三维模型下油气泡对流量计输出影响的研究

运用有限元软件ANSYS对电磁流量计中存在的非导电物体建立三雏立体仿真模型,研究了流量计流体中不同的径向位置存在球形气泡时流量计的响应特性,在流体中存在多个不同径向位置与不同大小球形气泡流量计的响应特性,为电磁流量计在多相流测量中提供一定依据.     

油气泡对电磁流量计影响径向仿真研究

电磁流量计开始应用于多相流流量测量,运用有限元软件Ansys对电磁流量计中存在非导电物体建立径向仿真模型,在径向截面上研究了流量计中含有非导电物质时流量计的响应特性,并以此分析了含水率不同对流量计信号的影响,为电磁流量计在多相流测量中提供一定的依据.     

气液两相流参数测量中弧状电极电磁流量计理论分析

常用电磁流量计的电极为点状形式,广泛用于管道流体速度分布呈轴对称的单相流参数测量,当流速呈非轴对称分布时则引起测量误差。为满足两相流参数测量要求,改善点状电极结构对流速分布的敏感性,提出了采用弧状电极结构形式电磁流量计对两相流参数进行测量。采用解析计算法研究了弧状电极电磁流量计的特性:对弧状电极测量敏感场的权重函数分布进行了计算,同时为降低管道流体流速分布对测量准确性的影响,根据权重函数分布均匀性,确定了弧状电极电磁传感器的结构参数;分析了垂直上升管气液两相流典型流型时弧状电极电磁流量计的响应特性。分析结果表明,弧状电极电磁流量计的权重函数分布相比点状结构形式要均匀得多,其响应特性分析给出了两相流测量中电极之间测量电压与流体速度之间的关系,从而为弧状电极电磁流量计在气液两相流参数测量中的应用提供了理论基础。     

环氧丙烷装置流量仪表的选型及应用

根据环氧丙烷装置中流体的不同物理化学特性、不同的精确度等级要求等,提出了几种流量计的选型方案。详细介绍了电磁流量计、质量流量计、涡街流量计等流量仪表。     

电磁流量计的正确选择

本文根据电磁流量计的工作特性,结合自己的实践经验,主要从电磁流量计的口径、量程、衬里材料、电极材料和防护等级等方面,探讨了电磁流量计在选择时的一些注意事项.     

电磁流量计在硝酸磷肥装置中的应用

由于天脊集团硝酸磷肥装置中相当多的介质为导电液体,故可用电磁流量计测定流体流量.阐述电磁流量计的工作原理、分类及特点;如何根据分类特点与生产工艺、介质特性、现场环境和精度要求选择合适的电磁流量计;电磁流量计应用中的注意事项.根据10余年的实践,认为一体型电磁流量计比分离型电磁流量计易于维护,指示稳定可靠,较适于硝酸磷肥装置的特殊环境要求.     

垂直管中油,气,水三相流总流量测量模型研究

基于集流型涡轮流量计与放射性低能源密度—持水率计在大庆生产测井研究所油、气、水三相流动环路中的实验响应结果，首先考察了用于气液两相流中涡轮流量计的Ａｙａ物理模型，进而提出了经过校正后用于确定油、气、水三相流总流量的测量模型，用此模型预测三相流总流量与流动环标定数据对比后其误差小于５％，满足了石油工业应用要求     

非牛顿流体中双喷嘴连续气泡的生成与聚并

采用VOF-CSF法模拟研究了幂律型非牛顿流体中双喷嘴气泡的生成及聚并行为,得到稳定状态下3种不同的气泡流型:1两喷嘴处的气泡在生成过程中发生聚并;2两喷嘴处的气泡交替生成并发生在线聚并;3两喷嘴处的气泡几乎同时生成,在上升过程中由相互吸引变为相互排斥,无聚并现象发生。第1、2种流型中,先前生成气泡的尾流会对正在生成的气泡产生显著影响,使气泡倾向液体流动的方向生成;第3种流型中,气泡间因涡流重叠面积的不同和液相惯性力作用,在上升过程中由开始的相互吸引逐渐变为相互排斥。     

Φ29电磁流量计基本原理及常见影响因素分析

电磁流量在油田开发中主要应用于水井的分层流量测试和验漏.电磁流量计受到测井环境、套管状况、井内流体性质等因素的影响,会出现示值偏差,介绍电磁流量计原理,同时就影响流量计测井的几个因素进行了浅析,对油田后期开发测井生产有指导作用.     

