We worked on the simulation of a cooling system simulation for design/optimization purposes.
We tried the "Kuli" software for the same purpose, but soon it cameout that written in house simulation code was more reasuble, manageble, and simple.
It was written in Matlab/Simulink, and from those host program we borrow the time solution and sevral built in functions (n-dimensional interpolation, data analisys and so on).
At the end we bridged the more expensive CFD codes writing a finite difference model of radiator components code which uses and couples with CFD code (Star CCM+).
Feel free to ask for more!
Regards,
mastro