利用LNG冷能的混合工质中低温热力循环开拓研究

为提高中低温余热回收动力系统性能,本文在常规混合工质热力循环（火用）分析基础上,提出了结合LNG冷能利用的新型混合工质热力循环。通过与LNG的有机结合,混合工质热力循环热效率提高14.5个百分点,（火用）效率达到53.6％。为进一步揭示效率提高的原因,我们比较了常规混合工质热力循环与LNG-混合工质热力循环的（火用）损失变化情况。结果表明:LNG-混合工质热力循环高效的关键在于循环平均放热温度的降低以及工质蒸发过程与冷凝过程换热的合理匹配。而LNG冷能的梯级利用则是系统具有较高（火用）效率的根本原因。

A NOVEL BINARY CYCLE WITH INTEGRATION OF LOW-LEVEL WASTE HEAT RECOVERY & LNG COLD ENERGY UTILIZATION

In this paper we have proposed a novel binary cycle, which integrates low-level waste heat recovery and Liquefied Natural Gas (LNG) cold energy utilization for power generation. By way of exergy analysis, we have pointed out the fatal defects of the conventional binary cycle, and then, identified the potential of improvement. Consequently, a novel cycle was developed through system synthesis on the basis of energy cascade utilization. Compared with the conventional binary cycle, the new cycle brings 14.5 percentage points increment in thermal efficiency and 13.2 percentage points in exergy efficiency. Thermal efficiency of the waste-heat recovery power system was upgraded to 31.5%, closed to the level of fuel-fired simple cycle. At the same time, LNG cold energy is effectively utilized, with exergy utilization ratio of 86%. The new system proposed here will make greatly contribution both on efficient recovery of low-level waste heat and utilization of LNG cold energy.