Thermal Analysis for Velocity,Kinetics, and Enthalpy Reaction Measurements in Microfluidic Devices

Abstract

The aim of this work is to present new devices for the measurement of velocity, kinetics, and enthalpy of chemical reactions occurring in a microfluidic chip, co-flow, or droplets flow. The thermal analysis goes from the macroscopic approach by microcalorimetry to microscopic analysis inside the microchannel by IR thermography. Concerning microcalorimetry, the enthalpy is deduced from the measurement of the global heat flux dissipated by the chemical reaction as a function of the molar flow rate. A validation is presented on a well-known acid-base reaction. This device can be combined with an IR camera for local characterization. The processing of the measured temperature fields allows the estimation of properties of great importance for chemical engineers, such as heating source distribution (i.e., the kinetics) of the chemical reaction along the channel. A validation experiment of a temperature field processing method is proposed with the Joule effect. From such a previous experiment, a Peclet field is estimated and used in a further step in order to study an acid-base co-flow configuration. Finally, a first tentative of thermal characterization inside droplets flow during an acid-base chemical reaction is also presented.     

The Exergy Losses Analysis in Adiabatic Combustion Systems including the Exhaust Gas Exergy

The entropy generation analysis of adiabatic combustion systems was performed to quantify the exergy losses which are mainly the exergy destroyed during combustion inside the chamber and in the exhaust gases. The purpose of the present work was therefore: (a) to extend the exergy destruction analysis by including the exhaust gas exergy while applying the hybrid filtered Eulerian stochastic field (ESF) method coupled with the FGM chemistry tabulation strategy; (b) to introduce a novel method for evaluating the exergy content of exhaust gases; and (c) to highlight a link between exhaust gas exergy and combustion emissions. In this work, the adiabatic Sandia flames E and F were chosen as application combustion systems. First, the numerical results of the flow and scalar fields were validated by comparison with the experimental data. The under-utilization of eight stochastic fields (SFs), the flow field results and the associated scalar fields for the flame E show excellent agreement contrary to flame F. Then, the different exergy losses were calculated and analyzed. The heat transfer and chemical reaction are the main factors responsible for the exergy destruction during combustion. The chemical exergy of the exhaust gases shows a strong relation between the exergy losses and combustion emission as well as the gas exhaust temperature.     

近共振传能放热对氧碘化学激光器性能的影响

在氧碘化学激光器(COIL)中,O2(1Δ)与I的近共振传能反应是一个放热反应;它与水汽等的猝灭放热反应一样会对激射过程产生不利影响,而且是不可避免的。计算了猝灭放热效应对光腔气动特性输出功率的影响。得到了近共振传能放热的大小与粒子数反转和激射的光子数相关,即与光腔内的增益、光场强度分布成正比,故主要发生在激光器的上游区前半部分。模型计算表明,其影响程度大致相当于7%水汽所致的对氧碘化学激光器的影响。完善了氧碘化学激光器理论计算模型。     

Soot volume fractions and primary particle size estimate by means of the simultaneous two-color-time-resolved and 2D laser-induced incandescence

An original approach of laser-induced incandescence consisting in the simultaneous recording of the two-color-time-resolved and 2D LII signal is described in this paper. The application of this approach in an atmospheric pressure diffusion flame fueled with isooctane as well as inside the combustion chamber of a diesel engine is presented. Soot volume fraction and primary particle diameters are calculated, and the results are discussed. The mean diameter estimated by fitting the LII modeled curve on the experimental one is compared with the results obtained through soot sampling and microscope analyzing. The influence of the thermal accommodation coefficient and soot refractive index function is also discussed. PACS 47.80.-v; 42.40.Pa; 42.62.Eh; 47.54.De     

A Rapid Method for Growth of Metal Nanoparticles on Nanowire Substrates

The production of nickel and platinum nanoparticles on silica nanowire substrates using plasma-enhanced chemical vapor deposition has been investigated. Determination of particle size and particle size distribution was done using transmission electron microscopy (TEM). Ni nanoparticle diameters were found to be between 2 and 6 nm, with particle size increasing as the substrate temperature increased from 573 to 873 K. The size of Ni nanoparticles was found to be dependent on the chamber pressure during growth. The results indicate a competition between pressure-related diffusion within the vapor and dissociation of the precursor. Pt nanoparticle diameters were consistently found to be 2.5–3.0 nm at all deposition conditions. Insufficient thermal energy within the studied range results in a minimal contribution from surface diffusion, the primary mechanism for nanoparticle growth.     

