Research on Dynamic Leakage Fault Characteristics of High-Pressure Heater Under Wide-Load Conditions of Coal-Fired Units

Tube bundle leakage occurs in high-pressure heaters of coal-fired units after long periods of variable-load operation. As these units increasingly participate in deep peak regulation, understanding leakage behavior over a wide load range becomes practically important. In this work, static and dynamic thermodynamic models of a three-section high-pressure heater were built for a 600 MW unit and checked against available design data of the No. 1 heater. For feedwater outlet temperature, the relative error stays below 1%. The dynamic model then simulates transient responses of feedwater outlet temperature, metal tube wall temperature, and shell-side drain volume under micro-leakage scenarios (1%, 5%, and 10% of feedwater flow) from turbine heat acceptance (THA) to 30% THA. Under THA, the final decreases in feedwater outlet temperature are about 1 K, 4.6 K, and 8.4 K for the three leakage levels, and similar patterns appear at partial loads. Taken together, the changes in temperature drop and drain volume can provide trend-level reference signals for engineering judgment within the studied operating conditions.