溴化锂填料吸收器中绝热吸收过程的实验研究

针对传热、传质分离的填料吸收器，设计、加工了一个溴化锂绝热降膜吸收的循环实验装置；实验研究了溴化锂水溶液在填料层上的绝热吸收特性；分析了溶液温度、浓度、降膜雷诺数对吸收效率和传质系数的影响。     

添加纳米粒子的溴化锂溶液传质特性

建立了纳米溴化锂溶液二维降膜传热传质数学模型,以实验数据对模型进行验证。研究结果表明,在溴化锂溶液中加入纳米粒子可以显著增强溴化锂溶液对水蒸气的吸收速率,并且随着纳米粒子添加量的增大,纳米溴化锂溶液对水蒸气的吸收速率越大;在纳米粒子添加量相同时,纳米溴化锂溶液的水蒸气吸收速率随着溶液流量的增大而增大,且水蒸气吸收速率随溶液流量的变化趋势为对数曲线趋势;溶液的传质强化比随着纳米粒子添加量的增加而增大;在溴化锂溶液中加入纳米粒子后,吸收器的传质系数随着纳米粒子添加量的增大而增大,在溶液流量为1.2 L/min时,添加0.05%纳米粒子后,吸收器传质系数增加1.32倍,添加0.1%纳米粒子后,吸收器传质系数增加1.41倍,但是,传质系数增幅随着纳米粒子含量的增加而逐渐减弱。     

太阳能溴化锂吸收式制冷系统溶液降膜吸收流动分析

溴化锂降膜式吸收器能在较小液流量和较小温差下获得较高的热流密度和传热传质系数,尤其是当液膜沿着水平管外作降膜流动时,传热传质效果更佳。为此建立溴化锂降膜吸收器溶液吸收过程流动的物理模型,通过对模型假设简化,对其进行数值求解,从而进行流动分析。与实验结果分析相结合,使得对吸收式制冷系统的分析更加全面。     

LiBr喷雾吸收器的传热传质分离研究

吸收器是溴化锂吸收式制冷系统中最大的部件，换热面积占机组的40％左右。文章介绍了稳定性能好适合船用的喷雾吸收器的原理和特点，提出通过预冷却和绝热吸收，实现传热传质的分离，使两者可以分别得到强化。在Newman的基础上建立数学模型，对传热传质分离的吸收器进行分析和计算，得出结论。     

添加剂和纳米粒子强化溴化锂水溶液／氨水吸收特性研究进展

吸收式制冷以其节能、环保等诸多优点得到了越来越广泛的应用。本文总结与分析添加剂和纳米粒子强化溴化锂水溶液及氨水吸收特性的机制和相关实验研究的发展现状。针对吸收式制冷系统中吸收器传质系数和换热系数小而导致的制冷效率低的问题,很多学者进行了添加剂和纳米粒子对吸收过程影响的实验研究,并据此采取措施增大传质传热效率。实验主要包括以下几个方面：表面张力实验、静态池吸收实验、降膜吸收实验和氨水鼓泡吸收实验。实验结果均表明添加剂和纳米粒子可以提高吸收器中溴化锂水溶液及氨水的传热传质性能。该研究对于提高吸收式制冷系统的制冷效率有很大帮助,同时为该技术在实际系统中的应用奠定基础。     

垂直管氨水降膜吸收传质研究

吸收器是影响氨水吸收式制冷系统的关键部件。对常用的垂直管氨水降膜吸收器进行绝热吸收模拟分析,并将模拟分析结果与实验结果进行了对比。在此基础上,通过实验进一步研究了稀溶液进口过冷和外部吸收冷却对吸收传质的影响,得到稀溶液进口过冷能够促进吸收传质的结论。结果表明:氨水吸收式制冷传质率的模拟结果与实验结果的偏差在20%以内,在冷却吸收和进口过冷的实验测试工况下,吸收传质率提高了132%。     

降膜和泡式等不同吸收模式的分析研究

本文的目的是针对降膜和泡式两种吸收模式,分析氨水吸收过程的复合传热传质,并企图对传热传质面积等重要参数对吸收量的影响进行参数分析。用在冷却剂侧有偏置肋片（OSF）的板式热交换器来设计降膜和泡式吸收器。已经发现,泡式吸收器的局部吸收量总是大于降膜式,使此种吸收器的尺寸比降膜式约小48．7％。对降膜式吸收器、液体侧的传质阻力是决定性的,而气体侧的热热和传质阻力的也很大。对泡式吸收器,液体侧传质阻力是决定性的,而比泡式吸收器大,而对泡式吸收器,传质系数的影响比降膜式更大。     

溴化锂风冷垂直降膜吸收过程数值模拟

通过对溴化锂溶液在降膜吸收过程中传热、传质特性的分析,建立了垂直降膜吸收过程的数学模型。在这个模型中,考虑了对流及变膜厚等因素对传热、传质性能的影响。并对风冷垂直管降膜吸收过程进行了数值模拟。得出的结论对垂直降膜吸收器的设计和优化具有指导意义。     

表面活性剂对溴化锂吸收式制冷机吸收过程强化机理的研究概况

吸收式制冷技术具有环保、节电和利用余热等不可替代的优点，在我国应用广范。溴化锂机组的吸收器是系统中换热面积最大、成本最高的换热部件，采用添加剂强化吸收器传热传质是一种不可缺少的手段。但是添加剂的强化机理却一直没有研究清楚，各国对添加剂的强化机理的研究很重视，已经有了不少研究成果，本文对国外添加剂对溴化锂制冷机吸收器的强化机理的研究进行简要介绍和分析。     

低雷诺数下溴化锂溶液降膜吸收热质传递的数值研究

溴化锂溶液降膜吸收是吸收式空调系统中常见的热质传递形式之一。本文对溶液降膜吸收过程的热质耦合传递分析,建立了溴化锂溶液垂直降膜吸收热质传递的二维数学物理模型,采用CFD-Fluent对模型进行求解。计算得到不同Re下的液膜界面温度、液膜内浓度分布、传热传质通量及传热传质系数等。分析了Re对降膜吸收过程中热质传递的影响。结果表明:当液膜Re150时,液膜界面平均温度与平均传质系数随着Re的增大而增大,而平均传热系数随着Re的增大而减少;平均传热传质通量均是随着Re的增大而先增大后减小,存在一个最佳液膜Re使降膜吸收过程的传热传质通量达到最大,即Re=50时,平均传热和传质通量分别达到最大值7.2 k W/m~2与2.9×10~(-3)kg/(m~2·s)。     

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)。