Issues with the calculator in ASPEN. .
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I have a question for everyone. Compressor inlet and outlet streams 1 and 2; in stream 1, the mass flow rate is a set value while the density is a calculated value. The normal set range for mass flow rate is wide enough to enable convergence in various processes. I want the calculator to make the density a function of the mass flow rate setting, no matter what that value is. Is this possible? Density can be determined based on the current pressure and temperature of the logistics 1. I tried it today by setting both the mass flow rate and density as output variables, in the order last; this allowed for an accurate calculation of the mass flow rate for Process 1. However, the mass flow rate for Process 2 remained at the value set for Process 1. This results in a non-conservation of mass flow rate. How can this problem be solved? This is done as a function of mass flow rate and density in order to define the volume flow rate; we want the volume flow rate of stream 1 to be a function of other variables in the process. Since there is no entry for volume flow rate in the stream variables, is this the only way to solve it?
This approach is wrong from the start; you set it to \"last\" merely so that the traffic is overwritten last. Any change will inevitably lead to issues with quality imbalance.
I really don’t have much experience with FORTRAN. Let me talk about the parts where I was successful: there are two processes within the loop, which result in a temperature difference of 2; this was achieved using LAST in FORTRAN. It seems to be a bug that VOLUME FLOW is not available in ASPEN’s STREAM VAR option (only the liquid phase is available, with no option for the gas phase); it can be set in STREAM, but not in STREAM VAR. What I had in mind was to define a function relationship for volumetric flow rate, but since that’s not possible, mass flow rate and density have to be used as substitutes. However, one of these two values is a preset value, while the other is a calculated value; both are part of the same process, which is still a process that involves only fixed parameters. It becomes quite difficult then. Do you have any good solutions? We discussed ProII yesterday; it allows for the acquisition of the VOLUME FLOW variable, which is very convenient. Why can’t ASPEN do this?
It seems to be a bug that VOLUME FLOW is not available in ASPEN’s STREAM VAR option (only the liquid phase is available, with no option for the gas phase); it can be set in STREAM, but not in STREAM VAR. It’s explained very clearly in this help section – why it’s not there. The fact that it was successfully created using Fortran and the LAST routine does not mean it is meaningful in practice. It’s just that there’s no problem with the algorithm.