热水解污泥在波节管中流动传热的数值研究
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摘要
利用数值模拟方法,考察了低湍流雷诺数(Re=4 000)情况下热水解污泥在几种型号波节管的管内流动和传热性能,系统研究了波节管的波节高度H、波谷圆角半径r、波节间距P以及波节长度S1对波节管的流动及传热性能的影响。结果表明,在相同管径及管长下,波节管的换热效果明显比光滑管好。由于管内形成径向二次流,湍动剧烈,传热得到强化,但是进出口压差也相应增大。波节高度H对波节管的强化传热起决定性作用,波谷圆角半径r、波节间距P以及波节长度S1主要对流动阻力产生影响。在研究中采用的波节管相对于光滑管,努赛尔数Nu和阻力系数f分别最大增加130%和129%,并且当H=4 mm,r=10 mm,S1=20 mm,S2=25 mm时,综合换热因子η达到最大值2.1。
The flow and heat transfer performance of thermal-hydrolyzed sewage sludge in smooth tubes and corrugated tubes with different geometrical configurations were numerically investigated in two-dimension at low turbulence Reynolds numbers of4 000. The effects of geometric parameters on the flow and heat transfer performance of corrugated tubes were analyzed,including corrugate height H,trough radius r,pitch P and length S1. The results showed that the heat transfer performance of corrugated tubes was better than that of smooth tubes with the same inner diameter and length,due to the generation of radial second flow and high turbulence intensity lead to the enhancements of heat transfer,but with increased flow resistance. The corrugated height H was the crucial parameter in strengthening heat transfer performance of corrugated tubes,and trough radius r,pitch P and length S1 mainly affected the flow resistance. Compared to the smooth tube,the average Nusselt number and friction factor of the studied corrugated tubes could be improved by 130% and 129%,respectively. The maximum thermal performance factor η could reach 2. 1 for the corrugated tubes with H = 4 mm,r = 10 mm,S1= 20 mm,S2= 25 mm.
The flow and heat transfer performance of thermal-hydrolyzed sewage sludge in smooth tubes and corrugated tubes with different geometrical configurations were numerically investigated in two-dimension at low turbulence Reynolds numbers of4 000. The effects of geometric parameters on the flow and heat transfer performance of corrugated tubes were analyzed,including corrugate height H,trough radius r,pitch P and length S1. The results showed that the heat transfer performance of corrugated tubes was better than that of smooth tubes with the same inner diameter and length,due to the generation of radial second flow and high turbulence intensity lead to the enhancements of heat transfer,but with increased flow resistance. The corrugated height H was the crucial parameter in strengthening heat transfer performance of corrugated tubes,and trough radius r,pitch P and length S1 mainly affected the flow resistance. Compared to the smooth tube,the average Nusselt number and friction factor of the studied corrugated tubes could be improved by 130% and 129%,respectively. The maximum thermal performance factor η could reach 2. 1 for the corrugated tubes with H = 4 mm,r = 10 mm,S1= 20 mm,S2= 25 mm.
引文
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[3]Weemaes M P J,Verstraete W H.Evaluation of current wet sludge disintegration techniques[J].Chem Technol Biotechnol,1999,73(2):83-92.
[4]Webb R L,Nae-Hyun Kim.Principles of Enhanced Heat Transfer[M].2nd Ed.New York.Taylor&Francis Group,2005.
[5]肖金花,钱才富,王凤林.波纹管对高黏度介质的强化传热研究[J].北京化工大学学报.自然科学版,2007,34(1):53-57.
[6]马小晶,胡申华,闫亚岭.波节管强化传热的三维数值模拟分析研究[J].水力发电,2012,38(1):87-90.
[7]徐建民,王晓清.波节管管内流动和传热的数值模拟[J].石油化工设备,2008,37(1):4-7.
[8]张伟玮,韩聪,韩怀志,等.波节形状对波节管结构稳定性和传热特性的影响[J].哈尔滨工业大学学报,2013,45(7):57-62.
[9]韩怀志,李炳熙,何玉荣,等.非对称型外凸式波节管内的传热和流动特性[J].化工学报,2013,64(6):1916-1924.
[10]Vicente P G.Mixed convection heat transfer and isothermal pressure drop in corrugated tubes for laminal and transition flow[J].Int Comm Heat Mass Transfer,2004,31(5):651-662.
[11]Vicente P G,Garcia A,Viedma A.Experimental investigation on heat transfer and friction characteristics of spirally corrugated tubes in turbulent flow at different Prandtl numbers[J].International Journal of Heat and Mass Transfer,2004,47(4):671-681.
[12]Rainieri S,Pagliarini G.Convective heat transfer to temperature dependent property fluids in the entry region of corrugated tubes[J].International Journal of Heat and Mass Transfer,2002,45:4525-4536.
[13]谭祥辉,朱冬升,张立振,等.扭曲椭圆管换热器研究进展及其应用[J].化学工程,2012,40(10):29-34.
[14]Tan X H,Zhu D S,Zhou G Y,et al.Experimental and numerical study of convective heat transfer and fluid flow in twisted oval tubes[J].International Journal of Heat and Mass Transfer,2012,55(17/18):4701-4710.
[15]Tang X Y,Dai X F,Zhu D S.Experimental and numerical investigation of convective heat transfer and fluid flow in twisted spiral tube[J].International Journal of Heat and Mass Transfer,2015,90:523-541.
[16]黄河洵,陈汉平,蔡兴飞.市政污泥流变特性及圆管流数值模拟研究[J].环境工程学报,2012,6(12):4642-4648.
[17]张涛,朱晓军,彭飞,等.近壁面处理对湍流数值计算的影响分析[J].海军工程大学学报,2015,25(6):104-108.
[18]周志军,林震,周俊虎,等.不同湍流模型在管道流动阻力计算中的应用和比较[J].热力发电,2007,36(1):18-22.
[19]陶文铨.数值传热学[M].2版.西安:西安交通大学出版社,2001:2-4.
[20]Spalart P R,Allmaras S R.A one-equation turbulence model for aerodynamic flows[R].AIAA-92-0439,1992.
[21]Webb R L,Eckert E R G.Application of rough surfaces to heat exchanger design[J].International Journal of Heat Mass Transfer,1972,15(9):1647-1658.
[22]Webb R L.Performance evaluation criteria for use of enhanced heat exchanger surfaces in heat exchanger design[J].Int J Heat Mass Transfer,1981,24(4):715-726.