为提高燃煤机组的效率和降低机组的度电成本,该文建立多压冷端多参数多目标优化模型,以高参数超超临界机组为对象,分析凝汽器汽室数量和汽室面积对冷端系统的影响规律,优化获得不同参数等级机组的最优凝汽器汽室数量、凝汽器面积及冷却水流量,得到不同参数等级机组的冷端设计方案.结果表明:多压冷端较单压冷端的总投资的增加量随凝汽器总面积的增大先减少再趋于平缓.对不同进汽温度进组而言,主蒸汽参数越高,多压冷端的经济性越好.当机组的度电成本一样时,采用多压冷端的机组的效率大于单压冷端.

在城市供热需求攀升的情况下,降低一次热网回水温度可提高供热能力且有利用回收低温余热资源.采用喷射式热泵可利用一次热网供水的高温热源降低回水温度,且有结构简单、运行稳定可靠的优点.本文构建了喷射式热泵系统模型,研究了集中供热质调节下喷射器热泵系统的变工况特性.结果表明:喷射式热泵可有效降低一次热网回水温度,在相同一次网供水温度下,一次网回水温度可降低22℃;随着一次网供水温度的升高,一次网回水温度、热泵系统COP和喷射器引射比逐渐升高但效率逐渐降低;在供热调节的过程中,随着室外温度的升高,一次网回水温度不断升高,效率逐渐降低;而当室外温度低于当地室外设计温度时,喷射器引射比和热泵系统COP急剧减小.

Cold-end systems are heat sinks of thermal power cycles, which have an essential effect on the overall performance of thermal power plants. To enhance the efficiency of thermal power plants, multi-pressure condensers have been applied in some large-capacity thermal power plants. However, little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be identified. Therefore, the design optimization methods of cold-end systems with single- and multi-pressure condensers are developed based on the entropy generation rate, and the genetic algorithm (GA) is used to optimize multiple parameters. Multiple parameters, including heat transfer area of multi-pressure condensers, steam distribution in condensers, and cooling water mass flow rate, are optimized while considering detailed entropy generation rate of the cold-end systems. The results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is constant. Moreover, the economic performance can be improved with the adoption of the multi-pressure cold-end system. When compared with the single-pressure cold-end system, the excess revenues gained by using dual- and quadruple-pressure cold-end systems are 575 and 580 k$/a, respectively.