Abstract: The Dual-loop Organic Rankine Cycle(DORC)system based on middle-high temperature as heat source is analyzed,and the thermal efficiency,exergy efficiency,mass flow rate of working fluids,the outlet temperature of flue gas,the net output power of the system are studied and in this paper. R141b-R245 fa, n-pentane-R600 and isopentane-R114 were respectively selected as working fluids of DORC. The supercritical cycle is used in high temperature loop(HT),and subcritical cycle in low temperature loop(LT). The research results show that:with the increasing of the HT evaporating pressure,for the system using n-pentane-R600 and isopentane-R114,the thermal efficiency and exergy efficiency firstly increase and then decrease,the net output power keep reducing,while the thermal efficiency and the exergy efficiency keep increasing of the system using R141b-R245fa;or three DORC systems the mass flow rate of the working fluids changes in a very small range over the HT evaporating pressure; the system has the potential to further improve because of the high temperature of the flue gas outlet.

Key words: SORC, supercritical cycle, subcritical cycle, thermodynamic properties