陈列柜研究现状及分析

概述了目前国内外陈列柜的研究状况,包括陈列柜的热负荷分析计算、风幕的CFD仿真计算、陈列柜蒸发器的结霜融霜特性、陈列柜节能及优化设计.通过对陈列柜研究的介绍和分析,指出了陈列柜研究中的一些问题,提出了进一步研究的方向.     

立式陈列柜双层风慕的CFD优化

风幕卷吸渗入的热负荷是超市陈列柜热负荷的主要来源,为减少热空气的吸入量通常设置双层风幕,两层风幕相互影响。本文采用雷诺应力模型对某带双层风幕的立式超市陈列柜的流场和温度场进行了仿真计算和实验验证。并在CFD理论模型基础上,对风幕的影响因数进行了调整和优化,为风幕系统的优化设计提供依据,     

商用陈列柜的设计方案与节能措施研究

本文概述了商用陈列柜作为冷藏、冷冻以及陈列商品的设备所具有的要求和特点，分别从设备方案和技术方案两方面对陈列柜的设计方案进行了介绍，并提出了能够有效降低陈列柜能耗的一些途径，阐述了陈列柜热负荷方面的特点，最后对商用陈列柜在节能设计方面的研究进展进行了展望。     

吹吸式非等温双层空气幕紊流特性数值分析

空气幕的紊流特性是设计空气幕的理论依据,在超市陈列柜等设备中,为减少热空气的卷吸量常采用双层空气幕,两层空气幕相互干扰,直接影响空气幕的作用。本文以某立式超市陈列柜为例,采用雷诺应力模型对吹吸式双层空气幕的紊流特性进行了数值计算与实验验证。在此基础上,对空幕参数进行了优化,     

立式开式陈列柜热负荷组成及分析

本文详细分析了立式开式陈列柜的热负荷组成；提出在陈列柜开机降温的非稳态运行过程中，除霜热负荷是引起柜温波动的主要原因；在陈列柜稳态运行过程中，通过风幕的渗人热负荷在其总的热负荷中占绝大部分(70％以上)。因此，为提高陈列柜的性能，必须从降低这两种热负荷人手。     

卧式陈列柜风幕的数值分析

利用CFD软件phoenics,通过对卧式陈列柜传热过程的分析,分别在忽略辐射和不忽略辐射2种情况下建立陈列柜风幕的k-ε数学模型,模拟计算不同送风速度下2种模型的风幕性能以及柜体热负荷,并与试验数据进行对比.结果表明,考虑辐射的模型的模拟结果更符合试验数据.同时对比不同送风速度对风幕性能的影响,风幕送风速度过小,冷射流不能到达回风口,不能形成完整的风幕;风幕送风速度的过大,增加了风幕射流与环境热空气的热质交换,使得柜内温度升高,所以必须选择合理的送风速度.     

立式敞开式陈列柜渗透热负荷影响因素分析

本文采用内外风幕送回风焓差计算通过风莫的渗透热负荷，在此基础上分析了立式陈列柜的风幕参数和环境参数对渗透热负荷的影响，本文的研究结果可以为立式陈列柜的优化设计提供依据。     

冷藏陈列柜减湿预冷器对蒸发器性能的影响分析

为了减缓冷藏陈列柜结霜,在一台中温立式敞开式冷藏陈列柜上加装减湿预冷器,并针对加装前后冷藏陈列柜的性能进行了实验。实验结果表明:在国家标准GB/T21001.1—2007《冷藏陈列柜第2部分:分类、要求和实验条件》中设定的Climate class 3实验条件下(测试环境温度为25℃,相对湿度为60%),加装减湿预冷器使冷藏陈列柜蒸发器的进口空气温度降低2.4℃,含湿量也相应降低;此外蒸发器的结霜速度变缓,在6h的融霜周期内融霜时间减少了28%,系统负荷降低了19.2%。     

确定陈列柜热负荷新方法的研究

以陈列柜为研究对象，在对其柜内空气进行热平衡分析的基础上，提出了利用风幕进出口的焓差确定陈列柜热负荷的方法。与传统的方法相比，这种方法需要给定的已知参数相对较少、应用方便，而且可以不通过实验获取已知参数，对新设计的陈列柜的热负荷可进行预测。通过与实验值的比较可以看出，这种方法具有实际的可行性和应用价值。     

采用系统仿真方法数值模拟双层风幕立式陈列柜

将制冷系统的仿真模型与立式陈列柜的热卷吸系数关联式模型结合,提出双层风幕立式陈列柜系统的系统仿真方法,并编制计算机程序进行了仿真实验。根据仿真实验的结果分析了陈列柜系统冷凝温度、蒸发器面积和柜体参数的变化对陈列柜风幕送回风温度变化的影响规律。仿真实验的结果和试验测试值进行了对比分析,其最大偏差为1.9℃,平均偏差为0.9℃,说明本仿真算法具有工程应用价值。     

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)。