Running the Simulation

The flowsheet is fully specifled at this point. AU the read buttons are blue, and we are ready to run the simulation. 

we want to look at the compositions of the product streams leaving the column to see if they satisfy their desired purities. We assume that the specification of the heavy impurity in the distillate (isobutane = rC4) is 2mol% and that of the light impurity in the bottoms (propane = C3) is 1 mol%. To look at the properties of these streams, we open the Cl block in the Data Browser window and click the item Stream Results, which is at the very bottom of the list. 

The specifications for product impurities are 1 mol% propane in the bottoms and 2 mol% isobutane in the distillate. To achieve these precise specifications, Aspen Plus uses the Design SpecA ary function. A desired value of some controlled variable is specified. 

In the example under study, we want to find the values of distillate flow rate and reflux ratio that drive the distillate composition to 2 mol% isobutane and the bottoms composition to 1 mol% propane. 

Another possible comphcation is multiplicity. Because the equations are nonlinear, there may be multiple solutions. Sometimes, the program will converge to one solution, and at other times, it will converge to another solution, depending on the initial conditions. 

Block Cl (RadFrac) Custom Stream Results - Data Browser 

D Interface Softies D Efnclencies and l-ETP a Transfer Coefficient n Dimensionless Numbers a EO Variables O EO Input O Spec Groups D Ports 

7 Using Design Spec/Vary Function in RadFrac 

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Due to the noncrystalline, nonequilibrium nature of polymers, a statistical mechanical description is rigorously most correct. Thus, simply hnding a minimum-energy conformation and computing properties is not generally suf-hcient. It is usually necessary to compute ensemble averages, even of molecular properties. The additional work needed on the part of both the researcher to set up the simulation and the computer to run the simulation must be considered. When possible, it is advisable to use group additivity or analytic estimation methods. 

Eq. 3 gives two examples of energy functions which either block one site (in the first case) or two sites (in the second case) in the ground state of each bond. If one runs the simulation at high density the situation occurs where it is impossible for all bonds to reach the ground state. This is called frustration. 

Run the simulation 1000 iterations, and then adjust the run time to observe a well-formed interface. 

Run the simulation for 1000 iterations. Average, over the last 200 iterations, the count of S cells in each of the five rows next to the border cells. 

Example 8.3 above showed that equilibrium was achieved when we started with reactants A and B, but what happens when we approach this from the opposite direction, i.e., starting from the product side We can test this by starting with [A]o = [B]o = 0 cells, and [C]o = [D]o = 500 cells. Run the simulation just as in Example 8.3, but with these changed initial values. Is equilibrium achieved from the product direction If so, what is the equilibrium constant Kgq (Include the uncertainty in Kgq.)... 

Run the simulation for a range of residence times. When are the steady states reached ... 

Calculate the steady state for n = 1 by hand. Run the simulation and compare. Change Cao for this case and run. Compare the effects on Cai and Cap... 

The file that is being read is displayed on the screen. The user can then decide whether to run the simulation as it stands or modify the model. Only one model can be operational at any one time. 

An output file can be stored and used for further applications, such as graphing with special graphing software. This done by reading the file as usual and before running the simulation give the command... 

To run the simulation, we decouple acetate from carbonate, and sulfide from sulfate, and suppress the iron sulfide minerals pyrite and troilite (FeS), which are more stable than mackinawite, but unlikely to form. We set the fluid composition, including an amount of HS small enough to avoid significantly supersaturating mackinawite, and define the rate law for the sulfate reducers. The procedure in REACT is... 

We take the results of a series of experiments conducted by Morgan (1967, his Fig. 23) at pH 9, 9.3, and 9.5. He used an initial Mn11 concentration of 4.5 x 10-4 molar, a carbonate concentration of 1.6 x 10-3 molar, and an oxygen partial pressure of 1 atm. We can figure an approximate value for the rate constant l<+ from oxidation rate at the end of the experiment, when the mass of catalyst is known from the depletion of Mn11, then estimate the initial catalyst mass from that value and the oxidation rate at the onset of reaction. Running the simulation, we can refine the two numbers until prediction matches observation. 

The Screenshot Guide in the Appendix provides a full explanation for the major features of BERKELEY-MADONNA and the mechanics of running the simulation examples. The Help menu of MADONNA should also be consulted. 

Run the simulation under disc-bursting conditions for both with and without... 

Run the simulation under the following conditions (a) Dry conditions time 0 to day 2, (b) spraying day 2 to day 5 and (c) rain day 8 to day 13. See how the concentrations of adsorbed and unadsorbed solute vary with time and depth. Vary the time of spraying to before, during and after rainfall. 

Table 9 presents a summary of the variables in a typical real-time run. The raw measurements are initially used to run the simulation with PROCESS (therefore, only the simulation switch is activated). The first column of the table shows the raw measurements, and the second indicates the results from PROCESS. It is clear that the results from the simulation are not in agreement with the measurements.1 It can be seen from Table 9 that the measurements of the condenser and reboiler duties are quite different from the simulation results. This suggests that there are gross errors in those measurements. The gross error detection and data reconciliation modules are then activated. The third, fourth, and fifth columns show the rectified and reconciled data. 

Data from PSpice can easily be exported to other programs by copying the traces displayed by Probe. To copy data from PSpice, you must run the simulation, display the results using Probe, and then copy and paste the data from Probe into MS Excel or another spreadsheet program. Once the data is in your spreadsheet, you can manipulate it or export it to other programs such as MATLAB by using comma separated values (.CSV) formatted data files. 

S0LUT10I1 Set up a bias point analysis, run the simulation, and then display the voltages on the schematic. 

The Temperature (Sweep) allows us to specify a single temperature or a list of temperatures. If you specify a list of temperatures, the simulation will be run several times, once for each temperature you place in the list. We only need to run the simulation once, so fill in the dialog box as shown ... 

Select PSpice and then Run to run the simulation and then display the diode current and voltage on the schematic ... 

Click the OK button to accept the settings. We can now run the simulation. Select PSpice and then Run from the Capture menus or press the F11 key. PSpice will run ... 

Click the OK button to accept the settings and return to the schematic. Run the simulation and then display the results with Probe. Generate a plot of Hre versus Ic. Three curves will be shown ... 

Run the simulation and the display the results with Probe. To show that the circuit keeps Ic and VCE relatively constant versus temperature, we will plot Ic and VCE versus temperature ... 

When we run the simulation and plot the capacitor current, we obtain the plot ... 

The time constant for our circuit is T = RyCx = 1 /JB 1 k 2 = lms. After five time constants the circuit should reach steady state, so we will run the simulation for five time constants. Remember that the switch closes at 1 ms. To let the capacitor transient run for 5 ms we need a total simulation time of 6 ms. We would like to see at least 500 points during the capacitor transient, so set the Maximum Step Size to 5 ms/500 or 0.01 ms. ... 

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