非极性有机物蒸发热与正常沸点的关联

通过对正烷烃蒸发热、正常沸点与碳数关系的研究,理论推导出蒸发热与正常沸点之间的关系,并拟合得一简单适用的公式:Hυ=23.234×BP1.21256+1502.13。应用于上百种常见非极性有机物,误差较小。     

1,4-丁二醇提取玉米芯木质素的研究

以1,4-丁二醇为溶剂提取玉米芯中的木质素,考察了反应温度、原料／溶剂固液比（g/mL）、1,4-丁二醇的质量分数、反应时间等因素对木质素收率的影响。最佳萃取条件为：反应温度200℃,固液比（g／mL）1：10,1,4-丁二醇的质量分数90％,反应时间1h,以少量硫酸作为催化剂,木质素收率37．03％。红外光谱分析结果表明,1,4．T-醇提取的玉米芯木质素较好地保存了木质素原有结构。     

计算脂肪醇沸点的新方法

直接从脂肪醇的分子结构提取4个结构参数:烷基的极化效应指数PEI、碳原子数目Nc、羟基所连接碳原子上的氢原子个数α-H和羟基与支链相对位置差ΔN,与118种脂肪醇的沸点进行相关分析,得到相关模型方程。运用留一法确证模型方程具有较好的稳定性和预测能力。方程所选用的参数计算简单,物理意义明确,能够被广泛使用。     

非共沸混合工质沸腾换热系数实验关联式比较

利用从文献中收集到的局部沸腾换热系数的实验数据,对混合制冷剂水平管内局部沸腾和管外池沸腾换热系数的计算方法及计算公式进行了分析比较,筛选出了与实验数据吻合较好的计算公式,从而为其进一步的研究提供了理论基础。     

Two types of a passive safety containment for a near future BWR with active and passive safety systems

The paper presents two types of a passive safety containment for a near future BWR. They are named Mark S and Mark X containment. One of their common merits is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. The PCV pressure can be moderated within the design pressure. Another merit is the capability to submerge the PCV and the RPV above the core level. The third merit is robustness against external events such as a large commercial airplane crash. Both the containments have a passive cooling core catcher that has radial cooling channels. The Mark S containment is made of reinforced concrete and applicable to a large power BWR up to 1830 MWe. The Mark X containment has the steel secondary containment and can be cooled by natural circulation of outside air. It can accommodate a medium power BWR up to 1380 MWe. In both cases the plants have active and passive safety systems constituting in-depth hybrid safety (IDHS). The IDHS provides not only hardware diversity between active and passive safety systems but also more importantly diversity of the ultimate heat sinks between the atmosphere and the sea water. Although the plant concept discussed in the paper uses well-established technology, plant performance including economy is innovatively and evolutionally improved. Nothing is new in the hardware but everything is new in the performance.     

A feasibility assessment of the use of nanofluids to enhance the in-vessel retention capability in light-water reactors

Nanofluids, colloidal dispersions of nanoparticles, exhibit a substantially higher critical heat flux (CHF) compared to water. As such, they could be used to enhance the in-vessel retention (IVR) capability in the severe accident management strategy implemented by certain light-water reactors. It is envisioned that, at normal operating conditions, the nanofluid would be stored in dedicated storage tanks, which, upon actuation, would discharge into the reactor cavity through injection lines. The design of the injection system was explored with risk-informed analyses and computational fluid dynamics. It was determined that the system has a reasonably low failure probability, and that, once injected, the nanofluid would be delivered effectively to the reactor vessel surface within seconds. It was also shown analytically that the increase in decay power removal through the vessel using a nanofluid is about 40%, which could be exploited to provide a higher IVR safety margin or, for a given margin, to enable IVR at higher core power. Finally, the colloidal stability of a candidate alumina-based nanofluid in an IVR environment was experimentally investigated, and it was found that this nanofluid would be stable against dilution, exposure to gamma radiation, and mixing with boric acid and lithium hydroxide, but not tri-sodium phosphate.     

