The use of system modelling tools for design and transient analysis of LRE is becoming more and more common since their accuracy is constantly improving. But for this kind of tools prediction of lm cooling e ectiveness is still a challenging problem. A lm cooling model capable of describing the bene ts of such a cooling technique, as well as the impacts on the propulsion system such as loss in performance and requirements induced on other subsystems, can support the preliminary design of LRE systems. EcosimPro is an object oriented tool capable of modelling various kinds of dynamic systems. The model described within this paper is implemented alongside ESPSS the propulsion system library compatible with EcosimPro. This paper covers a Quasi 2-D integral formulation to study the developed ow eld of a lm wall jet in combustion chambers. With this approach it is possible to have a fast prediction of the evolution in space and time of both coolant and wall temperature distribution therefore also of the lm cooling e ectiveness. A new model is here presented: a \layered model" based on the assumption that the mixing zone does not a ect the lm and mainstream ows but it is a result of their interaction. The geometry of the developed ow eld is based on the one carried out by Simon and it accounts for the core, mixing and lm regions. The governing equations already present in the original combustion chamber model are used as a starting point. The implementation here described can easily be embedded in an unsteady propulsion system analysis for simulating the its transient phases and steady state operation points. The code exibility allows for using the same model also for performance analysis in steady-state, and for o -design studies. First validation results are given here, in particular a DLR H2/O2 combustion chamber lm cooling test campaign has been taken as reference case for validation purposes.