moeslerfred

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These are questions asked by moeslerfred

Hello all,

 

I've been trying to recreate a simulation from a textbook, and the system of equations needs starting values to solve correctly. I've supplied all of the information that another program uses, and the degrees of freedom make sense, and I can even solve it with fsolve. However, as I try to supply the starting_values to the fsolve, I get the error "fsolve cannot solve on starting_values(...". Any help appreciated. I'm attaching the file...

 

Thanks in advance,

 

Fred

 

Gurus...

Any idea why I get the "Parts of the expression are ambiguous. Please select one of the suggested meanings." alert on some of this code, but not other parts? I want them all to be "table assignments" not "function definitions" (per my options in the window). I would really like to not have it keep asking me the question on each run, so is there a way for me to be more specific? Thanks in advance!

Fred

deq(i,XMethanol):=M*diff(X[i](t),t)=(L*(X[i-1](t)-X[i](t))+V*(Y[i+1](t)-Y[i](t)));

deq(i,XWater):=XW[i](t)=1-X[i](t);

Hello all!

I'm am trying to replicate a Berkeley MADONNA problem in MAPLE, and I'm having problems. For those with the great book "Chemical Engineering Dynamics" by Ingham, Dunn, Heinzle, Prevosil, Snape, it's the BUBBLE program.

Hi Folks, I have to believe this is an easy one, but it stumped me anyway. I'm trying to plot an ideal binary VLE curve for two components, and I have equations that describe both my x term and my y term as a function of temperature and pressure. Using the normal plot command, I can get x and y vs. T (if I specify pressure), but how do I get x vs. y (specifying pressure) and either plot T on a second Y axis or ignore it. Thanks in advance. I have my simple worksheet available... Fred Vie
Hello again,

I have another simple question. I have a dynamic simulation that I've put together, and I'm solving the system of equations using "dsolve(odeset,numeric)", and all is going well there. However, I added a "product totalizer" that integrates my exit flow with the command:

Ptotal := ptot(t) = int(Fexit, t)

And that works well if the Fexit is a fixed number in my simulation. However, I wanted to change the Fexit variable at certain points in time, so I used the piecewise command:

Fexit := piecewise(`and`(t >= 25, t < 30), 2, `and`(t >= 35, t < 34), 2, 0)

The simulation looks fine with the piecewise logic, but the integration above does not. It looks like the integration resets itself to zero where the steps occur. So my questions are:
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