共查询到19条相似文献,搜索用时 204 毫秒
1.
2.
3.
李永康 《稀有金属材料与工程》2021,50(2):519-524
为改善平面流铸冷却辊的换热特性,提高Fe-Si-B非晶薄带的横向厚度均匀性,建立了冷却辊轴向换热通道数值计算模型。在分析现有通道流动换热特性基础上,提出一种球面形换热通道设计方法。基于场协同理论,综合换热与流阻,对所提球面形通道进行优化,并进行实验验证。结果表明:通道内冷却水换热效率沿水流方向逐渐下降,与冷却辊换热主要发生在靠近冷却辊内壁位置,现有冷却辊宽度中部温度远大于两端,轴向温差明显;球面形通道可以加强冷却辊中部换热,降低外壁温度、热变形和轴向变形差,进而改善非晶薄带横向厚度均匀性;随着球面半径的减小,通道中部换热明显增强,但流阻随之急剧增大;综合流阻与换热特性,存在最优通道优化半径。 相似文献
4.
5.
采用钨极气体保护焊(TIG)的方法,通过多组试验探索可行的焊接工艺方法,并结合产品堆焊实践改良,完成在T22,316L和800H这3种不同材料小直径换热管表面堆焊铜覆层。通过试验及实践可知,常规堆焊的方法用于T22换热管表面堆焊铜覆层,存在产生渗透裂纹的风险,但T22换热管堆焊时抵抗渗透裂纹产生的能力强于800H和316L换热管的;采用冷体堆焊可成功完成800H,T22及316L换热管表面堆焊铜覆层。3种不同材质换热管表面堆焊铜覆层的成功实施,为蒸汽发生器换热管内流动特性热工水力试验提供了有利条件。 相似文献
6.
7.
8.
9.
10.
11.
The outside serrated integral-fin tubes fabricated by rolling-plowing-extrusion processing were surface-treated through different processes of annealing in hydrogen atmosphere, electrochemical corrosion or sandblasting. The purpose was to eliminate residual stress, clear secondary micro-fins and enhance heat transfer performance. By comparing the surface characteristics, it is found that the finned tubes treated by electrochemical corrosion have the most glabrous surfaces where the fins are almost perfectly reserved. Clear layer cracks can be observed on the top of the fins. These structures are effective in enhancing heat transfer performance when being applied to flow heat exchange. Therefore, the finned tubes treated by electrochemical corrosion are proper for the tubular exchanger with water coolant. The finned tubes treated by sandblasting have rougher surfaces with layer cracks and micro gaps removed. As these structures are useful to clearing adhesive feculence, the tubes are more suitable for the tubular heat exchanger with oil coolant. 相似文献
12.
13.
在连铸和随后的生产工艺中预测和控制钢材的微观结构是生产制造满足高质量要求的特殊钢的一项非常重要的任务。连铸过程是一个非常复杂的过程,在这一过程中伴随着热量传输、质量传输、凝固和相变。在CAFE模型中,元胞自动机方法与连铸过程中传热计算进行耦合。利用ProCAST软件对连铸圆坯的凝固过程进行仿真模拟,通过连铸坯温度测量证明预测的连铸坯表面温度与实际比较接近。应用CAFE法实现了连铸坯凝固过程三维微观组织及其形成过程的模拟,通过对比试验和模拟的圆坯的宏观结构对模拟的结果进行了评价,证明模拟结果与试验结果吻合。 相似文献
14.
15.
点腐蚀是一种在蒸汽发生器传热管上产生的微小直径穿孔性管壁腐蚀点,其原因是在该处形成了局部腐蚀电池.它的危害性不仅由于点腐蚀本身会造成穿孔性降质,更重要的是点腐蚀是应力腐蚀等局部腐蚀的先导,会引起核电站的强迫停堆.防止点腐蚀的措施包括:选择传热管材料、控制二次侧水化学杂质、对管板上泥渣堆和管子进行清洗、对传热管进行无损检测等. 相似文献
16.
17.
《International Heat Treatment & Surface Engineering》2013,7(4):188-193
AbstractKobasko et al. have primarily shown that rapid water quenching can create compressive residual stresses near the surface and thereby a significant increase in the fatigue-limit (Intensive Quenching). Such processes result in an increase in hardness. Depending on steel grade, dimensions of the component and quenching intensity through hardening or only shell hardening will result. In this work, shell hardening processes were investigated in a more detailed manner for cylinders made of two different unalloyed steels. The goal of the work was discovering the general requirements to reach, on the one hand, a sufficient surface hardness paired with a non-through hardened hardening profile. On the other hand, compressive residual stresses in the near surface area should be as high as possible to achieve huge lifetime cycles for the heat treated work pieces. The experiments were carried out with a device that was especially developed for high speed quenching. As a quenching medium only tap water or water with 10% salt were used. It was shown that with this equipment very high heat transfer coefficients up to 50?000 W m?2 K?1 can be reached. Within the experimental design, cylinder made out of C35 and C56E2 with diameters between 25 and 43 mm were quenched with heat transfer coefficients in the range of 20?000 to 50?000 W m?2 K?1. The quenching results were characterised by measuring the microstructure, the hardness and the residual stresses. The experiments show that compressive stresses in the near surface area of 1200 MPa can be achieved. 相似文献
18.
铸铁水平连铸圆结晶器优化设计数值模拟 总被引:6,自引:3,他引:3
建立了铸铁水平连铸用结晶器水冷套的传热模型,并用有限差分法模拟计算了不同高度比水道结构的水冷套系统传热过程。水道高度比K值对水冷套冷却能力的影响规律是:K值增加,水道内水流速、等效传热面积均减小,水套的冷却能力降低。并根据计算结果提出了圆结晶器水冷套的设计原则。 相似文献