两流非对称中间包不同湍流控制器流场的物理模拟研究

通过水模型实验和数值模拟,研究了不同控流装置下两流非对称中间包内流体流动特性.结果表明:圆形湍流控制器与单挡墙组成的控流装置中间包液面波动大,容易发生卷渣现象;非对称长方形湍流控制器和高低挡墙组成控流装置的中间包,两流之间的平均停留时间差异是圆形湍流控制器和单挡墙组成控流装置中间包的1/3,且近长水口侧出口的平均停留时...     

三流中间包中控流装置的冶金行为

中间包是连铸机中一个重要的冶金反应器,中间包内钢液流动行为直接影响着连铸坯的质量。因此,十分有必要利用水力学模型研究湍流控制器和多孔挡墙对三流中间包内流体流动的影响。研究结果表明,湍流控制器有助于提高活塞区体积分率,但是增大了死区体积分率;湍流控制器和多孔挡墙可以提高活塞区体积分率,同时减小死区体积分率;中间包内不安装控流装置或仅安装湍流控制器,中间包RTD曲线形状为细长型;而在中间包内安装湍流控制器和多孔挡墙后,中间包RTD曲线形状为矮胖型。     

两流非对称中间包内夹杂物行为

针对非对称两流中间包的生产实际,采用水模型实验、数值模拟相结合的方法分析了原中间包和优化后中间包在钢流流场、中间包流动特性、夹杂物运动轨迹方面的差异,并通过工业实验证实了优化方案的可行性。研究结果表明,非对称长方形湍流控制器能有效地减少两流之间钢液流动特性的差异,将2#出口的平均停留时间由194.4 s增加到206.4 s,优化后中间包2#出口的连铸坯80~200μm之间夹杂物降低为原中间包的15.4%。     

三流板坯中间包控流装置优化物理模拟研究及应用

创新性提出新型中间包控流装置-分流岛。通过物理模拟实验，研究了三流板坯连铸机采用不同分流岛、挡墙、挡坝及湍流控制器组合时中间包内钢液流动的特性。通过实验找到了本工程三流板坯中间包优化的控流装置。采用该控流装置组合有效地均衡了各流钢水流动，改善中间包内钢水流动形态，延长钢水在中间包内平均停留时间，降低死区比例，缩小边流与中间流之间钢水流动及温度的差异，实现了均匀各流钢水成分和温度，提高钢水纯净度，保障工艺顺行。项目投产后，生产稳定，最大日产铸坯10 890 t/d,平均日产量10 000 t/d。生产厚度200 mm铸坯时，稳定工作拉速可达到1.8 m/min。各流铸坯质量优良，实现三流板坯连铸机的建设初衷。三流板坯连铸机是大转炉匹配中窄宽度板坯生产的理想选择。     

四流T型中间包内流体流场物理模拟的研究

以某钢厂四流连铸中间包为研究对象,通过物理模拟的方式,研究了中间包设计控流装置内的流体流动行为及特点,提出了中间包的优化控流结构,即采用方形波浪底湍流控制器,其导流孔仰角为25°、中孔直径为30mm、侧孔直径为50 mm,优化控流结构后,钢液在中间包内平均停留时间增加了16%,包内死区体积减小了38%,此控流组合更有效地改善中间包流体流动,有利于非金属夹杂物的上浮,均匀钢液温度,有利于提高钢坯的质量。     

四流连铸中间包内流体流动行为的物理模拟

以某企业四流T型中间包为研究对象,建立模型与原型相识比为0.25的物理模型,并通过物理模拟方法系统研究了导流隔墙上的导流孔结构及湍流控制器结构对中间包内流体流动行为的影响。实验结果表明:优化导流孔结构及改变湍流控制器后,流体平均停留时间增加,相对增加率为21.1%;死区体积分率减小,相对减小率为32.4%;一流和二流的流动一致性增强,两流平均停留时间标准差仅为3 s。     

八流中间包控流装置优化水模实验

通过几何相似比为1:4.5的中间包水模实验对八流中间包在不同控流装置下的流场特性进行了模拟研究。结果表明:原型中间包内不同水口之间的流体流动特性存在很大差异,且死区比例较高;V型挡墙和C型挡墙优化方案均有效改善了中间包内流场,其中,V型挡墙优化方案优化效果最佳,使中间包死区比例由原来的29.7%降低为13.7%。     

