibrium and transfer rate relationships. 

If equilibrium between the two phases is assumed, the above balance equation can be solved in conjunction with the equilibrium relationship, as shown by Franks (1967) and as indicated in the information flow diagram. Fig. 3.35. 

Under normal circumstances, the use of a characteristic velocity equation of the type shown above can cause difficulties in computation, owing to the existence of an implicit algebraic loop, which must be solved, at every integration step length. In this the appropriate value of L or G satisfying the value of h generated in the differential mass balance equation, must be found as shown in the information flow diagram of Fig. 3.54. 

An information flow diagram showing the iteration for 6 is shown in Fig. 3.63. Examples of multicomponent equilibria with activity coefficients are given in the simulation examples BUBBLE and STEAM. 

The general solution approach, to this type of problem, is illustrated by the information flow diagram, shown in Fig. 4.8. The integration thus starts with the initial values at Z = 0, and proceeds with the calculation of r, along the length of the reactor, using the computer updated values of T and Ca, which are also produced as outputs. 

The model equations, I to V above, provide the basis for solution, for this case of constant temperature and pressure with a molar change owing to chemical reaction. This is illustrated by the information flow diagram. Fig. 4.10. The step-by-step calculation procedure is as follows ... 

Figure 4.10. Information flow diagram for a gas-phase tubular reactor with molar change.

Figure 4.5. (a) Process flow diagram hydrogenation of nitrobenzene to aniline (b) Information flow diagram... 

In an information flow diagram, such as that shown in Figure 4.5b, each block represents a calculation module that is, the set of equations that relate the outlet stream component flows to the inlet flows. The basic function of most chemical processing units (unit operations) is to divide the inlet flow of a component between two or more outlet... 

The block shown in Figure 4.6 represents any unit in an information flow diagram, and shows the nomenclature that will be used in setting up the material balance equations. 

The outlet streams from a unit can feed forward to other units, or backward (recycle). An information flow diagram for a process consisting of three units, with two recycle streams is shown in Figure 4.7. The nomenclature defined in Figure 4.6 is used to show the stream flows. 

The process flow diagram is shown in Figure 4.11. This diagram is simplified and drawn as an information flow diagram in Figure 4.12. Only those process units in which there is a difference in composition between the inlet and outlet streams are shown. The... 

Using the data given below, draw an information flow diagram of the process and calculate the process stream flow-rates and compositions for the production of 600 t/d ammonia. Use either the Nagiev split fraction method, with any suitable spreadsheet or manual calculations. 

Fig. 3.27 Information flow diagram for simple batch extraction.

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