Pool Boiling Heat Transfer in Dilute Water/Triethyleneglycol Solutions

Boiling of water/triethyleneglycol(TEG)binary solution has a wide-ranging application in the gas processing engineering.Design,operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution.In this investigation,nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition.The present experimental data are correlated using major existing correlations.In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible.This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface.Based on this prediction,the temperature of the interface and accordingly,the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface.It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero.The presented model excludes any tuning parameter and requires very few physical properties to apply.

Numerical Simulation on Subcooled Boiling Heat Transfer Characteristics of Water-Cooled W/Cu Divertors

In order to realize safe and stable operation of a water-cooled W/Cu divertor under high heating condition,the exact knowledge of its subcooled boiling heat transfer characteristics under different design parameters is crucial.In this paper,subcooled boiling heat transfer in a water-cooled W/Cu divertor was numerically investigated based on computational fluid dynamic（CFD）.The boiling heat transfer was simulated based on the Euler homogeneous phase model,and local differences of liquid physical properties were considered under one-sided high heating conditions.The calculated wall temperature was in good agreement with experimental results,with the maximum error of 5%only.On this basis,the void fraction distribution,flow field and heat transfer coefficient（HTC）distribution were obtained.The effects of heat flux,inlet velocity and inlet temperature on temperature distribution and pressure drop of a water-cooled W/Cu divertor were also investigated.These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor.

Characterization of solid particles sampled from condensates in boiling water reactor

The growth, activation and deposition of corrosion products are the primary sources of radiation buildup on the surface of out-of-core piping in nuclear power plants. The buildup of radiation can have negative effects on the performance of the facility and cause harm to staff during maintenance outages for refueling. This paper reports on the crystalline and amorphous structures of corrosion products sampled in the boiling water reactors in nuclear power plants of Kuo-Sheng and identified using an acid dissolving technique. X-ray diffraction, scanning electron microprobe and inductively coupled plasmaatomic emission spectroscopy were used to analyze the samples. The results indicate that the quantity of amorphous iron oxide at inlet of the condensate demineralizer in Unit 2 is higher than that in Unit 1. The proportion of crystalline to amorphous corrosion products can affect the efficiency of removal. Thus, these results can be used to explain the difference in removal efficiency of condensate demineralizers in different units. Moreover, the iron oxide structures with various properties were observed in different operational periods. It is probable that the higher proportion of amorphous structures with a smaller particle size would reduce efficiency in the removal of condensate demineralization in Unit 2.

Validation of the Monte Carlo Model Designed to Simulate the Neutronic Characteristics of Advanced Boiling Water Reactor Assembly

In the last few years, interest in burnup calculations using Monte Carlo methods has increased. Previous burnup codes have used diffusion theory for the neutronic portion of the codes. Diffusion theory works well for most reactors. However, diffusion theory does not produce accurate results in burnup problems that include strong absorbers or large voids. MCNPX code based on Mont Carlo Method, is used to design a three dimensional model for a BWR fuel assembly in a typical operating temperature and pressure conditions. A test case was compared with a benchmark problem and good agreement was found. The model is used to calculate the distribution of pin by pin power and flux inside the assembly. The effect of axial variation of water （coolant） density, and of control rods motion on the neutron flux and power distribution is analyzed. The effect of addition of Gd2O3 to natural uranium （0.711%） on both the thermal neutron flux and normalized power are analyzed. The concentration of U^235, U^238, Pu^239, and its isotopes is also calculated at burn-up 50 GWD/T.

Forced Convection Boiling Heat Transfer and Dryout Characteristics in Helical Coiled Tubes with Various Axial Angles

对水和水蒸汽汽液两相流体在螺旋轴呈各种倾角放置的螺旋管内强制对流沸腾传热与烧毁特性进行了系统地试验研究，试验中系统及结构参数范围如下：压力：Ｐ＝０．４～３．０ＭＰａ质量流速：Ｇ＝１００～２４００ｋｇ／ｍ２·ｓ进口水温：Ｔ＝３０～８０℃出口干度：ｘ＝－０．０５～１．２管内壁面热负荷：ｑ＝０～５４０ｋＥ／ｍ２试验段结构参数：总长Ｌ＝６４４８ｍｍ，管内径ｄ＝１１ｍｍ，螺旋直径Ｄ＝２５６ｍｍ，螺旋升角β＝４．２７°螺旋管轴向放置倾角：水平位置（０°）、向上倾斜４５°（＋４５°）、垂直向上（＋９０°）、向下倾斜４５°（－４５°）．共进行了１０５０个工况的试验．试验结果表明，螺旋管内汽液两相流强制对流沸腾传热可以划分为核态沸腾区、两相流强制对流区、烧毁及烧毁后传热区等３种区域．通过数据处理和分析总结，给出了３区域间转变的边界方程，和３个区域内两相流传热系数的计算公式．根据试验观察和数据结果，对烧毁现象及烧毁点或区域发生的条件及机理进行了深入的分析研究，发现一系列有关现象的规律和特点，指出了其主要影响因素，并给出了烧毁点临界质量干度的预报公式．

