OpenFOAM has two solvers (chtMultiRegionFoam and chtMultiRegionSimpleFoam ) for simulation of heat transfer across different materials. When a solver has the keyword simple in it’s name in OpenFOAM, it means it uses SIMPLE algorithm for pressure-velocity decouple, Moreover, it represent it is an steady solver.
I wrote the first edition of OpenFOAM book around 5 years ago in Persian. The book was based on OpenFOAM-1.6. The aim of that book was to shorten the process of OpenFOAM learning. It was 5 chapters that included some simple and introductory examples. It covered different parts of OpenFOAM utilities, solvers and programming.