基于RTD曲线优化八流中间包控流装置的研究

控流装置对钢液流动特性的影响较大,采用物理模拟结合数值模拟的方法对某钢厂八流中间包进行了挡墙优化,分析了不同挡墙方案中间包的RTD曲线并进行相关计算,根据计算结果选取较优方案。水模型实验和数值模拟结果表明,原型中间包加入控流装置后流场趋于合理,钢液的停留时间比较一致。其中,V-2方案的死区体积分数小,各流一致性好,有利于均匀钢液的成分和温度,促进夹杂物上浮,综合效果好。     

两流中间包流场模拟分析

以两流中间包为研究对象,利用中间包内的挡墙侧边垂直开槽方法,使钢水沿中间包墙侧向流动,改变中间包内钢液流动方向。中间包内的钢液水平旋转后,可延长钢液在中间包内的停留时间,有利于钢液中非金属杂质的上浮,同时使得钢液的流动方向与重力引起的势流方向相反,抵消了涡流的巨大吸力,减少了非金属夹杂物的吸入,确保后序工艺的钢水的纯净度。     

四流方坯连铸机中间包控流装置的研究

采用商业软件进行数值模拟和水模实验,考察了不同控流装置对南钢四流大方坯连铸机梯形中间包内钢液流动特性的影响,确定出湍流控制器+导流墙+坝的最佳控流方式.结果表明,原型中间包存在较大的死区,且各流间的流动特性差异较大,尤其是近水口的2流、3流存在明显短路流,不仅造成包内钢液温度分布不均匀,也不利于夹杂物的上浮,影响铸坯洁净度.采用优化后的组合控流装置能够显著改善中间包内钢水的流动状态,使钢液在各流间合理分配,并延长了钢水的平均停留时间,提高活塞流体积分率,降低死区体积分率,均衡了各流间的温度分布,有利于促进铸机生产顺行和铸坯质量的提高.     

非对称二流中间包夹杂物碰撞长大行为研究

采用数值模拟方法考察了非对称二流中间包内夹杂物碰撞长大行为,计算结果表明:挡墙对中间包流场影响较大,有利于控制中间包内钢液湍流流动;安装挡墙后中间包内湍动能耗散率分布更均匀,最大湍动能耗散率为无挡墙时最大值的I/5;挡墙对中间包夹杂物空间分布影响较大;挡墙的安装有利于提高夹杂物去除率,可有效地增强对直径＞ 50的大尺寸...     

Experimental Studies on Thermal Performance and Flow Resistance of Heat Exchangers with Helical Baffles

In this study, the shell-side heat transfer performance and flow resistance of the shell-and-tube heat exchangers with third-symmetrical, quarter-symmetrical, quarter-unsymmetrical helical baffles and segmental baffles were experimentally obtained. Except for the baffles, these heat exchangers had the same geometrical configuration and number of tubes. Cold and hot water were used as working fluids in the shell and the tube side, respectively. The experiments were done with the cold water volumetric flow rate ranging between 3 and 7 m³/h and the hot water volumetric flow rate constant at 5.5 m³/h. The results show that the heat exchanger with segmental baffles has higher shell-side heat transfer performance and flow resistance than those with helical baffles. Among the three helical baffles used, the third-symmetrical helical baffle offers the highest shell-side heat transfer performance and flow resistance. The quarter-unsymmetrical helical baffle offers the lowest shell-side flow resistance. Its performance of shell-side heat transfer is also the lowest one but close to that of the quarter-symmetrical helical baffle, so the quarter-unsymmetrical helical baffle provides the best conversion efficiency in all heat exchangers mentioned. Compared with the segmental baffle, the shell-side Nusselt numbers that the third-symmetrical, the quarter-symmetrical, and the quarter-unsymmetrical helical baffle offer decrease on the average by about 26%, 37%, and 38%, respectively, and the corresponding shell-side Euler numbers they provide decrease on the average by about 33%, 49%, and 55%, respectively. Thus, the relative shell-side conversion efficiencies increase by about 9%, 25%, and 39% on the average, respectively.     

