空冷凝汽器中流体流动传热特性影响因素的研究
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摘要
空冷机组以环境空气作为冷却介质,在运行时受环境影响较大,风机的进风量和空冷单元的换热效率对环境变化十分敏感,在有风情况下通过改变空冷岛的结构来改善其外部流场,达到提高换热效率的目的变得十分必要。
本文以数值模拟软件FLUENT作为基本的研究工具,对某600MW直接空冷机组空冷岛外部流场进行了详细的数值模拟研究,主要内容及结论如下：
1.分析了在不同环境条件下空冷岛的换热特性,即环境风速、风向、环境温度对每个空冷单元换热量的影响,对流场的影响。风速小于3m/s时,风不会对空冷岛外部流场形成较大的干扰；当环境风风速大于3m/s时,开始出现少量回流,随着风速的增大回流量增加；在不同风向条件下时,炉后风对空冷岛的换热效率影响最大；另外空冷岛的换热效率对环境温度十分敏感。
2.使用正交试验的方法对空冷岛的整体结构进行研究,分别对空冷平台高度、上挡风墙高度、下挡风墙高度以及空冷单元管排安装角进行了详细研究,得出了在不同结构组合下,空冷岛的换热量,以此为标准得出空冷岛的最佳结构。研究表明在上挡风墙高度为9m、空冷平台高度为47m、下挡风墙高度为7m和人字排夹角为55°时在炉后风影响下,空冷岛的换热效率最高。
3.由于空冷岛周圈单元无论是通风量还是换热量都较小,因此本文提出了一种新型的空冷岛结构,也就是抬高了两侧单元的高度,改善了风机的进口条件,使得整个空冷岛的换热效率有明显的提高,这对未来空冷岛的建设有积极的指导意义。
The air cooling unit used the air as cooling medium, its performance was greatly influenced by the external environment factors, the gas fluxes and the heat transfer efficiency of the air cooling unit were sensitive to the environment conditions. Therefore, it was of great necessity to enhance the heat exchange efficiency through the approach of modifying the structure of air-cooled islands thus improving their external flow fields.
Based on the platform of numerical simulation software FLUENT, this paper carried out extensive numerical simulation study on the external flow field of a 600MW direct air-cooled unit, and the main contents and conclusions were listed below:
1. Analyzing the heat transfer characteristic of the air-cooled island under different environment conditions, that was the effect of factors including ambient wind velocity, wind direction and ambient temperature on heat transfer amounts and the flow field of the air-cooled island. This study found that the flow field would not be obviously interrupted when ambient wind velocity was below 3m/s, however, when the ambient wind velocity exceeds 3m/s, a few recirculation emerged and increased with the increasing wind speeds. In the case of various wind directions, the wind behind the furnace had greatest effect on the heat exchange efficiency of the air-cooled island which was found to be easily influenced by environment temperature.
2. Studying on the overall structure of the air-cooled island via Orthogonal Test method. Based on the analyzing results that the total heat transfer amounts of the air-cooled islands with various combinations of the air-cooled platform, up-windbreak height, down-windbreak height and the arrangement angel of the tunes, this study revealed the optimal structure. The results showed that the air-cooled island displayed the highest heat exchange efficiency, when the up-windbreak height was 9m, the air-cooled platform was 47m, the down-windbreak was 7m, the angel was 55°and the wind behind the furnace was present..
3. Considering the fact that the units adjacent the air-cooled island exhibited small ventilation and low heat transfer efficiency, this study present a modified air-cooled island structure whose adjacent units were heightened to improve entry conditions of fans, so the heat transfer efficiency of the whole air-cooled island was enhanced evidently. This would provide instructions for the design of air-cooled islands.
