Thermal-hydraulic characteristics of the natural circulation evaporative cooling system of hydro-generator stator busbar under different loop heights

Abstract

Cooling technology plays an important role on the safe operation of hydro-generator. The natural circulation evaporative cooling system of hydro-generator stator busbar was proposed in China, which has the advantages of safety, energy-saving and high-efficiency and can meet better the requirements of generator cooling, compared with the traditional cooling technologies. In this paper, the thermal-hydraulic characteristics of this new cooling system under different loop heights were studied theoretically and experimentally, revealing the intrinsic relationship between the loop height and the system cooling performance. The increase of loop height can cause the mass flow rate increases gradually, enhancing the self-driven force and cooling capacity of system, and also makes the ratio of two phase region decrease and the system pressure increase, resulting in the rise of the wall temperature of the stator busbar. Hence the loop height should be selected optimally to ensure the adequate cooling capacity of system and the good cooling effects. Compared with the temperature of stator busbar by using the air cooling technology, it's shown that those by utilizing evaporative cooling technology can be reduced greatly, indicating that this new cooling system has great potential of application for larger capacity hydro-generator. The results in this paper can also provide some reference for other two-phase natural circulation systems.