底吹中间包两相流体流动及夹杂物传输行为的模拟研究

采用数值模拟手段,结合水模型实验,研究了中间包底部吹气过程对中间包内流场及夹杂物传输行为的影响。结果表明,在吹气条件下中间包采用挡墙控制有利于改善中间包流场,促进夹杂物上浮。在实验条件下双板多孔挡墙控制去除夹杂物效果优于堰－挡墙控制形式。     

Numerical study of a three-dimensional forced laminar flow in a channel equipped with a perforated baffle

The present work concerns a numerical study of a three-dimensional laminar flow in forced convection crossing a rectangular channel provided with a baffle attached on its lower wall. The conservation equations for mass, momentum, and energy are solved by the finite volume method based on the SIMPLE algorithm for pressure–velocity coupling scheme. The effect of the insertion of a perforated baffle at different perforation volumes was analyzed. The results presented show the temperature and velocity contours obtained for two different planes (XY and XZ) passing through the center of the baffle. The average friction coefficient, the average Nusselt number and the heat flux are presented for different perforation volumes of the baffle and for different Reynolds numbers. The study shows that although the solid baffle improves heat transfer, the use of a perforated baffle attached to the same position, further enhances heat transfer (from 0.03% to 14.52%), which provides, economically, a very good material reduction (from 5.18% to 82.96%) and mechanically, less flow resistance and therefore better performance.     

机械式搅拌锌浸出槽内流场和停留时间的数值模拟

采用标准的k-ε湍流模型、多重参考系稳态流动方法,对锌浸出槽内流动过程进行了数值模拟研究,并且采用示踪剂法,研究了流体在槽内停留时间的分布。模拟结果表明:浸出槽无阻尼板时槽内流体主要以周向流动为主,桨叶承受的压力较大,流体在槽内有局部"短路"现象出现。增加阻尼板后,流体在槽内由原来的周向流动为主转变为轴向流动为主,加速了槽内矿浆的混合,桨叶承受的压力明显降低,其最大压力降低15%,平均压力降低57%,流体在槽内停留时间分布与无阻尼板基本相同,但平均停留时间略有增大,有利于浸出过程的进行。     

Characteristics of Fluid Flow and Heat Transfer in the Shell Side of the Trapezoidal-like Tilted Baffles Heat Exchanger

Periodic whole cross-section computation models are established for segmental baffle heat exchanger, shutter baffle heat exchanger, and trapezoid-like tilted baffle heat exchanger. The reliability of models is verified by comparing the simulated results to the results obtained from the Bell-Delaware method. Due to the orthogonal assembly of the baffles, the shell side fluid shows the twisty flow of trapezoid-like tilted baffle heat exchanger. The essential mechanism on disturbing flow and heat transfer enhancement is revealed by defining the non-dimensional factor η of the shell side fluid flow direction of heat exchanger and the field synergy principle. The results show that at the same Reynolds number, the shell side fluid convection heat transfer coefficient of trapezoid-like tilted baffle heat exchanger is 12.43%-24.33% and 6.71%-11.51% higher than those of segmental baffle heat exchanger and shutter baffle heat exchanger, respectively. The shell side fluid flow velocity field and the pressure gradient field of trapezoid-like tilted baffle heat exchanger and shutter baffle heat exchanger decreases compared with that of segmental baffle heat exchanger, so the shell side fluid flow resistance and pressure drop is increased; the shell side comprehensive performance of trapezoid-like tilted baffle heat exchanger is 5.85%-9.06% higher than that of segmental baffle heat exchanger, and 15.27%-23.28% higher than that of shutter baffle heat exchanger. In this study, a baffle structure with higher efficiency of the energy utilization for the heat exchanger is provided.     

FTSC中间包控流装置的物理模拟

中间包内流体的流动状态对夹杂物的去除有重要的影响。依据相似原理,建立了一定相似比的薄板坯连铸中间包物理模型。比较了不同湍流控制器与堰坝组合,对中间包流体流动特征的影响,并尝试在中间包内采用坝上吹气的控流方式。结果表明:圆台型湍流控制器有效地限制了高速注流对包内流体的冲击,有利于稳定流体的流动状态。综合比较各项评价指标,坝上吹气方案的实验结果最佳。