The control of biofilms in tubes using wire‐wound inserts

As a possible alternative to the use of biocides in industrial water systems, studies have been made on the effectiveness of wire‐wound tube inserts for biofilm control. Comparisons of data obtained at two different empty tube velocities of 0.86 m/s and 1.27 m/s and a Reynolds number of 14 000 with and without inserts, show that a biofilm accumulation reduction approaching 50% can be achieved by the use of inserts under certain circumstances. Further work is required to establish the optimum design of insert for maximum effectiveness.     

高温包层内多层插件流道内液态铅锂MHD流动数值分析

包层是聚变反应堆能量转换和提取的关键部件,聚变高温制氢堆(FDS-Ⅲ)高温液态铅锂包层(HTL)中采用创新型多层插件(MFCI)技术,由SiC_f/SiC组成的流道插件使液态铅锂实现了1 000℃左右出口温度,从而达到更高的热电转换效率和制氢能力。液态金属磁流体动力学效应MHD效应是HTL包层的重点问题之一。本文以高温包层结构为参考,采用FDS团队自主开发的磁流体动力学与热工水力学耦合模拟软件MTC,对高哈特曼数下典型多层插件流道内的液态铅锂MHD流动特性进行了数值模拟,分析了不同插件电导率对流道之间电磁耦合现象的影响。     

2099 Aluminum-Lithium with Key-Locked Inserts for Aerospace Applications

The purpose of this study was to determine the acceptability of nonpenetrating, key-locked inserts in 2099 aluminum-lithium. The tests conducted to make this assessment were: (1) microscopic examination for thread damage and delaminations after key installation, (2) pull-out load at 21 °C (70 °F) and −179 °C (−290 °F), and (3) mechanical cycling tests at room temperature and −179 °C (−290 °F). The test results indicated that for the three sizes evaluated, key-locked inserts in 2099-T6 and 2099-T8 were acceptable and although delaminations did occur on some T6 temper specimens, it was only as a failure mode at ultimate load and such behavior was judged to be acceptable.     

Evaluation of turbulent forced convection of non-Newtonian aqueous solution of CMC/CuO nanofluid in a tube with twisted tape inserts

The present paper investigates the turbulent flow and heat transfer of non-Newtonian aqueous solution of Carboxymethyl cellulose (CMC) and CuO nanoparticles in a plain tube and also tube with twisted tape inserts. The aqueous solution of CMC and CuO/CMC nanofluid show a shear-thinning (pseudo-plastic) rheological behavior, resulting in a higher viscosity than that of water. The consistency index and the power law index are evaluated based on available experimental data. The single phase approach with temperature dependent thermo-physical properties is applied to simulate the nanofluid flow and heat transfer. Simulation results are presented at different nanoparticle concentrations and twisted tape ratios. Only an axial flow is identified in the plain tube whereas both axial and swirl flows are detected in the tube with twisted tape inserts. The turbulence kinetic energy in the tube with twisted tapes is significantly higher than that in the plain one, which is useful for non-Newtonian fluid with higher viscosity. Also, the temperature fields in the tube with twisted tapes are disturbed relative to those in the plain one, due to stronger turbulence intensity and better fluid mixing. Higher amounts of nanoparticles concentration and lower twist ratios, giving maximum values of total efficiency, display the advantage of using non-Newtonian nanofluid in the tube with twisted tape inserts rather than non-Newtonian base fluid in the plain one.     

近年来关于硬质合金刀片切屑控制研究的新成果

在当代技术背景下，对切屑控制问题进行深入的研究，具有重要的意义。研究的内容包括三个方面，即切屑的生成学、切居卷曲以及切屑的折断力学。本文主要阐述近年来关于硬质合金刀片切屑流向、切屑卷曲以及切清折断研究的一些新成果．     

Prediction of friction factors and heat transfer coefficients for turbulent flow in corrugated tubes combined with twisted tape inserts. Part 1: friction factors

A simple mathematical model following the suggestion of Smithberg and Landis has been created to predict the friction factors for the case of a fully developed turbulent flow in a spirally corrugated tube combined with a twisted tape insert. The flow field is divided into two principal regions--a helicoidal core flow modified by secondary circulation effects and a twisting boundary layer flow. The “wall roughness” has an effect simultaneously on the axial velocity, secondary fluid motion and the resulting swirl mixing. The model reflects the influence of the “wall roughness” on the axial and tangential velocity components. The calculated friction factors have been compared with 570 experimental points obtained from 57 tubes tested. Five hundred points (87.7%) have a relative difference of less than ±15%; fifty one points (8.9%) have a difference of within ±(15-20)% and only nineteen points (3.4%) have a relative difference greater than ±20%.     

EXPERIMENTAL STUDIES ON HEAT TRANSFER AND FRICTION FACTOR CHARACTERISTICS OF TURBULENT FLOW THROUGH A CIRCULAR TUBE FITTED WITH RIGHT AND LEFT HELICAL SCREW-TAPE INSERTS

Experimental investigation on heat transfer and friction factor characteristics of a circular tube fitted with right-left helical screw inserts of equal and unequal length of different twist ratios is presented. The experimental data obtained were compared with those obtained from plain tube published data. The heat transfer enhancement for right-left helical screw inserts is higher than that for straight helical twist for a given twist ratio. The effect of right-left twist length on heat transfer augmentation is presented. The empirical relations for Nusselt number, friction factor relating Reynolds number, twist ratio, and right-left twist distance were formed and found to fit the experimental data within 10% and 20% for Nusselt number and friction factor respectively. Performance evaluation analysis was made, and the performance ratio of more than one was obtained, indicating that the proposed twist inserts can be used effectively for heat transfer augmentation without any loss in pumping power.     

电热咖啡壶过滤器注射模设计

根据塑件的结构特点,电热咖啡壶过滤器注射模选用1模2腔的结构形式,采用点浇口从塑件的中心部位进料,保证了塑件使用的质量要求。对塑件外圆上的槽位,模具采用了斜导柱和瓣合滑块的侧向分型抽芯机构,解决了制件成型后的脱模问题。模具安装在注射机上成型时,要保证这种带有不锈钢过滤网和铜质螺纹嵌件在模内的定位和固定,使塑件在成型后获得了良好的质量。     

管壳式换热器强化传热研究进展

随着对节能减排重视程度的提高,换热器的强化传热问题得到了越来越深入的研究,本文介绍了近年来管壳式换热器强化传热研究的一些相关成果,列举了几种应用于管壳式换热器中管程与壳程强化传热的典型元件和结构,为下一步研究工作的开展奠定了基础.     

梯形波带扰流元件对高黏度流体强化传热效率影响的实验研究

在流体介质为高黏度流体下,对管内插入梯形波带强化传热效率进行了实验研究。实验过程中,采用水浴换热器。管壳外为85℃的水浴,管内介质流体为原油。实验在雷诺数Re为15.4～36.9进行测量。实验结果表明,与光滑管比较,插入梯形波带后虽然压差阻力略有增加,但强化传热效果提高显著。通过评价分析得出曲线图表,表明梯形波带内插件适用于高黏度流体。