A study of hydrate plug formation in a subsea natural gas pipeline using a novel high-pressure flow loop

The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content （10%） of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.

Experimental research on characteristic of start-up pressure wave propagation in gelled crude oil by large-scale flow loop

In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-up pressure wave speeds under various operation conditions were measured,and effects of correlative factors on pressure wave were analyzed.The experimental and theoretical analysis shows that thermal shrinkage and structural properties of gelled crude oils are key factors influencing on start-up pressure wave propagation.The quantitative analysis for these effects can be done by using volume expansion coefficient and structural property parameter of gelled crude oil.A new calculation model of pressure wave speed was developed on the basis of Large-scale flow loop experiment and theoretical analysis.

UPFC setting to avoid active power flow loop considering wind power uncertainty

The active power loop flow(APLF)may be caused by impropriate network configuration,impropriate parameter settings,and/or stochastic bus powers.The power flow controllers,e.g.,the unified power flow controller(UPFC),may be the reason and the solution to the loop flows.In this paper,the critical existence condition of the APLF is newly integrated into the simultaneous power flow model for the system and UPFC.Compared with the existing method of alternatively solving the simultaneous power flow and sensitivity-based approaching to the critical existing condition,the integrated power flow needs less iterations and calculation time.Besides,with wind power fluctuation,the interval power flow(IPF)is introduced into the integrated power flow,and solved with the affine Krawcyzk iteration to make sure that the range of active power setting of the UPFC not yielding the APLF.Compared with Monte Carlo simulation,the IPF has the similar accuracy but less time.

FLOW AND DIFFUSION IN SELF-ASPIRATED REVERSE FLOW JET LOOP REACTOR

1 INTRODUCTIONGas and liquid distributions in a self-aspirated reverse flow jet loop reactor dependchiefly on the aspiration and the breakup against gas phase by the liquid nozzle aswell as the redistribution in the draft tube.It has also been noted that effective diffu-sion or backmixing in the reactor has great influence on the flow and mass transferrates.In this case,accurate descriptions about the fluid flow and diffusion conditions inthe reactor are most necessary for effective amplification of them.

FRACTAL STUDIES IN A SELF-ASPIRATED REVERSED FLOW JET LOOP REACTOR

1 INTRODUCTIONSelf-aspirated reversed flow jet loop reactors,characterized by a well defined flow pat-tern,well better dispersing effects,relatively low power consumption and a high masstransfer coefficient,are widely used in chemical engineering,especially in biochemicalengineering.The characteristics of such reactors are highly random or stochastic due tothe influence of a variety of phenomena such as jetting and bubbling of the

Modeling of Continuous Cross-flow Microfiltration Process in an Airlift External-loop Slurry Reactor

New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.

Experimental Investigation on the Effection of Flow Regulator in a Multiple Evaporators/Condensers Loop Heat Pipe with Plastic Porous Structure

Multiple loop heat pipes which have two evaporators and two condensers in one loop are a kind of active heat transfer device. Since they have two evaporators and two condensers, the operating mode also becomes multiple. This work discusses the cases that multiple loop heat pipes were operated with one condenser at high temperature and the other at low temperature. To avoid the high temperature returning liquid and keep the multiple loop heat pipes work properly, the flow regulator which was made of polyethylene was designed, fabricated and applied in this test. The effect of flow regulator was confirmed and analyzed. In the test that large temperature difference existed between two sinks, it can be found according to the result that the flow regulator worked effectively and prevented the high temperature vapor to enter the inlet of common liquid line, which can keep the evaporators and returning liquid to operate at low temperature. With the increment of heat loads and the temperature difference between two sinks, the pressure difference between two condensers became larger and larger. When the pressure difference was larger than the flow regulator’s capillary force, the flow regulator could not work properly because the high temperature vapor began to flow through the flow regulator. According to the test data, the flow regulator can work properly within the sinks’ temperature 0°C/60°C and the two evaporators’ heat load 30/30 W.

Visual Study on Flow and Operational Characteristics of Flat Plate Closed Loop Pulsating Heat Pipes

This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.

Two-Phase Flow Modeling in a Single Closed Loop Pulsating Heat Pipes

Mathematical modeling of pulsating heat pipes through ‘first’ principles is a contemporary problem which remains quite elusive. Simplifications and assumptions made in all the modeling approaches developed so far render them unsuitable for engineering design. In this paper, a more realistic modeling scheme is presented which provides considerable try for thought toward the next progressive step. At high enough heat flux level, closed loop pulsating heat pipes experience a bulk internal unidirectional fluid circulation. Under such a condition, conventional two-phase flow modeling in capillary tubes may be applied. This has been attempted for single-loop PHPs. A homogeneous model and a separated two-fluid flow model based on simultaneous conservation of mass, momentum and energy, have been developed for an equivalent ‘open flow’ system. The model allows prediction of two-phase flow parameters in each sub-section of the device thereby providing important insights into its operation. The concept of ‘void fraction constraint’ in pulsating heat pipe operation is introduced and its relevance to future modeling attempts is outlined.

