中文摘要：

为了提高有机朗肯循环（Organic Rankine cycle，ORC）系统热力性能，减少ORC发电中不可逆损失，实现对低品位热量的充分回收，以363～463 K地热水为热源，基于热力学第一、第二定律，从减小换热器换热温差考虑，提出一种新型ORC-分流闪蒸系统并建立系统热力学理论模型，通过编制计算程序对两种系统在不同热源温度下随蒸发温度的变化进行分析及比较，并针对4种临界温度不同的低沸点有机工质对系统的影响进行研究。结果表明：当热源不足以使工质在近临界温度下蒸发时，采用分流闪蒸系统可以提高系统热力性能，在热源温度Tg=363 K、393 K、423 K时，其效率较ORC系统分别增加10.51%、8.9%及7.07%；同时，分流闪蒸有助于减小工质对系统性能的影响，各工质热力性能表现相近；但随热源温度变化，系统适用工质不同，当热源温度高于工质临界温度15 K左右时，系统可在近临界状态下蒸发，此时选用该工质热力性能最佳。

英文摘要：

In order to improve the thermal performance, reduce the irreversible loss and make full use of the low grade heat of the organic Rankine cycle （ORC） system, from reducing the temperature difference of the heat transfer into consideration, based on the first and second rules of thermodynamics, the new type ORC-bypass flash system is put forward and the thermodynamic model is established which regards the 363-463 K water as the heat source. The analysis and comparison with evaporation temperature under different heat source temperature of two type systems and the influence of fluids have been made by written the calculation program. When the heat source is not enough to make the refrigerant evaporates in the near critical temperatures, the bypass flash system can improve the performance, the exergy efficiency increase by 10.51%, 8.9%and 7.07% compare to the ORC system under the heat source of 363 K, 393 K and 423 K;At the same time, it is helpful in reducing the effect of working fluids on performance and which behaves similar to each other;but the optimum fluid changes with the heat source’s temperature, if the fluid is selected whose critical temperature less than the heat source about 15 K can make the system obtaln the maximum performance.