应用于工业余热的超临界二氧化碳布雷顿循环系统的热力学和[火用]分析

Thermodynamic and Exergetic Analysis of Supercritical Carbon Dioxide Brayton Cycle System Applied to Industrial Waste Heat Recovery

自主开发了一套基于分流再压缩的超临界CO2布雷顿循环的工业余热利用数值模拟程序,并结合?分析原理深入挖掘各参数对系统性能影响的内部机制。发现在任意选定状态参数下,存在一个最佳分流比使得热效率和?效率同时达到最优。透平入口温度变化对最佳分流比不造成影响。提高透平入口温度始终对系统最佳热效率和?效率起到积极促进作用。最佳分流比随主压缩出口压力的提高而单调递减。系统最佳热效率?效率随主压缩机出口压力提高先增加后趋缓,在低压段(15~23MPa)增加明显。随着压力的提高,系统?损失率的减少基本上是由高温回热器贡献的。最佳分流比随着主压缩机入口温度的提高而降低。主压缩机出口压力达25MPa时,主压缩机入口温度提高2℃,最佳热效率和?效率分别下降约3%和5%。主压缩机入口温度提高造成系统性能恶化的结果主要是通过预冷器的?损失率增加实现的。

A simulation program was independently developed for industrial waste heat recovery based on the supercritical CO2 recompression Brayton cycle.The exergetic analysis was applied to deeply explore the internal mechanism of the influence of various parameters on system performance.It was found that under any selected parameters,there was an optimal part-flow ratio that optimizes both thermal efficiency and exergetic efficiency.Turbine inlet temperature have no effect on the optimum part-flow ratio.Increasing the turbine inlet temperature always positively contributes to the system’s optimal thermal efficiency and exergetic efficiency.The optimum part-flow ratio monotonically decreases as the pressure increases on the outlet of main compressor.The optimal thermal efficiency and exergetic efficiency of the system increases first(especially in the pressure region 15-23 MPa)and then smooth with the increase of the main compressor outlet pressure.As the pressure on the main compressor outlet increases,the reduction in system exergy loss is mainly contributed by the high temperature recuperator.The optimum part-flow ratio decreases as the inlet temperature of the main compressor increases.At the pressure 25 MPa,when the inlet temperature of the main compressor increases by 2°C,the optimum thermal efficiency and exergetic efficiency are reduced by about respectively 3%and 5%.The result of a deterioration in system performance due to an increase in the temperature of the main compressor inlet is mainly achieved by an increase in the exergy loss of the precooler.