共查询到17条相似文献，搜索用时 250 毫秒
1.
程元萍 《杨凌职业技术学院学报》2003,2(2):31-34
针对陕西省延安地区泵站设备陈旧、装置效率低、耗能高、规划设计不够合理等问题，采取了水泵串并联运行的技术改造措施，采用三种不同形成的串并联方式：(1)两泵串联，两泵流量尽量相等，扬程高的水泵作为二级泵适用于水源条件差的地方；(2)两泵低处并联高处串联，两泵宜流量相等，扬程相等，应有满足两泵水量的水源；(3)水泵高处串联，低处分别送水灌溉，适用一泵或二泵流量的水源，此情况必须两泵流量相等，扬程高的作为二级泵，采用该措施后，提高了装置效率，降低了能源单耗，缩短了轮灌周期，扩大了灌溉面积，经济效益十分显著。 相似文献
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李晓勇 《胜利油田师范专科学校学报》2013,(4):30-31
胜利发电厂二期2暳300 MW机组在冬季供暖期间长期处于供热抽汽量较大、凝汽器热负荷较少的工况下运行。原凝汽器冷却水系统采用单元制运行方式,循环水流量较大,造成了胜利发电厂用电的浪费。在保证循环水系统安全可靠的前提下,胜利发电厂研究制定了二期机组在冬季供暖期双机一泵一塔方式的运行方案,通过系统改造,将循环水进行合理的分配,仅用一台循环水泵即能满足两台机组的冷却用水需求,有效地降低了用电率,达到机组节能目的。 相似文献
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调节阀门开度来改变水泵运行参数,是以消耗水泵运行能耗为代价,浪费能源;若采用水泵的变转速技术同样可以实现对系统的变流量调节,发展水泵的变转速技术是实现循环水泵的变流量调节和节能的有效途径,其中最理想的方法就是变频调速。 相似文献
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介绍了基于PLC和变频器实现恒压变频变流量供水系统的研究设计与改造应用,该系统能够根据管网压力自动调整泵的运行状态。设计了主电路接线图和主程序流程图,水泵可以自动启停、自动控制运行,实现了无级压力调整,真正做到了用水和供水的动态平衡,优化了系统运行特性,达到了恒压变频供水的目的。 相似文献
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冷冻水泵变频频率下限分析 总被引：3，自引：0，他引：3
王寒栋 《深圳职业技术学院学报》2002,1(3):7-13
分析了冷冻水系统中相关设备与装置对水流量的不同要求,在考虑冷冻水管路特性、冷冻水泵及其电机与变频装置的综合效率等因素的基础上,提出了确定冷冻水泵变频频率下限或频率范围的方法与步骤。通过考察冷冻水管路阻力系数随空调负荷变化的趋势,提出了冷冻水泵“等效静扬程”的概念,指出在空调冷冻水管路中不能直接应用泵的相似定律来确定冷冻水泵变频运行的工况点或运行频率。 相似文献
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针对中央空调系统运行管理中实际存在的启动时段内运行一台冷水机组、二台冷冻水泵和二台冷却水泵的现象（称为“一机多水泵运行”）,根据现场测试获得的中央空调系统运行数据,从冷冻水流量、冷水机组能效、冷冻泵效率、冷冻水侧能效和冷冻站能效等多个角度对该运行管理方式进行了分析和评价,指出应改变现有的运行管理方式,使空调系统保持良好的运行性能模式. 相似文献
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通过对现有循环水系统进行改进,在不同的循环水温度和负荷下,调节各机组的循环水流量或改变循环水泵的运行方式,达到凝汽器的最佳运行真空,降低机组发电综合煤耗,达到到节能降耗的目的。 相似文献
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变频水泵二次供水技术因具有"节能"和无水箱"二次污染"的优点而得到广泛应用,但变频水泵供水应用却存在普遍的"不节能"。二次供水变频水泵低效运行的成因在于:设计层面上随意主观确定设计参数,泵组选配缺乏理性;采用不合理的控制模式,无法完全发挥变频技术效能;阀件和管路损耗太大。因此,在设计阶段尽可能精确地把握设计参数,认真分析项目用水特性,合理匹配水泵,完善控制模式,最大程度降低供水装置内部局部损耗对于系统真正节能是非常关键的。 相似文献
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为了研究离心泵并联节流调节经济性,采用自制的并联泵节流调节试验系统,并引入并联折算转速的概念,推导了其表达式。分析了并联折算转速与流量比以及转速比的依变关系,对比不同负荷时共用阀门调节和非共用阀门调节的经济性,并验证了并联折算转速进行经济性分析的可靠性。结果表明,用并联折算转速进行经济性分析与试验结果吻合较好;非共用阀门调节时,并联折算转速与流量比以及转速比呈非线性关系;当负荷大于85%时,采用共用与非共用阀门两种节流调节方式的经济性相当;当负荷小于85%时,后者的经济性较好;当负荷小于50%时,单泵运行更节能。 相似文献
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基于山东半岛蓝色经济区视野下的烟台海洋产业协调发展探析 总被引：1，自引：0，他引：1
山东半岛蓝色经济区建设必须以海洋产业为重点,坚持海洋三次产业协调发展,实现海洋第一、二产业的优化升级和第三产业的快速发展。烟台市海洋产业的协调发展,要结合山东半岛蓝色经济区建设规划,提出可行性的举措。主要是:1.发展现代海洋渔业和休闲渔业,提升海洋第一产业;2.加大科技投入,培育现代海洋产业,提升海洋第二产业;3.以港口、滨海资源优势为依托,促进海洋第三产业的提升。 相似文献
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Jacinta Dalgety 《Assessment & Evaluation in Higher Education》2006,31(3):303-328
The research reported here examined factors that influence student tertiary level chemistry enrolment choices. Students enrolled in a first‐year chemistry class were surveyed, using the Chemistry Attitudes and Experiences Questionnaire (CAEQ), three times throughout their academic year: at the start of the year (n=126), the end of the first semester (n=109), and the end of the second semester (n=84). Additionally, 19 students were interviewed using a semistructured interview protocol at the same stages throughout the year. A number of influences on student enrolment intentions are posited based on a modified version of Ajzen’s Theory of Planned Behaviour: learning experiences, attitude‐toward‐chemistry and chemistry self‐efficacy. The extent to which the students believe they had control over enrolling in chemistry and normative beliefs about enrolling in chemistry, also were investigated. Influential factors include chemistry self‐efficacy (both positive and negative), prior secondary school experiences and the fact that chemistry is compulsory for some programs. Normative beliefs exert indirect effect with students having associates in a science related field more likely to enrol in second‐year chemistry. 相似文献
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Kormondy Edward J. 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2002,48(5):377-401
