Determination of thermophysical characteristics of multicomponent liquids

A new approach is developed for determining the specific isobaric heat capacity and thermal expansion coefficient of multicomponent liquids.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 2, pp. 262–267, August, 1984.     

Transfer coefficient of multicomponent air with sublimation products of graphite

An economical method of calculating the viscosity, thermal conductivity, binary diffusion coefficient, and thermodiffusion coefficient is proposed, for a mixture of dissociated air and subliming graphite.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 1, pp. 106–113, July, 1988.     

Sensitivity studies for the effective characteristics of periodic multicomponent composites

The main goal is to present the application of design sensitivity analysis in homogenization of periodic multicomponent composites. The effective modulus approach is used to determine homogenized characteristics of the composite together with some upper and lower bounds estimators for these quantities. The approach related to homogenization problem is presented in a general form for a linear elastic n-component periodic composite and is implemented in the finite element method homogenization-oriented computer program MCCEFF. Sensitivity coefficients are determined numerically for various components of homogenized elasticity tensor and, using symbolic analysis, for their bounds, in both cases with respect to material parameters of the components. Structural response functional for such a composite is proposed as the strain energy in various strain states of the composite cell to detect the most influential parameters of the most popular fiber-reinforced structures as well as in the case of multicomponent superconducting composite device.     

Calculation of the optical characteristics of a multicomponent multiply charged plasma

A theoretical model is developed and results of calculations of thermodynamic and optical characteristics of a plasma in the approximation of a radiative-collisional model that allows their calculation in wide temperature and density ranges are reported. Energy levels, ionization potentials, probabilities of transitions are calculated by quantum-mechanical methods in the Hartree-Fock-Slater approximation. For some chemical elements use is also made of extensive experimental spectroscopic information that provides the possibility of determining the energy levels and wavelengths of optical transitions with a high accuracy.     

Design and operating characteristics of evaporative cooling systems

Evaporative cooling systems are commonly used in countries where the climate is hot and dry, as found in most zones of India and Australia. The potential energy savings envisaged by replacing conventional refrigerated systems by evaporative systems is ≈75%. Indirect systems can achieve comfort conditions similar to refrigerated systems in climatic zones where the wet bulb temperature is usually <25°C. The comfort afforded by indirect evaporative systems is superior to that achieved by direct evaporative systems. An 8.5 ton indirect-direct evaporative cooling system has been fabricated and tested and its performance compared with a computer prediction. The system's scope for use in India and Australia is analysed.     

Design of cooling channels with improved thermohydraulic characteristics

A method is proposed for designing the profile of a slot channel so as to ensure a uniform temperature field in the cooled object.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 3, pp. 401–406, September, 1982.     

成核剂与增稠剂对甘露醇相变特性的影响

糖醇是一种用于储热的相变材料,具有较高的潜热,然而,糖醇的高过冷度阻碍了其应用。D-甘露醇作为一种糖醇,在中温储热方面具有广阔的应用前景。选用氧化铝和碳化硅作为成核剂,海藻酸钠和羧甲基纤维素作为增稠剂,观察了纯甘露醇、成核剂、增稠剂以及单独或联合添加成核剂和增稠剂的甘露醇的形貌。采用差示扫描量热法研究了成核剂和增稠剂对甘露醇相变特性的影响。实验结果表明,氧化铝、碳化硅和适量的海藻酸钠促进了甘露醇的成核结晶,当氧化铝、碳化硅、海藻酸钠的质量分数分别为7.0%、9.0%、0.5%时达到最低过冷度,样品相比纯甘露醇过冷度分别降低了17.4、12.2和17.3℃。联合添加相比单独添加成核剂和增稠剂改善了甘露醇的成核结晶;当联合添加氧化铝和海藻酸钠的质量分数分别为5.0%和1.0%,而碳化硅和海藻酸钠的质量分数分别为3.0%和1.0%时,样品相比纯甘露醇过冷度分别降低了19.7℃、16.5℃。探讨了成核剂和增稠剂对甘露醇相变特性的影响机理,发现增稠剂提高了成核剂在甘露醇样品中的分散性,因而提高了成核剂的诱导成核作用。     