基于微液层模型的单汽泡生长数值模拟研究

核态沸腾换热在传热传质方面有着重要的作用,其发生机理和传热传质过程仍是研究的重点。随着实验手段的提高,微液层模型得到了广泛的关注。通过对微液层中传热传质的分析,建立了微液层厚度与热流密度和气化率之间的关系。利用界面扩散法对汽液相界面进行追踪,并在汽泡与加热壁面之间构建微液层模型,研究在核态沸腾条件下,微液层的变化对汽泡生长和加热壁面温度分布的影响。结果表明,数值模拟得到的汽泡生长过程和加热壁面温度分布与实验结果吻合得很好,初步验证了模型的正确性。并通过数值模拟,进一步分析了汽泡生长过程中微液层、干性区域和汽泡底部半径的变化规律以及壁面温度的分布情况。     

基于LB方法的管内流动沸腾传热模拟

为研究竖直管内流动沸腾的传热情况及气泡行为学,采用格子玻尔兹曼（LB）方法,利用改进后的伪势模型和热模型分别模拟流动和传热过程。为验证模型的合理性,对模拟结果与经验关系式进行了定量对比。之后对气泡行为对沸腾传热系数的影响进行了研究,结果表明,随着气泡的核化、生长、滑移和脱离,传热系数呈现周期性波动。最后考察了重力加速度对气泡行为和沸腾传热的影响,重力越大,气泡生长周期越短,沸腾传热系数越大。     

5×5棒束通道中简单支撑格架对流动过冷沸腾传热的影响分析

采用壁面热分配模型(即RPI模型)对PSBT基准题中的5×5均匀加热全长棒束过冷沸腾传热进行了数值模拟研究。重点分析了加热段末端搅混格架（MVG）下游简单支撑格架（SSG）对棒束通道内流动过冷沸腾传热特性的影响。在水力特性方面,研究发现SSG的形阻压降约为MVG的53%,且对棒束通道内的横向流动具有显著抑制作用。为反映SSG对搅混过程的影响,采用子通道平均横流速度比沿轴向的发展过程对其进行了分析。分析发现,在SSG附近横流速度比迅速衰减,衰减后的横流速度比与光棒束时的大小相当。由于SSG对横流过程的破坏,改变了发热表面的传热特性,在其下游气相迅速包覆加热表面,蒸发热流密度较无SSG情况偏高5%,加热段末端空泡份额偏高0.006,壁面过热度偏高0.3 ℃。     

Heat transfer and flow characteristics of flow boiling of CO2‐oil mixtures in horizontal smooth and micro‐fin tubes

Experiments were carried out on the flow pattern, heat transfer, and pressure drop of flow boiling of pure CO₂ and CO₂‐oil mixtures in horizontal smooth and micro‐fin tubes. The smooth tube is a stainless steel tube with an inner diameter of 3.76 mm. The micro‐fin tube is a copper tube with a mean inner diameter of 3.75 mm. The experiments were carried out at mass velocities from 100 to 500 kg/(m²·s), saturation temperature of 10 °C, and the circulation ratio of lubricating oil (PAG) was from 0 to 1.0 mass%. Flow pattern observations mainly showed slug and wavy flow for the smooth tube, but annular flow for the micro‐fin tube. Compared with the flow patterns in the case of pure CO₂, an increase in frequency of slug occurrence in the slug flow region, and a decrease in the quantity of liquid at the top of the tube in the annular flow region were observed in the case of CO₂‐oil mixtures. With pure CO₂, the flow boiling heat transfer was dominated by nucleate boiling in the low vapor quality region, and the heat transfer coefficients for the micro‐fin tube were higher than those of the smooth tube. With CO₂‐oil mixtures, the flow boiling heat transfer was dominated by convective evaporation, especially in the high vapor quality region. In addition, the heat transfer coefficient decreased significantly when the oil circulation ratio was larger than 0.1 mass%. For the pressure drop characteristics, in the case of pure CO₂, the homogeneous flow model agreed with the experimental results within ±30% for the smooth tube. The pressure drops of the micro‐fin tube were 0–70% higher than those predicted with the homogeneous flow model, and the pressure drops increased for the high oil circulation ratio and high vapor quality conditions. The increases in the pressure drops were considered to be due to the increase in the thickness of the oil film and the decrease in the effective flow cross‐sectional area. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20287