共查询到20条相似文献，搜索用时 15 毫秒
1.
对R290家用空调的系统性能进行优化试验．并将优化结果与R22空调系统性能进行比较,结果表明：R290空调系统的能效比提高约10％,工质充注量减少约60％,毛细管长度增长30％,R290系统采用小管径换热器有利于提高空调的能效比。 相似文献
2.
A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±8% of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes. 相似文献
3.
Characteristics of R22 and its new alternative refrigerant R290 flowing through adiabatic capillary tubes are investigated based on the homogeneous model.Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity, Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further, a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40 ℃ to 50 ℃, the mass flow rate for R22 is increased by 16%, while the increasing rate for R290 is 13%. 相似文献
4.
Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat… 相似文献
5.
刘丽刚 《顺德职业技术学院学报》2007,5(4):26-28
为探索R290作为制冷剂在家用空调中应用的可行性,在相同型号的空调器中进行了R290与R22的性能对比实验。结果表明:家用空调器不仅可以用R290替代R22,而且还有环保和节能的效果,能效比可提高10.26%～19.53%。 相似文献
6.
不同烤烟品种叶片组织结构的比较研究 总被引：1，自引：0，他引：1
研究结果表明：不同的烤烟品种叶片组织结构不同，K358、云烟85与K326的叶片厚度、栅厚／海厚、栅厚／叶厚、海绵组织厚度和栅栏组织厚度基本上居于前三位，且较为接近；云烟201、云烟87、RG17、NC82居中，红大，DL01、DL02基本上位于倒数三位，厚度相差较大．NC82、DL01、云烟85、红大叶片组织结构厚度极差较小，云烟87、RG17、云烟201次之、K358、DL02、K326极差较大；综合分析得出：云烟85、RG17、云烟201、云烟87、NC82与K326品种的叶片组织结构较为接近或更好，红大、K358、DL01、DL02稍差． 相似文献
7.
Viswanathan Selvaratnam 《Higher Education》1988,17(1):41-68
This paper outlines the Western models of university development with its accompanying Eurocentric knowledge systems adopted by Third World countries. It discusses the various productive and counterproductive effects of these alien features to Third World universities, their research institutions and the knowledge output of their academic communities. It goes on to discuss the possible contributions that can be made within the ambit of South-South educational interchange for the development of a self-reliant higher education system among Third World nation states accompanied by an interdependent and more equitable world knowledge order. The final part of the paper examines the prospect of a self-reliant higher education and knowledge-generation system, developing in Third World countries, in the light of rapidly growing information technology which is dividing the world into information-rich and information-poor countries.This article is a revised and expanded version of a paper presented by the author at the 20th Annual Conference of the British Comparative and International Education Society held at the University of Hull in September 1985. The author acknowledges the critical comments and useful suggestions offered by S. Gopinathan, S.N.R. Kazmi and Peter Worsley on earlier drafts. 相似文献
8.
Seismic force modification factor for ductile structures 总被引：3，自引：0，他引：3
INTRODUCTION In codes for seismic design of buildings of many developed countries, elastic response spectra are adopted to calculate the base shear forces. For exam-ple, the base shear defined in Japan code 1997 is: FEK=DsFesC0ZAiRtW (1) where Rt is the elastic design spectrum; Ds is the structural coefficient changing among 0.25 to 0.50 to take account of different ductility of different struc-tures; W is the total weight of a structure; the others are site coefficient, irregular… 相似文献
9.
惠萍 《广东教育学院学报》2011,(3):26-30
利用B样条技术计算类氢InAs类氢杂质量子环基态和激发态能级的量子尺寸效应.当抛物势ω=0和ω=50meV时,基态能量的计算结果为常数E0,0=-4.98meV;当r0=0时,且无类氢杂质时,计算结果和精确的理论计算结果完全一致;当量子环较小时,杂质的库仑势对量子环的能量曲线Enr,m——r0影响较大;当量子环较大时,杂质的库仑势对量子环的能量的影响越来越小,库仑项可以近似地作为微扰项来处理.抛物禁闭关联势-μω02rr0对量子环的能量起关键作用,绝对不可能作为微扰项处理.量子环的基态和激发态随着抛物势ω的增加而增大.保持径向量子数nr不变,小量子环的能级随着角量子数｜m｜不同而明显分开,简并被破坏;当量子环变大时,基态和激发态的能级都趋于简并. 相似文献
10.
