CAPE-OPEN

You are creating unit operations that calculate heat loss?

The short answer in this case is: yes, create an input parameter, connect to a virtual information stream.

The somewhat longer answer: I get the impression that the type of calculation you want to do is some sort of post-processing step that relates to the entire flowsheet solution. To accomplish this, you are inserting unit operations that do parts of your overall calculations. Correct?

A way of dealing with such kind of systems has been proposed (that is, the proposal is undergoing further discussion and approval as official part of the CAPE-OPEN interface standard set in the Method & Tools Special Interest Group, the M&T SIG). This is called flowsheet monitoring. This concept is explained here:

• * http://cocosimulator.org/downloads/AICh ... Summey.pdf
  * http://cocosimulator.org/downloads/Flow ... E_2008.pdf
  * http://cocosimulator.org/down.php?dl=Su ... ECCE-8.pdf
  * Barrett, W.M., van Baten, J.M. and Martin, T., Implementation of the waste reduction (WAR) algorithm utilizing flowsheet monitoring, Computers and Chemical Engineering 35 (2011) 2680-2686

A prototype of monitoring is available in COFE, and can be used. However, to use it, some programming is required. Let me know if you would like further information on this.

Jasper
Thanks for providing the links. I can see possibilities for flowsheet monitoring, I will certainly start to try the WAR add in.

My current goal is to model the steam usage in a cane sugar factory, there will be at least 50 items of plant where heat loss is significant.
Would be good if each individual item was modelled and there was some Excel VBA code that changed the ambient temperature for each item.
What would the VBA code be to change the value for an information stream called AmbientT?
All my trials using Call and .SetProp have been unsuccessful.

You can look at the VBA code that obtains parameter values (note that the VBA code that comes with COFE.xlt is unprotected, you can just open the VBA editor and see it, and edit it). You can use the same code for setting parameter values.

I tried restarting, uninstalling and then reinstalling but it doesn't work, would anyone have a tutorial please?

Can you elaborate on what does not work? Are you not able to start a new Excel document based on COFE.xlt? Or when you do there is a problem with it?

To be clear the Flowsheet Monitoring interface specification has been published by CO-LaN. What is missing is an implementation in COFE. The WAR algorithm by US EPA is a Flowsheet Monitoring Component and is a tool openly available for use to evaluate chemical processes in eight environmental impact categories. You are looking at something slightly different, but that goes along also the Flowsheet Monitoring approach. How to access many different objects in a Flowsheet to extract from them some pieces of information and to combine all these pieces of information to get a result. What you are considering is an approach that was developed at University of Trieste using a CAPE-OPEN Unit Operation and presented at the CAPE-OPEN 2007 Annual Meeting. Cumbersome as a solution.
You may want to look at the scenarios of use described in the Flowsheet Monitoring interface specification (see section 3.7). CO-LaN would be happy to have your feedback on how Flowsheet Monitoring as per the CAPE-OPEN standard could fit your needs.

The monitoring implementation in COFE is there - but using a prototype set of the interfaces - the published set of interfaces is pending its actual publication, which should be any day now.