Research on operational flexibility and energy consumption characteristics of cogeneration considering primary network heat transfer constraints

High back pressure cogeneration units demonstrate superior energy utilization efficiency, but their operation is significantly influenced by primary network water temperature and flow rate. The analysis of operational flexibility and energy consumption characteristics must consider the heat transfer performance constraints of the primary thermal network. This study investigates a high back pressure heating unit with steam extraction through off-design performance calculations of its condenser using the efficiency-number of transfer units (ε-NTU) method. The research evaluates how air-cooled island flow rate, thermal network return water flow, and temperature parameters affect the heat allocation ratio between steam extraction and high back pressure heating, as well as overall energy consumption characteristics. Key findings reveal that under maximum steam extraction heat load conditions, the coal consumption rate decreases by approximately 0.1 g/(kW·h) with a corresponding 0.43% improvement in energy efficiency. These insights provide operational guidance for optimizing combined high back pressure and steam extraction units through refined control strategies.