间接空冷翅片管束临界防冻特性及防冻裕量研究

Anti-freezing characteristics and margin of indirect air-cooled finned tube bundle

间接空冷翅片管束目前缺乏全面的冬季防冻运行参数。为此,首先凝练了管束防冻模型,包括热平衡方程、水侧和空气侧输运准则方程、防冻约束条件;其次依托典型顺逆流式空冷翅片管束,分析了2类管束临界防冻特性和防冻裕量;最后探究了中间型、左侧型、侧面型进水方式管束的临界值特点。结果表明:环境温度和入口水温降低、风速增加,管束防冻流量增加,且入口水温越低,风速影响更突出;逆流式管束防冻性能劣于顺流式管束,随风速增加或入口水温降低,二者差异扩大;入口水温抬升对防冻裕量影响分为3个梯次,为显著增加区间(0℃, 10℃]、变化缓慢区间(10℃, 20℃]、基本不变区间(20℃, 40℃],不可一直增加入口水温来防冻;中间型管束防冻性能优于左侧型和侧面型,空冷燃煤火电或核电机组应优先选用。研究结果可为我国空冷机组冬季防冻运行提供指导。

The anti-freezing operation parameters of indirect air-cooled finned bundle are insufficient at present.To solve this problem,this research firstly concludes the anti-freezing model of finned tube bundle,including the thermal equilibration equations,water side and air side transport equations,as well as anti-freezing constrains.Secondly,based on the co-current and counter-current air-cooled finned tube bundles,the critical anti-freezing characteristics and margin are analyzed.Then,the critical values are discovered for finned tube bundles with middle inlet,left inlet and side inlet patterns.The research shows that,as the ambient temperature or inlet water temperature reduces,as well as the ambient wind increases,the critical anti-freezing water flow rate ascends.Besides,when the inlet water temperature decreases,the wind effects get intensified.The anti-freezing performance of counter-current finned tube bundle is inferior to that of the co-current type,meanwhile the difference becomes expanded if the wind increases or water inlet temperature decreases.The effects of inlet water temperature elevation on anti-freezing margin can be classified into three levels,which are termed as obvious range(0℃,10℃],slow range(10℃,20℃],and stable range(20℃,40℃].Therefore,power plants should not always increase the water flow rate for anti-freezing operation.The air-cooled finned tube bundle with middle inlet pattern has better anti-freezing performance than others,so it’s suggested preferentially for coal-fired or nuclear power plants.This research may provide guidelines of anti-freezing operation for dry-cooling power stations in China.