Anti-freezing performances of novel natural draft dry cooling tower with double-layer air-cooled heat exchanger

Abstract

To the purpose of lower initial cost, the novel natural draft dry cooling tower (NDDCT) with the double-layer air-cooled heat exchanger (ACHE) is employed in a $2\times 660{\mathrm {MW}}$ dry cooling power plant. In cold days, the NDDCT may encounter the frozen risk due to redundant cooling capability of the cooling air. To revealing the anti-freezing performances of the novel NDDCT, the coupling effects of the ambient temperature with the circulating water flow rate, the circulating water outlet temperature and the heat load are investigated by numerical calculation. As a result, the critical anti-freezing parameters are obtained. Furthermore, the precondition of the units working under the chocking turbine back pressure is assumed for the energy-efficient operation of the power plant. The results show that, when the power output drops, the critical anti-freezing circulating water flow rate decreases and the critical anti-freezing ambient temperature rises. The strategy of reducing the number of the sector in operation is able to diminish the critical anti-freezing ambient temperature significantly with better anti-freezing performances. The NDDCT with one unit in operation has better anti-freezing performances than that with two units due to the deteriorated heat flow performance of the NDDCT, which is caused by the large amount of cold air flows into the NDDCT via the disconnected sectors. With increasing the wind speed at 4 m/s, the critical anti-freezing water flow rate increases, but the critical anti-freezing ambient temperature varies little. In conclusion, this research may provide valuable references of the frozen protection to the safe and economic operation of this novel NDDCT with double-layer ACHE.