Numerical Simulation of a Scroll Expander for Use in a Rankine Cycle

This paper presents two simulation models of scroll expanders for use in heat recovery Rankine cycle applications: a detailed reference model and a simplified model. The reference model associates a detailed geometrical description of the expander to a thermodynamic modeling of the expansion process in the machine. Due to large computational effort, the reference model is not appropriate for simulation of the entire Rankine cycle system. The paper shows how a simplified model can be built from the reference model. This model involves a limited number of parameters, which describe the main features of the machine. An experimental study is carried out on a prototype of Rankine cycle working with HCFC-123. Based on detailed measurements, the validation of both models is conducted. It is found that both models are able to predict the mass flow rate, the delivered shaft power and the discharge temperature with a good accuracy.