Dynamic Performance

The performances of these control structures are evaluated by introducing several large disturbances. Stable regulatory control is achieved in all three systems. 

Overall the simulation results demonstrate that all three systems can be controlled by the basic control structures developed. The DMSO solvent is superior in both steady-state economics and dynamic controllability. It also provides the capability of achieving very high purity products, which is not possible using the other two solvents. 

5% feed flow rate increase with FVF2 ratio 1250 

In Chapters, the steady-state design of a heterogeneous azeotropic distillation process for the dehydration of ethanol using benzene as a light entrainer was studied. The process consisted of two distillation columns, one decanter and two recycle streams. One of the recycle streams was successfully closed, but the second would not converge using steady-state Aspen Plus. 

In this section, we demonstrate how this second recycle loop can be successfully converged in Aspen Dynamics. A plantwide control structure is developed and its 

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Adsorption. In the design of the adsorption step of gas-phase processes, two phenomena must be considered, equiUbrium and mass transfer. Sometimes adsorption equiUbrium can be regarded as that of a single component, but mote often several components and their interactions must be accounted for. Design techniques for each phenomenon exist as well as some combined models for dynamic performance. 

C. An interesting property of these elastomers is a stable dynamic performance over a wide temperature range however, the electrical properties ate only average. 

Mathematical modeling, using digital computers, aids in performing a systems-type analysis for either the entire system or parts of it. By means of integer or linear-programming techniques, optimum systems can be identified. The dynamic performance of these can then be determined by simulation techniques. 

For field-oriented controls, a mathematical model of the machine is developed in terms of rotating field to represent its operating parameters such as /V 4, 7, and 0 and all parameters that can inlluence the performance of the machine. The actual operating quantities arc then computed in terms of rotating field and corrected to the required level through open- or closed-loop control schemes to achieve very precise speed control. To make the model similar to that lor a d.c. machine, equation (6.2) is further resolved into two components, one direct axis and the other quadrature axis, as di.sciis.sed later. Now it is possible to monitor and vary these components individually, as with a d.c. machine. With this phasor control we can now achieve a high dynamic performance and accuracy of speed control in an a.c. machine, similar to a separately excited d.c. machine. A d.c. machine provides extremely accurate speed control due to the independent controls of its field and armature currents. 

With the availability of phasor control technology, by which one can separate out the active and magnetizing components of the motor s stator current and vary them individually, it is now possible to achieve higher dynamic performance and accuracy of speed control in an a.c. machine similar to and even better than a separately excited d.c. machine. 

Unlike stirred tanks, piston flow reactors are distributed systems with one-dimensional gradients in composition and physical properties. Steady-state performance is governed by ordinary differential equations, and dynamic performance is governed by partial differential equations, albeit simple, first-order PDEs. Figure 14.6 illustrates a component balance for a differential volume element. 

The hrst apparatus for nanotribology research is the Surface Force Apparatus (SFA) invented by Tabor and Win-terton [1] in 1969, which is used to study the static and dynamic performance of lubricant him between two molecule-smooth interactions. 

M. Joona, Non-carcinogenic tire extender oils providing good dynamic performance. Rubber World, 235(4), 15, 2007. 

Features. GEMM is written in a host-independent manner and it has been run with an Apollo, a VAX, and a MicroVAX II as a host. GEMM can currently perform the following operations perform molecular dynamics, perform energy minimizations, compute the energy and forces for a structure, and update the nonbond list (nonbond lists are usually automatic for the other operations). In addition, a wide variety of I/O sequences are possible, such as what is needed for interactive modelling work. 

A simplified version of the model in Table IX, neglecting accumulation of mass and heat as well as dispersion and conduction in the gas phase, predicts dynamic performance of a laboratory S02 converter operating under periodic reversal of flow direction quite well. This is shown by Fig. 13 taken from Wu et al. (1996). Data show the temperature profiles in a 2-m bed of the Chinese S101 catalyst once a stationary cycling state is attained. One set of curves shows the temperature distribution just after switching direction and the second shows the distribution after a further 60 min. Simulated and experimental profiles are close. The surprising result is that the experimental maximum temperatures equal or exceed the simu-... 