皮秒和纳秒单脉冲激光加热Al/NC复合纳米含能材料的热动力学分析

对纳米金属颗粒复合含能材料这一新兴体系的单脉冲激光作用的热动力学过程进行了理论分析. 推导了分散在介质中的纳米金属颗粒吸收脉冲激光能量的瞬时功率密度. 从热分解机理出发对纳米金属铝复合硝化纤维(Al/NC)薄膜吸收脉冲激光能量过程以及伴随着放热化学反应的热点热量传播过程进行了数值模拟,计算了不同质量分数的Al/NC薄膜样品分别在100ps,10ns,25ns脉冲激光作用下的化学反应直径. 计算结果与实验数据相比较,表明了热分解基本符合10ns,25ns脉冲激光引发含能材料反应的机理,但它并不符合100ps 关键词： 热分解 化学反应 脉冲激光 含能材料     

Study of Mechanical and Thermal Impact of a Plasma Focus Discharge on Diagnostic Elements of PFM-72M Installation

Mechanical and thermal impact of the plasma focus discharge on structural elements of diagnostic windows of the PFM-72m discharge installation are calculated. The absence of critical impact at early discharge stages and during the first 300 ns after the “plasma focus” formation is shown. The possibility of shock impact on the surface of diagnostic windows at later times, which may result in their substantial deformation and destruction, is demonstrated.     

合肥光源镀膜陶瓷真空室纵向阻抗计算

 在估计合肥光源新注入系统中回形镀膜陶瓷真空室的耦合阻抗时，对于规则轴对称边界，可以采用场匹配技术求解柱坐标系中Maxwell方程得到耦合阻抗解析表达式。对于非规则形状，解析求解困难，须根据同轴线方法测量纵向阻抗基本原理，数值计算镀膜陶瓷真空室耦合阻抗。计算结果表明，陶瓷真空室内表面镀金属膜可以大大降低束流耦合阻抗，但镀膜陶瓷真空室仍是合肥光源储存环的主要阻抗来源之一。     

等截面超-超引射器流场结构及引射性能

为考察超声速引射器直接引射超声速二次流时的性能,采用纹影技术和压力测量手段对一等截面超-超引射器的流场结构及其引射性能进行了实验研究。研究结果表明:一、二次流交汇后在混合室前段形成了复杂的超声速流场结构。根据二次流在混合室入口流动状态的不同,可将超-超引射划分为非饱和超-超引射和饱和超-超引射两种工作状态;二次流在混合室入口处产生的激波提高了引射器的压力匹配性能;在给定的引射系数下,引射器的增压性能随二次流马赫数的增大而降低,而引射马赫数对引射器压力恢复性能的影响不大。     

Introduction of a cryosectioning-ToF-SIMS instrument for analysis of non-dehydrated biological samples

Tof-SIMS and laser-SNMS are becoming increasingly important tools for analysing the elemental and molecular distribution in biological samples. We have developed the prototype of an in-vacuum cryosectioning instrument directly attached to a ToF-SIMS/laser-SNMS instrument, which allows preparing and analyzing frozen non-dehydrated biological samples. Due to unavoidable effects during the handling, storing, and preparation of frozen samples, even inside the vacuum, it must be ensured that the analyzed surface is from the sample and not a preparation artefact. To this effect, a model structure, similar to the biological samples and with a defined chemical composition, was analyzed under varying thermal treatment before and during analysis, respectively, in order to identify a balance between evaporating and subliming adsorbed materials and the effect of freeze-drying on the measured signal.     

Theory for formation of a low-pressure, current-free double layer

A diffusion-controlled theory is developed for the formation of a low-pressure, current-free double layer just inside an upstream insulating source chamber connected to a larger diameter, downstream chamber. The double layer is described using four groups of charged particles: thermal ions, monoenergetic accelerated ions flowing downstream, accelerated electrons flowing upstream, and thermal electrons. The condition of particle balance upstream is found to determine the double layer potential. The double layer disappears at very low pressures due to loss of ionization balance upstream and due to energy relaxation processes for ionizing electrons at higher pressures, in good agreement with experiments.     

On reasons of Si NMR chemical shift/structure relations for silicon oxides, nitrides, and carbides: An individual-gauge-for-localized-orbitals study

For -quartz, monoclinic ZSM-5, -and β-Si₃N₄ and SiC---6H polytype, the silicon chemical shifts have been calculated using the IGLO (individual gauge for localized orbitals) method and models of different size in real crystal geometry. The result is a theoretical chemical shift scale, which is very similar to the corresponding experimental scale from ²⁹Si MAS NMR experiments. It is shown that the assignment of isotropic silicon chemical shifts of crystallized solids based on theory is a method of practical applicability, also in cases where experimental methods or empirical relations fail. The two NMR spectral lines of -Si₃N₄ are for the first time assigned to the crystallographic positions. The partition of the silicon chemical shifts into localized contributions from different parts of the model allows insight into the interactions around the resonance nucleus due to substituent and geometry variations leading to silicon chemical shifts.     

DF/HF化学激光器HYLTE喷管的副喷管质量流量系数

 对DF/HF化学激光器HYLTE喷管的副喷管质量流量进行了数值和理论计算，得出入口滞止压力在0.01~0.4MPa之间、喉道半高度在0.1~0.9mm之间的喷管的氘气，氢气和氦气质量流量系数，总结出质量流量系数随入口滞止压力和喉道高度的变化规律，并给出拟合公式，为副喷管的设计提供依据。     

Visualization of secondary flow choking phenomena in a supersonic air ejector

The present study deals with the visualization of the air flow inside a supersonic ejector. Our attention is more precisely focused on the choked flow phenomenon which occurs along the mixing chamber of the secondary nozzle and which can be visualized by CFD. Laser tomography visualizations are used to validate the CFD model. The evolution of flow configuration in the ejector with the primary stagnation pressure is examined both in the case of zero secondary flow and in the case of free entrainment of induced air.     

