基于CFD的导叶进口角对轴流泵水力性能的影响

为研究后置导叶进口安放角对轴流泵水力性能的影响,在常规导叶基础上将导叶分为进口段和出口段两部分,运用数值模拟的方法研究了5种导叶进口安放角对轴流泵泵段水力性能的影响。结果表明,轴流泵在偏离设计工况下运行时,通过调节导叶进口角度可以减小导叶进口冲角,改善导叶体内流态。在后置导叶原设计进口角度的基础上,沿旋转轴顺时针调节适当角度可提高大流量处的泵段效率,逆时针调节适当角度可提高小流量处的泵段效率。不同导叶进口角主要是保证多种工况下水流无撞击进入导叶室,对泵段的其他过流部件水力性能基本无影响。研究成果有助于轴流泵导叶性能的优化设计。     

第二松花江下游洪水过程对河水——地下水交换的影响

为分析第二松花江下游洪水过程对河水-地下水交换的影响,以第二松花江下游德惠河段2016年10月15日~11月16日经历的一次涨洪—退洪过程为例,根据热示踪法,运用VFLUX2.0.0程序计算了该河段河水—地下水交换强度,探讨了洪水前和洪水过程中研究区河水—地下水交换模式及交换强度的变化。结果表明,洪水过程改变了河水—地下水交换模式,使交换强度增加。研究结果为该流域地下水资源的评价与管理、地表水与地下水的综合利用提供理论依据。     

挠力河流域地下水动态特征分析及预测

为分析和预测挠力河流域地下水动态特征,采用研究区2001~2014年16口潜水观测井水位检测数据和11个水文站降水数据,运用衬度系数方差分析法和相关分析法分析了地下水埋深影响因素,采用BP神经网络预测了地下水位埋深。结果表明,研究区地下水动态类型主要为入渗-蒸发型和入渗-开采型,地下水位埋深空间上呈现西北部略有升高,东部略有下降的特点;流域内地下水埋深波动幅度较大,东部及中北部波动幅度较大,西北部地区波动幅度最小;挠力河流域地下水埋深与降水量的相关性呈现明显的差异性,东部和西南部相关性较显著,中北部相关性较弱;BP神经网络预测得出2015年地下水水位仍存在一定的下降趋势。研究结果为挠力河流域地下水资源可持续利用和保护提供参考。     

Enhancing Heat Transfer and Energy Storage Performance of Shell-and-Tube Latent Heat Thermal Energy Storage Unit with Unequal-Length Fins

Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy storage unit.In this study,the novel unequal-length fins are designed from the perspective of synergistic benefits of heat transfer and energy storage performance,and the effects of arrangement,number and total length of unequal-length fins are numerically investigated.Results show t...     

Improving thermal comfort in mosques of hot-humid climates through passive and low-energy design strategies

Mosques have intermittent operational schedules with short-term occupancy during the five daily prayers. The occupancy level of the daily prayers is a fraction compared to the mandatory Friday prayers with full occupancy. Usually, the same thermal control mechanism is operated within the same large prayer hall to maintain the thermal comfort of the occupants. Yet, the comfort requirements are often not met due to the short span of operation during prayer times. Nevertheless, mosques have a very high energy usage as the same energy-intensive system is operated even during minimal occupancy profiles. The current research aims at using a passive approach towards design to achieve the comfort conditions during the low occupancy daily prayer times without employing mechanical intervention. Numerical simulations are carried out on a validated model of the case study building to investigate the impact of the west-facing Qiblah wall as the congregation stands in proximity to this wall. The design alternatives are tested in conjunction with ventilation strategies to holistically assess the thermal comfort of the occupants. Results show that as much as 4–6°C reduction in indoor wall surface temperature can be achieved with a suitable Qiblah wall design, which reduces the mean radiant temperature of the occupants by 2–4°C. Combined with ventilation strategies, thermal comfort can be significantly improved by at least 40% for the prayers during the hottest times of the day, and as much as 80% for night-time prayers. Results suggest that suitable comfort conditions can be achieved without the need for air-conditioning for at least two or three of the five daily prayers.     

新型栲胶聚丙氧基醚酯的合成及增塑PVC性能

以工业级杨梅栲胶粗品为原料，通过环氧丙烷醚化和脂肪酸（乙酸、丁酸和油酸）直接酯化的方式，构建增塑性能高、抗迁移性能好的栲胶聚丙氧基醚酯增塑剂（TEPEA、TEPEB和TEPEO）。利用凝胶渗透色谱仪、核磁共振氢谱、傅里叶变换红外光谱对栲胶聚丙氧基多元醇和栲胶聚丙氧基醚酯的分子量和结构进行表征，并对栲胶聚丙氧基醚酯增塑剂增塑后聚氯乙烯（PVC）制品（PVC/TEPEA、PVC/TEPEB和PVC/TEPEO）的表观形貌、力学性能、耐低温性能、耐挥发性能和耐溶剂迁移性能进行测试。此外，通过合成低分子量栲胶聚丙氧基乙酸酯（LTEPEA），并将其增塑后的PVC制品（PVC/LTEPEA）与PVC/TEPEA、PVC/TEPEB和PVC/TEPEO进行综合性能差异比较，研究丙氧基对栲胶基增塑剂综合性能的影响。结果表明，栲胶聚丙氧基醚酯增塑后PVC制品的综合性能与其结构中丙氧基聚合度及酯基上的烷基碳链长度有关；丙氧基聚合度大且酯基上碳链最短的栲胶聚丙氧基乙酯（TEPEA）增塑后的PVC制品的增塑、耐挥发和抗迁移性能均优于传统石油基邻苯二甲酸二辛酯（DOP）增塑后的PVC制品（PVC/DOP），表明...     

鲜切花凋萎的原因及其保鲜包装技术研究

从植物生理学和生物化学出发，根据鲜切花的膨压理论、生理代谢，乙烯作用机制和病菌污染等多种主要作用机量，分析了鲜切花产生衰老，凋萎的内部因素和外部影响，介绍了目前国内外在植物保鲜方面的方法和措施，进一步对鲜切花的保鲜包装技术及其所涉及的包装方法，包装材料及相关技术进行了探讨。