基于激光热成像的薄膜面向导热系数测试方法

提出一种基于激光热成像的薄膜面向导热系数测试方法。仿真论证了激光加热相较于常规电加热方案的热损失差异;分析了激光加热功率、表面换热系数、测温模型增益系数等关键参数标定问题,并设计了相应的方案。基于15个不同材料或厚度的薄膜和薄片样品进行了实验,测试结果和参考值相对偏差均<6%,其中导热系数<3 W/(m·K)的样品测试误差显著优于常规方法,这表明该方法可有效改善热流环路积分法对低导热薄膜的测试精度。

Numerical Simulation and Experimental Analysis of the Influence of Asymmetric Pressure Conditions on the Splitting of a Gas-Liquid Two-Phase Flow at a T-Junction

Dedicated experiments and numerical simulations have been conducted to investigate the splitting characteristics of a gas-liquid two phase flow at a T junction.The experiments were carried out for different gas-liquid velocities.The flow rates in the two branches were measured accurately to determine how the two considered phases distribute in the two outlets.The experimental results have shown that when the two outlet pressures are asymmetric,the two-phase flow always tends to flow into the outlet which has a lower pressure.As the inlet liquid velocity increases,however,the two-phase flow gradually tends to split evenly.Compared with the experiment results,the pressure difference between the two outlets can be determined more accurately by means of numerical simulation.The trends of experimental results and simulations are in very good agreement.

捻转血矛线虫LAMP-LFD检测方法的建立

为了建立一种用于检测捻转血矛线虫的特异、灵敏、快速的检测方法,用环介导等温扩增技术(LAMP)结合横向流动试纸条(LFD),针对捻转血矛线虫mt-COⅠ基因的保守序列设计特异性引物和探针,对反应温度、反应时间、Mg^(2+)浓度、dNTP浓度进行优化,建立了捻转血矛线虫环介导等温扩增技术与横向流动试纸条检测技术(LAMP-LFD)相结合的核酸检测方法。结果显示,建立的LAMP-LFD检测方法最低检测限为100 fg,对奥斯特线虫、夏伯特线虫、毛首线虫DNA检测均为阴性;50份临床样品检测结果与粪便虫卵检测法结果的符合率为96%。该方法操作方便、结果判定快速简单,有望成为流行区域和基层检测捻转血矛线虫的新方法。

应用于新型环路热管的两相引射器数值模拟

环路热管是一种高效被动式相变传热装置,广泛应用于高热流电子器件散热等领域。前期研究发现将小型两相引射器与平板式环路热管耦合,可大幅提高传热性能。然而,小型两相引射器内部流动及传热机理尚不清晰,难以对新型环路热管进行正向设计与理论建模。通过数值模拟研究了汽水参数和混合腔结构对两相引射器性能及内部流场分布的影响。结果表明,喉部下游存在凝结激波,随着背压增加,其位置逐渐向喉部移动;其强度与背压、蒸汽产量、混合腔长度呈正相关,与水温呈负相关。引射器最大工作背压在40~125 kPa,与蒸汽产量和水温呈正相关,与混合腔长度呈负相关。通过大量模拟,得到了设计功率下水温和混合腔长度对引射器工作模式和压比的影响规律。

热压作用下新风系统水力工况分析方法研究

热压作用导致通过竖直立管送风的空调新风系统水力失调且并联管路阻力不平衡,无法计算管网阻抗及进行水力工况分析,针对该问题提出了适用于热压作用下的新风系统水力工况分析方法。该方法将整体管网看作并联的各末端通风支管虚拟闭合环路,求解压阻平衡方程组,拟合了各闭合环路与管网的特性曲线方程,确定了虚拟闭合环路阻抗,实现了热压作用下管网流体流动及流量分配规律的描述。计算中考虑了管网流量与摩擦阻力系数、局部阻力系数的耦合关系。以某办公楼新风系统为例,利用环路阻抗方法对热压作用下管网的水力工况进行了分析,其计算结果与方程组迭代计算结果相吻合,表明了所提方法的准确性。

