Evaporation and Evolution of Suspended Solution Droplets at Atmospheric and Reduced Pressures

Thermal history and solute precipitation behavior of suspended solution droplets of sodium chloride (NaCl), magnesium sulphate (MgSO₄), and zirconium hydroxychloride (ZrO(OH)Cl) evaporating at atmospheric and reduced pressures are studied. Experimental measurements on the variation of droplet diameter, solution concentration, and temperature during the evaporation period are presented and discussed. The results of solute precipitation behavior in solution droplets observed under an optical microscope are displayed and discussed. Results indicate that reducing the pressure (∼ 33 kPa) results in a change in the solution droplet evaporation rate, but the thermal histories of a particular solution droplet are similar at the atmospheric and reduced pressures. At atmospheric and reduced pressures used in this study, the d² law for solution droplets is valid at early stages of the evaporation and before the solute precipitation initiates. Drying of MgSO₄ and ZrO(OH)Cl solution droplets results in the formation of spherical particles, whereas drying of spherical NaCl solution droplets results in the formation of cubic particles.     

Influence of Coherent Flow Structures on the Dynamics of Suspended Sediment Transport in Open-Channel Flow

The influence of suspended sediments on coherent flow structures has been studied by simultaneously measuring the longitudinal and vertical components of the instantaneous velocity vector and the instantaneous suspended particle concentration with an acoustic particle flux profiler. The measurements were carried out in clear water and in particle-laden open-channel flows. In both cases, they clearly show the predominance of ejection and sweep phases that are part of a burst cycle. The analysis further demonstrates the importance of the ejection and sweep phases in sediment resuspension and transport. Ejections pick up the sediment at the bed and carry it up through the water column close to the surface. It is shown that ejections and sweeps are in near equality in the near-bottom layer, whereas ejections clearly dominate in the remaining water column. The implications of these results for sediment transport dynamics are discussed.     

EFFECT OF SUSPENDED FIBRES ON MACRO-MIXING AND MICRO-MIXING IN A STIRRED TANK REACTOR

The effects of suspended fibre on macroscale and microscale mixing in a small stirred tank reactor were studied under batch conditions using the competitive, consecutive azo coupling between 1-naphthol and diazotized sulfanilic acid. The mixing quality was determined from the distribution between the mono and bis substituted reaction products. Nylon (2 and 3 millimeters in length) and fully bleached softwood kraft pulp (FBK) fibre suspensions were examined at volumetric concentrations up to the limit that complete suspension motion could be maintained in the vessel at impellet rotational speeds of 7 and 10s^-1. The adsorption of the product dyes on the fibre was found to be proportional or very nearly proportional to their concentrations in the aqueous phase and did not interfere with the assessment of mixing in the suspension.

Suspended fibres were found to slightly increase the 'critical feed time' of the diazotized sulfanilic acid, corresponding to an increase in the macromixing or bulk blend lime of the vessel. Continued increase in the fibre concentration led to the formation of a well mixed cavern centered on the impeller and the creation of stagnant regions adjacent to the vessel walls. The departure from the Newtonian fibre-free case is due to changes in the flow through and distribution of the energy dissipative regions in the vessel. The most effective location for chemical addition to ensure good microscale mixing remains in the impeller vicinity.     

淤浆鼓泡床中固体粒子的悬浮特性

研究了三相鼓泡床中的临界固含率,以空气作气相,水、乙醇-水、丙酮-水、萜松醇-二甲苯作液相,石英砂、煤、雷奈镍作为固相。分析了鼓泡柱的高径比、气体速度、固体粒子的大小和比重、液体的粘度对临界固含率的影响,提出了含有这些参数的无因次数群的关联式,讨论了本文提出的关联式和文献报导的差别。     

Removal of paraquat in aqueous suspension of TiO<Subscript>2</Subscript> in an immersed UV photoreactor

Experiments were performed to investigate the effect of operating parameters on the photodegradation efficiency of paraquat in a TiO₂-suspended photoreactor with immersed UV lamps. TiO₂ particles were prepared by a hydrothermal method. The removal rate of paraquat in the reactor was 0.54 mg/l/h with only air-sparging. The removal rate in 24 h with both the UV radiation and air-sparging was 50% higher than that with only the UV radiation. Variations of the paraquat concentration at the UV intensities of 4 and 8 W/m₂ decreased slowly with time, but that at 12 W/m₂ decreased more rapidly. The removal efficiency at the air-sparging flow rate of 1 //min increased as a UV light intensity increased. pH value in the reactor at the UV intensity of 12 W/m₂ decreased with time until 12 h and then increased with time over 12 h.     

低渗透中等偏强水敏油层储层保护技术的研究——以辽河油田强1块为例

强1块本身储层物性差,属于低孔、低一特低渗储层,粘土含量高,水敏表现为中等偏强。对于这种低渗区块进行注水开发时,储层的保护措施尤其关键。针对上述特点,确定各种工作液注入时相关临界值参数,同时开展防膨剂优选和注入水质的研究,采用离心法和X衍射法筛选了12种防膨剂的防膨效果,并进一步优化防膨剂的注入方式和注入浓度。结果表明,6#防膨剂效果好,现场可以先期采用注入质量分数为1％段塞,之后采用防膨剂质量分数为0．5％连续注入;从而实现该块自实施注水以来,注水压力稳定,且达到日配注量的要求,成功实施注水开发。     

3D numerical simulation of the behaviour of a spherical particle suspended in a Newtonian fluid and submitted to a simple shear

The 3D flow around a rigid spherical particle suspended in a Newtonian fluid and submitted to simple shear is numerically studied using Rem3D^® finite element code. The sphere motion is imposed by a sticking contact between the sphere and the fluid. The effect of the particle size as compared with the finite dimension of the shear cell was investigated. The direct calculations show that 3D modelling is necessary to correctly predict the sphere behaviour. The proximity of the particle and the cell walls strongly affects the flow velocities, the sphere motion (increase of the rotation period of the sphere) and the stress field (change of orientation angle and increase of maximal local stresses).     

基于HJ-CCD的漫湾坝区河流悬浮物浓度遥感反演

坝区河流悬浮物浓度监测对于评估水利水电工程对河流水质影响具有较大的意义。HJ\|CCD重返周期短、空间分率高等优点,应用于漫湾这种中小尺度坝区水体悬浮物浓度监测有着重要的现实意义。大气校正采用暗像元、FLAASH以及QUick Atmospheric Correction(QUAC)几种常见的基于图像的大气校正方法。大气校正结果表明:暗像元法效果较好,其第2波段和第3波段的平均相对误差分别为16.1%和17.9%。然后,应用其大气校正较好的波段构建适用于研究区的悬浮物浓度反演模型。结果表明,该模型的决定系数为0.92,均方根误差(RMSE)为4.83 mg/L,平均相对误差为33.1%。最后,将此反演模型应用于2014年影像质量较好的HJ\|CCD数据上,得到了其悬浮物浓度空间分布图,反映了漫湾坝区附近的悬浮物浓度的变化规律。