Frictional wear in high temperature thermotropic liquid crystalline polymers: correlation with glass transitions

Wholly aromatic thermotropic main chain liquid crystalline copolymers (LCPs) with varying glass transitions (T_g) were tested for wear resistance, particularly under high friction conditions, where surface temperatures can rise. Dynamic mechanical spectroscopy and DSC were used to characterize molecular relaxations. Three copolyester LCPs which all contain a substantial fraction of main chain 1,4-phenyl groups were chosen for this study. These included semi-crystalline Vectra^® A900, a semi-crystalline LCP containing phenyl hydroquinone (phHQ-LCP), and a low crystallinity LCP containing t-butyl substituted hydroquinone (t-butylLCP). These have glass transitions of 100, 160 and 175 °C, respectively, and heat deflection temperatures (HDTs) of 170, 260 and 174 °C, respectively. HDT is dependent in part on crystallinity. The wear performance was found to depend mainly on T_g and not HDT, suggesting a microscopic failure mechanism related to the amorphous phase. This is supported by the relatively poor elevated temperature wear performance of Vectra^® compared to the higher T_g LCPs. Shear strength measurements on the neat LCP resins did not correlate with wear properties of the blends, most likely because the measurements were made at room temperature and not elevated temperatures.     

HEAT TRANSFER IN A THIN LIQUID FILM IN THE PRESENCE OF AN ELECTRIC FIELD

Heat transfer enhancement in an evaporating thin liquid film utilizing a electric field under isothermal interfacial condition is presented. A new mathematical model subjected to van der Waals attractive forces, capillary pressure, and an electric field is developed to describe the heat transfer enhancement in the evaporating thin liquid film. The effect of the electrostatic field on the curvature of the thin film, evaporative flux, pressure gradient distribution, heat flux, and heat transfer coefficient in the thin film is presented. The results show that applying an electric field can enhance heat transfer in a thin liquid film significantly. In addition, utilizing electric fields on the evaporating film will be a way to expand the extended meniscus region to attain high heat transfer coefficients and high rates of heat flux.     

横掠椭圆钉头管换热及流阻特性的实验研究

利用热质比拟原理及萘升华技术 ,对空气横掠椭圆钉头管时的对流换热及流阻特性进行了研究。对管面上及椭圆钉头上的对流换热系数分别进行了测量 ,通过计算得到总体换热系数及流动阻力的实验关联式。实验结果表明 ,椭圆钉头管的对流换热系数高于光管 ,在实验规定的雷诺数范围内 ,椭圆钉头管的流阻小于圆形钉头管 ,有时也低于光管     

Inverse solution for a biochemical heat source in a porous medium in the presence of natural convection

The inverse problem approach by conjugate gradient with adjoint equations is adapted to the context of a non-isothermal bioprocess, controlled by internal heat generation from microbial oxidation, as could be found in a composting reactor for instance, to determine the heat source from internal temperature measurements. The volumetric heat source is assumed proportional to the rate of consumption of a substrate by a biomass, as described by a Monod model. Computations are performed for Rayleigh numbers equal to 0.25 and 25, for a representative biochemical reaction under typical boundary conditions, for constant and temperature-dependent model parameters. The influence of noisy input data is also considered. It is found that good solutions can be obtained when heat release and diffusion occur over very different time scales. The variation of the model parameters with temperature must be taken into account, but single sensor solutions are possible at relatively small Rayleigh numbers when convection is present.     

乙炔吸收系统倒开车实现装置产品快速合格

中国石油吉林石化公司聚乙烯厂700kt/a乙烯装置老区采用溶剂吸收技术脱出乙炔精制乙烯工艺。多年来,乙炔吸收塔塔顶回流泵开车初期不上量问题一直制约着装置开车进度。经过摸索,技术人员尝试对开车流程进行调整,攻克了难题。文中对该装置具体的调整措施进行了阐述。     

间歇窑窑墙温度场图形仿真研究

本文利用有限差分法求解间歇窑窑墙中的温度分布，并用Ｃ语言设计了窑墙温度场图形仿真软件。输入窑墙厚度和材料的物性参数等，系统可进行窑墙温度场分布的实时仿真及窑炉结构与操作的优化     

A three-dimensional model for suspension-to-membrane-wall heat transfer in circulating fluidized beds

A three-dimensional model is proposed for both furnace-side and wall-side heat transfer in circulating fluidized beds with membrane walls. Following previous publications (Int. J. Heat Mass Transfer (2003a, b)), a core-annulus flow structure is employed in the model, with consideration of the membrane wall influence on bed hydrodynamics. The model couples radiation, conduction and convection on the furnace side to conduction and convection on the wall side. Radiation in the wall layer is simulated by the moment method. A finite-element method is employed to solve the set of non-linear, partial differential equations. The solution is demonstrated for a typical example. The model gives predictions of suspension-to-wall heat transfer which show satisfactory agreement with published experimental data.     

Development of a comprehensive free radical photopolymerization model incorporating heat and mass transfer effects in thick films

A comprehensive kinetic model describing photopolymerization is developed which allows variation of temperature, species concentrations, and light intensity through the thickness of a photopolymerized film. Heat and mass transfer effects are included, as is the generation of heat by both reaction and light absorption. In addition to initiation, propagation, and termination mechanisms, both primary radical termination and inhibition are incorporated into the model. The possible presence and diffusion of an inert solvent are also accounted for. Thus, the model is useful for examining complex polymerization kinetics and behavior in industrially and commercially important thick film photopolymerizations, such as the curing of contact lenses, dental restorative materials, photolithographic resists, and optoelectronic coatings. The comprehensive model is used to predict polymerization rate, temperature, and conversion profiles in a variety of systems. The effects of heat generation and the thermal boundary conditions are explored, with the result that heat generation in thick samples leads to greatly increased conversions approaching 100 percent. Increased temperature in these samples also may lead to the appearance of two rate maxima, with the first due to the temperature increase and the second caused by the autoacceleration process. The magnitude of the temperature increase, along with the resultant effects, is more pronounced in insulated systems.     

氯化聚乙烯接枝氯乙烯聚合速率及传热

本文用气相色谱技术研究氯化聚乙烯(CPE)-接枝(g)-氯乙烯(VC)聚合动力学,对不同引发剂体系分析热负荷分布,并对7 m~3聚合釜传热面进行校核。