喷雾冷却临界传热特性试验研究

为了进行极限热工况下的喷雾冷却传热特性研究,设计并搭建采用蒸馏水及乙醇溶液喷雾冷却试验台,分析结构参数、喷雾流量、喷雾腔内压力等对喷雾冷却临界热流密度的影响。试验结果表明:临界热流密度随槽道深度增加先增大后减小,最佳槽道深度为0.8 mm,此时临界热流密度达到326 W/cm^2;随着喷雾流量的增加,临界热流密度始终增大;喷雾腔内压力对临界热流密度基本没有影响。计算结果表明,喷雾冷却效率随槽道深度增加而提升,随喷雾流量的增加而减弱。     

Assessment of adsorption-desorption characteristics of adsorbents for adsorptive desiccant cooling system

The performance of various dehumidification materials was assessed in terms of effective adsorption amount of water vapor based on the adsorption isotherms to find a suitable dehumidification element for an economical adsorptive desiccant cooling system being developed. The effective adsorption amount is an important factor for regeneration at lower temperatures. Three types of silica gels, S(a), S(b), and S(c), with different pore volumes and pore size distributions, and zeolite with various molar ratios of Si/Al, 5.6, 29, 47, 91, and 220, prepared from a Y-type zeolite treated with hydrochloric acid, an activated carbon with silica gel added to improve the hydrophobic surface, and MCM-41 were examined. Silica gels having effective adsorption amounts of 0.25 g/g, and activated carbon with silica gel added were assessed to be candidate desiccant materials.     

The hydraulic characteristics of porous materials for a system of transpiration cooling

As a result of laboratory and numerical experiments, data on hydraulic drag and structure of flow are obtained for the first time in samples of sheet porous material prepared using the ingenious technology of two-way strain cutting. The study is aimed at developing an efficient system of transpiration cooling with tangential injection of cooling gas onto a microrough surface.     

Reliability of multicomponent assemblages

The reliability of multicomponent assemblages is of interest to engineers in many disciplines. It has been shown that the reliability of a multicomponent assembly—a simple frame—may be estimated through the use of a causal network. The causal network approach does not require the modelling of a structure as series or non-series; it only requires that the network of component reliabilities by acyclical. Assumptions about local member influence are implicitly included only through the use of conditional probability matrices throughout the network. These matrices may be generated through the use of a noisy OR gate and/or a rule-based system. It is postulated that the system reliability of any multicomponent assemblage can be estimated in this manner. Testing of the application of the concept to problems of realistic dimensions is currently under way.     

A parametric study on the cooling characteristics of an infrared detector cryochamber

This work investigates the steady and transient cooling characteristics of an infrared (IR) detector cryochamber, which has a critical effect on the cooling load that a refrigeration system should carry away. The current thermal modeling considers the conduction heat transfer through a cold well, the gaseous conduction due to outgassing, and the radiation heat transfer. The steady cooling load is obtained by using a fin equation. The transient cooling performance, i.e., the cool-down time, is determined using a finite difference method. It is shown that the gaseous conduction plays an important role in determining the steady cooling load, whereas it has a negligible effect on the cool-down time due to a short thermal penetration depth. The steady cooling load increases linearly with the bore conductivity when it is high. However, when the bore conductivity is low and the gas pressure is high, the cooling load becomes more sensitive to the bore conductivity. The steady cooling load increases linearly with the difference between the ambient temperature and the detector operation temperature, but rather the cool-down time is proportional to the square of the temperature difference. The results of this work can be used to determine the thermally optimal design and operation conditions of the cryochamber.     

