Gas–liquid mass transfer and flow phenomena in the Peirce–Smith converter: a water model study

A water model with a geometric similarity ratio of 1：5 was developed to investigate the gas-liquid mass transfer and flow charac- teristics in a Peirce-Smith converter. A gas mixture of CO2 and Ar was injected into a NaOH solution bath. The flow field, volumetric mass transfer coefficient per unit volume （Ak/V; where A is the contact area between phases, V is the volume, and k is the mass transfer coeffi- cient）, and gas utilization ratio （t/） were then measured at different gas flow rates and blow angles. The results showed that the flow field could be divided into five regions, i.e., injection, strong loop, weak loop, splashing, and dead zone. Whereas the Ak/V of the bath increased and then decreased with increasing gas flow rate, and n steadily increased. When the converter was rotated clockwise, both Ak/F and t/increased. However, the flow condition deteriorated when the gas flow rate and blow angle were drastically increased. Therefore, these para- meters must be controlled to optimal conditions. In the proposed model, the optimal gas flow rate and blow angle were 7.5 m3.h-1 and 10°, respectively.

Sediment transport following water transfer from Yangtze River to Taihu Basin

To meet the increasing ：need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration （SSC） of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the ：river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.

Analysis of surface cracking in water-cooled rolls and heat transfer between furnace chamber and rolls in a direct flame furnace

In the direct fired furnace of a continuous annealing line, seal rolls are susceptible to deformation that leads to surface defects of steel strips. According to failure analysis, the reasons include improper structural design and heat imbalance. An improved design has been proposed to reduce stress concentration and thermal radiation. A heat transfer model has been employed to determine the proper water flow rate for roll cooling. Industrial application proves that seal rolls with the new design has less deformation and longer service life.

Identification of Water Quality Model Parameter Based on Finite Difference and Monte Carlo

Identification results of water quality model parameter directly affect the accuracy of water quality numerical simulation. To overcome the difficulty of parameter identification caused by the measurement’s uncertainty, a new method which is the coupling of Finite Difference Method and Markov Chain Monte Carlo is developed to identify the parameters of water quality model in this paper. Taking a certain long distance open channel as an example, the effects to the results of parameters identification with different noise are discussed under steady and un-steady non-uniform flow scenarios. And also this proposed method is compared with finite difference method and Nelder Mead Simplex. The results show that it can give better results by the new method. It has good noise resistance and provides a new way to identify water quality model parameters.

Effect of Crop Root on Soil Water Retentivity and Movement

The objective of this study was to clarify the effect of crop root on soil water retentivity and movement to improve the crop growth environment and irrigation efficiency. To simulate soil water movement considering the crop root effect on the physical properties of soil, a numerical model describing the soil water and heat transfers was introduced. Cultivation experiments were conducted to clarify the effect of the crop root on soil water retentivity and verify the accuracy of the numerical model. The relationship between soil water retentivity and the root content of soil samples was clarified by soil water retention curves. The soil water content displayed a high value with increasing crop root content in the high volumetric water content zone. The experimental results indicated that the saturated water content increased with the crop root content because of the porosity formed by the crop root. The differences of the soil water retentivity became smaller when the value of the matric potential was over pF 1.5. To verify the accuracy of the numerical model, an observation using acrylic slit pot was also conduced. The temporal and spatial changes of the volumetric water content and soil temperature were measured. Soil water and heat transfers, which considered the effect of the crop root on the soil water retentivity clarified by the soil water retention curves, were simulated. Simulated volumetric water content and temperature of soil agreed with observed data. This indicated that the numerical model used to simulate the soil water and heat transfer considering the crop root effect on soil water retentivity was satisfactory. Using this model, spatial and temporal changes of soil water content were simulated. The soil water condition of the root zone was relatively high compared with the initial conditions. This indicated that the volumetric water condition of the root zone increased with the soil water extraction and high soil water conditions was maintained because the soil water retentivity of root zone increased with the root effect.

