Solid Propellant Burning Rate From Strand Burner Pressure Measurement

Strand burner pressure–time data are analyzed to determine if the propellant burning rate can be extracted. This approach is based on strand burner pressure–time history that is related to the temperature change due to exothermic reaction heating of chamber gases and gas addition to the chamber by propellant combustion products. In support of this method, chemical equilibrium calculations were made to project product composition, internal energy, and other needed properties. A mathematical model was formulated and solved numerically and the calculated burning rates were compared with the experimental wire‐break time results provided simultaneously and with the propellant manufacturer's results, when available. The comparisons reveal that the approach has merit and that more accurate pressure determination coupled with additional thermochemical information and strand burner gas temperature measurements has the potential to make this approach a viable technique and one that can be applied in conjunction with other burning rate measurements. The proposed method is similar to a well‐developed technique which is commonly applied to ballistic powders but with adjustments for the differences in geometry, pressure, and time of event.     

Thermophysical properties of undercooled alloys: an overview of the molecular simulation approaches

We review the studies on the thermophysical properties of undercooled metals and alloys by molecular simulations in recent years. The simulation methods of melting temperature, enthalpy, specific heat, surface tension, diffusion coefficient and viscosity are introduced and the simulated results are summarized. By comparing the experimental results and various theoretical models, the temperature and the composition dependences of the thermophysical properties in undercooled regime are discussed.     

System of coupled non-linear reaction diffusion processes at conducting polymer-modified ultramicroelectrodes

The theoretical analysis of the steady-state amperometric response for conducting polymer-modified ultramicroelectrodes is discussed. The effect of substrate diffusion in the solution adjacent to the polymer film on both the concentration profile and current response is also examined. Simple analytical expressions for substrate and mediator concentrations and current responses for all values of reaction/diffusion parameters are presented. The model is based on non-stationary system of coupled reaction/diffusion equations containing a non-linear term related to Michaelis-Menten kinetics of the enzymatic reactions. He's variational iteration method is used to give approximate analytical solutions of coupled non-linear reaction diffusion equations. A good agreement with available limiting case results is noticed.     

Highly Accurate Prediction Method for Thermophysical Properties of Cryogenic Phase Change Materials

Considering the limitations of experimental studies on thermophysical properties of cryogenic phase change materials (PCMs), a highly accurate approach to predict the solid-liquid equilibrium (SLE) of PCMs is proposed, in which the method of referenced state by a hypothetic path is used in the fugacity of PCMs in the solid phase and the Soave-Redlich-Kwong (SRK)-UNIFAC model is applied in the liquid phase. Based on this method, the thermophysical properties of cryogenic composite PCMs including eutectic composition, eutectic temperature, and eutectic enthalpy are predicted with a minor deviation. Taking the liquid natural gas (LNG) air separation unit as an example, the established simulating method with high accuracy to predict the thermophysical properties of the PCMs is adopted for material selection and design for a cold storage unit in this project with high efficiency.     

Modeling of Diffusion in Capillary Porous Materials During the Drying Process

This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.     

Effect of heating rate on the heat-transfer characteristics in the thermal decomposition of phenolic carbon plastic

A carbon plastic based on a phenolic binder at heating rates up to ∼150 K/sec has been investigated by means of electrothermographic and thermogravimetric analysis. The thermokinetic constants for the thermal decomposition and thermophysical characteristics of the material have been studied as functions of the annealing temperature. It is shown that an increased heating rate the temperature dependences of the specific heat and thermal conductivity of the carbon plastic are shifted to the high-temperature region. The results of the study are summarized in the form of universal dependences which allow one, in the mathematical modelling of the thermochemical decomposition of thermal protecting coatings, to take into account the shift of the thermophysical parameter via the change in the material density during thermal decomposition. Scientific Research Institute of Applied Mathematics and Mechanics, Tomsk State University, Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 53–58, November–December, 1993.     

Machine learning specific heat capacities of nanofluids containing CuO and Al2O3

Empirical work and modeling approaches have shown that fundamental thermophysical parameters of constituents, nanoparticles, and base liquids have complex but synergistic effects on the specific heat capacity of nanofluids. In this work, we develop the Gaussian process regression model to investigate the statistical relationship among temperature, specific heat capacities of nanoparticles and base liquids, nanoparticle volume concentrations, and specific heat capacities of nanofluids. The model is developed with a dataset containing nanofluids with CuO and Al₂O₃ nanoparticles, and water and ethylene glycol (EG) as base liquids. The model also applies well to nanofluids containing mixtures of water and EG, and Al₂O₃ nanoparticles with different particle size distributions. The model is highly accurate and stable that contributes to fast and low-cost estimations of specific heat capacities of nanofluids over a wide range of compositions and temperature.     

Modeling of Diffusion in Capillary Porous Materials During the Drying Process

ABSTRACT

This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.     

