耦合0号高加可提高大型火电机组在低负荷时的给水温度进而改善机组运行经济性。基于质量守恒与能量守恒方程，经严密数学推导，建立了耦合0号高加的热力系统汽水分布模型，给出了确定汽轮机负荷下目标给水温度工况对应的热经济性指标计算方法；进一步，提出了耦合0号高加的火电机组变工况热经济性计算方法，实现了对耦合0号高加火电机组热经济性的全面评估。以600 MW机组为例进行了计算和分析，结果表明：本文所提变工况计算方法的指标计算误差不超过0.15%，具有较高精度，可用于大型火电机组耦合0号高加时的热经济性评估；在30% ~ 75%负荷段，增设0号高加可使机组给水温度提升19.1 ~ 32.3 ℃，循环热效率提升0.18% ~ 0.2%，机组热耗率降低29.3 ~ 34.6 kJ／（kW·h），且机组负荷率越低，损失的内部功越少，热耗率降幅越大。

It will raise their feedwater temperature and then improve their operating economy to add No. 0 HPH (high-pressure heater) in thermal power units. A steam-water distribution model for a thermal system coupled with No. 0 HPH was established based on the mass and energy conservation laws. And a variable-condition calculation method for its heat economics was also proposed. Furthermore, a derivative characterization approach was developed to represent the heat economics impact of No. 0 HPH extracted steam flowrate, which realize the quantitative evaluation before and after coupling with No. 0 HPH. Taking a 600 MW unit for example to carry out calculations and analysis, it indicates that the index calculation error of the method proposed in this paper is less than 0.15%, which has high precision and can be used for thermal economic evaluation of large thermal power units coupled with No. 0 HPH. Furthermore, after coupling No. 0 HPH, the feedwater temperature can be lifted by 19.1 ~ 32.3 ℃, the cycle heat efficiency raised by 0.18% ~ 0.2%, and the heat consumption rate decreased by 29.3 ~ 34.6 kJ/(kW·h). Moreover, the sacrificial internal work will be even smaller, and the heat consumption decrease be even larger if the turbine load was smaller.