Results of 0.5% cold-leg small-break LOCA experiments at ROSA-IV/LSTF: Effect of break orientation

Three 0.5% cold-leg small-break loss-of-coolant accident (SBLOCA) experiment were conducted at the ROSA-IV Large Scale Test Facility (LSTF) to investigate the effects of break orientation on system thermal-hydraulic responses. In these three experiments, the break hole was located at the side, bottom, and top of the horizontal cold leg, respectively. Although the key phenomena observed in the three experiments were basically the same, the break flow rate was affected by the break orientation when phase stratification occured in the cold leg; the break flow rate was largest for the side break and smallest for the top break. The RELAP5/MOD2 code failed to predict the difference in the break flow rate observed in the experiments. Modification to the break flow calculation models, for both subcooled and two-phase flow discharge conditions, resulted in good agreement between data and predictions.     

On Vaporizing Water Flow in Hot Sub-Vertical Rock Fractures

Water injection into unsaturated fractured rock at above-boiling temperatures gives rise to complex fluid flow and heat transfer processes. Examples include water injection into depleted vapor-dominated geothermal reservoirs, and emplacement of heat-generating nuclear wastes in unsaturated fractured rock. We conceptualize fractures as two-dimensional heterogeneous porous media, and use geostatistical techniques to generate synthetic permeability distributions in the fracture plane. Water flow in hot high-angle fractures is simulated numerically, taking into account the combined action of gravity, capillary, and pressure forces, and conductive heat transfer from the wall rocks which gives rise to strong vaporization. In heterogeneous fractures boiling plumes are found to have dendritic shapes, and to be subject to strong lateral flow effects. Fractures with spatially-averaged homogeneous permeabilities tend to give poor approximations for vaporization behavior and liquid migration patterns. Depending on water flow rates, rock temperature, and fracture permeability, liquid water can migrate considerable distances through fractured rock that is at above-boiling temperatures and be only partially vaporized.     

低渗透煤层气藏中气-水两相不稳定渗流动态分析

针对低渗透煤层渗流问题,考虑启动压力梯度及其引起的动边界和动边界内吸附气解吸作用的渗流模型研究目前仅限于单相流,而更符合实际的气-水两相渗流动边界模型未见报道.本文综合考虑了煤层吸附气的解吸作用、气-水两相渗流、非达西渗流、地层应力敏感等影响因素,进行了低渗透煤层的气-水两相渗流模型研究.采用了试井技术中的"分相处理"方法,修正了两相渗流的综合压缩系数和流度,并基于含气饱和度呈线性递减分布的假设,建立了煤层气藏的气-水两相渗流耦合模型.该数学模型不仅可以描述由于低渗透煤层中渗流存在启动压力梯度而产生的可表征煤层有效动用范围随时间变化的移动边界,还可以描述煤层有效动用范围内吸附气的解吸现象以及吸附气解吸作用所引起的煤层含气饱和度的上升;为了提高模型精度,控制方程还保留了二次压力梯度项.采用了稳定的全隐式有限差分方法进行了模型的数值求解,并验证了数值计算方法的正确性,获得了模型关于瞬时井底压力与压力导数响应的双对数特征曲线,由此分析了各渗流参数的敏感性影响.本文研究结果可为低渗透煤层气藏开发的气-水两相流试井技术提供渗流力学的理论基础.     

Aqueous two-phase systems: A viable platform in the manufacturing of biopharmaceuticals

The number of biotechnology-based pharmaceuticals in the late-stage pipeline has been increasing more than ever. As a result, there is an enhanced demand for more efficient and cost-effective processes. During the last years, the upstream technology for the production of biopharmaceuticals has been considerably improved. Continuous discoveries in molecular biology and genetics, combined with new advances in media and feed development, have significantly increased the production titres. In order to keep up this gain, it is now essential to design new, as well as to improve the existing downstream processes that remain an unresolved bottleneck. This review evaluates several alternatives to the currently established platforms for the downstream processing biopharmaceuticals, with main focus on aqueous two-phase extraction.     

