HFC134a与HFO1234yf用于汽车空调的理论分析

对HFC134a和HFO1234yf应用于汽车空调进行了理论分析,研究表明:HFC134a的排气温度明显高于HFO1234yf,HFC134a的排气温度随着蒸发温度的升高而降低,HFO1234yf的排气温度随着蒸发温度的升高而升高;HFC134a与HFO1234yf的单位制冷量都是随着蒸发温度的升高而增大,但HFC134a的单位制冷量明显高于HFO1234yf,其平均高于HFO1234yf约34.9kW/kg;HFO1234yf压缩机输入功率明显高于HFC134a;HFC134a的系统COP高于HFO1234yf的系统COP,且二者都是随着蒸发温度的升高而升高,蒸发温度为-10℃时,其系统COP分别为3.739和3.493,蒸发温度为18℃时,其系统COP分别为9.6和9.36。     

Numerical study of EHD-enhanced water evaporation

A numerical model has been developed for the investigation of water evaporation enhanced by corona wind. The corona wind is generated by a wire electrode charged at a high dc voltage. Only positive corona discharge is considered in the present study. The effect of cross-flow on EHD-enhanced water evaporation is also examined. The results show that water evaporation can be greatly enhanced by corona wind. However, a cross-flow with a high velocity may diminish the effect of corona wind. The numerical results are also compared with experimental data reported in the literature. A satisfactory agreement is found between these results.     

Transition probabilities of Mn(II) lines lying between 237 and 357 nm from arc emission measurements

The arc arc emission method has been used to determine transition probabilities for 326 lines of Mn(II) belonging to 134 multiplet. The spectra were emitted from a plasma produced in a wall-stabilized arc. A new method has been developed to introduce Mn vapour (created by evaporation of solid metal in a combined arc-spark discharge) into the Ar-H-plasma. Plasma have been performed by spectroscopic methods. The relative transition probabilities are placed on an absolute scale by using A-values deduced from lifetime measurements.     

Development paths of the instability of a highly charged viscous droplet

Analysis is presented of the effect on the instability of a droplet of viscous liquid induced by its self-charge of such physical factors as corona discharge initiated in its vicinity and self-sustaining due to photoionization, evaporation of the liquid, and field vaporization of the charge. It has been shown that droplets of micron and submicron size lose their excess charge primarily due to field vaporization.     

带膨胀机的HFC134a与HFO1234yf制冷系统分析

对带膨胀机的R134a与R1234yf制冷系统进行理论分析,并与不带膨胀机的系统进行比较。研究表明:HFC134a的排气温度明显高于HFO1234yf,HFC134a的排气温度随着蒸发温度的升高而降低,HFO1234yf的排气温度随着蒸发温度的升高而升高;HFC134a与HFO1234yf的单位制冷量都是随着蒸发温度的升高而增大,但HFC134a的单位制冷量明显高于HFO1234yf,其平均高于HFO1234yf约34.9kW/kg;HFO1234yf压缩机输入功率明显高于HFC134a,HFC134a的系统COP高于HFO1234yf的系统COP,且二者都是随着蒸发温度的升高而升高。在制冷系统中加入膨胀机后,对HFC134a产生了显著的影响,在蒸发温度-10℃时变化最为明显,其单位制冷量增大32%,压缩机输入功率降低12.1%,系统COP降低19.8%,膨胀机的加入并没有影响HFO1234yf系统,其各项参数均未发生明显变化。在HFO1234yf制冷系统中应用膨胀机的效果逊于HFC134a制冷系统。     

Excitation of metal spectra in combined glow discharge

Consideration is given to the special features of the excitation of spectra of metals (Ag, Au, Fe, Hg, Pt, and Sb) that manifest themselves in investigating spectral sources with combined glow discharge (glow discharge and capillary discharge). It is established that the proposed method for introducing a substance into a plasma makes it possible to realize two fundamentally different regimes: without evaporation and with complete evaporation and matrix atomization. It is shown that a spectral source of combined glow discharge with a nonequilibrium plasma has significant advantages for the most important analytical characteristics over quasi-equilibrium combined discharge at atmospheric pressure. The gold and platinum sensitivity in combined glow discharge is 10⁻⁷%, and the reproducibility of spectral determinations is 0.001–0.100, depending on the measurement range. A fractional separation of elements that makes it possible to analyze the phase composition of substances, particularly metals, with high sensitivity is revealed in glow discharge. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 143–147, March–April, 1997.     