本文以数值模拟软件FLUENT作为基本的研究工具,对某600MW直接空冷机组空冷岛外部流场进行了详细的数值模拟研究,主要内容及结论如下：
1.分析了在不同环境条件下空冷岛的换热特性,即环境风速、风向、环境温度对每个空冷单元换热量的影响,对流场的影响。风速小于3m/s时,风不会对空冷岛外部流场形成较大的干扰；当环境风风速大于3m/s时,开始出现少量回流,随着风速的增大回流量增加；在不同风向条件下时,炉后风对空冷岛的换热效率影响最大；另外空冷岛的换热效率对环境温度十分敏感。
2.使用正交试验的方法对空冷岛的整体结构进行研究,分别对空冷平台高度、上挡风墙高度、下挡风墙高度以及空冷单元管排安装角进行了详细研究,得出了在不同结构组合下,空冷岛的换热量,以此为标准得出空冷岛的最佳结构。研究表明在上挡风墙高度为9m、空冷平台高度为47m、下挡风墙高度为7m和人字排夹角为55°时在炉后风影响下,空冷岛的换热效率最高。
3.由于空冷岛周圈单元无论是通风量还是换热量都较小,因此本文提出了一种新型的空冷岛结构,也就是抬高了两侧单元的高度,改善了风机的进口条件,使得整个空冷岛的换热效率有明显的提高,这对未来空冷岛的建设有积极的指导意义。
The air cooling unit used the air as cooling medium, its performance was greatly influenced by the external environment factors, the gas fluxes and the heat transfer efficiency of the air cooling unit were sensitive to the environment conditions. Therefore, it was of great necessity to enhance the heat exchange efficiency through the approach of modifying the structure of air-cooled islands thus improving their external flow fields.
Based on the platform of numerical simulation software FLUENT, this paper carried out extensive numerical simulation study on the external flow field of a 600MW direct air-cooled unit, and the main contents and conclusions were listed below:
1. Analyzing the heat transfer characteristic of the air-cooled island under different environment conditions, that was the effect of factors including ambient wind velocity, wind direction and ambient temperature on heat transfer amounts and the flow field of the air-cooled island. This study found that the flow field would not be obviously interrupted when ambient wind velocity was below 3m/s, however, when the ambient wind velocity exceeds 3m/s, a few recirculation emerged and increased with the increasing wind speeds. In the case of various wind directions, the wind behind the furnace had greatest effect on the heat exchange efficiency of the air-cooled island which was found to be easily influenced by environment temperature.
2. Studying on the overall structure of the air-cooled island via Orthogonal Test method. Based on the analyzing results that the total heat transfer amounts of the air-cooled islands with various combinations of the air-cooled platform, up-windbreak height, down-windbreak height and the arrangement angel of the tunes, this study revealed the optimal structure. The results showed that the air-cooled island displayed the highest heat exchange efficiency, when the up-windbreak height was 9m, the air-cooled platform was 47m, the down-windbreak was 7m, the angel was 55°and the wind behind the furnace was present..
3. Considering the fact that the units adjacent the air-cooled island exhibited small ventilation and low heat transfer efficiency, this study present a modified air-cooled island structure whose adjacent units were heightened to improve entry conditions of fans, so the heat transfer efficiency of the whole air-cooled island was enhanced evidently. This would provide instructions for the design of air-cooled islands.
引文
[1]谢林.直接空冷技术的发展和应用[J].电力学报,2006,186-189
[2]刘季江,蒋苏红.发电厂直接空冷系统的可行性探讨[J].节能.2005(2)：8-10
[3]王佩璋.我国火力发电厂直接空冷技术发展[J].电力设备,2007,52-56
[4]“十二五”电力发展思考.中国能源报(http://paper.people.com.cn/zgnyb/html/2011-02/28/content 756352.htm?div=-1) 2011.2
[5]温高,王胜捷,张子敬,等.发电厂空冷技术[M].中国电力出版社.2008.155-156
[6]王佩璋.空冷技术在火力发电上的应用与发展[J].电站辅机.2006,32-38
[7]杨立军,杜小泽,杨勇平,刘登瀛.火电站直接空冷凝汽器积灰监测[J].热能动力工程.2007,22(2)：172-175
[8]邱丽霞,郝艳红,李润林,等.直接空冷汽轮机及其热力系统[M].北京：中国电力出版社,2006,56-57
[9]赵文升,王松岭,汤世凯.基于CFD软件的直接空冷系统热风回流现象的分析[J].汽轮机技术.2007,49(5)：346-351
[10]YangL J, DuX Z, YangY P, etal. Influences of wind on flow and heat transfer of cooling air in direct air-cooled condenser[C]. The Eighteenth International Symposium on Transport Phenomena, Aug,2007, Daejeon,Korea.27-30,
[11]段会申,刘沛清,赵万里.电厂直接空冷系统热风回流的数值模拟[J].动力工程.2008,28(3)：395-399
[12]Michael Trevor Foxwell Owen. A numerical investigation of air-cooled steam condenser performance under windy conditions. For the degree Master of Science in Engineering at the University of Stellenbosch.2010.3,25-26
[13]高道仁.超临界直接空冷技术的特点分析及改进措施[J].江西电力,2009.33(3)：1-2
[14]杨立军等.直接空冷机组空冷系统运行问题分析及对策[J].现代电力,2006,23(2)：52-55
[15]陈念重.600MW直接空冷机组空冷凝汽器热态冲洗[J].热力发电,2009,38(2)：62-65
[16]杨立军,郭跃年,杜小泽等.环境影响下的直接空冷系统运行特性研究[J].现代电力,2005,22(6)：39-42.
