Abstract
Low-grade thermal energy can be used for superheating the working fluid in the steam ejector. The purpose of the present study is to investigate the relationship of two-phase heat transfer with the ejector performance in the condensing flow regime under the condition of primary steam superheating. The condensation and evaporation phenomena occur in two-phase ejectors. The heat and mass transfer between the liquid and vapor phases change the flow pattern inside the ejector. The results show that the wet steam model has better fitting with experimental data than the ideal gas model. The primary steam superheating influences on the intensity of shock-wave patterns of supersonic flow, liquid mass fraction and two-phase heat transfer in the ejector. By increasing the superheating level, the two-phase heat transfer and exergy destruction are decreased, entrainment ratio in the wet steam model gets closer to entrainment ratio in ideal gas model, critical and limiting pressure are decreased and on-design and off-design regions become smaller. Also the effects of primary steam superheating in the ejector are investigated on the performance of a renewable refrigeration cycle. Superheating the working fluid reduces the generator energy consumption and increases exergy destruction in a refrigeration cycle. At degree of superheating 100 K, two-phase latent heat, energy consumption, and ejector exergy destruction decrease by 40%, 3.9%, and 11.7%, respectively, and entrainment ratio and total exergy destruction increase by 10% and 50%, respectively.
NSTL
Elsevier