改善间冷塔换热性能方案分析
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摘要
环境风速变化使间冷塔内外空气流场发生改变,导致其换热性能发生变化,因此如何优化间冷塔内外空气流场具有重要意义。以某660 MW机组SCAL型间冷塔为研究对象,建立了三维模型并利用CFD换热器中简单效能法结合多孔介质模型,在不同环境风速下,对间冷塔空气流场分布及换热性能进行了数值模拟。根据间冷塔流场分布提出了3种改善方案,并定义了反映改善程度的改善系数。结果表明:间冷塔内外同时布置挡风墙(D方案)对其换热性能改善最大,间冷塔内部布置挡风墙(C方案)对其换热性能改善最小;D、C两方案分别在18 m/s和8 m/s时对间冷塔换热性能改善最大,改善系数约为17.34%和4.29%;D方案和B方案相比C方案换热性能均有一定改善,在18 m/s时均取得最大值,分别约为14.69%和15.39%。因此,对于风向较固定的地区,D方案可以有效改善间冷塔的换热性能。
The change of crosswind alters the air flow field inside and outside the tower, which causes the heat transfer performance of tower to change. Therefore, how to optimize the air flow field is significant. Taking a 660 MW SCAL indirect dry cooling tower as the object, a 3 D model was established and the air flow field and heat transfer performance were simulated in different crosswind by using simple effectiveness model and porous medium model of CFD. Three improvement schemes were proposed and the improvement coefficient which corresponds to the degree of improvement was defined. Results show that the scheme D where the windbreak wall is arranged inside and outside the tower has the greatest improvement in heat transfer performance, while the scheme C where the windbreak wall is arranged inside the tower has the least improvement in heat transfer performance. Scheme C and scheme D have the greatest improvement coefficient at 18 m/s and 8 m/s, which are about 17.34% and 4.29% respectively. Compared with scheme C, the heat transfer performance of scheme B and D is improved, and the maximum value is obtained at 18 m/s, which are about 14.69% and 15.39% respectively. Therefore, scheme D can effectively improve the heat transfer performance of the tower in areas with a fixed wind direction.
The change of crosswind alters the air flow field inside and outside the tower, which causes the heat transfer performance of tower to change. Therefore, how to optimize the air flow field is significant. Taking a 660 MW SCAL indirect dry cooling tower as the object, a 3 D model was established and the air flow field and heat transfer performance were simulated in different crosswind by using simple effectiveness model and porous medium model of CFD. Three improvement schemes were proposed and the improvement coefficient which corresponds to the degree of improvement was defined. Results show that the scheme D where the windbreak wall is arranged inside and outside the tower has the greatest improvement in heat transfer performance, while the scheme C where the windbreak wall is arranged inside the tower has the least improvement in heat transfer performance. Scheme C and scheme D have the greatest improvement coefficient at 18 m/s and 8 m/s, which are about 17.34% and 4.29% respectively. Compared with scheme C, the heat transfer performance of scheme B and D is improved, and the maximum value is obtained at 18 m/s, which are about 14.69% and 15.39% respectively. Therefore, scheme D can effectively improve the heat transfer performance of the tower in areas with a fixed wind direction.
引文
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[12]LU Y,GUAN Z,GURGENCI H,et al.Windbreak walls reverse the negative effect of crosswind in short natural draft dry cooling towers into a performance enhancement[J].International Journal of Heat and Mass Transfer,2013(63):162-170.
[13]王蓝婧,刘康,付文锋,等.660 MW SCAL型间接空冷塔夏季安全运行改造方案研究[J].动力工程学报,2018,38(1):55-61.
[14]GOODARZI M,KEIMANESH R.Heat rejection enhancement in natural draft cooling tower using radiator-type windbreakers[J].Energy Conversion & Management,2013,71(3):120-125.
[2]GOODARZI M.A proposed stack configuration for dry cooling tower to improve cooling efficiency under crosswind[J].Journal of Wind Engineering & Industrial Aerodynamics,2010,98(12):858-863.
[3]杨立军,张凯峰,杜小泽,等.空冷凝汽器椭圆翅片椭圆管束外空气的流动与传热特性[J].动力工程学报,2008,28(6):911-914.
[4]李慧君,杨长根.间冷塔散热器圆环布置对换热性能的影响[J].电力科学与工程,2018,34(11):66-73.
[5]韩中合,张垚鹏,李恒凡.侧风环境下间接空冷塔百叶窗开度调节方案[J].汽轮机技术,2018,60(1):41-44.
[6]WU T,WEI H,GE Z,et al.Cooling water mass flow optimization for indirect dry cooling system of thermal power unit under variable output load[J].International Journal of Heat and Mass Transfer,2019(133):1-10.
[7]MA H,SI F,LI L,et al.Effects of ambient temperature and crosswind on thermo-flow performance of the tower under energy balance of the indirect dry cooling system[J].Applied Thermal Engineering,2015(78):90-100.
[8]吴韬,席新铭,杜小泽,等.大型间接空冷塔内部空气流场导流研究[J].汽轮机技术,2018,60(3):181-184.
[9]ZHAO Y,LONG G,SUN F,et al.Effect mechanism of air deflectors on the cooling performance of dry cooling tower with vertical delta radiators under crosswind[J].Energy Conversion and Management,2015(93):321-331.
[10]WANG W,ZHANG H,LI Z,et al.Adoption of enclosure and windbreaks to prevent the degradation of the cooling performance for a natural draft dry cooling tower under crosswind conditions[J].Energy,2016(116):1360-1369.
[11]GU H,WANG H,GU Y,et al.A numerical study on the mechanism and optimization of wind-break structures for indirect air-cooling towers[J].Energy conversion and management,2016(108):43-49.
[12]LU Y,GUAN Z,GURGENCI H,et al.Windbreak walls reverse the negative effect of crosswind in short natural draft dry cooling towers into a performance enhancement[J].International Journal of Heat and Mass Transfer,2013(63):162-170.
[13]王蓝婧,刘康,付文锋,等.660 MW SCAL型间接空冷塔夏季安全运行改造方案研究[J].动力工程学报,2018,38(1):55-61.
[14]GOODARZI M,KEIMANESH R.Heat rejection enhancement in natural draft cooling tower using radiator-type windbreakers[J].Energy Conversion & Management,2013,71(3):120-125.