0D Dynamic Modeling and Experimental Characterization of a Biomass Boiler with Mass and Energy Balance

The paper presents an experimental study and a 0D dynamic modeling of a biomass boiler based on the Bond Graph formalism from mass and energy balance. The biomass boiler investigated in this study is an automatic pellet boiler with a nominal power of 30 kW with a fixed bed. The balances allow to model as time function the flue gas enthalpy flux variation and the thermal transfers between the flue gas and the walls of the boiler subsystems. The main objective is to build a model to represent the dynamic thermal behavior of the boiler. Indeed, small domestic boilers have discontinuous operating phases when the set temperature is reached. The global thermal transfer coefficients for the boiler subsystems are obtained according to an iterative calculation by inverse method. The boiler has an average efficiency of 67.5% under our operating conditions and the radiation is the dominant thermal transfer by reaching 97.6% of the total thermal transfers inside the combustion chamber. The understanding of the dynamic behavior of the boiler during the operating phases allows to evaluate its energy performances. The proposed model is both stimulated and validated using experimental results carried out on the boiler.     

核物质中的力学和化学不稳定性

用有效的手征模型和Brown-Rho标度在相对论平均场近似下研究在有限温度下的核物质,再现了核物质的基本性质,计算热力学系统的力学和化学不稳定性,得到相变图.     

气体NO／SO2／N2／O2等离子体反应机理及动力学分析

本文研究了在低温等离子体条件下,电子碰撞NO/SO2/N2/O2气体引发离解反应的反应机理.应用碰撞理论和波尔兹曼方程分析,对能量分布函数及反应速率常数进行数值模拟,得到离解反应速率常数与温度的曲线,分析预报各反应过程及表现.最后将速率常数拟合为Arrhenius公式的形式.     

烟气中Hg的氧化机理的研究

本文对Ｈｇ与Ｃｌ２在烟气中的氧化反应进行了热力平衡计算和动力学计算。平衡计算的结果表明有ＣＩ元索存在时Ｈｇ的氧化率为１００％，而在相同的条件下动力学计算纺果为Ｈｇ的氧化率在２０％～８０％之间变化，与实验结果吻合。实际的氧化反应是一种超平衡状态，不能达到理想的平衡状态。因此应采用动力学与热力平衡分析相结合的方法研究Ｈｇ在烟气中的反应机理。同时，计算结果显示Ｃｌ含量对Ｈｇ的氧化率的影响很大．     

In-phantom dose verification of prostate IMRT and VMAT deliveries using plastic scintillation detectors

The goal of this work was to demonstrate the feasibility of using a plastic scintillation detector (PSD) incorporated into a prostate immobilization device to verify doses in vivo delivered during intensity-modulated radiation therapy (IMRT) and volumetric modulated-arc therapy (VMAT) for prostate cancer. The treatment plans for both modalities had been developed for a patient undergoing prostate radiation therapy. First, a study was performed to test the dependence, if any, of PSD accuracy on the number and type of calibration conditions. This study included PSD measurements of each treatment plan being delivered under quality assurance (QA) conditions using a rigid QA phantom. PSD results obtained under these conditions were compared to ionization chamber measurements. After an optimal set of calibration factors had been found, the PSD was combined with a commercial endorectal balloon used for rectal distension and prostate immobilization during external beam radiotherapy. This PSD-enhanced endorectal balloon was placed inside of a deformable anthropomorphic phantom designed to simulate male pelvic anatomy. PSD results obtained under these so-called “simulated treatment conditions” were compared to doses calculated by the treatment planning system (TPS). With the PSD still inserted in the pelvic phantom, each plan was delivered once again after applying a shift of 1 cm anterior to the original isocenter to simulate a treatment setup error.The mean total accumulated dose measured using the PSD differed the TPS-calculated doses by less than 1% for both treatment modalities simulated treatment conditions using the pelvic phantom. When the isocenter was shifted, the PSD results differed from the TPS calculations of mean dose by 1.2% (for IMRT) and 10.1% (for VMAT); in both cases, the doses were within the dose range calculated over the detector volume for these regions of steep dose gradient. Our results suggest that the system could benefit prostate cancer patient treatment by providing accurate in vivo dose reports during treatment and verify in real-time whether treatments are being delivered according to the prescribed plan.     

The thermophysical properties of low‐temperature Pb plasma

The thermophysical properties of low‐temperature Pb plasma are calculated at temperatures 10–100 kK and densities below 0.2 of the solid‐state value. The thermodynamic values (pressure and internal energy) and transport coefficients (electrical conductivity, thermal conductivity, and thermal power) are considered. The plasma composition and thermodynamic parameters are obtained within the chemical approach, namely by means of the solution of the corresponding system of the coupled mass action law equations. Atom ionization up to +4 is taken into consideration. The electronic transport coefficients are calculated within the relaxation time approximation. The results obtained by means of the present model are compared with the available data of other models and experiments.