Papers by Keyword: Thermophysical Property

Abstract: t is introduced about the characteristics, structure and application of refrigerator for vaccine transportation. From the test of thermophysical properties of cool storage material in cold closet using for vaccine transportation and the insulation performance of cold closet with different cool storage materials, it turned out that the thermophysical properties of the novel cool storage material is similar to the imported; the insulation performance of cold closet with the novel cool storage material is slightly less than the imported. Since this novel cool storage material can keep the temperature within 8°C for more than 80h, which totally satisfies the request of domestic vaccine transportation, it's worthy of promotion.

Abstract: A high-temperature, high-pressure evaporation model for HAN-based liquid propellant droplet was built, which considered the multicomponent droplet, the unsteady heating-up, the droplet surface regression, and the nonideal gas effect. Based on the state equation of the real gas, a computation method applicable to high-pressure thermophysical property parameters was established. By use of the evaporation model, the evaporation process of a LP1845 droplet in the nitrogen atmosphere for pressures of 100–300 atm and temperatures of 1600 K was studied. The results indicate that the droplet radius increases firstly and reduces afterward as the evaporation goes on, and the reduction rate of the radius satisfies the D2 law. The droplet temperature rises rapidly at the beginning, then maintains stable gradually at an equilibrium value. When the ambient temperature remains constant, with increasing ambient pressure, the time to reach the equilibrium temperature lengthens, but the droplet lifetime shortens.

Abstract: SiC ceramics were synthesized by polymer derived method and microwave sintering processes. The as-produced SiC composites were developed by oxidizing the amorphous Si-C raw materials derived from a polymer precursor polycarbosilane. The products analyzed by X-ray diffraction (XRD), Fourier transmittance infrared spectroscopy (FTIR), and electronic microscopye consist of excess free carbon, β-SiC and SiO₂ produced by the partial oxidation of amorphous Si-C on the surface of the starting particles. The thermophysical properties of the partially oxidized SiC composites were investigated by measuring the thermal diffusivity, the specific heat and thermal conductivity. The amount of SiO₂ increased as the sintering temperature is increased, resulting in a reduction of thermal diffusivity and an increase of density due to improved liquid phase sintering of SiC particles. The thermal conductivity of samples decreased, instead of increased, as the sintering temperature was increased from 1100 °C to 1200 °C. The sample dwelled at 1200 °C, in this study, has highest density and a relatively low thermal conductivity, slightly over 0.7 W/(m·K) at room temperature.

Abstract: Pulsating heat pipes are high efficiency heat transfer components having a great potential application in the field of electronic cooling and space applications. In this investigation, an experiment was conducted to study the influence of working fluid thermophysical properties on the thermal performance of flat-plate closed loop pulsating heat pipes (FCLPHP). The analysis of the forces acting on the liquid-vapor mixture shows that the surface tension, viscosity and latent heat of vaporization have important impact on the thermal performance of FCLPHP. The overall thermal resistance decreases with the decrease in surface tension, viscosity and latent heat of vaporization, leading to the heat transfer improvement of FCLPHP. An experimental correlation was developed to describe the relationship among the relative overall thermal resistance and the relative thermophysical properties. With the correlation, a sensitivity analysis was made. The results show that latent heat of vaporization is the prior factor to the all others to impact the thermal performance of FCLPHP.

Abstract: The influence of Re and Ru on creep rupture strength has been investigated using a new in-house designed alloy-series comprising 9 experimental nickel-base superalloys with stepwise increased Re and Ru additions. The presented creep data reveals a significant increase in creep rupture strength by additions of Re. For additions of Ru an increase of creep rupture strength can only be found for low Re contents. The present article, which is part of an extensive and systematic investigation on Re and Ru influences, shows, that an improved creep resistance by an influence of Re and Ru on the γ’-solvus temperature is rather improbable. Likewise, the influence of Re and Ru on liquidus temperature is not expected to play an important role. However, the creep rupture strength is suggested to be highly modified by γ/γ’-microstructure changes.

