Organic Rankine Cycle, Off-Design Conditions, Experimental Investigation, Charge Distribution, Mass Conservation
An experimental study is conducted to investigate the thermal-hydraulic characteristics of organic Rankine cycle in off-design conditions using R245fa as the working fluid. The effects of off-design conditions are monitored by varying the boundary conditions of the system in a total of 97 data sets. The charge distribution in the system is examined by applying the density-volume-measurement method in each component while the void fraction model is used for the prediction of captivated mass inside the heat exchangers. The simulation results of the heat exchanger models were validated with the experimental results within 5% error range. The working fluid charge ratio is varied between 30~70% in both basic and recuperative cycle configuration. A passive-design is proposed to determine the liquid level of the liquid receiver in the perspective of mass conservation. The impact of fluid over-charge and under-charge phenomena are thoroughly examined which result in system failure. The heat source and sink operating conditions are varied in order to observe the part-load response of the system. The results indicate that there exists a significant disadvantage when applying the recuperator in the cycle. Dominant factors that determine the evaporation and condensation pressure are discussed in terms of charge distribution.