Thermophysical properties of polymer-probe pairs by gas chromatography

The chromatographic technique of measuring thermophysical parameters at infinite dilution is applied for polyisobutylene (PIB), antishock polystyrene (high-impact polystyrene) and styrene-butadiene rubber (SBR) using benzene, cyclohexane, n-hexane and n-pentane as probes. The experiments were performed for antishock polystyrene in the temperature range of 313.3 to 402.3 K, for SBR in the temperature range of 343.3 to 363.2 K and for PIB at 313.1 and 323.1 K. The chromatographic retention data obtained at these temperatures were used to determine the Flory-Huggins interaction parameter, weight fraction infinite dilution activity coefficient and diffusion coefficient. In addition, the glass transition temperature of antishock polystyrene was estimated.     

Water sorption and diffusion through saturated polyester and their nanocomposites synthesized from glycolyzed PET waste with varied composition

A new system of saturated polyester and their nanocomposites synthesized from glycolyzed PET with varied composition is investigated for the sorption and diffusion studies in water. The kinetics of sorption is studied by using the equation of transport phenomena. The values of ‘n’ from transport equation are found to be below ‘0.5’, showing the non-Fickian or pseudo-Fickian transport in the polymer. The dependence of diffusion coefficient on composition and temperature has been studied for all polymeric samples. The diffusion coefficient of saturated polyester samples decreases with an increase in glycolyzed PET contents. The nanocomposite samples show less diffusion coefficient than pristine polymer and it decreases with an increase in nano-filler up to 4 wt%. The diffusion coefficient increases with an increase in temperature for all the samples. The sorption coefficient shows a little change with variation in composition as well as temperature for all the samples and it is in a range of 1. The activation energy for diffusion and permeation is positive for all the samples. The heat of sorption is also positive for all the samples, indicating Henry type mode of sorption.     

含油污泥化学热洗技术研究现状与进展

含油污泥是石油生产与加工过程产生的含有油、固体颗粒、重金属、水等的复杂组成体系,其稳定性高、处理难度大,已被列入危险废物名录。我国含油污泥产生量大,未经处理外排会对环境产生严重污染,各石油生产及加工企业均投入较大的人力、物力进行含油污泥的处理,形成了热洗、热解、加温加压调理、微生物处理等技术,其中热洗具有油回收率高、残渣含油率较低、成本低廉等优点。本文对国内外含油污泥处理标准进行了总结对比,对化学热洗技术的研究进展进行了阐述,重点论述了清洗剂种类和浓度、热洗温度、热洗时间、搅拌速度、液固比等因素对含油污泥处理效率的影响,提出了化学热洗技术未来的发展方向,以期对含油污泥化学热洗技术的发展提供参考。     

生物质与煤（共）热解/气化过程中挥发分-半焦交互作用研究与进展

生物质和煤协同热化学转化是实现非化石能源和化石能源耦合高效利用的技术手段,对实现“双碳”目标具有重要现实意义。基于生物质等含碳燃料高挥发分组成和富氧特性,热化学转化过程不可避免地发生挥发分-半焦交互作用并影响原料性质和设备过程参数。综述了生物质与煤（共）热解/气化过程中挥发分-半焦交互作用的研究进展,总结了交互作用对挥发分的催化裂解规律、对半焦结构与性质的影响及生物质和煤协同热化学转化下的解耦研究思路三方面具体内容。针对目前挥发分-半焦交互作用机制解析过程所采用的研究方法及思路,提出了新的见解并对未来交互作用的重点研究方向进行了展望,以期为进一步认识交互作用的物理化学本质提供理论指导。     

Modelling the heat release rate of aircraft cabin panels in the cone and OSU calorimeters

A computer model was developed to calculate the heat release rate of aircraft cabin panels in the OSU calorimeter based on their thermophysical, thermochemical and geometrical properties. It calculates the temperature profile through the panel as a function of time and uses the measured kinetic constants of the individual materials to deduce the mass loss rate. The mass loss rate is multiplied by the heat of combustion of the volatiles to obtain the heat release rate which would be measured in the Cone calorimeter. This heat release rate is used in an energy balance at the surface of the specimen to calculate the rise in enthalpy of the flue gases in the OSU calorimeter and thus the specimen's heat release rate in that apparatus. The calculated heat release rates are in reasonable agreement with measurements in the Cone and OSU calorimeters.     

Modeling the thermochemical degradation of biomass inside a fast pyrolysis fluidized bed reactor

A fast pyrolysis process in a bubbling fluidized bed has been modeled, thoroughly reproduced and scrutinized with the help of a combined Eulerian/Lagrangian simulation method. The 3‐D model is compared to experimental results from a 100 g/h bubbling fluidized bed pyrolyzer including such variables as particle composition at the outlet and gas/vapor/water yields as a function of fluidization conditions, biomass moisture concentrations, and bed temperatures. Multiprocessor simulations on a high‐end computer have been carried out to enable the tracking of each of the 0.8 million individual discrete sand and biomass particles, making it possible to look at accurate and detailed multiscale information (i.e., any desired particle property, trajectory, particle interaction) over the entire particle life time. The overall thermochemical degradation process of biomass is influenced by local flow and particle properties and, therefore, accurate and detailed modeling reveals unprecedented insight into such complex processes. It has been found, that the superficial fluidization velocity is important while the particle moisture content is less significant for the final bio‐oil yield. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3030–3042, 2012     