During a visit in October 1997 the author studied six higher education institutions in Inner Mongolia and three in Tibet, as well as several elementary and secondary schools in both provinces. A brief history of these provinces is followed by a survey of primary, secondary and tertiary education in each one, highlighting both the similarities and contrasts between the more urbane and economically vital Inner Mongolia and the more rural and economically disadvantaged Tibet. Aspects examined by the author include admission policy, fees, curricula, language of instruction, preservation of cultural identity and transition to work. 相似文献
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Edward J. Kormondy 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2002,4(2):377-401
During a visit in October 1997 the author studied six higher education institutions in Inner Mongolia and three in Tibet, as well as several elementary and secondary schools in both provinces. A brief history of these provinces is followed by a survey of primary, secondary and tertiary education in each one, highlighting both the similarities and contrasts between the more urbane and economically vital Inner Mongolia and the more rural and economically disadvantaged Tibet. Aspects examined by the author include admission policy, fees, curricula, language of instruction, preservation of cultural identity and transition to work. 相似文献
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Susan Capel Paula Zwozdiak-Myers Julia Lawrence 《Educational research; a review for teachers and all concerned with progress in education》2013,55(3):283-300
The purpose of this study was to identify how information about physical education is exchanged between secondary schools and their respective feeder primary schools, what information is exchanged and how this information is used. A secondary purpose was to look at whether there is any relationship between schools engaging in liaison activities and exchanging information about physical education, and between exchanging information and the number of associated secondary schools to which pupils are sent or feeder primary schools from which pupils are received. Questionnaires were sent to 177 secondary and 538 feeder primary schools. Responses from 80 secondary schools and 299 primary schools showed that the highest percentage of teachers exchanged information through written documentation, followed by discussion at cross phase liaison meetings. The type of information exchanged by the highest percentage of teachers was identified as generic information about key stage 2 and 3 of the National Curriculum for Physical Education (NCPE) areas of activity and schemes of work, rather than information about the specific physical education content covered or information about individual pupils, such as levels of attainment or ability. Further, results suggest that information may be used for pastoral purposes and that only a small percentage of teachers used the information exchanged to plan for continuity and progression in the physical education curriculum. There was a significant positive relationship between engagement in liaison activities and information received about the physical education curriculum followed by pupils, but a significant negative relationship for primary teachers between the number of different secondary schools to which pupils' progress and knowledge about the key stage 3 schemes of work that Year 6 pupils will follow in their associated secondary schools. These results are discussed in relation to continuity and progression in physical education in the transfer of pupils from primary to secondary schools. 相似文献
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李继中 《深圳职业技术学院学报》2013,12(4):11-16
目前我国的职业教育只有中职和大专两个学历层次,没有学位。本文通过职业教育与学科教育、工程教育的比较,从职业知识、职业理论、职业能力三个方面,阐述了职业教育的学历结构及其人才规格、教学定位。职业教育作为一种类型教育,与职业培训有本质区别,其学历结构应该低、中、高搭配,人才规格齐全,并突出学生职业能力中社会能力的培养。 相似文献