Time lag characteristics of sap flow in seed-maize and their implications for modeling transpiration in an arid region of Northwest China

Plant capacity for water storage leads to time lags between basal stem sap flow and transpiration in various woody plants. Internal water storage depends on the sizes of woody plants. However, the changes and its influencing factors in time lags of basal stem flow during the development of herbaceous plants including crops remain unclear. A field experiment was conducted in an arid region of Northwest China to examine the time lag characteristics of sap flow in seed-maize and to calibrate the transpiration modeling. Cross-correlation analysis was used to estimate the time lags between stem sap flow and meteorological driving factors including solar radiation（R_s） and vapor pressure deficit of the air（VPD_（air））. Results indicate that the changes in seed-maize stem sap flow consistently lagged behind the changes in R_s and preceded the changes in VPD_（air） both on hourly and daily scales, suggesting that light-mediated stomatal closures drove sap flow responses. The time lag in the maize＇s sap flow differed significantly during different growth stages and the difference was potentially due to developmental changes in capacitance tissue and/or xylem during ontogenesis. The time lags between stem sap flow and R_s in both female plants and male plants corresponded to plant use of stored water and were independent of total plant water use. Time lags of sap flow were always longer in male plants than in female plants. Theoretically, dry soil may decrease the speed by which sap flow adjusts ahead of shifts in VPD_（air） in comparison with wet soil and also increase the speed by which sap flow adjusts to R_s. However, sap flow lags that were associated with R_s before irrigation and after irrigation in female plants did not shift. Time series analysis method provided better results for simulating seed-maize sap flow with advantages of allowing for fewer variables to be included. This approach would be helpful in improving the accuracy of estimation for canopy transpiration and conductance using meteorological measurements.

Effect of SEN structure on the mold level fluctuation and heat transfer for a medium thin slab caster

It is important to select suitable parameters of a submerged entry nozzle （SEN） for optimizing the flow and temperature patterns in a mold. The effect of SEN design on the mould level stability, meniscus steel flow velocity, and heat transfer of the mold of a medium thin slab caster was studied by means of 1：1 water modeling and industrial testing. The advantages of a 2-port SEN compared with a 3-port SEN are the following： more optimal flow patterns with a lower mold level fluctuation and a lower meniscus steel flow velocity; proper powder consumption without slag bears due to a reasonable liquid powder thickness. The argon flow rate can be reduced and the mold average heat flux and temperature near the edges of the copper plate are reduced. At a casting speed of 2.5 m·min^-1, the mold level fluctuation lies within ＋5 mm. In addition, soft cooling of the steel shell in the mold is realized, which is suitable for casting crack susceptible steel grades.

Latitudinal and Scan-dependent Biases of Microwave Humidity Sounder Measurements and Their Dependences on Cloud Ice Water Path

The relationship between differences in microwave humidity sounder(MHS)–channel biases which represent measured brightness temperatures and model-simulated brightness temperatures, and cloud ice water path(IWP) as well as the influence of the cloud liquid water path(LWP) on the relationship is examined. Seven years(2011–17) of NOAA-18 MHS-derived measured brightness temperatures and IWP/LWP data generated by the NOAA Comprehensive Large Array-data Stewardship System Microwave Surface and Precipitation Products System are used. The Community Radiative Transfer Model, version2.2.4, is used to simulate model-simulated brightness temperatures using European Center for Medium-Range Weather Forecasts reanalysis data as background fields. Scan-angle deviations of the MHS window channel biases range from-1.7 K to1.0 K. The relationships between channels 2, 4, and 5 biases and scan angle are symmetrical about the nadir. The latitudedependent deviations of MHS window channel biases are positive and range from 0–7 K. For MHS non-window channels,the latitudinal deviations between measured brightness temperatures and model-simulated brightness temperatures are larger when the detection height is higher. No systematic warm or cold deviations are found in the global spatial distribution of difference between measured brightness temperatures and model-simulated brightness temperatures over oceans after removing scan-angle and latitudinal deviations. The corrected biases of five different MHS channels decrease differently with respect to the increase in IWP. This decrease is stronger when LWP values are higher.

Evaluation of Soil Water Management Difference in Mango Orchards between Thailand and Japan

The objective of this study is to evaluate the difference of the soil water management in mango orchards between the varieties of “Irwin” in Japanand “Nam Dok Mai” inThailand. Field observations were conducted in mango orchards in Okinawa, Japan and Phrao, Thailand to clarify the water management practices. Measurement of the hourly soil water content in Phrao indicated that the irrigation was scarce and the volumetric water content in the soil was maintained almost constant. in the flowering season. This can be the farmers’ practice for flower induction. After the flowering season, irrigation was frequent in order to produce the large fruit. In the harvest season, the soil water content was relatively high because of frequent irrigation and rainfall. In Okinawa, the volumetric water content was maintained at the same level in a relatively deep layer. The result at the5 cmdepth indicated that the farmer carefully controlled the soil water content. In the flowering season, the soil water content was relatively low. While the orchard was managed empirically, the volumetric water content near the soil surface was maintained over 25% during the harvest season. This result indicates that the farmer performed the good soil water management to enhance mango fruit quality even without technical measurement. A numerical model describing the soil water and heat transfers was introduced to predict the farmer’s empirical soil water management in Okinawa. Using the meteorological data in March 2010, the irrigation regime was predicted using the simulated soil water content. In the flowering season, the farmer irrigated when the soil surface water content reached 14%. Based on this criterion for the empirical soil water management, the simulation result indicated that the farmer irrigated four times in this period. The numerical model presented here can be useful for evaluating the differences in water management practices of local farmers.

