Abstract
Air-cooled heat exchanger faces a severe freezing risk in cold winter, especially for the finned tube bundles of windward sectors. Therefore, it is beneficial to the safe and energy-efficient operation of natural draft dry cooling system to take anti-freezing measures. In this work, the natural draft dry cooling system with auxiliary heat exchanger in front of windward sectors is proposed. By applying macro heat exchanger model to finned tube bundles and three-dimensional modeling on the air side, the freeze-proofing and performance improvement of natural draft dry cooling system with auxiliary heat exchanger are numerically studied. The air velocity, pressure, and temperature fields, air mass flow rate, outlet water temperature and anti-freezing turbine back pressure are presented under winter conditions. Moreover, the air flow rate, heat rejection and turbine back pressure are obtained in warm days. The results show that the auxiliary heat exchanger can prevent the air-cooled heat exchanger from freezing at various wind speeds in winter. In warm days, the natural draft dry cooling system with auxiliary heat exchanger is superior to the conventional one at high wind speeds. In the absence of winds, its cooling performance gets deteriorated.
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