房间空调器R290替代R22的可行性分析 总被引：4，自引：0，他引：4
通过比较基本热力性质和进行理论循环计算,结合安全性、环保性,经济性等因素对丙烷(R290)替代R22的可行性进行了综合分析比较,并通过实验进行了验证,结果表明,在房间空调器中,R290作为R22的替代物具有极其优良的特性。 相似文献
11.
Identification of Rhodiola species by using RP-HPLC 总被引：2，自引：0，他引：2
INTRODUCTION The roots of Rhodiola species, one of the im-portant traditional Chinese herbal medicines, have anti-viral (Sun et al., 1993), anti-tumor (Wang et al., 1992), anti-ageing (Yi et al., 1992), anti-oxygen de-ficiency, anti-radiation (Luo et al., 1996) effects and other pharmacological properties (Xu et al., 2000). Ten Rhodiola species distribute in the Tianshan Mountains areas of China. Biologically active com-pounds content in the roots has large variation and the value of… 相似文献
12.
对中国云南大理主栽品种红大和K326以及自选品种（系）DL01和DL02烤后烟叶的香味物质进行了分析比较，结果表明：香味物质品种差异性较大，其中总香味物质、类胡萝卜素及其降解物、有机酸、潜香物质的含量DL02居首位，当地栽培具有丰富的香气物质，优于亲本红大及其它品种；DL01在美拉德反应物、西柏烷类降解物及含量高的重要香味物质等方面优于其它品种，具有一定的推广价值． 相似文献
13.
利用Gaussian03W在LANL2DZ基组水平对有机锡氧四元杂环结构化合物(μ-O)2Sn2R4(R:Me,Et)进行理论研究,优化了几何构型,获得键参数,分析了化合物的Mayer键级,计算出分子体系能、分子最高占据轨道能和分子最低未占据轨道能,经Mulliken布居分析原子净电荷分布,计算出原子轨道对分子轨道的组成贡献。结果表明,除(μ-O)2Sn2Me4外的标题化合物均稳定,为有机锡氧四元杂环化合物(μ-O)2Sn2R4(R!Me)的合成提供理论基础。 相似文献
14.
本文介绍了卷烟厂风力送丝系统中影响烟丝造碎率的两个主要因素：输送风速与料气比。基于目前大多数卷烟厂风送系统不具备调速功能或者调速效果欠佳,造成风速过高、烟丝造碎高、烟尘增加、能耗大等问题,提出了风速平衡控制的设计方法与调节手段,有效控制烟丝输送风速在18-22m/s范围内,降低烟丝造碎,系统运行稳定。 相似文献
15.
Patricia Baggett Andrzej Ehrenfeucht 《Educational technology research and development : ETR & D》1983,31(1):23-32
This study shows that when viewers watching an educational movie are presented simultaneously with information in two media-visual
and verbal /auditory, there is no competition fa resources. When encoding information in one medium, one is not hindered from
encoding information in the other; even when visual and linguistic information are presented sequentially, doubling study
time, the extraction of information is not increased. College students appear to be good dual media processors.
This work was supported by the Office of Naval Research, Contract #N00014-78-C0433, and National Institute of Mental Health
postdoctoral fellowship #5 F32 MH07588-02, to the first author. Some of the results were presented at the 1980 annual meeting
of the Psychonomics Society in St. Louis. We thank Agda Bearden for helping with data collection and scoring and R. Michael
Perry for implementing the computer package for data analysis. Requests for reprints should be sent to Patricia Baggett, Psychology
Department, University of Colorado, Campus Box 345, Boulder, Colorado, 80309. This report is #108 of the Institute of Cognitive
Science’s Technical Report Series. 相似文献
16.
