Anti-freezing of air-cooled heat exchanger with rolling-type windbreaker

On cold days with even high wind speeds, the excessive cooling capacity of ambient air may result in a freezing risk for air-cooled heat exchanger. In this work, an anti-freezing approach is proposed based on the air flow control by pulling-down adjustment of rolling-type windbreakers, to ensure that the lowest outlet water temperature of each sector in air-cooled heat exchanger is not less than 0 degrees C. The coupled heat transfer models of natural draft dry cooling system with steam condenser are developed and experimentally validated. The opening degrees of rolling-type windbreakers and air mass flow rates for various sectors are obtained, and the outlet water temperature of each sector with rolling-type windbreakers is calculated. The correlating equations of the opening degree with wind speed at various ambient temperatures are also fitted. The results show that the opening degree of rolling-type windbreaker for each sector varies widely with the ambient temperature and wind speed. At the ambient temperature of -5 degrees C, only the windbreakers of windward sectors are regulated. While at -10 degrees C and -15 degrees C, the windbreakers of lateral and leeward sectors should also be adjusted. The configuration and regulation of rolling-type windbreakers can realize the anti-freezing of air-cooled heat exchanger with the low cost and high energy-efficiency. (C) 2019 Elsevier Ltd. All rights reserved.