Study on Optimum Design of Rectangular Sedimentation Tanks

In this paper,the flow velocity fields,suspended solids concentration fields and flow-through curves in rectangular sedimentation tanks with different reaction baffles location,inlet horizontal velocity and length height ratio are simulated in detail using a developed mathematical model given in Reference 2.According to the numerical results,the influence of different reaction baffles location,inlet horizontal velocity and length height ratio on the operating efficiency is analyzed.Finally,the rational reaction baffles location,inlet horizontal velocity and length height ratio are presented.     

立式浮放储罐三维地震动台模型试验分析

为分析立式浮放储罐在三维地震动作用下的结构反应,进行了1000m3储罐模型地震动模拟试验,通过输入水平、竖向、三维地震激励,测试立式浮放储罐的地震响应。结果表明:储罐在三维地震动激励下的地震反应与一维激励相比具有较明显的放大效应。加速度反应放大1.76%~79.08%,平均放大幅度42.86%;三维激励下位移主要表现为放大趋势,平均放大幅度为31.83%;三维激励条件下储罐发生提离的概率及提离高度明显增大,增幅在20.47%~79.54%。建议立式浮放储罐应考虑三维地震动进行地震反应分析。     

面向储罐碳排放溯源的油品蒸发及油气扩散研究进展

储罐油品蒸发及油气扩散行为会对大气环境、社会经济、罐区安全等造成不利影响.以面向储罐碳排放溯源的油气蒸发扩散研究为脉络,从理论、实验及模拟3方面归纳总结了储罐油气蒸发扩散的研究现状及研究成果:通过理论分析揭示了罐内气液相变、气相中的油气传质及气体扩散的潜在机理;通过对现场实测及风洞实验成果进行分析,发现实验研究主要集中...     

露天水泥池方斑东风螺养殖技术探讨

报道了2009年8月10日和2010年7月10日,二批次进行露天水泥池养殖方斑东风螺试验的结果。表明在福建闽南沿海养殖方斑东风螺7月初前后投放壳高0．6～1cm螺苗是最佳时间,整个养殖过程水温平均26．1℃,日均增长和日均增重高达0．16mm和0．037g。特定增长率和特定增重率平均达到0．97％和2．74％,养殖商品...     

平流二沉池中计及温差影响的异重流数值模拟

【目的】在同时考虑进水与池内水的污泥质量浓度差异和温度差异的条件下,对平流式二沉池内的异重流现象进行数值模拟,重点研究异重流对池内流场及污泥沉降规律的影响,为优化沉淀池结构设计及提高沉淀池工作效率提供理论支持。【方法】选取Mixture模型和RNGκ-ε2方程紊流模型,设初始时刻二沉池内水为清水,进水为含一定质量浓度污泥的污水,并通过设置池内水与进水的不同温差模拟夏季与冬季环境,利用模拟数据分析不同时刻各工况下异重流的演变规律。【结果】池内水与进水的单纯污泥质量浓度差异会产生下异重流,小温差低温水与夏季大温差低温水进入均会导致下异重流产生,温差增大,下异重流作用更为明显;高温水进入会同时产生上异重流与下异重流,冬季温差高温水进入时上异重流起主导作用,异重流产生的旋流作用明显,对沉淀池工作效率的影响很大。【结论】温差异重流与污泥质量浓度差异重流本质均为密度差异,低温水进入增强下异重流,高温水进入削弱下异重流,温度影响会消失,污泥质量浓度差异重流作用时间更长。     

立面阳台式太阳能热水器的性能特性

以阳台平板太阳能热水器和全玻璃真空管太阳能热水器为对象,研究太阳能集热器南立面横排和竖排放置,自然循环和强制循环对系统热性能和水箱分层的影响。结果表明,对于立面阳台式全玻璃真空管太阳能热水器,集热器横排放置比竖排放置系统循环快,热效率提高12%。对于立面阳台式平板太阳能热水器,自然循环时无论是横排放置还是竖排放置,液体循环不流畅,系统热效率均小于30%;采用强制循环能有效改善循环状况,平均进出口温差稳定,系统热效率约为63%。     

