Anti-Freezing Mechanism Analysis of a Finned Flat Tube in an Air-Cooled Condenser

In cold winter weather, the air-cooled condensers (ACCs) face serious freezing risks, especially with part load of the power generating unit. Therefore, it is of benefit to investigate the heat transfer process between the turbine exhaust steam and cooling air, by which the freezing mechanism of the finned tube bundles can be revealed. In this work, the flow and heat transfer models of the cooling air coupling with the circulating water, are developed and numerically simulated for the anti-freezing analysis on basis of the finned tube bundles of the condenser cell. The local air-side heat transfer coefficient, condensate film development, and non-condensable gas development are obtained and analyzed in detail. The results show that, the most freezing risk happens at the fin base due to the highest air-side cooling capacity, besides the windward velocity, ambient temperature and turbine back pressure all determine the freezing risk with the constant inlet flow rate of the non-condensable gas. Furthermore, increasing fin thickness and decreasing fan rotating speed are the most effective anti-freezing measures. Additionally, increasing turbine back pressure can also be adopted to avoid ACC freezing, however the adjustment of outlet steam-air flow is not recommended.