气泡上浮运动与传热传质的耦合模型

针对舰船主机尾气消尾流技术中的气泡上浮运动,分别建立气泡非等温传热、瞬态非平衡传质及其速度、半径等各微分方程,进而构建液体中高温气泡上浮运动的耦合模型。将模型仿真结果与实验、文献研究比对,获得并分析气泡半径及运动速度的误差值,证明模型能够模拟不同温差的气泡在液体中的上浮过程,并得到气泡运动特性的影响规律:传质加速小气泡消失,使中等气泡半径持续减小,但对大气泡影响微弱;气泡运动初期为迅速的非等温传热过程,随气泡半径增大,热流密度变化幅度及热传导效率均下降;压强对气泡运动影响基本保持不变。三者综合作用使非等温传热初期气泡半径迅速下降。随后大气泡平缓增大;中等气泡缓慢地先减小后增大;而小气泡逐渐溶解在液体中。     

Distribution of the free and oil‐trapped air bubbles in simulated broths containing fungal biomass

The location of air bubbles (i.e. inside oil drops or free in the aqueous phase) was studied by image analysis as a function of the oil and biomass concentrations in a 2 L stirred tank using a simulated fermentation medium (aqueoussalt solution, castor oil, air and fungal biomass) agitated by a Rushton turbine. The solid (fungal) phase plays an important role in defining the location of bubbles, as the percentage (in bubble volume) of bubbles trapped in oil increases threefold when biomass is added to the medium. The bubbles located inside oil drops were found to occupy 60% of the total bubble volume and to be 40% smaller than those which were non‐oil associated. This phenomenon has important implications for oxygen mass transfer in multiphase fermentations.     

An optical approach for identifying the nature and the relative 3D spatial position of components of complex structures formed in multiphase dispersion systems

This paper describes a novel method that makes possible the identification of the nature and the 3D relative spatial position (free or embedded) of the components of complex structures (oil drops, water droplets, air bubbles and multiphase drops) formed in dispersions occurring in fermentation systems, without disturbing (either chemically or physically) the dispersion. Using the refraction index differences between each phase and the image-forming properties of the complex objects formed in addition to the relative size of the bright part of the spheres, it was possible to determine the nature of each type of structure, as well as to discern whether these structures were located inside or outside of the multiphase oil drops. This method allowed determining unequivocally that the small droplets observed within the complex oil drops are part of the aqueous phase and are trapped inside the oil drops, together, in some cases, with air bubbles.     

Effect of microwave energy dissipation on drying process of berry puree under microwave foam drying conditions

ABSTRACT

Microwave foam drying (MFD) is a novel drying technology particularly for the drying of agricultural products with high viscosity and thermal-sensitive components. The effect of dissipation of microwave energy on the drying process of berry puree was investigated in MFD conditions. The results show that the dissipation of microwave energy induces the vapor pressure inside the berry puree to improve the formation of bubbles. The changes of pressure inside bubbles of berry puree follow Sine equations. The favorable conditions of bubbles formation inside berry puree are the temperature of 70–80°C with the corresponding viscosity of 70–80?pa?s and moisture content of 80–85% (wb). The dissipation of microwave energy in berry puree tends to decaying trend due to the changes of dielectric properties. Moisture content has the most significant positive effect on both dielectric constant and dielectric loss factor of berry puree, followed by the density, and the drying temperature has the least but significant effect on both indicators. The focusing phenomenon of microwave irradiation depended on the dielectric properties determines the distribution of temperature of berry puree. The findings in current work contribute to a better understanding the MFD behavior of berry puree and will help to optimize the drying conditions of MFD for enhancing energy efficiency and drying quality.     

超声波场中蒸汽气泡凝结过程及传热特性

利用高速摄像仪记录有、无超声波时注入过冷水中蒸汽气泡的凝结过程,以分析超声波对蒸汽气泡凝结过程及传热特性的影响。结果表明:在超声波场中,蒸汽气泡表面会形成晶格状毛细波,有效增加气泡表面积,并加强气泡周围流体热边界层扰动,从而导致凝结换热的强化及气泡凝结速度加快。基于15~60 K过冷度下,有、无超声波时较大蒸汽气泡凝结的实验数据,拟合得出有、无超声波时的气泡凝结换热经验关联式,预测误差在±30%以内。     