双侧进气突扩燃烧室内液雾燃烧的数值模拟

本文采用全双流体模型对部分切向进气管式双侧进气突扩燃烧室内的液雾燃烧过程进行了数值模拟，将液雾群按初始尺寸分组，数值模拟结果表明不同尺寸液雾的蒸发及燃烧过程显著不同，小尺寸的液雾是先蒸发后燃烧，而较大尺寸的液雾则是边蒸发边燃烧．模拟结果还表明，部分切向进气方式有利于在燃烧室的头部产生大面积的中心回流区，该回流区的存在有利于加强混合及火焰稳定．     

机械加工多孔层在大气压和高于大气压时的沸腾换热

1引言在过去的二十年中，已研制出诸如HighFI。、Thermoexcel－E、Ge、－T、CIT等多种高性能强化沸腾换热结构［‘－’］，其中ThermoexcelE型结构是机械加工多孔层中有代表性的一种，并进行了较多研究＊‘］。但迄今为止，研究工作多限于一个大气压时的沸腾工况［‘，’］，而较少涉及非大气压时的情形。本文对一种ThermoexcelE型机械加工多孔层在大气压和高于大气压时的沸腾传热进行了实验，提出了简化物理模型，进行了流动与传热分析，综合实验数据，建立了相应的传热关联式。2实验研究实验装置参见文献＊。多孔层基体为厚壁紫铜管…     

螺旋管锅炉反应器管内汽液两相流压力降脉动研究

本又根据闭式循环热动力推进系统中锅炉反应器的各种可能的航行方向及运行参数，对螺旋管内汽液两相流压力降脉动特性进行了系统的试验研究，首次区分了两类不同特征的压力降脉动并得到了各主要因素的影响现律和发生脉动的界限准则。     

水轮机转轮内部的三维固液两相紊流计算

1引言本文利用两相流动的多流体模型和k－。－A。两相索流模型计算水轮机转轮内部的三维固液两相紊流。在索流两相流动的多流体即多连续介质模型中，离散相看成是Euler坐标中处理的拟流体。与小滑移和无泪移模型不同的是，多流体模型可以分别考虑大滑移和离散颗粒扩散，其间无直接联系，并且能够充分考虑离散相质量、动量及能量的湍流扩散山本文利用速度压力校正法之一：SIMPLEC法进行数值计算。该法最早使用在S．VPatankar和D．B．Snalding在1972年提出的SIMPLE算法中间，本文将其推广到具有交错网格的非正交贴体坐标系中计算三维…     

Relationships between distributions of chord lengths and distributions of bubble sizes including their statistical parameters

The performance of fluidized beds is strongly influenced by bubble behavior. Among various hydrodynamic properties, bubble size distributions are of prime concern, but in practice, bubble size is not readily measured. When a probe is used to determine bubble size, it intersects a bubble with a chord length other than the largest vertical dimension. The relationships between the size distribution of bubbles in the bed, the size distribution of bubbles touching the probe and the distribution of chord lengths must be resolved for correct interpretation of probe signals. A method for translating statistical parameters, namely mean and standard deviation of chord lengths to mean and standard deviation of bubble sizes, and an approach to infer the size distribution of bubbles touching the probe and the size distribution of bubbles in the bed system by using the distribution of chord lengths measured by a probe in closed form are proposed for the first time.     

Effects of Relative Permeability History Dependence on Two-Phase Flow in Porous Media

Hysteresis phenomena in multi-phase flow in porous media has been recognized by many researchers and widely believed to have significant effects on the flow. In an attempt to account for these effects, a theoretical model for history-dependent relative permeabilities is considered. This model is incorporated into 1-D two-phase nondiffusive flow system and the corresponding flow is predicted. Flow history is observed to have a notable impact on the saturation profile and fluids breakthrough.