Fluid and heat transfer enhancement of synchronous condenser rotor with alternating contraction ventiducts based on global fluid network model

Abstract

To address the issues of overheating and thermal imbalance in the existing dual radial ventilation duct for synchronous condenser (SC) rotor, the alternating contraction ventiducts (ACVDs) and the corresponding global fluid network model (GFNM) are proposed in this article. The key is to introduce alternating connection of single-branch and double-branch ventiducts, which increases the heat transfer area and reduces the total thermal resistance, thereby lowering the temperature of rotor winding. Firstly, a two-dimensional (2-D) electromagnetic field-circuit-grid coupling model of the SC is established, and the excitation currents as well as eddy current losses on the surface of the rotor teeth are iteratively obtained as the boundary of thermal calculation. Secondly, the influences of different ACVDs on the flow rate and node pressure in the key zones of the entire ventilation system are studied via GFNM . Also, the correlation between the internal flow distribution inside the rotor and ACVDs has also been explored. The GFNM is verified by comparing the results with the numerical calculations of three-dimensional (3-D) fluid-heat transfer. Further, the effects of different ACVDs on the heat transfer coefficient, Nusselt number, and winding temperature are clarified through the coupling of the numerical model with the GFNM. Some key fluid-thermal features of the selected scheme are provided, and the design considerations for the ACVDs are summarized on this basis. The prototype and test results further validate the correctness of the proposed ACVDs and GFNM. It is shown that due to the effective suppression of hot spot temperature, the unequal design of $W_j$ and $H_j$ as well as the larger $W_3$ are worth being chosen at the expense of the heat transfer coefficient.