引汉济渭工程调水区多源风险评估与对策研究

为评估引汉济渭跨流域调水工程本身及运行管理行为中多源风险导致供水不足的可能性,构建了跨流域调水工程水库-泵站-电站的风险评估框架。将工程管理中的行为与经验以随机、模拟、优化三种调度模式进行数学表达,设置了兼顾工程失能与运行管理的单源、多源调度风险模式和方案集;建立并仿真计算了三种调度模型,获得了不同风险方案的动态调度过程及造成的供水风险;制定了跨流域调水工程的调度风险分级基准,采取专家打分法获取事件发生的初始概率区间,采用集值统计法和改进耦合度模型定量估计各方案发生概率,基于供水风险指标定量估算各方案的损失严重度;划分了风险矩阵的等级标准,结合最低合理可行(ALARP)准则明确了风险可接受程度,提出了非工程措施以管控风险,为引汉济渭工程调水区风险评估和防控提供了理论依据。研究发现:(1)三种调度模式中仅优化调度可满足调水15亿m 3、95%供水保证率的供水目标,且相较于随机调度方式,供水能力提升了13%;(2)单源风险方案的供水风险逐渐向长时间缺水过程发展,多源风险方案面临的调度情况更加复杂,供水风险在各个维度均处于危险状态;(3)处于ALARP区域的风险事件占比超过60%,与工程相关的风险多为小概率高危害式风险,应优先解决处于ALARP区域并预防不可接受区域的风险事件;(4)针对发生概率小但危害性高的供水风险,制定了水库下游人员转移等应急方案,以降低潜在的供水损失。研究结果对于跨流域调水工程的风险管理具有积极的推动作用,强化了ALARP准则在调水工程风险评估中的应用价值。

南水北调中线工程水源地南阳推进EOD模式的路径研究

近年来,生态环境导向的开发(EOD)模式受到广泛关注。南阳作为南水北调中线工程核心水源地,也是渠首所在地,推进EOD模式有助于其将“绿水青山”转变为“金山银山”,能够为生态环境治理与产业协同发展提供有力支撑,同时促进共同富裕。农产品资源丰富但竞争力不强、生态产品价值实现周期长、保水质任务艰巨制约着其推进EOD模式。基于此,建议采用“授权—建设—运营”(ABO)模式进行运营,从打造特色名片、构建农产品平台服务体系以及加强合作等方面着手推进。

Physical Modeling of the Vacuum Circulation Refining Process of Molten Steel

The available studies in the literature on physical modeling of the vacuum circulation (RH, i.e. Ruhrstahl Heraeus) refining process of molten steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was employed to investigate the flow and mixing characteristics of molten steel under the RH and RH KTB (Kawasaki top blowing) conditions and the mass transfer features between molten steel and powder particles in the RH PTB (powder top blowing) refining. The geometric similarity ratio between the model and its prototype (a multifunction RH degasser of 90 t capacity) was 1:5. The effects of the related technological and structural factors were considered. These latest studies have revealed the flow and mixing characteristics of molten steel and the mass transfer features between molten steel and powder particles in these processes, and have provided a better understanding of the refining processes of molten steel.

Simulation of Radiant Heat Transfer on the Border of Coke Bed and Metal Surface of Heat Transfer Passage

The article is dedicated to the issues of heat transfer, radiant heat transfer in particular, between fluidized bed of coke and water-cooled panels arranged inside it in a staggered order. The model by A.F. Chudnovsky describing radiant heat transfer in a porous body (disperse medium) as applied to coke bed has been updated.

