片材机头中物料温度分布的模拟分析

本文利用ANSYS和MATLAB软件,对衣架型和T型片材机头中熔体的温度分布进行三维有限元模拟和分析。通过对机头流道内温度分布的模拟,得出了衣架型机头流道的温度分布优于T型机头。     

Temperature effects during practical operation of microfluidic chips

The temperature dependent fluorescence of Rhodamine B was used to investigate the temperature effect of several system parameters in a microfluidic chip. This was combined with computational fluid dynamics calculations. Limited air movement over the chip had no significant effect on the temperature of the fluid running through the chip. Also, fluid flow through the channels at had no effect on the chip temperature or heating and cooling dynamics. The temperature varied greatly over the length of the chip. During transient operation of the chip, the heat up and cool down rates varied over the chip, and were dependent on the distance to the heater. The thermal time constant for heat up was four to five times lower than for cool down. The results can be used as tools for operating a temperature controlled microfluidic chip.     

TiN/O''''-Sialon原位复合材料的抗氧化性能

通过对不同条件下原位复合制备的各种TIN／O′Sialon材料在空气中的氧化行为研究,考查了氧化温度、气孔率和TiW含量对材料抗氧化性能的影响。结果表明：当氧化温度升高到一定值时,通常材料表层会形成致密的“保护膜”,阻碍材料的进一步氧化;材料的气孔率和TIN含量越低,越易形成“保护膜”,反之,越不易形成“保护膜”。当材料的气孔率为30％以上,TiO2添加量为30wt％以上时,即使在更高的氧化温度下也不能形成“保护膜”。     

Comparison Between Heat-Transfer Conditions and Setting Up of Strain in Glass During Heat-Treatment

The properties of transparency and artificial anisotropy in glass were utilized in making a film recording of the development and evolution of thermal strains in glass specimens undergoing rapid cooling or heating. Discussed as examples are the traditional tempering treatment and the more original "temnization" treatment (to use a word coined by the writer several years ago). The mean temperature of the specimens was measured during these treatments by a calorimetric method, and from the representative curve of the mean temperature the temperature distribution at each instant throughout the specimens was deduced by calculation, using simple hypotheses. It was then possible to compare the distribution curves of strain with the distribution curves of temperature and from this comparison to explain certain phenomena such as the existence of conditions for "strain inversion" during tempering and conditions for "strain reversion" during temnization. This investigation is the preliminary stage of a more detailed examination of the behavior of a visco-elastic body under variable temperature conditions when its viscosity is temperature-dependent.     

High temperature electrochemical heat pump using water gas shift reaction. Part I: Theoretical considerations

A new electrochemical heat pump using a combination of an electrolytic reaction at lower temperature to absorb low grade thermal energy and a thermochemical reaction at higher temperature to produce more efficient thermal energy is proposed. At a lower temperature, an endothermic reaction which cannot occur thermochemically proceeds with electrolysis. At a higher temperature, an exothermic reaction which is the reverse of the electrolysis reaction occurs thermochemically to produce high grade thermal energy. The water gas shift reaction, CO₂(g) + H₂(g) CO(g) + H₂O(g), in molten carbonate is one possible candidate for the new electrochemical heat pump and can lead to an increase in the temperature of the thermal energy from 1100 to 1200K. A heat pump system using the shift reaction is also considered theoretically.     

Filtration Combustion of an Energetic Material in a Cocurrent Flow of Its Combustion Products. Critical Combustion Conditions

The paper reports results of a numerical calculation using the threetemperature model developed previously by the authors. In addition to the temperature difference between the gas and the solid phase (skeleton), the model approximately takes into account the temperature distribution in skeleton elements. It is shown that quenching is possible (after burnout of part of the charge) with variation in a number of input parameters: the thermal conductivity of the charge, the ignition temperature, the weight of the igniter, the initial temperature, the porosity of the charge, and the local rate of its decomposition.     

