Freeze protection performance of natural draft wet cooling tower with different partition water distributions

Abstract

With the construction of the deep peak regulation of thermal power units, the freezing risk of cooling towers under low load conditions is aggravated. Therefore, in order to keep natural draft wet cooling towers from freezing and enhance the shock resistance elasticity of thermal power units to cope with deep peak shaving, three partition water distribution schemes are proposed in this paper. The heat and mass transfer zones are divided along the radial direction, and the water spray density of the outermost sub-zone is gradually raised while maintaining an unchanged total circulating water volume. The effects of different spray densities on the freezing of cooling towers under different number of zones are studied. The three-dimensional numerical model of NDWCT is established and verified. The standard k-ε model is used to solve the turbulence characteristics. The main heat and mass transfer zones are solved by UDF. The temperature distribution, velocity vector and gas–water ratio at the bottom of the fill zone and outlet water temperature are analyzed. The results show that the three partition water distribution schemes can realize the anti-freezing of the cooling tower, with the increase of the spray density in the outermost sub-zone, the temperature of the frozen area gradually rises and the frozen area shrinks. NDWCT low load anti-freezing research will become an effective driving force for the construction of new power system under multi-coupled power supply mode on the basis of ensuring the safe operation of the unit in winter.