A combined system utilizing LNG and low-temperature waste heat energy

This paper has proposed a combined system, in which both the exergy of liquefied nature gas (LNG) and low-temperature waste heat energy can be effectively utilized. A multi-objective optimal model containing four factors: net output power, total investment cost, heat availability and dynamic investment recovery period has been built. Based on it, a thermodynamic and thermal-economic analysis on the system has been conducted with eight organic working fluids. Cycle performance of both the novel system and separated LNG and ORC system has been comparatively analyzed. The results show that the combined system has more net output power, lower total investment cost and larger heat availability factor than separated systems. And n-pentane emerges as the most suitable working fluid. Meanwhile, the influence of temperature and LNG parameters on F(X) is also analyzed. Moreover, the turbine's share is the largest; accounting for 43% to 50% of the total cost, and the condenser's exergy loss in the combined system is the most.