Some remarks concerning the WLF-relation

Summary The limitations of the WLF-relation are discussed with respect to their inherent demands concerning universality. The problem of the reference temperature is discussed in some detail, and their constants are related to the temperature T where the apparent activation energy of flow gets infinite, as well to the characteristic activation energy of viscous flow at infinitely high temperature, E.It is concluded that the use of experimentally derived temperature dependent apparent activation energy of flow, E(T), from the slopes of crossing isochrone and isotherm viscoelastic curves substitutes the WLF-relation favourably. Thus, the problematic choice of a reference temperature is avoided. The two kinetically specific constants, E and T, may be admitted to characterize the energetic and entropic contribution, respectively, to the viscous flow. Experimental data are presented for some polymers.Herrn Prof. Dr. B. Vollmert zum 65. Geburtstag herzlichst gewidmet     

甲醇氧化重整制氢过程(Ⅱ)反应器构型对制氢过程的影响

在质子交换膜燃料电池 (PEMFC)移动氢源———甲醇氧化重整制氢自热体系中 ,研究了反应器构型对产氢能量效率和床层内“热点”温度的影响 ,得到了反应器设计准则 ,提出了实际应用中可采用的反应器型式     

Fatigue-fracture mechanism of slowly notched poly(ethylene terephthalate) polymers

Summary Fatigue fracture behavior of slowly notched polyethylene terephathalate (PET) polymers were investigated at temperatures close to their transition temperatures up to well above their glass transition temperatures. Detailed characterization on the morphology of the notched roots showed that the crack tip during crack propagation became more dull with increasing testing temperature. The failure cycle (N_f) of these samples increased with increasing temperatures until it reached the transition temperatures of PET polymers, and most of the increase in N_f is due to the increased time consumed in the initiation period. On the other hand, the initial crack growth rate increased significantly and N_f of these samples decreased dramatically as the temperature increased well above the glass transition temperature. This interesting temperature dependence of fatigue behavior is explained due to the change of molecular motion of PET polymers at this temperature range.     

Studies on mechanism of phase transformation of carboxylated poly(phenylene oxide) and polystyrene blend by Fourier transform infrared spectrometry

Summary The thermally-induced phase transformation behaviors of carboxylated poly(phenylene oxide)(CPPO)/polystyrene(PS), and PPO/PS blends were studied by using a difference-spectrum method of Fourier Transform Infrared Spectrometry (FTIR). The difference intensities() and vibration frequency shifts() of the characteristic infrared absorption bands in both CPPO/PS and PPO/PS increased with raising temperature. A linear temperature dependence in the band frequency vs. temperature plots was observed for PPO/PS system, while three slopes corresponding to the three temperature ranges: below 190°C, 190°–215°C, and above 220°C, appeared in frequency-temperature curves for the CPPO/PS blend. These temperature ranges are consistent with the UCST area, the miscible area and the LCST area obtained by our previous works. The mechanism of phase transformation of CPPO/PS was discussed.     

Prediction of temperature conditions in laser treatment of chemical fibers

A method was developed for measuring the temperature of a fiber in the region of exposure to laser radiation. It was shown that the temperature is not only a function of the energy flux density but also the fiber speed. The reason why the interplanar distances stop increasing with an increase in the energy flux density of the laser radiation was given based on an analysis of the temperature transitions in polycaproamide fibers. It was found that the temperature of the sample remained constant in thawing of the molecular mobility.St. Petersburg Institute of Textile and Light Industry. Translated from Khimicheskie Volokna, Vol. 25, No. 1, pp. 22–24, January–February, 1993.     

小型沸腾炉木柴升温空炉开车中的几个问题

分析小型沸腾炉木柴升温时的最佳投矿温度 ,局部高温或“暴涨期”高温结疤的原因及其预防措施。     

自结合莫来石浇注料的相变化及结构特征

用硅溶胶结合超细粉为莫来石浇注料提供一种“自结合相”，以使结合相与颗粒的结合浑然一体，充分发挥浇注料整体性优良的特点。研究表明这种“自结合相”结合的莫来石浇注料与低水泥浇注料等品种相比，具有在整个温度范围内整体性好，莫来石反应温度低、生成量及长大情况良好，并在大颗粒周边形成致密环带，这种显微结构和相变化特征对浇注料的使用性能极为有利。     

