CHARACTERISTICS OF HEAT TRANSFER FROM A SPHERICAL SOLID BODY UNDER PULSATING FORCED CONVECTION

Heat transfer from a solid sphere having a Biot number Bi ? 0.1 to a flow medium in a cooling process under pulsating forced convection is experimentally examined. In the experiment, two kinds of pulse modes, which are the type of pulsating forced convection with continuous feed and the feed type mixing forced and natural convection, are considered as a pulse feed technique. Initially, the evaluation method of the Nusselt number Nu is derived in the cooling process and the validity of that method is verified by comparison with the experimental results. With regard to the effect of pulsating feed, it is shown that the pulsating feed conditions have a great influence on the characteristics of the heat transfer. The enhancement of heat transfer under the condition of the forced convection pulsatively fed with continuous feed is recognized, and the characteristics of heat transfer for the pulsating feed including natural convective heat transfer region are aggravated. Besides, it is clear that the decrease in the heat transfer characteristics is dependent on the duration of the natural convective heat transfer. Furthermore, Ranz-Marshall correlations for each pulsating feed condition are presented.     

Bioactivity of sol–gel derived organically modified silicates: Part I: In vitro examination

Bioactivity was investigated for several organically modified silicates (Ormosils) prepared through sol–gel processes. Ca(II)-free samples were biocompatible only, but Ca(II)containing samples were bioactive and deposited apatite during immersion in a simulated body fluid. The ease of silanol (Si–OH) group formation on the ormosils was considered a predominant factor controlling the bioactivity, while the effect of dissolved Ca(II) ions to increase the degree of supersaturation in the simulated body fluid is secondary.     

Anionic Conduction in Lead Halosilicate Glasses

Electrical conductivity due to halide ions has been measured for the glasses in the system 30SiO₂· (70 − x )PbO · x PbX₂ (0 < x < 17.2 mol%; X = F, Cl). The conductivity increases with x by several orders of magnitude for both series of glasses. The contribution of principal factors to the conductivity has been examined. The analysis of the activation energy on the basis of the Anderson-Stuart model shows that the strain energy is a predominant term in the Cl glasses, while both the strain energy and the electrostatic energy have a comparable contribution in the F glasses. The decrease in the activation energy with increasing PbX₂ content is related to the decrease in the shear modulus for the Cl glasses and to the increase in the permittivity for the F glasses.     

An Expert System for Tunnel Design

In this article, we describe the development of an expert system (ES) for tunnel design and preent some applications of the system. The system has been developed by our research group consisting of 21 people closely involved with the tunnel design under the leadership of Nagoya University. The system consists of four subexpert systems (1) ES for standard tunnel design methods, (2) ES for framed structure method, (3) ES for theoretical design methods, and (4) ES for numerical analysis design method; a common part to control the overall system; and two data base systems (tunnel data base system and rock mass data base system).     

热化学蓄热系统研究进展

热化学蓄热通过可逆化学反应来储存和释放热量,其蓄热密度高于显热蓄热和相变蓄热,且能够实现能量的长期储存,在未来能源利用领域具有广阔前景。根据热化学蓄热系统的结构,可将其分为开式系统和闭式系统。本文针对开式系统和闭式系统,对蓄热材料、环境气氛条件、反应过程优化以及反应器设计等影响系统性能的重要因素进行概述与讨论,为热化学蓄热系统的发展和实际应用提供参考。     

栏栅式山溪取水工程取水特性的试验研究

通过水工模型试验,对栏栅式山溪取水工程的取水特性进行了研究,探讨了在有足够大的集水廊道的前提下,该取水工程的潜在取水能力。结果表明,在影响栏栅取水量的诸因素中,栅条长度、栅隙和栏栅的设置角度对取水量的影响程度不同;其取水量主要由栏栅的设置角度决定,而栅条长度和栅隙对取水量的影响程度较小;栏栅的设置角度小于50°时,栏栅有较大的引水比,栏栅的设置角度大于50°后,栏栅的引水比大幅度下降。     

钛金属低温生物活化

利用含微量TaCl5的双氧水溶液在低于100℃温度下与钛金属之间的化学反应,在钛金属表面直接生成具有良好生物活性的锐钛矿与金红石混合结构晶态二氧化钛薄膜.研究了双氧水浓度和处理温度的影响.结果表明,80℃下,双氧水浓度大于6wt.%时即可在钛金属表面获得具有良好生物活性的晶态二氧化钛薄膜,进一步增加双氧水浓度直到30wt.%对结果没有明显的影响.处理温度强烈影响钛金属表面的产物及其在模拟体液中诱导沉积羟基磷灰石的能力.     

Vapour Pressures and Heats of Sublimation of Some Disperse Dyes

The vapour pressures, latent heats of sublimation and associated entropy changes of anthraquinone and monoazo disperse dyes have been obtained by the transpiration method. These compounds have vapour pressures of 0.0005-0.193 mm Hg over the temperature range of 120–215°C. The heats of sublimation are discussed in terms of their molecular structure.     

低温驱动沸石-水吸附式制冷机的性能研究

本文研究的合成沸石-水吸附式制冷机采用FAMZ01沸石作为吸附剂,吸附床选择翅片涂抹式吸附床,通过实验研究该制冷机的制冷功率、制冷性能系数(COP)随热源温度、冷冻水进口温度的变化规律。结果表明,该吸附式制冷机在55℃的热源下就可以稳定输出制冷量,并在驱动热源为65℃左右展现其较佳的性能。