Developing ORC engineering simulator (ORCES) to investigate the working fluid mass flow rate control strategy and simulate long-time operation

Abstract

Based on the experimental data of R245fa, R123 and their mixtures, the engineering simulator for a 3 kW organic Rankine cycle (ORC) test rig by 3KeyMASTER (3KM) simulation platform is constructed. The simulation behaviors of the pump and expander are examined and validated with the experimental results, while the effect of mass flow rate is addressed. Meanwhile, human machine interface (HMI) monitor system and superheat control system are developed. The system behaviors at three different control strategies are discussed, while a further investigation of long-time operation test under varying heat source temperature and environmental temperature is explored. Results demonstrated that an optimum operation condition could be obtained for the proposed superheat control strategy. The VFD control strategy is preferred for small-scale ORC. The superheat control methodology is a good approach to adjust the working mass flow rate to reflect the heat source and sink temperature variation. The best operation is 0.67R245fa/0.33R123 at environmental temperature of 293 K with the net power of 1.78 kW and system efficiency of 5.14%. It indicates that the organic Rankine cycle engineering simulator (ORCES) is a good tool to predict the ORC operation characteristic, which could further guide advanced evaluation and the long time-varying cases.