Hydraulic Characteristics of Gabion-Stepped Weirs

Experimental studies on the hydraulics of flow through and over gabion-stepped weirs are presented. Two flow components were observed, i.e., base flow through the void between filled stones and overflow on the gabions. The energy loss ratios in the gabion-stepped weirs are greater than those in the corresponding horizontal stepped weirs by approximately 7, 10, and 14% for weir slopes of 30, 45, and 60°, respectively. As a result, the velocity at the outlet is lower. Stone size and shape have little influence on the energy loss and flow velocity as compared to the increasing effect of the weir slope. The pressure acting on the step face for the gabion-stepped weirs is less than that of the horizontal steps owing to the cushioning effect generated by filled stones. To reduce pressure on a step face at a fixed discharge for different weir slopes, the void ratio of the filled stones should be low to allow a small amount of base flow. The pressure distribution pattern on the horizontal face of a step is provided.     

井漏失返条件下的吊灌作业安全时间计算方法

"吊灌"作业是在井漏失返条件下保持井内压力动态平衡、获得安全作业时间的重要措施。但在实施吊灌作业时,由于反映井筒内环空液面变化规律的动态数模分析方法缺失,不能为工程实践提供吊灌的合理依据,使其基本处于"盲吊"状态。为此,笔者根据"吊灌"技术实际工况,首次采用井筒漏失动态分析方法,建立起吊灌安全作业时间数学模型,给出了多种漏失速率的积分结果,并结合现场实例对计算结果进行了验证。结果表明:(1)利用计算实例对数学模型的可靠性进行检验,计算结果与实际数据高度吻合;(2)适当增加吊灌量可以增加安全作业时间;(3)适当减少吊灌钻井液密度也可以增加安全作业时间。结论认为:该成果可以从根本上解决"吊灌"技术的安全作业时间准确计算问题,对于规避井漏失返条件下的井控安全风险、实现"吊灌"技术优化、降低工程费用等都具有重要意义。     

适用无源射频识别标签的集成压力传感器设计

针对无源射频识别 (RFID) 传感器标签发展的需求,采用商业化互补金属氧化物 (CMOS) 工艺,设计了一种集成电容式压力传感器及其接口电路。集成压力传感器采用金属层M1作为下电极,牺牲的金属层M2作为间隙层,通过过孔连接的金属层M3和M4及其介质构成上电极。传感器接口电路基于锁相环原理,采用全数字结构,将传感器信号转移到频率域处理。后期测试结果显示,所设计的压力传感器线性度高,温度稳定性好,接口电路在1 V电源电压下,只消耗了0.6 μW功率,尤其适用于无源RFID标签的设计。     

低流速下涡流二极管单向性实验研究

为研究氟盐冷却高温堆(Fluoride-salt-cooled High temperature Reactor,FHR)非能动余热排出系统的控流装置——涡流二极管在低流速下的性能参数,建立了实验装置,测试了在水工质下由3D打印尼龙材料涡流二极管的单向特性,并由实验结果得到相同结构尺寸的涡流二极管在FliBe工质下的压降值。研究结果表明,本文实验流量范围内测得的涡流二极管单向性随雷诺数的增加不断升高,最大值为23。正向流动阻力系数随雷诺数的升高不断降低,反向流动阻力系数随雷诺数的增大先增大后降低。研究结果还表明本文研究的涡流二极管结构不适用于小功率氟盐冷却高温堆非能动余热排出系统的设计。     

