600MW煤基超临界二氧化碳循环PCHE预冷器设计及传热特性研究

Design and Heat Transfer Characteristics of 600MW Coal-based Supercritical Carbon Dioxide Cycle PCHE Pre-cooler

为对超临界二氧化碳循环预冷器进行概念设计并探究其传热特性,构建了印刷电路板式换热器(printed circuit heat exchanger,PCHE)预冷器的变结构分段设计模型,对600MW煤基超临界二氧化碳循环PCHE预冷器开展设计计算和传热特性研究,在定换热量条件下分析冷热侧质量流量与预冷器设计参数的变化关系,探讨其内部传热特性,并给出预冷器设计方案。结果表明:预冷器内S-CO_(2)拟临界工况使温度呈非线性变化,热侧工质物性变化对预冷器整体传热性能的影响更加明显;热侧单通道入口质量流量增加3倍能使平均传热系数提高54.21%,但最小温差值降低53.38%,冷侧单通道入口质量流量的增加仅能强化冷侧传热;设计时可优先选取体积为优化目标以确定截面通道数及热侧入口参数,冷侧水量选取应权衡尺寸及压降关系;最终,该方案选取预冷器内冷热侧单通道入口质量流量分别为2.2和0.75g/s,与已有结果相比该预冷器体积可减小10.50%,夹点温差提高1℃。

To investigate the heat transfer characteristics of the supercritical CO_(2) cycle pre-cooler,the design and heat transfer characteristics of the 600MW coal-based supercritical CO_(2) cycle PCHE pre-cooler are studied in a variable structure segmental design model.The design parameters of the pre-cooler are optimized and determined under constant heat flow,and the internal heat transfer characteristics are discussed.The results show that S-CO_(2) pseudo-critical conditions in the pre-cooler make the temperature variation non-linear;the influence of the hot-side properties on the overall heat transfer performance in pre-cooler is more significant;a 3 times increase in the inlet mass flow of the hot side can increase the average heat transfer coefficient by 54.21%but it will decrease the minimum temperature difference by 53.38%,and the increase in cold-side inlet mass flow rate only enhances cold-side heat transfer.It is recommended to choose the volume as the optimization target to determine the number of cross-sectional channels and hot-side inlet parameters,and the determination of the cold mass flow should be a balance of both size and pressure drop;the inlet mass flow of single channel in the cold and hot side of the pre-cooler is selected as 2.2g/s and 0.75g/s,respectively,which reduces the volume of the pre-cooler by 10.50%and increases the minimum temperature difference by 1℃.