利用地热能的双压有机朗肯循环性能分析

根据地热利用系统回灌的要求,对热源在系统出口处的温度进行限制,研究了双压有机朗肯循环（DPORC）中的热量分配以及随运行时间的系统性能变化,针对5种不同的有机工质进行了计算分析。研究表明：系统热力学性能的最大值和有机工质流量的最小值在同样的k值（热源提供给高压循环的热量与热源为DPORC提供的热量比）处获得。而采用R600和R245fa系统的净输出功率较大;相比R601,采用R245fa可以将系统的净输出功率提高168.06 kW（5.55%）,热效率和效率分别可提高0.70%和2.86%。相比于单压有机朗肯循环（SPORC）,DPORC可以有效减小系统随运行时间净输出功率降低的幅度。经过40 a的运行,采用R601的系统净输出功率降低幅度最低（428.11 kW, 14.14%）,而采用R600系统的净输出功率降低幅度最大（526.75 kW, 16.55%）。

THERMODYNAMIC PERFORMANCE ANALYSIS OF DOUBLE PRESSURE ORGANIC RANKINE CYCLE DRIVEN BY GEOTHERM

According the requirement of system injection in geothermal utilization, the temperature of the heat source at the exit of the system is specified and 5 kinds of organic working medium with different critical temperatures are selected for thermodynamic calculation. The heat distribution and the performance of DPORC with running time were studied, and the results indicated that the maximum value of the thermodynamic parameters of the system and the minimum value of the flow of organic working medium were obtained at the same k （Ratio of heat provided by the heat source to the high-pressure cycle to heat provided by the heat source to DPORC） value. The net output power of system with R600 and R245fa as working fluid is larger. Compared with R601, the net output power of system with R245fa as fluid can increase by 168.06 kW （5.55%）, while thermal efficiency and exergy efficiency can increase by 0.70% and 2.86% respectively. Compared with single-pressure organic （SPORC）, DPORC can reduce the decrease of net output power with variable running time effectively. After 40 a of operation, R601 has the lowest net output power reduction （428.11 kW, 14.14%）, while R600 has the highest net output power reduction （526.75 kW, 16.55%）.