跨流域调水工程“用户枢纽”群联合优化调配

针对跨流域调水工程运行中存在枢纽群调水与用户群需水不匹配的问题,构建了兼顾水源区枢纽工程运行关键指标和受水区用户侧多目标需求的“用户-枢纽”群联合优化调配模型,用户侧量化了受水区水资源、生态环境、社会经济子系统间函数关系,嵌套于供水子系统的水量配置模型中,枢纽侧考虑水源区枢纽侧调水、发电、能耗等多重效益目标,确保最大化实现用户侧需水过程和枢纽侧调水过程的匹配。将模型应用于陕西省引汉济渭调水工程联合调配模拟,结果表明:联合优化调配模型可提高跨流域调水工程的整体运行效率,灵活调控“用户枢纽”群的需水与运行需求;水量联合优化调配后,各用户缺水率约为7%,经济效益提升了3.6%,水库群基本完成了调水任务,电站群发电量超过5.43亿kW·h,库空率约为8%,降低了系统缺水风险。

A soil water and heat transfer model including changes in soil frost and thaw fronts

Freeze-thaw processes in soils,including changes in frost and thaw fronts(FTFs),are important physical processes.The movement of FTFs affects soil hydrothermal characteristics,as well as energy and water exchanges between the land surface and the atmosphere and hydrothermal processes in the land surface.This paper reduces the issue of soil freezing and thawing to a multiple moving-boundary problem and develops a soil water and heat transfer model which considers the effects of FTF on soil hydrothermal processes.A local adaptive variable-grid method is used to discretize the model.Sensitivity tests based on the hierarchical structure of the Community Land Model(CLM)show that multiple FTFs can be continuously tracked,which overcomes the difficulties of isotherms that cannot simultaneously simulate multiple FTFs in the same soil layer.The local adaptive variable-grid method is stable and offers computational efficiency several times greater than the high-resolution case.The simulated FTF depths,soil temperatures,and soil moisture values fit well with the observed data,which further demonstrates the potential application of this simulation to the land-surface process model.

废旧金属旋转偏析纯化再生机理与方法

针对传统废旧金属回收方法流程长、效率低、传质慢的问题,借助水模型试验开展旋转偏析过程杂质强化去除的机理研究,为旋转偏析技术回收废旧金属提供动力学基础。试验分别通过流场可视化处理和流速的测定对溶质在废旧金属熔体中的传输进行分析,发现旋转偏析技术可以有效提高杂质原子在熔体中的传质效率,降低生长界面处杂质的传质阻力。水模型试验结果表明,旋转偏析炉内流场的循环运动模式有利于杂质向远离生长界面处运动,但在低转速条件下循环流动较弱,杂质的排除能力随着转速的增加而增加,但当转速增加到800r/min时,杂质无法有效向远结晶器端输送,不利于杂质去除;平均流速随着结晶器转速的增加而增加,结晶器转速从200r/min增加到800r/min时,各点流速平均增大2倍;流场平均流速随着结晶器浸入深度的增加而增加,结晶器转速为200r/min时,随着结晶器浸入水深的1/2增加到4/5,近结晶器液面端流速从0.02m/s增加到0.04m/s,其他各测速位点流速均有明显提高,平均流速增大1倍;流场平均流速随着结晶器直径与坩埚直径比例增大而增大,直径比从1/7增大到1/2,流场内平均流速增大了4倍左右。试验证明,适当增大转速、结晶器浸入深度以及结晶器与坩埚的直径比都能提高旋转驱动力,从而提高溶质在熔体中的传输速率,获得高效、均匀的浓度场。本研究中,在结晶器与坩埚直径比为1/3、结晶器浸入深度为4/5时,杂质的传输效果和浓度场的均匀度均较好,有利于旋转偏析过程杂质的有效脱除。在水模型基础上开展的铝熔体旋转偏析除杂研究结果表明,在结晶器转速为400r/min时,铅的去除效率最高可以达到66%,旋转偏析回收废旧金属资源可以改善传统回收方法流程长、效率低的问题,实现金属杂质的深度高效去除,满足金属资源的高值化回收利用需求。

基于数据驱动的锅炉水冷壁壁温分布实时预测模型

水冷壁等高温受热面超温及由此导致的爆管事故是影响燃煤发电机组安全运行的痛点问题之一。管壁超温一般发生在锅炉受热面局部区域,为预测并缓解超温问题,就必须实时监测受热面壁温的详细分布,并做出针对性调整。由于测量手段受限且CFD数值模拟方法耗时较长,目前仍缺少一种能实时、准确地反映锅炉运行过程中壁温详细分布的技术手段。为此采用将耦合传热模型与人工神经网络相结合的方法。以某350 MW超临界对冲燃烧锅炉为研究对象,首先以壁温耦合传热预测模型为基础,通过改变耦合模型的46个锅炉关键运行参数,生成220个典型工况,并通过快速扩充方法以极低时间成本衍生出4400个扩充工况。然后,基于典型工况与扩充工况组成的综合数据库,以锅炉的46项运行参数及壁面坐标为输入,以对应位置的壁温为输出,构建深度学习模型。模型MSE误差仅为0.0053,准确率AUC5为0.988,且计算时长在0.1 s以内。结果表明,提出的基于数据驱动的水冷壁壁温分布预测模型通过泛化有限工况的数值模拟结果,实现了锅炉全工况下水冷壁管壁温度详细分布的实时预测,且针对模型在低负荷工况时难以准确预测传热恶化的问题,提出快速扩充数据库的方法,以极低时间成本明显提高模型对传热恶化问题的预测准确率。

