高位收水冷却塔冷却性能的数值模拟研究
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摘要
高位收水冷却塔底部采用斜板与U型槽组合的方式集水,由于在节能、环保和经济方面的优势使其在大型核电站等工程领域具有广阔的应用前景。基于Popper理论,建立高位收水冷却塔三维计算模型,通过自定义函数在Fluent中加载质量、动量和能量计算程序,与实测对比,模拟结果准确。分析了淋水密度、入塔水温、填料高度和环境风速等运行条件对高位收水冷却塔冷却性能的影响规律。环境风速从1m/s增加到9m/s,出口水温提升了2.61K,并发现当环境风速大于6m/s时,流场内出现涡漩和穿膛风,使流场的均匀性遭到破坏。淋水密度增加2.53kg/m~2s,出口水温升高4.72K,表明淋水密度增加,液滴数量增多,降低了空气与液滴间传热传质。此外,填料高度从1.25m增加到2m,虽然空气阻力有所升高,但与换热面积提高引起蒸发潜热增加相比,总的冷却性能提高。入塔水温升高使得高位塔内外区密度差增大,抽力增加,传热传质能力增大。
The collecting water way uses the combination of sloping plate and U-type channel for the high-level water collecting natural draft wet cooling tower(HNDWCT). Due to the advantages in energy saving, environmental protection and economy, the HNDWCT has promising application foreground in large nuclear power plants and other engineering field.Loading the mass, momentum, energy equation by user defined function was computed in Fluent. The numerical calculation result was accurate enough by comparing with the field measurement data. Then, the influences of water mass flow rate,inlet water temperature, fill height and environmental crosswind on cooling performance of the HNDWCT were simulated numerically. It is found that environmental crosswind increased from 0 m/s to 9 m/s, the outlet water temperature increased by 5.30 K. When the environmental crosswind is more than 6 m/s, eddies appears which might damage the homogeneity of the air flow field greatly. The water ?ow rate increased by 2.53 kg/(m2 s), the outlet water temperature improves 4.72 K. This implies the heat exchange capacity of the flow in the tower weakens with water ?ow rate and the droplet number increasing. In addition, fill height increases from1.25 m to 2 m, cooling performance improves because the increase of heat exchange area causes the increase of latent heat of evaporation although air resistance rises. Increase of water temperature improves the density difference between the inner and outer areas of the HNDWCT, which enable the pumping force and the mass and heat transfer capacity enhances.
The collecting water way uses the combination of sloping plate and U-type channel for the high-level water collecting natural draft wet cooling tower(HNDWCT). Due to the advantages in energy saving, environmental protection and economy, the HNDWCT has promising application foreground in large nuclear power plants and other engineering field.Loading the mass, momentum, energy equation by user defined function was computed in Fluent. The numerical calculation result was accurate enough by comparing with the field measurement data. Then, the influences of water mass flow rate,inlet water temperature, fill height and environmental crosswind on cooling performance of the HNDWCT were simulated numerically. It is found that environmental crosswind increased from 0 m/s to 9 m/s, the outlet water temperature increased by 5.30 K. When the environmental crosswind is more than 6 m/s, eddies appears which might damage the homogeneity of the air flow field greatly. The water ?ow rate increased by 2.53 kg/(m2 s), the outlet water temperature improves 4.72 K. This implies the heat exchange capacity of the flow in the tower weakens with water ?ow rate and the droplet number increasing. In addition, fill height increases from1.25 m to 2 m, cooling performance improves because the increase of heat exchange area causes the increase of latent heat of evaporation although air resistance rises. Increase of water temperature improves the density difference between the inner and outer areas of the HNDWCT, which enable the pumping force and the mass and heat transfer capacity enhances.
引文
[1]Zhao Yuanbin,Sun Fengzhong,Long Guoqing,et al.Comparative study on the cooling characteristics of high level water collecting natural draft wet cooling tower and the usual cooling tower[J].Energy Conversion and Management,2016,116:150-164.