Assessment of the Application of Subcooled Fluid Boiling to Diesel Engines for Heat Transfer Enhancement

The increasing demand of cooling in internal combustion engines(ICE)due to engine downsizing may require a shift in the heat removal method from the traditional single phase liquid convection to the application of new technologies based on subcooled fluid boiling.Accordingly,in the present study,experiments based on subcooled flow boiling of 50/50 by volume mixture of ethylene glycol and water coolant(EG/W)in a rectangular channel heated by a cast iron block are presented.Different degrees of subcooling,velocity and pressure conditions are examined.Comparison of three empirical reference models shows that noticeable deviations occur especially when low bulk subcooling and velocity conditions are considered.On the basis of the experimental data,a modified power-type wall heat flux model is developed and its ability to represent adequately reality is tested through numerical simulations against a reference rig case and a practical diesel engine.Computational results show that this modified model can effectively be used for practical engine cooling system design.

Studies on Extracting Microcystin-Lr from Microcystis Aeruginosa by Water Bath

Different temperatures of water bath was used to extract the intracellular microcystin-LR(MC-LR) of Microcystis aeruginosa. Researching the extraction efficiency under the suitable temperature, so that it could find out the best temperature and time for extracting MC-LR from Microcystis aeruginosa cells. Five equal Microcystis aeruginosa was used to find out the best temperature, extracting at 60℃, 70℃, 80℃, 90℃ and 100℃ for 15 minutes, respectively. Results showed that the content of MC-LR extracted with the water under 100℃ was the highest. But meanwhile, the type and the content of impurities was the highest, too. In addition, another six equal Microcystis aeruginosa was extract with the water under 100℃ for 5min, 10 min, 15 min, 20 min, 25 min and 30 min respectively. It was proved that 20 minutes was enough for extracting MC-LR from Microcystis aeruginosa, no long time was needed.

Cavity formation during water entry of heated spheres

We experimentally study the cavity formation when heated spheres impact onto water at low and high subcooling.The observations present that the formation and appearance of the cavity are affected by the boiling modes and the heat transfer intensity. In the nucleate-boiling regime, a rough cavity can be formed at a rather low impact velocity, while at the same velocity, the cavity formed in the film-boiling regime may have a very smooth interface with a stable vapor layer around the sphere. We discuss the effects of the impact speed, water and sphere temperatures on the stability of the vapor layer. For low subcooled water, the stable vapor layer will be disturbed when increasing the impact velocity, leading to a disturbed cavity. For high subcooled water, the film boiling has a particular boiling model in which the vapor layer around the sphere cannot keep its stability. In this particular film-boiling regime, no cavities can be formed at low impact velocities and only broken cavities can be formed at high impact velocities.

The Evaluation of Water Treatment Methods Utilized among Households in Kyegegwa District, Uganda

Introduction: The Health sector continues to prioritize interventions defined in the Uganda National Minimum Health Care Package under a Sector-Wide Approach arrangement, with emphasis on recommendations of the HSSIP 2010/11-2014/15 Mid-Term review. This is further supported by the resolutions of the World Health Assembly, the International Health Partnerships, the Paris Declaration on Harmonization and Alignment and the Accra Agenda for Action and related initiatives. Objective: The purpose of this study was to evaluate the various water treatment methods utilized among the various households in Kyegegwa district in Uganda. Methodology: A cross-sectional study was carried out among 397 different house-holds in Kyegegwa district. Data were analyzed using SPSS to generate descriptive data. Results: Slightly more than half of the households used boiling as the treatment methods of choice 206 (51.9%), filtration 104 (26.2%), chlorination 24 (6%), solar disinfection 16 (4%) and I don’t treat water 47 (11.8%). Conclusion: The identified water treatments methods used among the households in Kyegegwa district were boiling, filtration, chlorination and solar disinfection. Recommendation: Health education should be provided on the importance of treating water by boiling and storing them in a cleaned and covered container.