[17]畅巨敏.直接空冷机组的防冻措施及冬季运行[J].山西焦煤科技,2011,30-32
[18]赵维忠.直接空冷系统的真空严密性与冬季防冻的初步探讨[J].电力技术.2009.11：33-37
[19]马瑞明,张峻岭,王国栋.直接空冷机组凝汽器真空度低的原因分析[J].黑龙江信息科技.2010.07：36
[20]FW Yu, B Eng. Condensing temperature control to enhance the efficiency of air-cooled chillers [J]. Building Serv. Eng. Res.Technol.2004,25 (4):279-294
[21]C.J.Meyer, D.G.Kroger. Numerical simulation of the flow field in the vicinity of an axial flow fan[J]. International Journal for Numerical Methods in Fluids,2001,36:947-969
[22]C.J.Meyer. Numerical investigation of the effect of inlet flow distortions on forced draught air-cooled heat exchanger performance[J]. Applied Thermal Engineering,2005, 25(11):1634-1649.
[23]C.J.Meyer, D.G.Kroger. Numerical investigation of the effect of fan performance on forced draught air-cooled heat exchanger plenum chamber aerodynamic behavior[J]. Applied Thermal Engineering,2004,24(2):359-371.
[24]C.J.Meyer, D.GKroger. Plenum chamber flow losses inforced draught air-cooled heat exchangers[J]. Applied Thermal Engineering,1998,18(9):875-893
[25]D.G.. Kroger., C.J.Meyer. Air-cooled heat exchanger inlet flow losses[J]. Applied Thermal Engineering,2001,21(7):771-786.
[26]Bredell G R, Kroger D G, Thiart G D. Numerical investigation of the effect of fan performance on forced draught air-cooled heat exchanger plenum chamber aerodynamic behavior[J]. Applied Thermal Engineering,2006(26):864-852.
[27]Van Staden, Martin P, Pretorius Leon. Numerical modeling of the effects of ambient conditions on large Power station air-cooled steam condensers. American Society of Mechanical Engineers, Fluids Engineering Division(Publication)FED, v221. Industrial and Environmental Applications of Fluid Mechanics,1995,145-150
[28]刘刚.关于自然风对直接空冷机组运行的影响[J].华北电力技术,2006(A01)：35-36.
[29]周兰欣,杨靖.600MW直接空冷机组变工况特性的研究[J].动力工程,2007,27(2)：165-168.
[30]周兰欣,杨靖,杨祥良.300 MW直接空冷机组变工况特性[J].中国电机工程学报.2007,27(17)：78-82
[31]周兰欣,李建波,李卫华,吴琼.600MW机组空冷岛外部流场的数值模拟与结构优化[J].中国电机工程学报.2009,29(17)：38-42
[32]周文平,唐胜利.空冷凝汽器单元流场的耦合计算[J].动力工程.2007.27(5)：766-770
[33]杨立军,杨勇平,杜小泽,等.风机群分区调节对空冷岛传热特性的影响[J].工程热物理学报.2010,31(1)：146-148
[34]Yang L J,Du X Z,Yang Y P,Liu D Y.Influences of wind on flow and heat transfer of cooling air in direct air-cooled condensers[C]. The Eighteenth International Symposium on Transport Phenomena, Daejeon, Korea,27-30, Aug,2007,
[35]Yang L J, Du X Z, Yang Y P, etal. Performance evaluation for direct air-cooled steam condensers in power plant[J]. Proceedings of the CSEE,2007,27(2):59-63
[36]贾宝荣,杨立君,杜小泽等.导流装置对直接空冷单元流动传热特性性能的影响[J].中国电机工程学报,2009,29(8)：14-19
[37]Gu Zhifu, Chen Xuerei, Lubitz W. Wind tunnel simulation of exhaust recirculation in an air-cooling system at a large power plant [J]. International Journal of Thermal Sciences,2007, 46(3):308-317.
