Transitioning to cleaner sources of energy and improving the efficiency of power generators are crucial in combating global warming. Organic Rankine Cycles (ORC) when coupled to heat emitting power generators allows for waste heat recovery; thus increasing the engine overall efficiency and reducing atmospheric pollution. Additionally, implementing engine life cycle management is another way to improve the overall efficiency of power systems. The condition monitoring tool that has been developed in this research comprises a true model and a surrogate model. The true and surrogate models describe the real and ideal state of the ORC respectively and a comparison of both models reveals the health status of the ORC. The research has succeeded in creating a tool that is capable of performing accurate diagnostics in the shortest possible time and also in the development of a simple but unique method to derive thermodynamic relations for two phase fluids.