Abstract: Thermo-physical properties of diamond reinforced Al composites were investigated. Volume fraction of diamond particles was up to 55%. In order to improve the interfacial bonding between diamond and aluminum, diamond particles were pre-coated with titanium using molten salt method. XRD and SEM observation showed that the Ti coating on diamond consists of carbide layer and metal layer, which mainly depend on temperature and time. The influences of the Ti coating on interfacial characteristic and the thermo-physical properties of the composites were studied. The interfacial characterization and thermal diffusivity measurements indicated that Ti coated diamond was more favorable on interfacial bonding and thermal properties. Ti coating on diamond resulted in an increase of thermal conductivity of the composites, from 200 to 430 W/mK along with a coefficient of thermal expansion of 6.40 × 10-6/K.

Abstract: The Monte Carlo method with EAM potential is applied to simulate the liquid Al-Ce binary alloy system and the thermophysical properties including surface tension (), viscosity () and diffusion coefficient (D) of liquid Al-8at%Ce alloy are determined. The simulated  values decrease with temperature. Based on the relationship between ,  and D, the various viscosity and diffusion coefficient of liquid Al-Ce alloys under different temperatures were determined. The comparison of the simulated results with some experimental measurements is performed and discussed, indicating that the simulation method and EAM parameters in simulation are acceptable. The dependence of viscosity and diffusion coefficient of liquid Al-Ce alloys on temperature is established to be helpful in further investigation of amorphrization ability of Al-Ce alloys.

Abstract: This review aims at reporting on very recent developments in the, properties and applications of Green Composites. One very important aspect of green composites is that they can be designed and tailored to meet different requirements. Recent advances in natural fiber development offer significant oppurtunities for improved materials from renewable resources. Biocomposites offer a significant non-food market for crop-derived fibres and resins. Considerable growth has been seen in the use of biocomposites in the automotive and decking markets over the past decade or so, but application in other sectors has hitherto been limited. Recent developments of different biodegradable polymers and biocomposites are discussed in this review article.

Abstract: Thermophysical and tribological measurements have been performed on carbon nanotube added silicon nitride composites. Higher thermal conductivity values were observed in the case of the sample with CNT than for the reference sample. As was observed from tribological measurements, nanocomposite Si3N4 without carbon nanotubes shows a higher friction coefficient than carbon nanotube - Si3N4. The results of wear study indicate that the Si3N4 ball (used as static partner) was more damaged with MWCNTs addition nanocomposite than with pure Si3N4 ceramic. A pronounced difference was observed in the wear rate: there was a much higher wear for carbon nanotube - Si3N4 than for Si3N4 without MWCNTs.

Abstract: A current challenge of physical, chemical and engineering sciences is to develop theoretical tools for predicting structure and physical properties of hybrid organic inorganic nanocomposite from the knowledge of a few input parameters. However, despite all efforts, progress in the prediction of macroscopic physical properties from structure has been slow. Major difficulties relate to the fact that (a) the microstructural elements in multiphase material are not shaped or oriented as in the idealizations of computer simulations, and more than one type can coexist; (b) multiple length and time scales are generally involved and must be taken into account, when overall thermodynamic and mechanical properties wish to be determined, and finally (c) the effect of the interphases/interfaces on the physical properties is often not well understood and characterized. As a consequence, their role is often neglected in the development of new theoretical tools or they are treated in a very empirical way. In this work, we focused on issues (b) and (c) in a multiscale molecular simulation framework, with the ultimate goal of developing a computationally-based nanocomposite designing tool. In particular, we developed a hierarchical procedure in which lower scale (i.e., QM, MD and /or MC) simulations are performed to obtain parameters for higher scale (i.e., mesoscopic and/or finite element) calculations, from which the bulk properties of the hybrid nanocomposite material can be ultimately estimated.