熔融盐法合成锂离子电池正极材料纳米LiNiO2

采用熔融盐法,在较低的温度和较短的时间制备了符合理论化学计量比的纳米LiNiO₂.研究表明,经过空气中的低温预烧,可以使制备的纯相纳米LiNiO₂具有更加优良的结晶性能和更佳的电化学特性.添加预烧步骤前后所得最终产物的初始容量分别为151和148 mAh ·g^-1,经过100周的循环,容量衰减到55和118 mAh ·g^-1,容量保持率分别为36.4%和79.7%.原因在于预烧后再进行煅烧降低了阳离子无序度,减少了混杂 关键词： 2')" href="#">LiNiO₂ 熔融盐法 锂离子电池 电化学性能     

Evaporation waves in a metastable single-component liquid

In this paper, evaporation waves appearing at rapid depressurization of a vessel filled with liquid Freon R11 have been investigated experimentally. Regimes with a high-speed evaporation front have been revealed. It has been shown that the disintegration of a metastable liquid takes place in the form of a surface evaporation wave with a cellular structure of the front and anomalously high values of the coefficient of heat transfer from the liquid. The dependence of the evaporation front velocity on the initial temperature of the liquid has been obtained. A critical temperature value below which evaporation waves are not observed has been determined. Visualization of the evaporation front structure and dynamics with the use of a high-speed video camera has been performed. It has been found that the evaporation front motion has a pulsatory character. A method to calculate the surface evaporation wave with a quasi-plane interphase boundary has been developed. It is based on a model of nonequilibrium evaporation of the liquid and experimentally measured coefficients of the heat transfer from the liquid.     

Preparation of hydrogenated amorphous germanium by reactive thermal evaporation

Hydrogenated amorphous germanium was prepared by the thermal evaporation of high purity polycrystalline germanium in an atmosphere of hydrogen plasma produced by high voltage AC discharge of molecular hydrogen. The addition of hydrogen during the thermal evaporation of germanium is shown to improve the electrical properties of the resulting amorphous germanium films considerably by saturation of dangling bonds, if the dissociation of molecular hydrogen takes place. Hydrogenated sample deposited at 200°C has shown a high resistivity and an activation type conduction (with an activation energy of 0.38–0.39 eV) in measuring temperature range (above room temperature).     

CO_2跨临界压缩式制冷循环理论分析

环保工质CO_2作为制冷剂用于空调领域再次受到广泛关注。文中对CO_2跨临界循环进行了热力学理论分析,分析结果表明:循环系统存在最优高压压力,使得其COP达到最大值;蒸发温度的升高或者冷却压力的降低都能提高COP,但都会降低效率;实际运行系统中,应该尽可能提高蒸发温度或者降低气体冷却器的出口温度。     

超半球透镜减反射膜

本文简单地介绍了超半球透镜减反射膜膜厚分布的理论计算结果。通过调节蒸发源与基片间的相对位置和“散乱”淀积技术获得了与理论要求基本一致的膜厚分布。通过离子轰击、基板烘烤和热处理获得了满意的膜层牢固度。     

吹样法中样品蒸发的蒸气压效应

作者根据多年来从事吹样法光谱分析的经验，对不同挥发性元素该方法同时具有的高灵敏度，提出了理论解释，这对深刻认识和掌握这种方法会有帮助。     

The anode space of short-time high-intensity electric discharges

The influence of electrode evaporation on the forming of an anode region of short-time discharges has so far been neglected. A comparison of the amount of vapours produced in spots and the magnitude of the thermal flow to the electrodes for anodes of different materials shows the important connection between the formation of spots on electrodes and the flow of vapours and permits the characteristic effects (high current density in spots, splitting of spots, two forms of contraction) of the anode region of the given type of discharge to be explained.In conclusion the author thanks J. Chudoba and B. Grycz for valuable remarks.     

Simulations of dynamic resistive evaporation in a vacuum

The model of dynamic resistive evaporation in vacuum has been considered, and the model takes into account the structural peculiarities of the corresponding evaporator. In the model, the dependences to determine the time of material heating up to evaporation temperature as well as dynamic characteristics of the evaporation have been obtained. It has been shown that the obtained characteristics are nonharmonic and periodically repeated. The adequacy of the developed model to the physical model has been corroborated. It has been found that the discrepancy between the experimental and calculated time characteristics of shutter movement is not higher than 5%. The recommendations for using the suggested model to fabricate of thin films of multicomponent materials via thermal evaporation have been considered.     

