For the use of low-temperature waste heat (about 150℃) and cold energy of liquefied natural gas (LNG

about -162℃)

this paper presents a combined system. The thermodynamic and thermo-economy properties of the system are analyzed in detail

with comparative analysis on the proposed combined system and a separated system composed of a conventional organic Rankine cycle (ORC) and a low temperature ORC. Propane and R601a are adopted as work fluids in three cycles of the system

different temperature in internal heat exchanger and that in evaporator are selected to examine the system performance and obtain the best working condition. The results show that

for the combined system

the net work output increases 41.55%. The thermal efficiency and exergy efficiency are increased by 18.09% and 19%

while the area power ratio is only 61.03% of the separated system. The exergy lost among different components of the combined system is analyzed with the pressure exergy of LNG taken into account

and an appropriate system is proposed.