What i had in mind (still need refinements, take note):
- Place elements in a GUI or a XML input file
- Solve the flow rate (by correlating backpressure vx flow data of each element)
- then solve the heat with flow / heat data
- finally with add up heat transfer coefficients and solve the temperature
Adding tubing is quite easy, it will be treated as strict equivalent height. Actually, one will just have to input approx. total length, # of elbows, tees and other fittings. All fittings will be treated has having a flat backpressure vs flow response (= constant backpressure) but if anyone has more data about this, it will be no problem.
Since87: i am a software engineer, that helps

XML is just a text format. The good thing is it's universal. You can export XML files from Excel for example. And parsing XML files in Java is about my day job.
For each component i'll make a 'black box' object model in Java.
I envision releasing first the XML file format so ppl can contribute easily, by adding components. You'll just copy the file in the appropriate directory, launch the software and you'll be able to include it in a sim run.
All i have to do then is to code the simulator itself (rather quick) and the GUI (rather long)
I'll get back there to make sure my maths are all right.