基于动态规划法的调水工程闸泵切换优化调度方案

针对跨流域调水工程运行线路中经验型闸泵切换启闭形式的问题,选取位于山东省德州市中心城区潘庄引黄灌区马颊河左岸辛店闸至沟盘河水库整条线路为研究区域,基于动态规划的正向递推法,以调水线路经济最优、调水最快为目标函数分别建立2个调水过程模型;利用Python语言对2个调水过程模型进行计算,确定不同运行阶段的闸泵切换方式、开启时刻及开启时长,得到流量与水位相结合的经济优且调水快的闸泵切换优化调度方案。结果表明,沟盘河水库初始水位为影响总运行费用及总调水时间的主要因素,闸泵切换优化调度方案可使运行费用降低20%,总调水时间缩短8%,提升了调水线路的经济效益与运行效率。

长江流域水源涵养服务价值及其空间转移评估

水源涵养服务价值在不同区域之间的转移是流域上下游之间进行横向生态补偿需要考虑的关键内容。然而,水源涵养服务价值的转移依赖于流域的水文循环路径和河流的水量输送。现有的生态系统服务价值转移量评估方法缺乏对水源涵养服务转移中水文特征的描述,评估结果的合理性有待加强。针对此问题,从转移方向和转移路径2个方面改进断裂点-场强模型,通过引入河流方向系数判断流域上下游以及干支流地区之间的水力联系,在水源涵养服务转移评估中考虑河流的水文特征,并在长江流域应用,提高评估结果的合理性与可用性。结果表明,2020年长江流域水源涵养量为11 538.45亿m3,水源涵养服务的价值量为11 953.83亿元。相比现有模型的评估结果,研究改进的断裂点-场强模型突出了水源涵养服务价值从流域上游向下游转移的特征、增加了转移强度和范围。长江流域水源涵养服务价值的转出量由大到小依次为:四川>江西>湖南>贵州>湖北>安徽>重庆>云南>浙江>青海>陕西>广西>西藏>河南;各省份水源涵养服务价值的转入量由大到小依次为:云南>安徽>湖北>重庆>江苏>湖南>四川>上海>西藏。

液态金属快堆螺旋管蒸汽发生器一、二次侧耦合传热数值研究

螺旋管蒸汽发生器是液态金属快堆中能量传递的核心设备,其运行的稳定性、安全性对核电站的运行有至关重要的影响。为此,本文构建了液态金属快堆螺旋管蒸汽发生器一次侧、二次侧耦合传热的三维数值模型,分别基于经济合作与发展组织核能署(The Organisation for Economic Co-operation and Development,OECD/NEA)物性手册和美国国家标准与技术研究院(National Institute of Standards and Technology,NIST)数据库建立液态金属和水-水蒸气变物性计算关联式,采用Lee相变模型计算二次侧水-水蒸气蒸发过程中两相间的质量传递。基于实验数据,分别对本文模型一次侧传热以及二次侧传热的计算可靠性进行了验证。最后以铅铋快堆为例,研究了不同一次侧进口参数下蒸汽发生器一、二次侧之间的耦合传热特性,并与传统水冷堆进行了对比。结果表明:在同等条件下,相比于传统水冷堆,一次侧采用铅铋液态金属时,一、二次侧之间的壁面热流密度明显提升,热流密度峰值可达1439.97 kW·m^(-2),比水冷堆相应数值提升5~6倍,这导致二次侧管内气相蒸发过程明显加剧,体积含气率急剧上升;同时,一、二次侧之间的沿程热流密度分布更加不均匀,沿程热流密度分布相对偏差值比水冷堆相应数值增大3~4倍。随着一次侧进口铅铋温度从350℃增大到450℃,一、二次侧之间的壁面热流密度随之增大,对应的热流密度峰值从950.7 kW·m^(-2)增大到1439.97 kW·m^(-2),提升约1.5倍,同时一、二次侧之间的沿程热流密度分布更加不均匀,不均匀度增大20%。