HFC-134a螺杆冷水机组中满液式蒸发器回油设计讨论

本文讨论了HFC-134a螺杆冷水机组中满液式蒸发器回油设计的三种方法直接回油、气体引射回油和手动回油.在HFC-134a满液式蒸发器中使用一种合成冷冻机油,采用三种回油组合方式是可行的,满液式蒸发器中的含油量可以控制在1%以下.     

满液式螺杆式冷水机组回油设计

以满液式螺杆式冷水机组研发样机的设计和测试为基础,对机组采用的回油方式进行分析讨论,认为对于采用R134a制冷剂配POE酯类合成油的半封闭螺杆式压缩机及满液式蒸发器的冷水机组,多种回油方式组合运用是有效和可行的。     

满液式螺杆式冷水机组回油和跑油分析

对满液式螺杆式冷水机组的回油方式进行介绍,尤其针对引射回油展开详细分析,具体讨论机组增加引射回油的必要性及其增加引射回油对系统的影响,并且简要分析不同引射回油系统的优缺点;然后对满液式螺杆式冷水机组跑油情况进行分析论述,并针对每种情况给出相应的解决方案。     

制冷剂充注量及布管方式对降膜式蒸发器性能影响的试验研究

水平管降膜蒸发器由于其较少的冷媒充注量和较高的换热性能在制冷空调领域得到广泛的应用。本文以R134a为工质,对冷媒充注量和两流程下管程布置方式对采用降膜式蒸发器性能的影响进行了试验研究,并与满液式蒸发器进行对比。结果表明:随着冷媒充注量的增加降膜式蒸发器换热性能逐渐提升,但提升趋势逐渐缓慢;冷冻水进出水管采用下进上出的方式机组性能优于上进下出;同等能力下,采用降膜式蒸发器机组的冷媒充注量比满液式蒸发器可减少34%。     

引射器出口背压对满液式蒸发器回油的影响

压缩机失油是满液式冷水机组常见的问题。通过制作引射器模型并测试引射器出口在不同的背压下引射管的流量值,探讨压缩机失油的成因。测试结果表明：在产品设计或生产中不注意引射器出口背压,是压缩机失油的主要原因之一;在出口处安装弯头、截止阀,会使背压增大,流量减小,甚至出现倒流。因此提出建议：在满液式蒸发器的回油管路中,引射器出口尽量不要使用截止阀、弯头等类似管件;引射管出口管路应水平或向下布置。     

满液式蒸发器回油的一个方案

本文总结分析了采用满液式蒸发器的冷水机组的几种回油措施，提出一个新的回油方案，并进行理论计算和分析，最后提出采用这种回油方案所应注意的几个问题。     

替代工质HCFC-22/HFC-152a汽车空调系统的特性研究

保有汽车的空调系统大多采用CFC-12制冷剂,若改用HFC-134a制冷剂系统将面临很多困难.HCFC-22/HFC-152a的混合制冷剂同原CFC-12制冷系统相容,又符合CFC替代的国际协议的规定,本文对HCFC-22/HFC-152a为制冷剂的汽车空调的性能进行了分析,并与CFC-12、HFC-134a系统进行了对比.HCFC-22/HFC-152a混合制冷剂可作为过渡替代工质,在保有的汽车空调系统中可以直接替代CFC-12.     

全降膜蒸发器应用于冷水机组的研究

在分析蒸发器性能对冷水机组性能影响的基础上,探讨降膜式蒸发器的关键技术,并通过试验研究降膜式蒸发器的换热系数和回油浓度,同时与满液式蒸发器的换热性能进行对比。结果表明,在分配器供液充足时,降膜管束蒸发性能优势显著,表现在换热系数高、回油浓度高等方面。     

新型PVE油对R32分体式空调性能的影响

R32作为新一代替代制冷剂的应用范围很广,专用冷冻机油的开发和使用成为R32应用的关键问题之一。本文选取了一种新型PVE油搭配R32,通过实验对比R410A/POE油、R32/POE油以及R32/PVE油组合时2匹热泵分体式空调的制冷性能,研究了不同PVE油含油率下的空调蒸发器及冷凝器侧热阻的变化,PVE油量影响系统COP的原因。结果表明:PVE油的使用明显提升了R32空调的制冷性能,随着油量的增加,蒸发器侧热阻先增大后减小,冷凝器侧热阻逐渐增大,从而影响蒸发温度先升高后降低,冷凝温度持续上升,系统COP先增大后减小,在PVE充注油量270 m L附近达到最大值。     

替代工质与润滑油的匹配性研究

选取 5台YZG - 2 7R型压缩机、4台PH112× 2 - 9KC型松下万宝压缩机和 2台YZB - 2 0R型变频压缩机进行加速寿命试验 ,对替代工质R32 R134a和R4 0 7C与不同型号的酯类POE油的配合性进行试验研究。结果表明 :RO- 32油和RO - 4 0油不宜作为替代工质R32 R134a的YZG - 2 7R型压缩机用油 ,EAL - 4 6油可以作为R32 -R134a的YZG - 2 7R型压缩机用油 ;RO - 5 0油可以作为R32 R134a的PH112× 2 - 9KC型压缩机用油 ;EAL - 6 8型POE润滑油加入少量添加剂可以作为R4 0 7C的YZB - 2 0R型变频压缩机用油     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。