均匀受热垂直上升管内的流动压降特性及界限质量流速
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摘要
界限质量流速G_0是垂直管圈水冷壁直流锅炉的重要设计参数之一。当水冷壁管中的质量流速小于G_0时,水冷壁呈现正流量响应特性。目前普遍认为G_0的范围在1 000~1 200kg/(m~2·s)。在公开文献中,关于G_0的影响因素的系统研究还相对较少。该文基于经验关联式和经典的流动压降计算方法,分析了超临界/亚临界压力条件下,均匀受热垂直上升管内水的流动压降随热流密度的变化情况,系统研究了热流密度、管长、管径等因素对G_0的影响规律。计算结果表明:热流密度减小,G_0增大;管长变短,G_0增大;管内径增加,G_0增加。
The critical mass flux,G_0,is a key parameter in the design of vertical water wall in once-through boilers.A vertical water wall has positive flow characteristic only when the mass flux inside the parallel tubes is less than G_0.While G_0 has been reported to be 1 000-1 200 kg/(m~2·s),there are few studies on the factors influencing G_0 in the literature.This paper presents a hydrodynamic model based on the classical pressure loss computation method and empirical correlations. The model predicts the pressure drop variation for water flowing upward inside a uniformly heated tube at supercritical/subcritical pressures for various heat fluxes,tube lengths and tube inner diameters.The results show that G_0 increases with decreasing heat flux and tube length and decreases with increasing inner diameter.
The critical mass flux,G_0,is a key parameter in the design of vertical water wall in once-through boilers.A vertical water wall has positive flow characteristic only when the mass flux inside the parallel tubes is less than G_0.While G_0 has been reported to be 1 000-1 200 kg/(m~2·s),there are few studies on the factors influencing G_0 in the literature.This paper presents a hydrodynamic model based on the classical pressure loss computation method and empirical correlations. The model predicts the pressure drop variation for water flowing upward inside a uniformly heated tube at supercritical/subcritical pressures for various heat fluxes,tube lengths and tube inner diameters.The results show that G_0 increases with decreasing heat flux and tube length and decreases with increasing inner diameter.
引文
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[21]周星龙,程乐鸣,夏云飞,等.600MW循环流化床锅炉水冷壁和中隔墙传热特性[J].中国电机工程学报,2014,34(2):225-230.ZHOU X L,CHENG L M,XIA Y F,et al.Heat transfer characteristic of water wall and partition wall in a 600 MW CFB boiler[J].Proceedings of the CSEE,2014,34(2):225-230.(in Chinese)
[22]ZHANG M,BIE R S,YU Z Z,et al.Heat flux profile of the furnace wall of a 300 MWe CFB boiler[J]. Powder Technology,2010,203(3):548-554.
[23]ZHANG R Q,YANG H R,HU N,et al.Experimental investigation and model validation of the heat flux profile in a 300MW CFB boiler[J].Powder Technology,2013,246:31-40.
[24]吕俊复,于龙,岳光溪,等.循环流化床锅炉水冷壁的热流密度分布[J].动力工程,2007,27(3):336-340.LJ F,YU L,YUE G X,et al.Heat flux distribution along water walls of circulating fluidized boilers[J].Journal of Power Engineering,2007,27(3):336-340.(in Chinese)
[2]王为术.超临界锅炉内螺纹水冷壁管流动传热与水动力特性[M].北京:中国电力出版社,2012.WANG W S.Convective heat transfer and hydrodynamic characteristics of supercritical boiler rifle tube[M].Beijing:China Electric Power Press,2012.(in Chinese)
[3] GRIEM H,KHLER W,SCHMIDT H.Heat transfer,pressure drop and stresses in evaporator water walls[J].VGB Power Tech,1999,79(1):26-35.