[38]Gu Zhifu, Li Hui, Peng Jiye, et al. Wind tunnel simulation on condensers of a power plant[J]. Journal of Wind Engineering and Industrial Aerodynamics,2005,93(6):509-520.
[39]顾志福,张文宏,李辉,彭继业.电厂直接空冷系统风效应风洞模拟实验研究[J].热能动力工程,2003,18(104)：159-1628
[40]江瀚,薛海君,张健.谈减弱环境横切风对直接空冷机组运行影响的解决方案[C].浙江,杭州,中国电机工程学会火电分会空冷专委会第四届学术交流年会论文集,2007：11-18
[41]戴真会.直接空冷凝汽器管外空气流动与换热特性的数值研究[D].山东大学硕士学位论文,2010.46-47
[42]F. P. Ricou, D. B. Spalding Measurement of entrainment of axi-symmetrical turbulent jets[J]. FluidMech,1961,11:21-32.
[43]中华人民共和国机械行业标准.JB/T7510-1994.工艺参数优化方法,正交试验法
[2]刘季江,蒋苏红.发电厂直接空冷系统的可行性探讨[J].节能.2005(2)：8-10
[3]王佩璋.我国火力发电厂直接空冷技术发展[J].电力设备,2007,52-56
[4]“十二五”电力发展思考.中国能源报(http://paper.people.com.cn/zgnyb/html/2011-02/28/content 756352.htm?div=-1) 2011.2
[5]温高,王胜捷,张子敬,等.发电厂空冷技术[M].中国电力出版社.2008.155-156
[6]王佩璋.空冷技术在火力发电上的应用与发展[J].电站辅机.2006,32-38
[7]杨立军,杜小泽,杨勇平,刘登瀛.火电站直接空冷凝汽器积灰监测[J].热能动力工程.2007,22(2)：172-175
[8]邱丽霞,郝艳红,李润林,等.直接空冷汽轮机及其热力系统[M].北京：中国电力出版社,2006,56-57
[9]赵文升,王松岭,汤世凯.基于CFD软件的直接空冷系统热风回流现象的分析[J].汽轮机技术.2007,49(5)：346-351
[10]YangL J, DuX Z, YangY P, etal. Influences of wind on flow and heat transfer of cooling air in direct air-cooled condenser[C]. The Eighteenth International Symposium on Transport Phenomena, Aug,2007, Daejeon,Korea.27-30,
[11]段会申,刘沛清,赵万里.电厂直接空冷系统热风回流的数值模拟[J].动力工程.2008,28(3)：395-399
[12]Michael Trevor Foxwell Owen. A numerical investigation of air-cooled steam condenser performance under windy conditions. For the degree Master of Science in Engineering at the University of Stellenbosch.2010.3,25-26
[13]高道仁.超临界直接空冷技术的特点分析及改进措施[J].江西电力,2009.33(3)：1-2
[14]杨立军等.直接空冷机组空冷系统运行问题分析及对策[J].现代电力,2006,23(2)：52-55
[15]陈念重.600MW直接空冷机组空冷凝汽器热态冲洗[J].热力发电,2009,38(2)：62-65
[16]杨立军,郭跃年,杜小泽等.环境影响下的直接空冷系统运行特性研究[J].现代电力,2005,22(6)：39-42.
[17]畅巨敏.直接空冷机组的防冻措施及冬季运行[J].山西焦煤科技,2011,30-32
[18]赵维忠.直接空冷系统的真空严密性与冬季防冻的初步探讨[J].电力技术.2009.11：33-37
[19]马瑞明,张峻岭,王国栋.直接空冷机组凝汽器真空度低的原因分析[J].黑龙江信息科技.2010.07：36
[20]FW Yu, B Eng. Condensing temperature control to enhance the efficiency of air-cooled chillers [J]. Building Serv. Eng. Res.Technol.2004,25 (4):279-294
[21]C.J.Meyer, D.G.Kroger. Numerical simulation of the flow field in the vicinity of an axial flow fan[J]. International Journal for Numerical Methods in Fluids,2001,36:947-969
[22]C.J.Meyer. Numerical investigation of the effect of inlet flow distortions on forced draught air-cooled heat exchanger performance[J]. Applied Thermal Engineering,2005, 25(11):1634-1649.