基于关键PMU量测的智能配电网跨供区合环潮流计算方法

为了降低功率损耗,提高潮流计算精度,提出基于关键同步相量测量装置(PMU)量测技术的跨供区合环潮流计算方法。在高次谐波作用下,利用变压器模型和电力线路模型,构建跨供区合环主要元件谐波模型,采用标准化残差检测法的思想,处理跨供区合环的不良数据。通过关键PMU量测估计不良数据量测的残差分量,利用增益矩阵定义跨供区合环不良数据检测的残差协方差矩阵,完成跨供区合环不良数据的检测,结合跨供区合环潮流计算流程设计,实现跨供区合环潮流的计算。算例结果表明,所提方法可以将潮流计算的各支路功率损耗控制在0.04 kW以内,通过将节点电压计算误差控制在0.004以内,提高了潮流计算精度。

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO_2

This work investigated the flow-accelerated corrosion （FAC） behavior of 13Cr in a wet CO2-containing environment at different flowing gas velocities mid impinging mlgles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet sys- tem. Surface molphology determination, electrochemical measurements, mid hydromechaziics numerical analysis were cmlied out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13Cr stainless steel. High-flow-rate gas destroyed the passive film mid decreased the pitting potential, resulting in more serious corrosion. The corrosion degree witk various im- pact mlgles showed the following order： 90~ 〉 60~ 〉 45~. The shear force and the electrolyte from the flowing gas were concluded to be the determinm^t factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.

Investigation of asphaltene deposition under dynamic flow conditions

Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially asphaltene, can lead to wellbore blockage and impacts well economics due to reduction in oil production. Therefore, it is necessary to pay more attention to finding some solution to overcome this problem. In this study, a pipe-loop apparatus for investigation of oil stability was employed to measure deposition thickness using a thermal method. The effects of many factors such as oil type, oil temperature, oil velocity, inhibitors, and solvents on asphaltene deposition were investigated. The results showed that the deposition increased with the increasing value of the colloidal insta- bility index. Besides, the deposition thickness increased with the decreasing velocity of oil, but did not change with oil temperature. In addition, n-heptane could result in more deposition; however, toluene had no effect on the deposi- tion. Branched dodecyl benzene sulfonic acid （Branched DBSA） and Linear DBSA as inhibitors decreased the rate of asphaltene deposition.

大屯锡矿尾砂膏体环管管输数值模拟研究

膏体管输沿程阻力是影响管道设计与采场充填质量的关键因素之一,采用Fluent建立与实际环管实验系统一样的管道输送的几何模型,分析得到不同管线沿程阻力损失之间的关系以及膏体配比参数对沿程阻力损失的影响规律。研究表明:膏体在管道中弯管处的速度和压力都发生急剧的变化,弯管外侧压力和速度明显大于弯管内侧,有着明显的梯度。在水平管段速度和压力在管道径向上存在明显的梯度,呈结构流的特点,分为柱塞流动区和边界层区域。在膏体管道输送中管道内膏体的速度和压力均存在着边界效应,随着流速的增大,管输阻力增大;随着膏体质量浓度增加,沿程管道阻力损失变大;随着屈服应力与塑性黏度的增加,沿程阻力损失也增大,获得了不同物料组成、管道内径、管流流速下水平段膏体压力损失,为大屯锡矿最终输送泵、充填管道选型提供了依据。

水源多联式空调系统设计实践与分析

以地处夏热冬暖地区的福州市某集团办公楼为例,阐述了水源多联式空调系统的构成、公共水环路的科学规划、循环水泵组变频控制策略的制定、冬季外部热源的选择等设计要点,并分析了其主要技术指标。分析结果显示,水源多联式空调系统经过科学、合理设计,制冷工况下较风冷多联式空调系统更节能、低碳、环境友好。在夏热冬暖及夏热冬冷地区空调供暖时,受限于室外机对水流量的低限要求,循环水泵组能耗居高不下,水源多联式空调系统能耗则高于风冷多联式空调系统。建议设备厂商在水源多联机的换热效率方向进行优化,降低室外机对水流量的低限要求。

多室内环流反应器中液体循环量的试验验证与模拟

目的对液相氧化脱硫多室内环流反应器液体循环量的影响因素进行模拟和验证。方法采用CFD数值模拟,基于欧拉-欧拉多相流模型,对液相氧化脱硫多室内环流反应器进行气液两相流模拟,考查了酸气流量和空气流量对液体循环量的影响。结果利用数值模拟得到的液体循环量与利用靶式流量计测得的液体循环量误差小于10%。当酸气中H 2S体积分数不超过3%时,液体循环量(z)与酸气流量(x)、空气流量(y)之间的关系式为:z=-474.996+0.358 x+0.4873 y。结论欧拉-欧拉两相流模型能够准确地预测液相氧化脱硫反应器内液体循环量。