The Basic Theory Research Of The Inner Evaporative Cooling System For The Large Hydro-generator And The Simulation Of The CLSC System

The relating problems of two-phase flow and heat-transfer in the evaporative cooling loop are very complicated with no common design and calculation methods in use up to the present and no criterion has developed from the technologic point of view, which results in the design calculation of the evaporative cooling system should to be perfected. Aiming at this situation, this paper provides a general and effective theoretical calculative method for the operational states of the stator windings' close-loop-self-circulating - CLSC evaporative cooling system of hydro-generators. Among the theoretical calculative methods, the evaporative point was more accurately computed; ONB and FDB were calculated; the Friedel method was selected to compute the two-phase frictional resistance and it was reasonably corrected on the basis of the experimental results; for the heat exchange between two-phase fluid and conductor's wall, a kind of partition of flow patterns was adopted and the corresponding convective heat exchange coefficients were calculated according to the different flow patterns, which make the computing result of the temperature distribution more accurate than ever. On the basis of the theoretical algorithm, a kind of professional applied software with GUI was developed. This software has complete functions and can be used easily. At the same time, the experiment was done in a cooling system model in order to verify the validity of the simulation. Comparative results show that the maximum relative errors between them are less than 10 percent. This result fully validates the mathematical model of the circulating cooling system is justified and the algorithm of the numerical simulation is correct.JBesides, in order to have further knowledge about the characteristics of the two-phase flow, the theoretic model experiment of the two-phase flow and heat transfer was done in vertical hollow conductors with different inner sizes. According to the experimental results, for the amplification ratio of the general two-phase pressure drop to the liquid flowing resistance in rectangular hollow conductors, the experimental correlation was developed, which simplifies the engineering calculation, reduces the error sources and improves the simulating precision.