Comparative Analysis Of (Organic) Rankine Cycle With Ejector And Working Fluids In Sub-/trans-/supercritical Conditions

This paper conducted thermodynamic analysis of cycle and fluids on organic Rankine cycle with ejector proposed by our group in sub-/trans-/superciritical conditions.For subcritical organic Rankine cycle with ejector, thermodynamic analysis for cycle performance using zeotropic mixtures as working fluids was studied, in which target parameters were net power output and exergy loss efficiency. The results shows that, cycle performance of zeotropic mixtures is better than pure working fluids in the same contions in certain ranges of heat source temperature. Particularly, second law and exergy loss ratio analysis of organic Rankine cycle with ejector using zeotropic mixtures(R245fa-R152 a, R245fa-isobutane, R245fa-R245ca)as working fluids was performed. Results show that it could enhance the ability of heat source utilization(higer ?2_ext)and heat source conversion into power(higher ?2_int)when using mixture fluids.Optimization of pure working fluids for traditional transcritical organic Rankine cycle was performed, and it was concluded that there was different appropriate working fluids for different heat source temperature(as shown in table 3-2). On the basis of this conclusion, comparative performance analysis was conducted for traditional transcritical organic Rankine cycle and organic Rankine cycle with ejector, it is shows that ETORC performance could be enhanced in the higher heat source temperature and appropriate heating pressure conditions compared to TORC.For supercritical(organic) Rankine cycle, optimization of pure organic fluids was conducted, it shows that performance of R125 was best. Comparative analysis of R125 and CO2 in conductance coefficient, first law, second law aspects was also performed, it shows that CO2 is better. At last, CO2 was selected as working fluid in the comparative analysis of four different cycles(ESRC/ETRC/SRC/TRC). Results shows that, the maximum exergy efficiency of cycle could be ranked from high to low, ESRC>ETRC>SRC>TRC. The minimum exergy loss of cycle could be ranked form low to high, ESRC<ETRC<SRC<TRC.