Validated dynamic model of an organic Rankine cycle (ORC) for waste heat recovery in a diesel truck

Abstract

Recovering waste heat from the exhaust gas of diesel trucks using an organic Rankine cycle (ORC) is considered a promising option to reduce emissions and fuel consumption. As the system operates under highly transient boundary conditions, the development of a predictive model accounting for its dynamic behavior is of high relevance. In this contribution, such a model is presented. Evaporator and condenser are modeled using a dynamic moving boundary model, while pump and turbine are represented with pseudo-steady state models, as dynamics are assumed to be negligible here. A fundamental thermodynamic equation of state based on the free Helmholtz energy is implemented for the working fluid ethanol. As unknown parameters, e.g., in heat transfer, occur, a parameter estimation is conducted with the use of measurement data. The model is then validated using different experimental data. It is able to capture the system dynamics well both qualitatively and quantitatively, e.g., the mean relative temperature deviations are all smaller than 4%.