Change value of stream mass flow in HYSYS using matlab

I want to set the value of stream 'PFD136' to flow_136. Seems I have a syntax error. Please help

Answer 1

[Umar]

Hi Alma,

It seems like you are encountering an issue while trying to set the value of stream 'PFD136' to 'flow_136'. The error message "Invoke error. Dispatch exception. Access is denied" indicates that there might be a permission or authorization problem with the operation you are trying to perform.

To troubleshoot this issue, you can start by checking the syntax of your code or command to ensure that it is correctly formatted and follows the expected structure for setting values to streams. Make sure that you have the necessary permissions and access rights to modify the stream 'PFD136' in your system.

If the syntax error persists, you may need to review the documentation or guidelines provided by the platform or software you are using to interact with streams and data sources.

Additionally, consider reaching out to technical support or consulting online resources for further assistance in resolving this error. It's important to address any access restrictions or authentication issues that may be causing the denial of access to perform the desired operation.

By verifying your permissions, revising the syntax of your code, and seeking help from relevant resources, you can work towards resolving this problem and successfully setting the value of stream 'PFD136' to 'flow_136'.

[Alma Maria]

Yes! The problem was in HYSYS with a recycle loop that forwarded molar instead of mass flow into stream PFD136. Sinse the mass flow of PFD136 was specified by the system I was not allowed to change it through Matlab.

Switching from specifying molar flow to mass flow solved the issue!

Answer 2

[Andreas Goser]

Could it be you want to write 'kg/s' instead of "kg/s"?

[Umar]

Hi Andreas, That was a good catch. Appreciate your input. Let’s wait for Alma’s feedback.

[Attaf Ahmed]

1. Dear All
2. I got similar issue with aspen plus 15 in fact i want to select the best compostion of mixture of 6 components which will give the lowest temp after cooling and expansion
3. in the begining i want to test matlab 2025a and aspen v15 but the matlab can run aspen but he cannot replace the mass flow by showing AE_UNDERSPEC issue
4. pressure and temperature can be changed by matlab but mass flow rate cannot

thank you inadvance for your help and support

[Umar]

Hi @Attaf, thanks for sharing your experience. It sounds like a bit of a tricky issue with MATLAB and Aspen Plus integration! After digging through online documentations, I was able to find out that The AE_UNDERSPEC error usually happens when Aspen Plus can't find all the info it needs to complete the simulation, and in your case, it seems like the mass flow rate is the one that’s being left out.

Since you're able to change pressure and temperature but not the mass flow rate, it’s likely that the mass flow is defined as an output or tied to another part of the simulation that MATLAB isn’t able to control directly. A quick fix could be to double-check how the mass flow rate is defined in your Aspen Plus flowsheet. It needs to be an input variable for MATLAB to be able to adjust it, not an output.

Also, make sure that the connections between MATLAB and Aspen Plus are set up correctly. You might want to test controlling simpler parameters first (like temperature or pressure) to ensure everything’s linked up properly before tackling the more complex ones.

I’d also suggest looking into whether there are any additional constraints or settings in Aspen that could be interfering with MATLAB’s ability to modify the mass flow. Sometimes, Aspen automatically locks certain parameters based on the system configuration, so that might be a good place to start.

Hopefully, that helps! Let me know how it goes.