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[19]赵顺安.冷却塔工艺原理[M].北京:中国建筑工业出版社,2015:484-485.Zhao Shunan.Principle of cooling towers[M].Beijing:China Architecture&Building Press,2015:484-485(in Chinese).
[20]Klimanek A,Bia?ecki R A.Solution of heat and mass transfer in counterflow wet-cooling tower fills[J].International Communications in Heat and Mass Transfer,2009,36(6):547-553.
[21]金台,张力,唐磊,等.自然通风湿式冷却塔配水优化的三维数值研究[J].中国电机工程学报,2012,32(2):9-15.Jin Tai,Zhang Li,Tang Lei,et al.Three-dimensional numerical study on water-distribution optimization in a natural draft wet cooling tower[J].Proceedings of the CSEE,2012,32(2):9-15(in Chinese).
[22]节能减排技术中心.神华神东电力重庆万州港电有限责任公司1号机组性能考核试验报告[R].西安:西安热工研究院有限公司,2016.Technology centre of energy conservation and emission reduction.Performance evaluation test report of Shenhua Shendong Electric Power in Chongqing Wanzhou gang power co.,LTD.Unit 1[R].Xian:Xi'an thermal research institute co.LTD,2016(in Chinese).
[23]张惠超.自然通风逆流湿式冷却塔数值模拟及配水系统优化[D].北京:华北电力大学,2013.Zhang Huichao.Numerical simulation and water distribution system optimization of natural draft counter-flow wet cooling tower[D].Beijing:North China Electric Power University,2013(in Chinese).
[24]Al-Waked R,Behnia M.The effect of windbreak walls on the thermal performance of natural draft dry cooling tower[J].Heat Transfer Engineering,2005,26(8):50-62.
[25]Al-Waked R,Behnia M.The performance of natural draft dry cooling towers under crosswind:CFD study[J].International Journal of Energy Research,2004,28(2):147-161.
[2]汉佩.冷却塔[M].胡贤章,译.北京:电力工业出版社,1980:56-70.Hampe E.Cooling towers[M].Hu Xianzhang,trans.Beijing:Publishing House of Electronics Industry,1980:56-70(in Chinese).
[3]杨护洲,杨若松.节能降噪冷却塔的应用综述[J].电力勘测设计,2015(S1):300-301,310.Yang Huzhou,Yang Ruosong.Summary on energysaving and Noise Reduction cooling tower[J].Electric Power Survey&Design,2015(S1):300-301,310(in Chinese).
[4]李志华,张广桢,王政权.九江电厂高位冷却塔节能技术应用研究[J].江西电力,2017(2):49-51.Li Zhihua,Zhang Guangzhen,Wang Zhengquan.Study on energy saving technology of high-level cooling tower in Jiujiang power plant[J].Jiangxi Electric Power,2017(2):49-51(in Chinese).
[5]Merkel F.Verdunstungskühlung[J].VDI-Z e itch rift,1925,70:123-128.
[6]Poppe M,Rogener H.Berechnung von ROckk ohlwerken[J].VDI Warm eat last,1991:1-15.
[7]Kloppers J C,Kr?ger D G.Loss coefficient correlation for wet-cooling tower fills[J].Applied Thermal Engineering,2003,23(17):2201-2211.
[8]Williamson N,Armfield S,Behnia M.Numerical simulation of flow in a natural draft wet cooling tower-the effect of radial thermofluid fields[J].Applied Thermal Engineering,2008,28(2-3):178-189.
[9]周兰欣,蒋波,陈素敏.自然通风湿式冷却塔热力特性数值模拟[J].水利学报,2009,40(2):208-213.Zhou Lanxin,Jiang Bo,Chen Sumin.Numerical simulation for thermal performance of natural draft wet cooling tower[J].Journal of Hydraulic Engineering,2009,40(2):208-213(in Chinese).
