The goal is to predict the system behaviour.
The sun-absorber heating the water that circulate spontanously to a container taht holding the warming water.
The container and the pipes are isolated from open air. The absorber build of isolating box cith glass cover toward the sun.
Inside the box there is a copper pipe labyrinth uncovered toward the sun through the glass.
It looks like that it should be an external flow simulation with thermal conduction through solids.
All direct and indirect radiation should be consideredalso.
Is there any example that dealt with such a problem?
Yes, you can do this with Flow Simulation. It is best handled with Flow Sim 2011 with both of the new modules, Electronics (for orthotropic PCB definitions, joule heating, thermal interface materials) and HVAC (for adavanced radiaiton modeling allowing for semi-transparent materials with spectrum dependency). These are based on the FloTHERM and FloVENT technologies from what was Flomerics but is now Mentor Graphics.
Here is a sample of a real world solution: http://www.mentor.com/products/mechanical/success/schuco-international/fileContent/Flomerics_-_Schueco_case_history-7_11_08__2_.pdf