CPL蒸发器多孔芯传热传质特性的新数学模型

毛细循环泵(CPL),由于具有高热传输性能,目前已经成为大功率载荷的电子芯片排热系统的一个重要发展方向,尤其是在航空航天飞行器上。选择一种具有较大相变潜热的工质,例如甲醇, CPL可以传输相当大的热流。本文对CPL蒸发器多孔芯流动和传热的数值模拟提出了一个新的发展方向,就是在计算中加入非饱和模型数值计算。文中阐述了加入非饱和计算的三层模型对真实模拟蒸发器多孔芯流动和传热问题的重要性,并给出了应用新的三层模型所得到的初步计算结果。     

Recuperation of IRSL after bleaching and consequences for dating young sediment

Recuperation of the infrared-stimulated luminescence signal that occurs after bleaching of fine grain samples has been studied, using samples that have been obtained from British alluvial deposits less than 5000 years old. Different durations and wavelengths of bleaching have been investigated along with the effect of different preheats and repeated cycles of bleaching and preheating. The build up of recuperation with storage at room temperature has also been studied. The consequences of this recuperation signal on evaluating young ages is then considered.     

Isotopic ratio of evaporated ions,critical ionization distances,and ionization regions in the process of the field evaporation of molybdenum at high temperatures

A magnetic mass spectrometer with a field ion source has been used to study the steady-state field evaporation of molybdenum at a temperature of 1000–2000 K. Ions of all seven molybdenum isotopes have been observed in the process of evaporation; only low-charge ions Mo⁺² and Mo⁺ have been detected. The critical ionization distances and ionization regions for single- and double-charge Mo ions have been identified based on the measured ion energies and the experimentally determined intensity of the evaporation field. It has been demonstrated that ions are produced in the process of field evaporation of surface atoms at certain distances from the emitter surface in a very narrow spatial region.     

扫描隧道显微镜中场蒸发过程的理论分析

从电热动力学(Electrothermodynamics)角度出发，分析了扫描隧道显微镜(STM)中场蒸发过程.引入了一个有效结合能，并推导得到了STM中的蒸发场强计算公式.用该公式计算得到了与实验一致的金离子的蒸发场强.同时发现传统的电荷交换模型与成象势垒模型，由于它们要求被蒸发原子完全电离并被蒸发到无穷远处，因而对STM计算的蒸发场强偏高. 关键词：     

One-step synthesis of Pt-Pd catalyst nanoparticles supported on few-layer graphene for methanol oxidation

In this study, Pt-Pd nanoparticles (NPs) supported on few-layer graphene (FLG) have been firstly prepared by one-step arc discharge evaporation of carbon electrodes containing both Pt and Pd elements. The few-layer graphene and Pt-Pd nanoparticles were achieved simultaneously through the evaporation process. After a high-temperature hydrogen treatment, the Pt-Pd/graphene was applied in the study of methanol oxidation in direct methanol fuel cell. The total weight of electrocatalyst keeps 2 wt% of the electrode. The sample with a mass ratio of Pt:Pd = 3:1 (H-Pt₃Pd₁/G) exhibits better electrocatalytic activity (198 mA mg-1 pt) and better tolerance to carbon monoxide(CO) poisoning (I_f/I_b = 1.26). It is noteworthy that the value of I_f/I_b can reach to 1.55 for the sample with the mass ratio of Pt:Pd = 2:1 (H-Pt₂Pd₁/G),which implies its excellent ability of CO tolerance. The introduction of Pd element may open a new strategy to improve the CO tolerance by arc discharge evaporation.     

蜂巢蓄热体传热性能的数值研究

蜂巢蓄热体是高温空气燃烧技术的关键部件．为加速这项新型燃烧技术在我国的国产化进程,本文对蓄热体内的传热过程进行了深入研究．首先,用数值计算的方法得出了蓄热体内的温度和速度分布,模拟了蓄热过程和放热过程的烟气和空气温度的变化情况．此后,进一步研究了气流速度和材料比热对蓄热体性能的影响．