核电站主变重复出现乙炔气体问题分析与处理

对变压器进行了检查和分析,找到了产生乙炔气体的直接原因是裸金属低能放电,根本原因是高压套管与均压球连接结构存在问题,并采取了多种措施来处理该缺陷。     

新型井壁承压增强剂的制备及评价

海上钻井过程中经常会钻遇易漏层,从而影响钻进速度,严重损害储层。研制了一种由刚性粒子、软性粒子及可变形粒子组成的新型井壁承压增强剂ENPRES-Seal,通过可视砂床实验确定刚性粒子、软性粒子、可变形粒子的配比为2:1:2。评价结果表明,ENPRES-Seal在钻井液中建议加量为2%~3%,其对钻井液流变性影响小,抗温可达200℃,用于钻井液时不糊筛,对孔径为0.180 mm筛的通过率大于85%,能够改善钻井液润滑性能,较好地封堵各孔径砂床,使地层承压能力达17 MPa,且泥饼质量较好。该剂在上海平湖区块一口高温高压井的应用表明,ENPRES-Seal有效地提高了地层承压能力,该井井底温度超过180℃,完钻密度为1.90 g/cm3。      

Density of organic binary mixtures from equilibrium measurements

A reduction model for equilibrium measurements data (pressure–temperature–weight data) was developed. The model allows indirect measurements of the refrigerant concentration at the liquid and the gas phases and the solution density. The reduction model was validated by both comparing the obtained pressure–temperature–concentration relation at equilibrium conditions and solution densities with experimentally direct measurements carried out by Kriebel and Loffler [M. Kriebel, J. Loffler, Therodynamische eigenschaften des binary systems difluormono-chlormethan (R22) – tetraäthylenglykoldimethyläther (E181), Kältetechnik 17 (1965) 266–271] (up to 80 °C) and by us (up to 120 °C) over a wide range of pressure and temperature.     

Ice slurry: Pressure drop and deposition velocity

Ice slurries are used in indirect refrigeration systems. The storage tank of ice slurry systems decreases the maximum required cooling capacity of the equipment and smooths down the installation consumption. An advantage of ice slurry systems compared to chilled water systems is the higher cooling energy that can be delivered to customers using the same installed pipes. This paper gives a complete investigation of ice slurry pressure drops and deposition velocity. A model for the friction factor, obtained by empirical and semi-empirical approximation, is discussed. A new simple and efficient method is introduced to find the deposition velocity in an ice slurry fluid flow. Finally a variety of experimental results and some theoretical calculations of ice slurry flow patterns are shown.     

Friction factor correlation and pressure loss of single-phase flow inside herringbone microfin tubes

Pressure drop of single-phase turbulent flow inside herringbone microfin tubes of different fin dimensions has been measured experimentally to develop a general correlation of single-phase friction factor for the herringbone tubes. Water has been used as a working fluid and the mass flow rate has been varied from 0.03 to 0.2 kg/s, where the Reynolds number range is 10⁴ to 6.5 × 10⁴. Comparison of experimental data of the herringbone microfin tubes with those of helical microfin and smooth tubes shows that pressure drop of the herringbone tube is significantly higher than the helical and smooth tubes depending on the fin geometric parameters and mass velocity of the working fluid. Through semi-analytical approach and using the present experimental data, a new correlation of single-phase friction factor for the herringbone microfin tubes has been proposed incorporating the effects of fin geometric parameters. The proposed correlation can predict the experimental data within ±10%.     

Liquid side heat transfer and pressure drop in finned-tube cooling-coils operated with secondary refrigerants

In this study full-scale experiments with two different conventional cooling-coils aimed for display cabinets were performed. Heat transfer and pressure drop on the liquid side for three different single phase secondary refrigerants were studied and compared to predictions by existing correlations. Predominantly, the laminar flow regime was studied. The results show that when predicting the heat transfer performance on the liquid side of a cooling-coil the Gnielinski correlation for thermally developing flow and uniform wall temperature boundary conditions (T) leads to good agreement for 0.0014 < x^* < 0.017 if 50 < Re < 1700, assuming a new entrance length is formed after each U-bend. In addition, these entrance lengths must also be accounted for, when predicting the pressure drop on the liquid side of the cooling-coil. The uncertainty of measurement can be a problem in this type of investigations and this has been taken into consideration when analysing the results.