[10]赵元宾,杨志,高明,等.填料非均匀布置对大型冷却塔冷却性能的影响[J].中国电机工程学报,2013,33(20):96-103.Zhao Yuanbin,Yang Zhi,Gao Ming,et al.Impact of fill non-uniform layout on cooling performance of large-scale cooling towers[J].Proceedings of the CSEE,2013,33(20):96-103(in Chinese).
[11]Liu Dongqiang,Sun Fengzhong,Zhao Yuanbin.Impact mechanism of different fill layout patterns on the cooling performance of the wet cooling tower with water collecting devices[J].Applied Thermal Engineering,2017,110:1389-1400.
[12]田松峰,王少雷,陈曦,等.环境风速对高位收水冷却塔运行特性影响的数值模拟及优化[J].汽轮机技术,2017,59(1):53-57.Tian Songfeng,Wang Shaolei,Chen Xi,et al.Numerical simulation of high wind speed affect the operating characteristics of the cooling tower water and yield optimization[J].Turbine Technology,2017,59(1):53-57(in Chinese).
[13]Fluent Inc.Fluent user’s guide[EB/OL].2003.http://www.fluent.com.
[14]Al-Waked R,Behnia M.Enhancing performance of wet cooling towers[J].Energy Conversion and Management,2007,48(10):2638-2648.
[15]Williamson N J.Numerical modelling of heat and mass transfer and optimisation of a natural draft wet cooling tower[D].Sydney:University of Sydney,2008.
[16]陈友良.基于控风和导流机理的湿式冷却塔内部空气动力场的优化与重构[D].济南:山东大学,2013.
[17]Ferziger J H,Peric M.Computational methods for fluid dynamics[M].3rd ed.Berlin,Heidelberg:Springer,2002.
[18]中国人民共和国国家发展和改革委员会.DL/T 933-2005冷却塔淋水填料、除水器、喷溅装置性能试验方法[S].北京:中国标准出版社,2005.National Development and Reform Commission.DL/T933-2005 Test methods for determining the performance of cooling tower of transfer packing drift eliminator and sprayer[S].Beijing:Standards Press of China,2005(in Chinese).
[19]赵顺安.冷却塔工艺原理[M].北京:中国建筑工业出版社,2015:484-485.Zhao Shunan.Principle of cooling towers[M].Beijing:China Architecture&Building Press,2015:484-485(in Chinese).
[20]Klimanek A,Bia?ecki R A.Solution of heat and mass transfer in counterflow wet-cooling tower fills[J].International Communications in Heat and Mass Transfer,2009,36(6):547-553.
[21]金台,张力,唐磊,等.自然通风湿式冷却塔配水优化的三维数值研究[J].中国电机工程学报,2012,32(2):9-15.Jin Tai,Zhang Li,Tang Lei,et al.Three-dimensional numerical study on water-distribution optimization in a natural draft wet cooling tower[J].Proceedings of the CSEE,2012,32(2):9-15(in Chinese).
[22]节能减排技术中心.神华神东电力重庆万州港电有限责任公司1号机组性能考核试验报告[R].西安:西安热工研究院有限公司,2016.Technology centre of energy conservation and emission reduction.Performance evaluation test report of Shenhua Shendong Electric Power in Chongqing Wanzhou gang power co.,LTD.Unit 1[R].Xian:Xi'an thermal research institute co.LTD,2016(in Chinese).
[23]张惠超.自然通风逆流湿式冷却塔数值模拟及配水系统优化[D].北京:华北电力大学,2013.Zhang Huichao.Numerical simulation and water distribution system optimization of natural draft counter-flow wet cooling tower[D].Beijing:North China Electric Power University,2013(in Chinese).
[24]Al-Waked R,Behnia M.The effect of windbreak walls on the thermal performance of natural draft dry cooling tower[J].Heat Transfer Engineering,2005,26(8):50-62.
[25]Al-Waked R,Behnia M.The performance of natural draft dry cooling towers under crosswind:CFD study[J].International Journal of Energy Research,2004,28(2):147-161.