摘要
针对低温环境及负荷减小时,间接空冷系统管内水至冰点状态导致传热管变形开裂,威胁机组安全运行问题,对某2×350 MW机组垂直间接空气冷却塔(间冷塔)在冬季低温环境下的散热情况进行数值模拟。通过调节间冷塔百叶窗开度获得间冷塔的不同流场和温度场,据此,分析研究了百叶窗开度对间冷塔散热能力的影响。结果表明:仅降低迎风、背风区域的百叶窗开度,反而会恶化其他扇段的运行环境,增加冻结危险,建议在冬季低温、低负荷防冻运行时,采用调节全部百叶窗的方式;所有百叶窗开度调至适合值时可使间冷塔出水温度高于其极限出水温度(20℃),可保证散热器管束极低温运行的安全性。
In indirect air-cooling systems,at extremely low ambient temperatures and with low heat flux operation conditions,the water temperature can reach freezing point near the end of the tubes,resulting in deformation and cracking of the heat transfer tubes,which affects the safety operation of the unit.Thus,taking the vertical indirect air-cooling tower in 2×350MW units as the example,this paper numerically simulate the heat transfer performance of the towers at low temperatures in winter,by computational fluid dynamics（CFD）method.Through adjusting the opening degree of the louvers,different flow fields and temperature fields inside the indirect air-cooling tower can be obtained.Then,the influence of louvers opening degree on cooling capacity of the air cooling tower is investigated.The results show that,the air-cooling system can avoid freezing phenomenon by regulating the opening degree of the louvers into a proper value when the wind leakage rate of the closed louver is below the limit value.However,only reducing opening degree of the louvers at windward and leeward side will aggravate the harsh operation environments of other sector radiators,causing high risk in heat transfer tube cracking and deformation.Therefore,it is recommended that all the louvers should be adjusted simultaneously during anti-freezing operation at low heat flux condition with extremely low ambient temperature.
出处
《热力发电》
CAS
北大核心
2016年第4期70-75,共6页
Thermal Power Generation
基金
国家自然科学基金项目(51276144)
关键词
垂直间冷塔
防冻
扇段
百叶窗开度
迎风
背风
侧风
出水温度
数值模拟
vertical indirect air-cooling tower
anti-freezing
sector
opening degree of louver
windward section
leeward section
crosswind section
effluent temperature
numerical simulation
