带疏冷段低压加热器特性分析

Analysis on the Performance of a Feedwater Heater with Drain Cooling Zone

基于能量平衡方程和效能-传热单元数法(ε-NTU),提出了变工况下带疏冷段加热器的端差计算方法,利用自编计算机程序,开展了加热器性能分析。以某660MW超临界纯凝机组5号、6号低压加热器为例,分析了带疏冷段加热器的性能。分析结果表明:加热器给水负荷与端差的变化并非线性关系;上端差相对额定端差值的比率比对应的负荷率小得多,不能根据负荷变化来估算端差的数值;下端差相对额定端差值的比率与负荷率比较接近,但是否可利用负荷率来估算下端差还要根据具体问题具体分析。只有根据各加热器的变工况性能,才能合理、准确地分析热力系统的热经济性,判断加热器的实际运行状态。

Based on the energy balance equation and effectiveness-number of heat transfer unit （ε-NTU） , the method for calculating a terminal temperature difference （TFD） of heater with drain cooling zone at part load is proposed, and then the TTD calculating program is developed. Taking feedwater heater No. 5 and No. 6 for Chongxin 660MW supercritical units for example, the heater performance analysis is carried out . The analysis results show that the relationship between feed water load and TTD is not linear. The ratio of terminal temperature difference relative to rated ones is much smaller than the corresponding load rate, so we cannot estimate terminal temperature difference according to load rate. The ratio of drain cooler approach relative to rated ones is similar to the corresponding load rate, but whether it is available to estimate drain cooler approach also accords to the concrete analysis. Only according to variable operation performance of each heater, can we analyze the thermal efficiency of thermodynamic system reasonably and accurately and judge actual states of heaters.