Fundamentals of the refractory wear in an industrial anode furnace used in the copper-making process

This paper presents a combination of different useful techniques to identify the fundamentals of the infiltration and chemical degradation of the refractory used in the lining of an anode furnace for fire refining of blister copper. In practice, this work was carried out at the Atlantic Copper Smelter (Huelva; Spain) by a post-mortem study of the refractory used in a one-year campaign, and thermochemical calculations using the FactSage^® database. The combination of both techniques created enhanced value thanks to their synergy.The infiltrations and the formation of new phases in the reaction layer were identified using microstructural analyses. The nature of these infiltrations were identified; all the refractory brick samples had been substantially infiltrated by copper and slag elements (mainly copper and iron oxides). The new phases formed were the result of the complex chemical interaction between the slag and the constituent of the refractory. Additionally, copper was incorporated to the spinel.In order to propose a model to represent this complex process, thermochemical calculations were carried out to define a baseline to explain the microstructures obtained as a consequence of the interactions between the bath and the refractory.     

High-order approximations for noncyclic and cyclic adsorption in a biporous adsorbent

An accurate and realistic model for transient diffusion and adsorption in a biporous pellet is typically represented by two coupled second-order partial differential equations. The model, however, has been rarely used in practice because of its mathematical complexity and bulky numerical computation, and approximations of the model have been used instead. But the accuracy of the available approximations has been limited and not enough for detailed analysis and simulation of the mass transfer process. Therefore, in this study, we develop for the first time high-order approximations, of up to third order, for noncyclic and cyclic adsorption in a biporous pellet, respectively. The approximations are in the form of a state equation which consists of first-order differential equations ; the number of the equations is the same as the approximation order. The approximations are easy to use and their accuracy dramatically increases with increasing approximation order, so that the second-or the third-order approximations can effectively substitute the complex biporous diffusion model.     

耦合相变储热的金属氢化物反应器吸氢过程模拟

基于金属氢化物储氢反应,建立了相变材料蓄热的固体储氢反应器模型,模拟研究了吸氢压力等操作参数及相变材料的相变温度、固(液)态导热系数、相变潜热等物性参数对固体储氢反应器工作过程的影响. 结果表明,相变材料的固态导热系数和相变潜热对固体储氢反应器性能的影响较小,相变温度和液态导热系数对反应器性能影响较大. 相变温度越低,液态导热系数越大,储氢反应器性能越好. 在使用最优的相变材料储能时,提高充入氢气的压力可加快反应速率,强化相变材料的传热,有助于进一步优化反应器的储氢性能.     

低阶固体燃料热化学转化过程中挥发分与半焦相互作用的基本原理

挥发分-半焦相互作用是低阶含碳固体燃料热化学转化过程中普遍存在的一种重要现象。挥发分-半焦相互作用可以影响低阶燃料热化学转化过程的各个方面:促进碱金属/碱土金属(AAEM)的挥发、抑制气化、催化焦油分解、碳-碳结构重排及稳定化(抑制气化)、促进半焦上N的迁移等。回顾了低阶燃料热化学转化过程中的挥发分-半焦相互作用的最新研究进展,为更好的利用低阶固体燃料提供理论指导。     

Polymer–Metal Interfacial Friction Characteristics under Ultrasonic Plasticizing Conditions: A United-Atom Molecular Dynamics Study

Understanding the properties of polymer–metal interfacial friction is critical for accurate prototype design and process control in polymer-based advanced manufacturing. The transient polymer–metal interfacial friction characteristics are investigated using united-atom molecular dynamics in this study, which is under the boundary conditions of single sliding friction (SSF) and reciprocating sliding friction (RSF). It reflects the polymer–metal interaction under the conditions of initial compaction and ultrasonic vibration, so that the heat generation mechanism of ultrasonic plasticization microinjection molding (UPMIM) is explored. The contact mechanics, polymer segment rearrangement, and frictional energy transfer features of polymer–metal interface friction are investigated. The results reveal that, in both SSF and RSF modes, the sliding rate has a considerable impact on the dynamic response of the interfacial friction force, where the amplitude has a response time of about 0.6 ns to the friction. The high frequency movement of the polymer segment caused by dynamic interfacial friction may result in the formation of a new coupled interface. Frictional energy transfer is mainly characterized by dihedral and kinetic energy transitions in polymer chains. Our findings also show that the ultrasonic amplitude has a greater impact on polymer–metal interfacial friction heating than the frequency, as much as it does under ultrasonic plasticizing circumstances on the homogeneous polymer–polymer interface. Even if there are differences in thermophysical properties at the heterointerface, transient heating will still cause heat accumulation at the interface with a temperature difference of around 35 K.