Thermodynamic performance of improved organic flash cycle driven by geothermal heat source

Improved organic flash cycle (OFC) exhibits perfect temperature matching during heat absorption and low throttling loss. Zeotropic mixtures could decrease the irreversible loss during the phase change process due to their non-isothermal characteristic. This study combines improved OFC with R۶۰۰a/R۶۰۱a mixtures to efficiently utilize low-grade thermal energy. The proposed system is compared with the basic single flash OFC using R۶۰۰a/R۶۰۱a mixtures. The high- and low-stage flash pressures are optimized for maximal net power output. The influences of the R۶۰۰a mole fraction and the heat source temperature on net power output, exergy efficiency, and cycle parameters are analyzed. Research shows that the optimized flash pressures have upper limits as heat source temperature increases. The net power output decreases with increasing R۶۰۰a mole fraction when the heat source temperature is high. The proposed system has more net power output than that using pure working fluid. Moreover, the net power outputs of improved OFC are higher than basic single flash OFC.

کلیدواژه ها:

Organic flash cycle ، Zeotropic mixture ، Exergy loss ، Low-grade thermal energy ، Thermodynamic evaluation