管内置梯形波带强化传热实验研究

设计了3种梯形波带内插件并对其强化换热特性进行实验研究,得出管内插入梯形波带扰流组件的传热系数h提高率为126%～220%,并对扰流组件引起的管程阻力进行了分析。通过传热性能评价准则(PEC)对插入梯形波带后的换热管进行传热的综合评价,证明梯形波带内插件确实是一种良好的加强换热能力的组件,并对实验数据线性回归拟合出了传热关系型。     

Wear behavior of PVD TiN coated carbide inserts during machining of Nimonic 90 and Ti6Al4V superalloys under dry and MQL conditions

This paper mainly deals with the tool wear characteristics of PVD TiN coated carbide inserts during turning of two aerospace alloys (Nimonic 90-Ni based alloy and Ti6Al4V- Ti based alloy). To fulfill the sustainability criteria the experiments have been conducted under dry and minimum quantity lubrication environment (MQL). To further enhance the effectiveness of MQL the specially prepared biodegradable emulsion of sunflower oil in water has been used as the cutting fluid. For better understanding of the cutting characteristics the same set up is employed for both the aerospace alloys. Due to high chip tool contact during machining of Nimonic 90, more intense nose wear has been observed over the cutting inserts. High strength of Nimonic 90 as compared to Ti6Al4V also resulted in high notch wear over the tool inserts during turning. The use of biodegradable emulsion under MQL mode has produced better results for Ti6Al4V. The attributes like good wettability and high penetration provided significantly less flank wear and rake wear during machining of Ti alloy under MQL condition. Furthermore due to the controlled wear during turning of Ti6Al4V, the cutting forces were found to be stable and significantly low as compared to Nimonic 90.     

含字符按键的双色塑件的注塑模设计

根据双色按键塑件材质的结构特点及生产要求,设计了一套双色注塑模具。通过一次注射为塑件主体聚碳酸酯（PC）材质,针对塑件结构上设置的多处薄壁状骨位填充困难及注射压力过大的问题,模具采用细水口多点进胶的方式解决;二次注射为塑件外观面热塑性弹性体（TPE）软胶材质,优化设计的3点细水口通过滑块抽芯机构转后模垂直翻转搭底进胶的方式配合排气槽、排气针和排气镶件结构,解决外观表面无法进胶和TPE材质易困气产生流痕、气纹和结合线的问题;特殊的后模浮板结构解决了产品上字母R/e/o/a及中间环形圈封闭的孤岛进胶问题。经过实际生产验证,一次注射时完整的填充注射压力减少了16%,二次注射时未出现流痕、气纹和结合线不良,产品成型质量良好,模具设计达到实际生产的要求。     

Numerical investigation of an enhanced PTC absorber tube using cylindrical inserts

The main purpose of this study is to investigate numerically the thermal performance of a parabolic trough solar collector's absorber tube that contains a novel kind of inserts with the objective to improve the heat transfer between the heat transfer fluid and the absorber tube. In the first part of this paper, the diameter and the length of the cylindrical inserts are investigated based on finite volume method and Monte Carlo ray tracing method for Reynolds number ranges from 2.36 × 10⁴ to 7.09 × 10⁴. In the second part, the eccentricity of the cylindrical inserts is investigated under the same operating conditions. The Therminol®VP1 is the HTF that is used in this investigation's intermediate fluid. The numerical simulation indicates that the perturbators enhance the thermal behavior of the receiver and reduces the absorber tube's temperature difference.