超低甲醛释放木质素基胶黏剂的制备及应用

针对脲醛树脂耐水、耐候性能差和潜在甲醛释放的问题,以工业碱木质素(L)为原料,通过与苯酚(P)、尿素(U)和甲醛(F)共缩聚反应制备了符合ENF级Ⅰ类胶合板要求的木质素基胶黏剂(LPUs)。考察了L、P和U质量比对LPUs凝胶时间、游离甲醛含量、储存稳定性、固化反应活性以及胶合板理化性能的影响。结果表明:mL/(mP+mU)为1∶1时制备的树脂LPU1~LPU4中,随着尿素用量的增加,LPUs树脂的凝胶时间逐渐缩短,m(P)∶m(U)=30∶70时制备的LPU4,其凝胶时间为(18±2)min,约为LPU1(m(P)∶m(U)=90∶10)的凝胶时间(30±2)min的40%,游离甲醛含量从0.05%(LPU1)升高至0.18%,储存期由127 d缩短至14 d,表现出脲醛树脂的理化特性。DSC监测固化过程焓变行为表明,LPUs树脂反应活化能仅为商业酚醛树脂和脲醛树脂的2%~7.8%。mL/(mP+mU)=1且苯酚用量不低于尿素时制备的LPU1~LPU3树脂胶合板耐沸水胶合强度和甲醛释放量满足ENF级Ⅰ类胶合板要求,其中LPU2树脂的施胶量可降低至工业生产工艺的66.7%,此时,依然可以确保胶合板的耐沸水胶合强度和甲醛释放量满足ENF级Ⅰ类要求,可有效降低胶合板生产成本。

土壤有效硼提取及测定方法比较

本文提出一种沸水浴提取–ICP-OES测定土壤有效硼的方法,并着重比较分析沸水提取–姜黄素比色法、沸水提取–ICP-OES法、沸水浴提取–ICP-OES法和沸水浴提取–姜黄素比色法对土壤有效硼的测定结果。通过讨论4种方法的测定下限、方法检出限和测定精密度及正确度,及对来自不同地区高中低有效硼含量的6种土壤有效态成分标准物质和4种实际土壤样品的测定比较,探讨4种方法分析测定的关键因素、方法相关性。结果表明,沸水浴提取–ICP-OES法操作简单便捷,方法的检测下限低、干扰因素少、重复性好,可适用于各类型批量样品分析及研究。本研究可为实验室开展土壤有效硼测定方法研究提供借鉴,也可为承担“第三次全国土壤普查”土样检测的实验室在土壤有效硼测定的方法选择、效率提升和质量保证上提供技术支撑。

玻纤增强尼龙6材料水煮后性能变化

玻纤增强尼龙6材料因其独特的材料特性在使用过程中会吸水,进而会引起性能和尺寸的变化,在实际的使用过程中材料性能是处于一个动态的变化过程的,会对产品造成应用功能的波动。为了更好地掌握此变化规律,进而在使用过程中进行控制,通过研究水煮时间对玻纤增强尼龙6材料吸水率的影响,分析不同吸水率下物理性能和尺寸的变化;再将煮水后的尼龙6复合材料放置在23℃±2℃,相对湿度为50%±5%的标准环境中对其吸水率的变化及物性性能的变化进行研究分析,得出变化规律曲线图。结果表明:玻纤增强尼龙6材料吸水速度和水温存在较大关系,水温越高吸水率越快,吸水后其拉伸强度、弯曲弹性模量等刚性指标下降,冲击强度指标则上升;在23℃±2℃,相对湿度为50%±5%的标准环境放置后随着时间的增加,复合材料的吸水率会趋向一个平衡值,拉伸强度、弯曲弹性模量、冲击强度等指标会有不同程度的变化;最终得出30%玻纤增强尼龙6材料的饱和吸水率在6.67%左右,平衡吸水率值在2.53%左右,在实际应用中可参考此值进行水处理。

不同脱皮方式对榄钱品质的影响

以鲜榄钱为原料,采用沸水漂烫、蒸汽热烫和80℃超声辅助3种方式脱皮处理,探究不同脱皮方式对榄钱脱皮率、色泽、质地等物理性质,可溶性蛋白质、淀粉、可溶性糖等营养成分及总叶绿素、可溶性单宁、抗坏血酸、类黄酮、总酚等化学成分变化的影响,结果表明:沸水漂烫法脱皮率最高;沸水漂烫与蒸汽热烫均能起到护色效果;80℃超声辅助脱皮对硬度、脆度、黏性、咀嚼性影响最小;沸水漂烫脱皮的榄钱抗坏血酸含量和总酚含量最高,可溶性糖含量与蒸汽热烫脱皮无显著差异;蒸汽热烫脱皮的可溶性蛋白质含量和类黄酮含量最高;80℃超声辅助脱皮的榄钱总叶绿素含量最高,脱涩效果最好;3种脱皮方式处理的榄钱淀粉含量均无显著差异。经加权分析可知,采用沸水漂烫脱皮的榄钱品质优于蒸汽热烫和80℃超声辅助脱皮的榄钱品质。

