Heat transfer coefficient distribution in inner surface of stator ventilation duct for large capacity air-cooled turbine generator

The stator ventilation duct is the main path for fluid flowing to cool the stator bar and the core. Considering the complexity of the ventilation system, the investigation on the relationship between the air motion law in the ventilation duct and its surface heat transfer coefficient is crucial for the accurate calculation of the temperature field. Therefore, this paper takes the 150 MW air-cooled turbo-generator as a research object. Firstly, a new calculation model of the stator taking the air gap under rotor rotation state, and the yoke back into account is proposed to calculate the heat transfer coefficient in inner surface of stator ventilation duct. The relationship among the velocity vector, temperature of fluid and heat transfer coefficient in the ventilation duct is analyzed. Secondly, the temperature field of the new model calculated by finite volume method is compared with the measured values to verify the accuracy of calculation method. Finally, the influence of the varied rotational velocity on the heat transfer coefficient is investigated. The correction coefficient of the heat transfer coefficient related to the velocity is proposed. The calculation of the heat transfer coefficient and the correction of the fitting formula can provide theoretical guidance for the ventilation design of generators.