Synthesis of zeolite rho: Aging temperature effect

This paper focuses on deciphering the gel aging temperature effect on the crystallization of zeolite rho(RHO). Increased gel aging temperature (from room temperature to 55°C and no aging) caused an increase in induction periods and decreased the crystallization rate during the synthesis of RHO. Other crystalline phases such as chabazite were formed along with increasing aging temperature. The largest crystal size of RHO increased proportionally to aging temperatures up to about 9 m. These results suggest that aging temperature greatly affected the crystallization, the crystal sizes, the purity and the formed crystalline phases during the synthesis of zeolite rho. This study suggests that most of RHO nuclei are formed during gel aging and their formation is depressed by the increased aging temperatures.     

Differentiation between conformational transitions of polymers and the transition observed near the theta conditions

Summary The differentiation between the conformational transitions of polymers and the transition observed near the conditions has been investigated. The conformational transitions are related with side-group effects and vanish under the influence of an appropriate amount of a polar solvent. In the contrary, the transition observed in the vicinity of the temperature is related with chain-backbone effects. The addition of a polar solvent shifts this transition to a different temperature in accordance with the resulted change of the temperature of the system.     

Liquid crystal polyarylates containing 2,6-naphthalene dicarbonyl group (I): Effects of kinky monomers on thermal and anisotropic behaviors

A series of copolyarylates primarily based upon 2,6-naphthalene dicarboxylic acid, hydroxybenzoic acid and 4,4-biphenol were prepared by slurry-melt polymerization with Santotherm 66 as a heat exchange medium. The frequently used kinky monomer, resorcinol or isophthalic acid, was introduced into these copolyarylates to modify the chemical strcture. The relationship of the thermal behavior and the crystalline structures for these copolymers was studied by means of DSC and wide angle X-rays diffraction. The amount of mcorporated kinky modifier was found to produce a significant effect on the liquid crystalline phase and the melting temperature of the copolyarylates. All of these liquid crystal polymers exhibited nematic textures; shreaded and/or Schlieren type, depending upon the incorporated kinky monomer. The liquid crystal polymers modified by isophthalic acid (up to 40 mole % of 2,6-naphthalene dicarboxylic acid replaced by isophthalic acid) possessed shreaded texture however high the temperatures of the polymer melts were. The liquid crystal polymers modified by resorcinol (60 to 100 mole % of 4, 4-biphenol replaced by resorcinol), however, would have two types of nematic textures: the shreaded texture occurred when the temperature of the polymer melt was between the melting temperature and the anisotropic transition temperature; the Schlieren texture existed when the temperature of the polymer melt was high above the anisotropic transition temperature. The Schlieren texture formed only when a liquid crystal polymer revealed good flowability and lower rigidity. The polydomain concepts could be utilized to explain the observed textures of these copolyarylates clearly.     

Study of siloxane-modified epoxy resin using thermally stimulated current

Summary The low temperature relaxation of epoxy resin modified with siloxane oligomers was investigated by using thermally stimulated current (TSC) and relaxation map analysis (RMA). The -relaxation of epoxy resin and the glass transition temperature of siloxane oligomer were folded and shifted to higher temperature as the concentration of trifluoropropyl (TFP) in siloxane oligomer increased. In the systems containing over 50% of TFP a new relaxation peak due to the dipole orientation was observed at around-45°C. As the concentration of TFP increased the compensation temperature (T_c) and the degree-of-disorder (DOD) were increased while the compensation time, _c was decreased.     

Relaxation fluctuations in poly(2-hydroxyethyl methacrylate) gels swollen in butanol

Summary Quasielastic light scattering measurements on transparent poly (2-hydroxyethyl methacrylate) (PHEMA) gels were performed under temperature equilibrium conditions at several temperatures from 40 to 80°C. All observed correlation functions departed from the single exponential decay with a long-time limit. The asymptotic value relaxation frequency _a decreased steeply with decreasing temperature. The observed temperature dependence of _a is interpreted as resulting from polymer fluctuations near the glass transition of weakly swollen PHEMA gels.