微通道中液氮的流动沸腾——两相流动压降分析

对液氮在直径为0.531 mm,加热长度为250mm的圆管中的流动沸腾压降和传热特性进行研究.作为第一部分,主要对微通道中液氮的两相流动压降进行试验研究与分析.结果表明:在核态沸腾起始时,质量流量迅速降低,而压降突然增大,并伴随着明显的温度滞后,幅度约为4.0～5.0 K.由于压降很大,在微通道内液氮的两相流动中会出现闪蒸,从而对质量干度产生重要影响.最后,利用均相模型和三个两相流动模型(L-M模型,Chisholm B系数模型和Friedel模型)对微通道沿程压降进行分析和比较.不同于常规通道的是,均相模型可以很好地预测压降试验结果,而三个两相流动模型的预测偏差较大,这是由于在微小通道中的高速流动情况下,汽相和液相混合比较均匀;同时液氮的液汽密度比很小,这也有利于均相模型的预测.     

Smart optical measurement probe for autonomously detecting nano-defects on bare semiconductor wafer surface: Verification of proposed concept

We propose a new method of inspecting a surface for fine defects that combines the optical inspection method with observation of the physical behavior of a liquid. A liquid thin film on a substrate behaves as a near-field physical probe that autonomously captures nano-particulate defects. Optical observation of the interfacial behavior of the liquid thin film is used to detect minute defects. This method combines the characteristics of optical detection (i.e., detection from a remote field and simultaneous detectability on a plane) and the high sensitivity of a physical near-field probe. We examined the basic principles of the proposed method through numerical calculation and applied it in experiments to detect fine particulate defects on a silicon substrate for semiconductor manufacturing to demonstrate the validity of the basic concept of the proposed method.     

The influence of the waveguide on the quality of measurements with ultrasonic Doppler velocimetry

The article is devoted to the study of the influence of geometric parameters of sound-conducting walls on the quality of measurement of liquid metal flow velocities by ultrasonic Doppler velocimetry. It was shown that the thickness and radius of a sound-conducting wall (waveguide) have a notable effect on the resulting velocity profiles. The flow in a round pipe, the length of which is much larger than its diameter, is considered as a reference flow. The positive effect of a stepwise waveguides with a diameter smaller than the diameter of the piezoelectric element of an ultrasonic transducer on the quality of velocity measurements was verified experimentally. It was found that the accuracy of the resulting velocity profiles largely depends on the length and the material of the waveguides, as well as the velocity of the incoming flow of liquid metal.     

Experimental study on free and submerged multi-jets

The flow characteristics of the hydraulic jump due to parallel jets are different from the classical jump emerging from a single gate. Due to the highly complex flow field at the downstream pool, deciding about the tailwater measuring location is a challenging issue affecting the flow measuring accuracy. Experiments are conducted herein, on different parallel jets’ configurations for both free and submerged flow conditions. To quantify the flow uniformity, for any downstream cross section, the associated momentum correction factors, β₂, were estimated for the free-flow condition. It is found that β₂-values depend significantly on the measuring location, and consequently the available conjugated depths relationship results in poor estimation when measuring location moves downstream. Employing Buckingham analysis, a general formula is proposed to calculate the momentum correction factors associated with the free hydraulic jump at different downstream measuring locations. The experimental results of this study indicated that such a formula enhances distinguishing between free and submerged flow conditions of the gates installed in parallel. Finally, a dimensionless stage-discharge formula is presented to predict the submerged flow rate through parallel gates of different gate openings and widths.     

Flow pattern identification and measurement techniques in gas-liquid-liquid three-phase flow: A review

The simultaneous flow of gas, oil, and water forms various flow patterns due to the complex interfacial relationships. Three-phase flow patterns are classified as the gas-liquid and liquid-liquid flow patterns. Pressure drop, void fraction, liquid holdup, and phase distribution are important characteristics of the three-phase flow. These characteristics are generally associated with the three-phase flow patterns. Hence, the knowledge about flow patterns can help to predict the overall behavior of the three-phase flow. Studies have been conducted to identify three-phase flow pattern and their characteristics at various superficial velocities of gas, oil, and water. The major purpose of the studies is to gather information about the three-phase co-current flow and use it for improvement of the efficiency of the flow systems. Therefore, the accuracy of the measurement technique is critical. Several types of flow pattern identification and measurement techniques have been developed to improve accuracy and provide high-quality results. In this article, classical and advanced techniques used for the three-phase flow identification and measurement have been reviewed. The survey will help the researchers working in the area of multiphase flow to choose the right technique based on the objectives of the studies.     

基于单片机实现的容错式锅炉液位传感器

依据现有锅炉液位检测的现状，设计了一种数字式锅炉液位传感器。该传感器利用单片机的并口测量液位数据，串口与上位机进行通讯，并能对传感器的故障进行诊断。经现场试运行表明：该传感器系统设计合理、可行，具有一定的容错能力，为系统维护及故障查找提供了方便，具有较高的性价比。     

基于单片机的超声波液位测量系统

介绍了超声波液位测量系统的工作原理和系统框图，给出了详细的超声波发射电路和环境温度采样电路。通过对接收信号采取一系列有效的处理方法：首先对接收信号采取STC(灵敏度时间控制)方式进行信号放大，接着对信号进行线性包络检波，最后采用微分电路和零点交叉检测，生成输出信号，基本上消隐了测量盲区和时间检测误差，并进行了温度补偿计算。采用模块化方式设计系统软件，成功地研制了基于单片机的超声波液位智能测量系统。实测表明，系统具有较高的测量精度和较强的适应性。     

基于光干涉原理的液晶空盒盒厚测量

液晶空盒厚决定了液晶盒中液晶层的厚度,对整个液晶显示器件的光电特性、底色及响应速度等有很大的影响。因此,如何准确地测量空盒盒厚具有实际的应用价值;本文从光干涉原理出发,推导出测量液晶空盒盒厚的简单而准确的方法,此方法适用于各种排列及任意扭曲角的液昌空盒,具有误差小、设备简单、操作简便等特点,充分满足了液晶显示器件生产厂家进行盒厚过程监控和优化年设计的需要。     

烟气粉尘脱硫治理喷射系统的计算

阐述烟气粉尘脱硫治理和喷射系统的结构。计算治理塔内液膜的层流底层和湍流层的速度、液膜的总流量及雾化旋动流体的附加流量。分析了治理塔内旋动气--固微粒流的分离性能,通过实验求得塔内旋流的准自由涡区的速度分布,计算分离的最小粒子直径。文中研究脱硫剂的动态喷雾与烟气含硫化合物的化学反应过程,讨论影响脱硫除尘治理效果的主要因素和喷射器的作用。最后介绍在工业炉窑烟气脱硫(SO     

固相萃取/等梯度高效液相色谱快速分析地表水中痕量多环芳烃化合物

利用固相萃取技术,进行水样吕痕量多环芳烃化合物的富集,克服了传统的液－－液萃取过程中超纯溶剂用量大和乳化现象;利用等梯度淋洗技术,实现了水中痕量多环芳烃化合物的快速分离,克服了以生梯度淋洗分离中的基线漂移和分析时间长的问题,每个样品的分析时间小于１５ｍｉｎ,利用荧光检测技术实现了水中７种多环芳烃的痕量分析,７种多环芳烃的检出限（ｎｇ／Ｌ）分别为：荧蒽１．１７,苯并（ａ）蒽０．６８,苯并（ｂ）荧蒽１