Another instability mode of interest is due to the flow regime itself. For example, it is well known that the slug flow regime is periodic and that its occurrence in an adiabatic riser can drive a dynamic oscillation (Wallis and Hearsley, 1961). In a BWR system, one must guard against this type of instability in components such as steam separation standpipes. The design of the BWR steam separator complex is normally given a full-scale, out-of-core proof test to demonstrate that both static and dynamic performance are stable. 

Marlin Process Control Designing Processes and Control Systems for Dynamic Performance... 

Marlin, T. E. (2000) Process Control Designing Processes and Control Systems for Dynamic Performance, 2nd edition, McGraw-Hill College. 

Testing the dynamic performance of the model could not be done in such detail... 

Integral action degrades the dynamic response of a control loop. We will demonstrate this quantitatively in Chap. 10. It makes the control loop more oscillatory and moves it toward instability. But integral action is usually needed if it is desirable to have zero offset. This is another example of an engineering trade-off that must be made between dynamic performance and steadystate performance. 

Compare quantitatively by digital simulation tbc dynamic performance of the three coolers sketched below with countercurrent flow, cocurrent flow, and circulating water systems. Assume the tube and shell sides can each be represented by four perfectly mixed lumps. 

There are two purposes for cascade control (1) to eliminate the effects of some disturbances, and (2) to improve the dynamic performance of the control loop. 

This system also is a good illustration of the improvement in dynamic performance that cascade control can provide in some systems. As we will show quantitatively in Chap. 11, the closedloop time constant of the reactor temperature will be smaller when the cascade system is used than when reactor temperature sets the cooling water makeup valve directly. Therefore performance has been improved by using cascade control. 

The dynamic performance of a system can be deduced by merely observing the location of the roots of the system characteristic equation in the s plane. The time-domain specifications of time constants and damping coefficients for a closedloop system can be used directly in the Laplace domain. 

Figure 10.9 shows the time-domain performance of these PI and PID controllers. The disturbance is a step change in Qp. Note the improved dynamic performance of the PID controllers. 

We would like to compare the closedloop dynamic performance of two types of reboilers. 

Changes in steam flow are achieved by increasing or decreasing the area used for condensing steam in the reboiler. This variable-area flooded reboiler is used in some processes because it permits the use of lower-pressure steam. However, as you will show in your calculations (I hope), the dynamic performance of this configuration is distinctly poorer than direct manipulation of steam flow. 

But keep in mind that from a purely technical control performance standpoint, an analog controller can do a better job than a sampled-data controller in most applications. The process of sampling results in some loss of information we don t know what is going on in between the sampling periods. Thus there is an inherent degradation of dynamic performance that no amount of high-tech sales hype and blue smoke can change. 

A. Lozano, L. Valino, R Barreras, and R. Mustata. Fluid dynamics performance of different bipolar plates. Part II. Flow through the diffusion layer. Journal of Power Sources 179 (2008) 711-722. 

The results for this test and for the responses to disturbances in feed compositions of B and C are summarized in Table 4. A consistent trend with the servo tests was observed, in the sense that one option provides the best common choice for the control of the system under feed disturbances on the extreme components of the mixture, but a different arrangement yields a superior dynamic performance for the control task under a feed disturbance on the intermediate component. From Table 4, the lAE values indicate that the PUL system shows the best behavior for feed disturbances in the light and heavy component. However, the PUL arrangement shows the worst response when the feed disturbance in the intermediate component was considered, in which case both the Petlyuk and the PUV systems show fairly similar rejection capabilities. 

Better dynamic performance in a column—quicker restoration of sorption capacity... 

Design techniques for gas-phase adsorption range from empirical to theoretical. Methods have been developed for equilibrium, for mass transfer, and for combined dynamic performance. Approaches are available for the regeneration methods of heating, purging, steaming, and pressure swing. Several broad reviews have been published on analytical equations... 

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