[4]吕俊复.超临界循环流化床锅炉水冷壁热负荷及水动力研究[D].北京:清华大学,2005.LJ F.Investigation on heat flux and hydrodynamics of water wall of a supercritical pressure circulating fluidized bed boiler[D]. Beijing:TsinghuaUniversity, 2005.(in Chinese)
[5]周旭,杨冬,肖峰,等.超临界循环流化床锅炉中等质量流速水冷壁流量分配及壁温计算[J].中国电机工程学报,2009,29(26):13-18.ZHOU X,YANG D,XIAO F,et al.Mass flow rate profile and metal temperature calculation in water wall of an supercritical circulating fluidized bed boiler at medium mass flow rate[J].Proceedings of the CSEE,2009,29(26):13-18.(in Chinese)
[6]王为术,朱晓静,毕勤成,等.超临界W型火焰锅炉垂直水冷壁低质量流速条件下热敏感性研究[J].中国电机工程学报,2010,30(20):15-21.WANG W S,ZHU X J,BI Q C,et al.Study on thermal sensitivity characteristics of vertical membrane water wall in supercritical pressure W shaped flame boiler[J].Proceedings of the CSEE,2010,30(20):15-21.(in Chinese)
[7]崔鹏.超超临界锅炉垂直管屏水冷壁流动特性研究[D].保定:华北电力大学,2010.CUI P.The study for the flow characteristics of vertical tube platen water cooled wall in the ultra-supercritical boiler[D].Baoding:North China Electric Power University,2010.(in Chinese)
[8]张大龙,吴玉新,张海,等.低质量流率垂直管圈超临界煤粉锅炉的水动力特性分析[J].中国电机工程学报,2014,34(32):5693-5700.ZHANG D L,WU Y X,ZHANG H,et al.Hydrodynamic characteristics of vertical tubes with low mass flux in supercritical pulverized coal boiler[J].Proceedings of the CSEE,2014,34(32):5693-5700.(in Chinese)
[9] WANG H,CHE D F.Positive flow response characteristic in vertical tube furnace of supercritical once-through boiler[J].Journal of Thermal Science and Engineering Applications,2014,6(3):031002.
[10]SIEMENSAG. BENSONboilersformaximum cost-effectivenessinpowerplants[R]. Power Generation,2000.
[11]黄承懋.锅炉水动力学及锅内传热[M].北京:机械工业出版社,1982.HUANG C M.Boiler hydrodynamics and heat transfer[M].Beijing:China Machine Press,1982.(in Chinese)
[12]CHURCHILL S W. Friction-factor equation spans all fluid-flow regimes[J]. Chemical Engineering, 1977,84(24):91-92.
[13]吕俊复,吴玉新,李舟航,等.气液两相流动与沸腾传热[M].北京:科学出版社,2017.LJ F,WU Y X,LI Z H,et al.Gas-liquid two phase flow and boiling heat transfer[M].Beijing:Science Press,2017.(in Chinese)
[14]ОСМАЧКИНВС.Труды имеждународно йконферециип отеплоперед аче:Париж,1970.
[15]CHISHOLM D.The influence of mass velocity on friction pressure gradients during steam-water flow[J].Proceedings of the Institution of Mechanical Engineers, Conference Proceedings,1967,182(8):336-341.
[16]PAN J,YANG D,CHEN G M,et al.Thermal-hydraulic analysis of a 600MW supercritical CFB boiler with low mass flux[J].Applied Thermal Engineering,2012,32:41-48.
[17]PAN J,WU G,YANG D.Thermal-hydraulic calculation and analysis on water wall system of 600 MW supercritical CFB boiler[J]. AppliedThermalEngineering, 2015,82:225-236.
[18]WANG L,YANG D,SHEN Z,et al.Thermal–hydraulic calculation and analysis of a 600 MW supercritical circulating fluidized bed boiler with annular furnace[J]. Applied Thermal Engineering,2016,95:42-52.
[19]TUCAKOVIC D R,STEVANOVIC V D,ZIVANOVIC T,et al.Thermal–hydraulic analysis of a steam boiler with rifled evaporating tubes[J].Applied Thermal Engineering,2007,27(2-3):509-519.
[20]SANKAR G,RAO A C,SESHADRI P S,et al.Techniques for measurement of heat flux in furnace waterwalls of boilers and prediction of heat flux–A review[J].Applied Thermal Engineering,2016,103:1470-1479.
[21]周星龙,程乐鸣,夏云飞,等.600MW循环流化床锅炉水冷壁和中隔墙传热特性[J].中国电机工程学报,2014,34(2):225-230.ZHOU X L,CHENG L M,XIA Y F,et al.Heat transfer characteristic of water wall and partition wall in a 600 MW CFB boiler[J].Proceedings of the CSEE,2014,34(2):225-230.(in Chinese)
[22]ZHANG M,BIE R S,YU Z Z,et al.Heat flux profile of the furnace wall of a 300 MWe CFB boiler[J]. Powder Technology,2010,203(3):548-554.
[23]ZHANG R Q,YANG H R,HU N,et al.Experimental investigation and model validation of the heat flux profile in a 300MW CFB boiler[J].Powder Technology,2013,246:31-40.
[24]吕俊复,于龙,岳光溪,等.循环流化床锅炉水冷壁的热流密度分布[J].动力工程,2007,27(3):336-340.LJ F,YU L,YUE G X,et al.Heat flux distribution along water walls of circulating fluidized boilers[J].Journal of Power Engineering,2007,27(3):336-340.(in Chinese)