Dynamic Model of an Organic Rankine Cycle System. Part II – The full Model: Description and Validation.

In order to gather a deep understanding on the way Organic Rankine Cycle (ORC) systems behave, and to assess new system arrangements and geometries, a detailed dynamic model of the plant has been developed using the Simulink® models of each subcomponent described in ‘Part I’ of this paper. The different components have been assembled together according to the typical ORC lay- out. Two further state determined components (drums) are introduced in order to calculate the dynamic behaviour of the pressure in the evaporator and condenser and to define all the state variables required by the whole model. The cause-effect approach used to create the complete model leads to alternating not state determined and state determined elements, favouring the numerical stability of the solution, since algebraic loops are avoided. A set of simulation results is proposed assuming the ORC working fluid to be R123, diathermic oil used as heat transfer medium and water to cool the condenser.