中文摘要：

首先建立三段式加热器变工况数学模型，并根据疏冷段传热系数的计算对加热器低水位运行情况进行了模拟；其次以某330MW机组1#高压加热器为例，应用模型分别计算了正常水位运行端差、低水位运行时疏冷段换热状况及端差的变化；然后通过与试验数据的比较对计算结果进行验证，定量分析了加热器水位及负荷对端差的影响；最后重新设定0．14～0．15m为安全水位，设定0．2m为经济水位，比设计控制水位提高了近60min，可降低下端差2～3℃．

英文摘要：

A mathematical model of three-section heater for varying condition was established. The heater operation of low liquid level was simulated by this model with the calculation of the heat trans- fer coefficient of drain cooler. Taking #1 high pressure feedwater heater of a 330 MW steam turbine for example, the model was used to calculate the heater terminal temperature difference at regular liquid level, and the heat transfer condition of drain cooler and the terminal temperature difference at low liquid level. The calculation results were verified by the experimental data. The influence of heater liquid level and power load on terminal temperature difference was also quantitatively ana- lyzed. Finally, the security liquid level and the economic liquid level were reseted. The security liq- uid level was reseted as 0.14 to 0.15 m, and the economic liquid level was reseted as 0.2 m. The reseted liquid level is nearly 60 mm higher than the design control level, which can reduce the termi- nal temperature difference of the heater as 2 to 3 ℃.