竹纤维/氨纶包覆纱的制备及性能

竹纤维具有较好的拉伸强度、良好的尺寸稳定性和热稳定性以及抗紫外线性,但是竹纤维的弹性较差。为解决上述问题,将竹纤维包覆弹性氨纶,获得集竹纤维的功能性及氨纶优异的弹性于一体的包覆纱。将不同类型的氨纶和竹纤维分别作为芯线和外包覆纱线制备了包覆纱,探究不同细度竹纤维包覆在氨纶表面的形貌、力学性能(拉伸性能、弹性性能和蠕变性能)、沸水收缩率、抗菌性能和防紫外线性能。结果表明,竹纤维/氨纶包覆纱力学性能优异,包覆纱断裂强度最高达14.87cN/tex,在10%拉伸时弹性回复率为99.12%,60min的蠕变伸长率仅为0.77%,沸水收缩率最低为1%。制备的抗菌包覆纱具有优异的抗菌性,抑菌率达到99.9%。用竹纤维/氨纶包覆纱制成的针织织物具有优异的防紫外性能,UPF值高达109.5。

广东某水厂自来水煮沸结垢成因分析及解决方案

针对广东省A水厂愈加频繁的自来水煮沸结垢投诉问题,需要系统探究其成因及解决方案。研究采用X射线衍射能谱(XRD)和扫描电镜电子能谱(SEM-EDS)分析A水厂水垢样品的成分。采用雷兹纳稳定指数(RSI)分析了近10年A水厂出厂水加热煮沸的结垢趋势,应用卡方检验统计模型探究RSI<6与频繁出现投诉月份之间的关联性,通过皮尔逊相关性分析法筛选出对RSI数值具有显著影响的水质参数。统计分析历年水质指标数值,反演水质参数发生的变化及结垢成因。研究表明:A水厂出厂水煮沸产生的垢样主要成分为碳酸钙。结垢趋势预测显示,出厂水RSI(80℃)指数月均值由2014年—2020年的6.11降低至2021年—2023年的5.78,显示出更强的结垢趋势。RSI(80℃)<6的月份与频繁的居民投诉之间具有极显著关联性(χ^(2)=34.90,p=3.498×10^(-9))。结垢问题的加剧与pH、总硬度、总碱度的变化呈极显著负相关(r<-0.8,p≤0.01)。历年枯水期总硬度、总碱度的同时上升导致了偶发的结垢问题;而2021年初以来,氯消毒剂的更换和西江流量减少引起的原水水质变化共同导致了出厂水pH的上升,引发频繁的结垢问题。对此,A水厂应以科学引导民众为主、工艺调节为辅,同时可将RSI(80℃)用于结垢趋势的监测和预测。

发泡水对泡沫沥青粘聚/粘附性的多尺度影响研究

综合采用分子动力学模拟、水煮法实验、表面自由能实验和拉拔实验等宏微观方法,研究发泡水对沥青粘聚和粘附性的影响机制。结果表明,分子尺度上水分子排斥沥青分子,从而削弱沥青间界面能量;宏观尺度发现泡沫沥青与集料的抗水煮剥落性有所降低,发泡水对沥青的粘聚及粘附性不利,且发泡水越多对沥青的粘聚和粘附性损害越明显。泡沫沥青界面能与其粘聚和粘附性能具有高度相关性,可从宏观尺度和微观分子尺度解释发泡水对泡沫沥青粘聚/粘附性的多尺度影响。

Paramagnetism and improved upconversion luminescence properties of NaYF4：Yb,Er/NaGdF4 nanocomposites synthesized by a boiling water seed-mediated route

In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4：Yb,ErlNaGdF4 core-shell structured upconversion nanoparticles （CSUCNPs） have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4：Yb,Er to 350℃ and increases its upconversion （UC） luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln^3＋-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging （MRI）o The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW.cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance （EPR） spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.

二段式超声辅助沸水提取香菇多糖工艺研究

为了实现对香菇多糖的高效提取,本文采用二段式超声辅助沸水提取香菇多糖,在单因素的基础上,运用响应面法优化二段式超声最佳提取工艺条件。结果发现,二段式超声辅助沸水提取香菇多糖条件为料液比1∶20(g/mL),超声功率300 W,超声温度60℃,一段超声时间30 min,二段时超声时间5 min,香菇多糖得率可达13.38%。二段式超声辅助沸水提取工艺比传统沸水提取工艺能显著提高香菇多糖得率,可为香菇多糖工业化生产提供可靠的理论依据。