R410A-油混合物在5 mm内螺纹强化管内流动冷凝的摩擦压降实验研究

实验研究了环保制冷工质R410A-润滑油混合物在5 mm内螺纹强化管内流动冷凝的摩擦压降特性,探索了平均油浓度、干度和质流密度对摩擦压降的影响。实验测试工况为：冷凝温度为40℃,质流密度为200～400 kg•m^-2•s^-1,热通量为4.21～8.42 kW•m^-2,测试段入口干度为0.3～0.9,油浓度为0～5%。实验结果表明,对于纯制冷剂R410A和R410A-油混合物,摩擦压降随着质流密度和干度的增大而增大;对于R410A-油混合物,油的存在对混合物的摩擦压降的影响与干度有很大关系,中低干度时会减小压降,而高干度时会增加压降。在中低干度时,R410A-油混合物的摩擦压降当平均油浓度从0增长到5%时,最大可减小29%;在高干度时,当平均油浓度从0增长到5%时,最大可增加8%。     

ANALYSIS OF CONVECTIVE HEAT TRANSFER DURING IMMERSION FRYING

Immersion frying was studied as a high temperature drying process and analogies drawn between periods found in drying and similar periods in immersion frying. Analysis of external heat transfer during immersion frying showed a highly complex system of free and forced convection augmented by boiling conditions. Oil flow was found to be driven downward by buoyancy forces due to cooling at the sample surface then upward due to entrainment in vapor bubbles during boiling conditions. Experimental work showed the convective heat transfer coefficient to be a dynamic property ranging from 300 to 1100 W/m²°C and to be strongly coupled with bulk movement of the oil. Heat flux measurements found a peak flux of nearly 30,000 W/m³. Based on analysis of bubble dynamics it is hypothesized that heat flux increases with increased oil degradation through a reduction in vapor bubble size and increase in bubble frequency due to changes in interfacial properties of the oil.     

Shock induced condensation in a fuel-rich oxygen containing bubble in a flammable liquid

Shock induced dynamics and explosion of a single oxygen containing bubble in liquid cyclohexane is calculated. The possibility, in principle, of fuel vapor condensation during bubble compression is shown. This condensation takes place, if the gas inside the bubble has a relatively high initial temperature or a low initial pressure. As a result of fuel vapor condensation the bubbles, which have an initial gas composition above the upper flammability limit, can, nevertheless, explode.It is shown that the fuel vapor condensation in fuel-rich bubbles is possible during compression stages of oscillations and during a few milliseconds after the end of bubble dynamics. The rate of the condensation process is estimated. According to estimations, this process is fast enough to significantly change the chemical composition of the bubble and shift it into the flammable range even during the compression stage of the first bubble oscillation.Explosion limits of a single bubble as a function of initial temperatures and pressures are calculated. It is shown that condensation processes extend the explosion range.The influence of a chemically inert gas (argon), on the bubble ignition threshold and parameters of bubble explosion is analyzed. It is shown that argon addition in a bubble can reduce the ignition threshold and therefore increase the explosion hazard. On the other hand, such additions reduce explosion pressure and can be used for mitigation of explosions in bubbly liquids.     

R410A-油混合物在7 mm强化管内流动沸腾的换热特性

实验研究了环保替代制冷工质R410A-润滑油混合物在强化管内的流动沸腾换热特性,探索了质流密度、干度和平均油浓度对换热特性的影响。实验测试管为内螺纹强化管,长度为2000 mm、外径为7.0 mm。实验结果表明,纯制冷剂R410A的传热系数随干度的增大先增大后减小,峰值出现在干度为0.7～0.8左右;对于R410A-油混合物,在干度小于0.5的工况下,油的存在增强换热,在干度大于0.6的高干度情况下,传热系数随平均油浓度和干度的增大迅速降低。基于混合物性开发了R410A-油混合物在7 mm强化管内流动沸腾的换热关联式,新的关联式预测值与89%的实验数据的误差在±30%以内,平均误差为17.3%。     

超声波流量计用于原油大流量贸易计量的方案论证

超声波流量计现阶段多应用于天然气贸易计量上,对于原油贸易计量国内还没有相关标准。本文对超声波流量计用于海上平台原油大流量外输贸易计量做了方案的论证:针对海上平台空间有限的特点,对比了标准容积法、基准流量计法、标准体积管法等常用方案,采用标准体积管与基准流量计共同检定的方案,保证了计量精度,减小了流量计的尺寸和重量,降低了维护、运营成本,降低了能耗,满足国内原油贸易计量的要求。