[23]C.J.Meyer, D.G.Kroger. Numerical investigation of the effect of fan performance on forced draught air-cooled heat exchanger plenum chamber aerodynamic behavior[J]. Applied Thermal Engineering,2004,24(2):359-371.
[24]C.J.Meyer, D.GKroger. Plenum chamber flow losses inforced draught air-cooled heat exchangers[J]. Applied Thermal Engineering,1998,18(9):875-893
[25]D.G.. Kroger., C.J.Meyer. Air-cooled heat exchanger inlet flow losses[J]. Applied Thermal Engineering,2001,21(7):771-786.
[26]Bredell G R, Kroger D G, Thiart G D. Numerical investigation of the effect of fan performance on forced draught air-cooled heat exchanger plenum chamber aerodynamic behavior[J]. Applied Thermal Engineering,2006(26):864-852.
[27]Van Staden, Martin P, Pretorius Leon. Numerical modeling of the effects of ambient conditions on large Power station air-cooled steam condensers. American Society of Mechanical Engineers, Fluids Engineering Division(Publication)FED, v221. Industrial and Environmental Applications of Fluid Mechanics,1995,145-150
[28]刘刚.关于自然风对直接空冷机组运行的影响[J].华北电力技术,2006(A01)：35-36.
[29]周兰欣,杨靖.600MW直接空冷机组变工况特性的研究[J].动力工程,2007,27(2)：165-168.
[30]周兰欣,杨靖,杨祥良.300 MW直接空冷机组变工况特性[J].中国电机工程学报.2007,27(17)：78-82
[31]周兰欣,李建波,李卫华,吴琼.600MW机组空冷岛外部流场的数值模拟与结构优化[J].中国电机工程学报.2009,29(17)：38-42
[32]周文平,唐胜利.空冷凝汽器单元流场的耦合计算[J].动力工程.2007.27(5)：766-770
[33]杨立军,杨勇平,杜小泽,等.风机群分区调节对空冷岛传热特性的影响[J].工程热物理学报.2010,31(1)：146-148
[34]Yang L J,Du X Z,Yang Y P,Liu D Y.Influences of wind on flow and heat transfer of cooling air in direct air-cooled condensers[C]. The Eighteenth International Symposium on Transport Phenomena, Daejeon, Korea,27-30, Aug,2007,
[35]Yang L J, Du X Z, Yang Y P, etal. Performance evaluation for direct air-cooled steam condensers in power plant[J]. Proceedings of the CSEE,2007,27(2):59-63
[36]贾宝荣,杨立君,杜小泽等.导流装置对直接空冷单元流动传热特性性能的影响[J].中国电机工程学报,2009,29(8)：14-19
[37]Gu Zhifu, Chen Xuerei, Lubitz W. Wind tunnel simulation of exhaust recirculation in an air-cooling system at a large power plant [J]. International Journal of Thermal Sciences,2007, 46(3):308-317.
[38]Gu Zhifu, Li Hui, Peng Jiye, et al. Wind tunnel simulation on condensers of a power plant[J]. Journal of Wind Engineering and Industrial Aerodynamics,2005,93(6):509-520.
[39]顾志福,张文宏,李辉,彭继业.电厂直接空冷系统风效应风洞模拟实验研究[J].热能动力工程,2003,18(104)：159-1628
[40]江瀚,薛海君,张健.谈减弱环境横切风对直接空冷机组运行影响的解决方案[C].浙江,杭州,中国电机工程学会火电分会空冷专委会第四届学术交流年会论文集,2007：11-18
[41]戴真会.直接空冷凝汽器管外空气流动与换热特性的数值研究[D].山东大学硕士学位论文,2010.46-47
[42]F. P. Ricou, D. B. Spalding Measurement of entrainment of axi-symmetrical turbulent jets[J]. FluidMech,1961,11:21-32.
[43]中华人民共和国机械行业标准.JB/T7510-1994.工艺参数优化方法,正交试验法