Counter flow cooling characteristics with liquid nitrogen for superconducting power cables

Counter flow cooling is one of effective cooling systems for superconducting power transmission cables to save space. In designing of HTc superconducting power cables, investigating cooling characteristics with liquid nitrogen is important. We have conducted counter flow cooling tests of a 100-m long duplex-counter-flow tube with liquid nitrogen and obtained basic data of initial cooling and temperature distributions along the tube. Measured temperature distributions are compared with those calculated that are based on our previous study. They agree with temperature distributions of inner tube but not for outer tube. During cooling tests, mass flow rate oscillations are observed. Relation between oscillation period and tube length is discussed. Reservoir pressure dependence of measured initial cooling time is also shown and compared with analytically estimated time in this paper.     

Deformation and fracture model for a multicomponent elastoplastic porous medium with continuous variation of physicomechanical characteristics

A mathematical model and a procedure of solving problems for the development of functionally gradient porous materials ensuring the desired distribution of stress-strain state parameters over the volume of the structure under explosion and impact loadings are proposed. The choice of the model is based on general theoretical concepts and is validated by comparison of the calculated results with experimental data. Research Institute of Applied Mathematics and Mechanics, Tomsk University, Tomsk, Russia. Translated from Problemy Prochnosti, No. 2, pp. 139–150, March–April, 1999.     

Numerical study on cooling characteristics of two-phase closed thermosyphon embankment in permafrost regions

The two-phase closed thermosyphon (TPCT) is an effective heat transfer device decreasing the ground temperature around it in cold season, but not absorbing heat energy in warm season. In this paper, in order to research the efficiency of the TPCT applied to the embankment in permafrost regions, a three-dimension model for the TPCT embankment was presented based on the work characteristics of the TPCT and on the related heat transfer theories. The numerical results showed that 1) the model can reasonably solve the coupled heat transfer problem of air-TPCT-soil for TPCT embankment; 2) the TPCT embankment is effective to protect the underlying permafrost and to ensure the stability of roadway in permafrost regions; furthermore, it could play rapidly a cooling effect and approach a thermal balance state after 5 years of construction; and 3) the TPCT, if combined with other engineering methods such as insulation, crushed rock, etc., can be an more effective engineering measure to ensure the stability of roadway engineering in warm permafrost regions.     

Conductivity of multicomponent heterogeneous systems

A method is proposed for calculating conductivity of a multicomponent heterogeneous system, taking account of its structure.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 4, pp. 593–600, October, 1981.     

Characters of multicomponent lead-free solders

In the process of electronic packaging, such as flip chip technology, under bump metallization (UBM) can be consumed gradually by solder during soldering. Then dissolution of Ni, Au and Cu from UBM into the solder may change the original solder to a multicomponent one especially under the trend of miniaturization. It is quite necessary to evaluate the properties of the multicomponent solders that have new composition after soldering. In this study, the microstructure, thermal and mechanical properties of five types of multicomponent lead-free solders, i.e. Sn–2Cu–0.5Ni, Sn–2Cu–0.5Ni–0.5Au, Sn–3.5Ag–0.5Ni, Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni (all in wt% unless specified otherwise) were investigated. Comparison with eutectic Sn–0.7Cu, Sn–3.5Ag and Sn–3.5Ag–0.7Cu solders was made. There was no obvious difference of the melting point between the multicomponent lead-free solders and the eutectic ones. For Sn–2Cu–0.5Ni solder, Cu₆Sn₅ and (Cu,Ni)₆Sn₅ intermetallic compounds (IMCs) formed. In the case of Sn–2Cu–0.5Ni–0.5Au, besides (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni,Au)₆Sn₅ were also observed. The IMCs formed in Sn–3.5Ag–0.5Ni solder were Ag₃Sn and Ni₃Sn₄. In both Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni solders, Ag₃Sn and (Cu,Ni)₆Sn₅ were detected. The mechanism for the formation of the IMCs was discussed. Tensile test was also conducted. The fractography indicated that all of the multicomponent lead-free solders exhibited a ductile rupture.