加气灌溉对温室葡萄生长及不同形态氮素吸收利用影响

为探讨地下穴贮滴灌条件下根际注气对"红地球"葡萄幼苗生长及不同形态氮素吸收代谢的影响,以2年生"红地球"葡萄幼苗为试验材料,通过地下穴贮滴灌注气技术和15N示踪技术研究根际注气条件下葡萄对铵态氮(NH+4-N)和硝态氮(NO-3-N)吸收、分配和利用的影响。研究结果表明,地下穴贮滴灌根际注气可促进葡萄新梢增长,茎粗增加,显著提高葡萄新梢、细根等植株干物质量的积累。在同一灌水周期内,地下穴贮滴灌根际注气可提高叶片叶绿素、净光合速率,延缓植株胁迫,但对植株叶片瞬时水分利用效率具有负面影响。通过氮同位素示踪标记表明,地下穴贮滴灌条件下无论是否注气,葡萄新生部位对硝态氮的征调能力、吸收利用效率均显著高于铵态氮;与不注气相比,注气处理可显著促进新生部位对硝态氮的吸收,抑制铵态氮的吸收利用。地下穴贮滴灌根际注气可促进葡萄的生长,提高叶片光合效率,15N示踪表明根际注气并未影响葡萄根系对硝态氮的偏好,在地下穴贮滴灌注气条件下氮素形态宜选择硝态氮作为氮肥来源。     

两种教槽料对仔猪断奶前生长性能和腹泻发生率的影响

该试验主要是针对本场两种不同性状教槽料对哺乳仔猪生长性能及腹泻发生率进行对比分析试验,并评估其经济效益。试验选取了54头出生时发育良好,体况健康的仔猪,随机分成两个处理组,每个处理组3个重复,每个重复9头仔猪。分别饲喂两种教槽料：试验Ⅰ组饲喂康地5900,试验Ⅱ组饲喂安佑人工乳,试验期为20d。结果表明：康地5900和安佑人工乳进行比较,平均日增重差异显著（P〈0．5）,平均日采食量差异显著（P〈0．5）,料肉比差异显著（P〈0．5）。仔猪断奶前,饲喂康地5900可明显提高仔猪的生长性能和降低腹泻率。     

Review and quantitative assessment of ex situ household rainwater harvesting systems in Ethiopia

Ex situ household rainwater harvesting (RWH) systems have been introduced at a large scale in Ethiopia to increase the water availability for smallholders through supplementary irrigation. The first objective of this paper is to review the performance of these systems in Ethiopia based on various assessment studies. The second objective is to provide quantitative biophysical and socio-economic analyses of ex situ household RWH systems contributing to the better understanding of their performance and the identification of options to improve their performance. Uptake of RWH systems by smallholders in Ethiopia is limited and the available information suggests that this is associated among others with poor planning and implementation, poorly functioning input and output markets and the lack of farmers’ skills to use these systems effectively. Our quantitative meta-analyses illustrate that water availability of three studied RWH systems is low in relation to crop water needs, particularly for maize. The variation in area that can be irrigated across years exposes users of RWH systems to considerable risks as the availability of irrigation water depends on prevailing rainfall conditions. The area that can be irrigated varies greatly depending on amount and distribution of rainfall, type of RWH system and crop type. The economics of onion (cash crop) are promising only for plastic lined RWH systems, but those for maize are unfavourable independent of the studied RWH systems. Associated labour requirements especially for water lifting and application are high and possibly constraining the sustainable use of RWH systems. The potential of ex situ household RWH systems to increase agricultural production and income is site-specific depending on biophysical, institutional and socio-economic conditions, and depends on household-specific conditions.     

Multiple-Use Management in a Large Irrigation System: Benefits of Distributed Secondary Storage

Large-scale canal irrigation projects are commonly seen as profligate users of water. Their low water productivity has been attributed by many authors to deficiencies in management or to actions by farmers to circumvent management control over water distribution. Inadequate design has sometimes been cited as a contributing factor, but the relationship between design and manageability has received too little attention. In most conventional large-scale irrigation systems imperfect matching between water supply and demand is an inescapable fact of life that leads to operational spillages and low efficiency. Provision of auxiliary storage reservoirs at strategic points within the canal system can buffer this mismatch and improve service delivery and also aid recovery of return flows. Such reservoirs may bring additional benefits in that they provide opportunities for multiple-use management and increased productivity of irrigation water. This paper presents a case study of Mahaweli System H in Sri Lanka, which incorporates a large number of secondary reservoirs within its 25000 ha command area. The paper examines current operational performance and considers scope for and constraints to multiple-use management.