Shi L Huang XQ Shi L Tao YF Yao YF Yu L Lin KQ Yi W Sun H Tokunaga K Chu JY 《Journal of Zhejiang University. Science. B》2011,12(6):428-435
A study of the human leukocyte antigen (HLA) genetic characteristics in the Zhuang, the largest ethnic population in China, would provide insight into Zhuang history and give a useful tool for disease associations, transplantation, and anthropology. In the present study, we report the comprehensive HLA-A, HLA-B, HLA-C, and HLA-DRB1 alleles and haplotypes in the Zhuang population of southern China for the first time. A total of 13 HLA-A, 24 HLA-B, 22 HLA-C, and 18 HLA-DRB1 were identified in 104 Zhuang individuals. The frequencies of HLA-A*11:01, A*02:07, A*24:02, A*02:03, and A*33:03 on A loci, B*15:02, B*58:01, B*46:01, and B*13:01 on B loci, C*03:04, C*08:01, C*01:02, C*03:02, and C*07:02 on C loci, and DRB1*15:01, DRB1*16:02, DRB1*14:01, DRB1*15:02, and DRB1*03:01 on the DRB1 loci were >10%. The A*33:03-C*03:02-B*58:01-DRB1*03:01 and A*02:07-C*01:02-B*46:01-DRB1*14:01 haplotypes were predominant in the Zhuang. The phylogenetic tree, as well as the analysis of haplotypes, suggested that the Zhuang are genetically similar to southern Chinese populations, especially the Zhuang-Dong language-speaking populations, such as the Bouyei, Dai, and Maonan. Even though the Zhuang and southern Chinese populations shared common alleles and haplotypes, the Zhuang has maintained its unique genetic characteristics. 相似文献
17.
通过对钢筋混凝土网格框架结构体系进行试验与有限元模拟实现了对该新型结构体系承载力的理论研究,分析了网格框架受力性能的影响因素,归纳总结出了网格框架正截面承载力的计算公式,为工程应用提供了理论依据。 相似文献
18.
本研究以全钒液流电池储能系统为研究对象,通过电力系统分析综合程序建立了包含能量限制模块的全钒液流电池储能系统模型。综合考虑了储能系统换流器的容量大小、荷电状态等因数,通过仿真分析对比两种控制策略以及模型在不同大小的储能电池中的适用性,验证了理论分析的准确性及模型的工程实用性。仿真结果表明,该模型既能通过限制无功功率传输保证传输的能量不超出换流器容量,又能根据实际有功功率大小调整无功功率上限,充分发挥储能系统的调节作用。 相似文献
19.
应用Car-Parrinello从头分子动力学(CPMD)及限定性动力学方法对水二聚体在300K时不同距离和角度的相互作用能进行了研究,计算结果表明:水二聚体在R=3.0,θ=170°附近形成的氢键结构最为稳定,其相互作用能量约为-18～-17kJ/mol。随着氧氧间距离R的增加,角度θ对氢键能量的影响逐渐减小,当R>4.0时角度θ对氢键能量的影响已经很弱。 相似文献
20.
探讨不同专项运动员的心肺机能适应性特征和能量代谢特征,为不同体育项群的项目特点提供生理学基础.通过对武汉体育学院男子公开级赛艇运动员与男子轻重量级古典式摔跤运动员在递增负荷运动过程中气体代谢变化特征进行比较研究发现,递增运动至力竭时,赛艇组心率（HR）、呼吸频率（RR）和氧通气当量（VE/VO2）显著低于摔跤组,最大摄氧量（VO2max）显著高于摔跤组;运动中后期呼吸商（RQ）非常显著低于摔跤组;达到无氧阈（AT）时,赛艇组潮气量（Vt）、通气量（VE）、摄氧量（VO2）和氧脉搏（VO2/HR）非常显著高于摔跤组. 相似文献