喷射器临界背压对喷射制冷系统性能的影响

为了确保喷射器在良好的工况条件下运行,文中针对太阳能喷射制冷系统的工况范围,以R134 a为工质建立了喷射器运行特性计算模型,计算分析了临界背压随喷射器运行工况的变化关系,以及对制冷系统性能的影响。结果表明:喷射器的临界背压随发生温度和蒸发温度的增大而增大,极限喷射系数随发生温度的升高而降低,随蒸发温度的升高而升高;喷射制冷系统COP随喷射器背压(冷凝压力)的升高先保持不变后减小,当Tg=353K,Te=281K和Te=283K时,喷射器分别在Tc=307K左右和Tc=308K左右时,达到临界状态,临界背压分别为0.85MPa、0.88MPa,COP分别为0.2和0.227。     

Effects of process parameters on electrical properties of n-type Bi2Te3 prepared by mechanical alloying and spark plasma sintering

n-Type Bi₂Te₃ thermoelectric materials were prepared by spark plasma sintering (SPS) using mechanically alloyed powders. Seebeck coefficient and electrical conductivity of the resultant materials were measured, with emphasis on the effects of sintering process parameters on the electrical properties. The power factor was improved from 1.5 to 1.6 mW/mK² when the SPS pressure was increased from 20 to 50 MPa at 623 K, and was further increased to 2.1 mW/mK² under 50 MPa by raising the SPS temperature from 623 to 673 K. The maximum power factor was obtained for the sample sintered under optimized SPS process parameters, in which the sintering temperature and the sintering pressure are 673 K and 50 MPa, respectively.     

乙醇溶液的电感耦合等离子体发射光谱研究Ⅱ——乙醇对ICP激发特性的影响

本文研究了乙醇对ICP激发温度、气体温度、电子数密度以及易电离元素基体效应的影响,讨论了“有机ICP”的局部热平衡特性及扩张效应。     

稠密氦气辐射不透明度的实验研究

用二级氢气炮作为冲击压缩加载工具和多通道瞬态辐射高温计作为主要测量系统,测量了冲击压缩氦气等离子体的光辐亮度历史(初始温度293 K,初始压力为0.6 MPa和1.2 MPa两种).根据实测记录信号波形的有关特征量,计算得到了氦等离子体的光谱吸收系数κ(λ)和冲击压缩铝基板表面的光反射率R.结果发现:受冲击铝基板表面的光反射率～0.4(比其初始反射率0.8约降低一半),与Erskine的数据相同;对于光谱吸收系数的实测数据,本文目前未能给出合理的物理解释.     

Contribution to the evaluation of transport coefficients in plasmas containing krypton and sodium

Electrical and thermal conductivities for low-temperature (2000 K to 20000 K) and high-pressure (0.1 MPa to 2.5 MPa) krypton plasma with some sodium (1% and 10%) as additive are presented. The plasma is treated as weakly non-ideal and having attained the local thermodynamical equilibrium states. The problem of the plasma non-ideality according to standard criteria is of the plasma Debye radius, with an improved cut-off length. Use is made of a previously derived modified Debye radius with the Landau length instead of the smallest ionic radii which allowed to regard the plasmas investigated as weakly non-ideal. This alteration in the evaluation of the Debye radius profoundly alters the equilibrium plasma compositions and their transport coefficients.     

Ignition of cyclopropane in shock waves

The values of the ignition delay time of cyclopropane–oxygen–argon (cyclo-C₃H₆–O₂–Ar) mixtures of different compositions (φ = 0.333, 1, and 3) behind reflected shock waves at temperatures of 1200–1640 K and a pressure of (0.55 ± 0.05) MPa are measured. A kinetic mechanism of cyclopropane ignition using the known rate constants for the most important elementary reactions is developed. The mechanism closely describes both our own and published experimental data on the delay time of ignition of cyclopropane in shock waves over wide ranges of temperature (1200–2100 K), pressure (0.1–0.55 MPa), cyclopropane concentrations (0.05–11 vol %), and oxygen concentrations (0.25–21 vol %). It is shown that, with increasing fraction of diluent gas in the mixture, the dependence of the ignition delay time on the fuel-to-oxidizer equivalence ratio changes.     

高气压Ar气对激光诱导Cu等离子体电子温度的影响

用高能量钕玻璃激光器产生的脉冲激光(0～25 J)烧蚀Ar气氛中的Cu靶,观测了激光诱导Cu等离子体的发射光谱强度随环境气压(0.1～0.5 MPa)的增强规律。为了探讨辐射增强的机理,在局部热平衡(LTE)近似条件下,测量了等离子体的电子温度随环境气压的变化。实验结果表明,等离子体的电子温度随着环境气压的升高而正比增加。为了进一步了解等离子体的空间行为,测量了Ar气气压分别为0.1,0.3,0.5 MPa时,等离子体电子温度的空间分布。     

高温高压流体在线毛细管黏度测量

提出了一种适用于高温高压条件下的在线毛细管黏度测量方法,设计并搭建了相应的实验系统。通过与高温高压循环系统连接,可实现压力（约30MPa）、温度（约773K）范围内的流体黏度在线测量。利用该实验系统,在线测量了压力分别为12、23、25、28MPa下,温度303．46－383．28K范围内纯水的动力黏度。较之NIST文...     

CH4水合物生长速率影响因素的分子动力学模拟

采用分子动力学模拟,研究了温度、压力和电解质溶液对CH4水合物生长速率的影响.通过分析势能、均方位移、氢键数量、径向分布函数和四体结构有序参数,表征了CH4水合物的生长动力学.模拟结果表明,降低温度和提高压力可以显著提高CH4水合物的生长速率.当压力恒为15MPa,温度高于290K时,势能升高,CH4水合物晶体发生分解;温度由290K降至260K时,势能降低,CH4水合物持续生长.当温度恒为275K,压力由3MPa增至50MPa时,CH4水合物生长速率提高12%.此外,电解质离子的存在抑制了水合物的生长,电解质溶液浓度由1.5wt%增加到3.5wt%时, CH4水合物生长速率降低25%.     

高温高压下草酸脱羧反应中的拉曼光谱研究

应用水热金刚石压腔结合拉曼光谱技术研究了高温高压下草酸溶液的热稳定,使用拉曼光谱对其脱羧反应及产物进行监测。结果表明低温升温过程中,草酸的拉曼谱图中各个特征振动峰没有发生变化,随着温度的继续升高,其特征振动峰逐渐变弱。达到一定温度后,羧基的拉曼特征峰消失,草酸发生脱羧反应:C2H2O4—2CO2+H2生成CO2和H2。高温高压下草酸发生热分解的温度压力之间呈线性关系,其线性回归方程为P(MPa)=12.839 T(K)-5 953.7,R2=0.99。草酸脱羧反应的摩尔体积变化与温度压力的关系为ΔV(cm-3.mol-1)=16.69-0.002P(MPa)+0.005 2T(K),R2=0.99。     

高效率的低温混合工质J-T节流制冷机的试验研究

1JIto节流制冷机是一种结构简单、运行可靠的制冷机械，它广泛地用于工农业生产和国防军事工业之中。采用混合工质的J－T节流制冷机本世纪三十年代就有报道，但由于实验不太成功而没有受到注意，直到1959年，前苏联基辅气体研究所的A．P．Klimeenko教授利用内复叠循环在液化天然气的流程中采用了混合物作为J－T节流制冷循环的工质高效地液化天然气后而得到重视山。70年代，前苏联的另外一批学者M．BTOdyllsky等研究了适合于获得液氮温度的高效率的混合工质p」。他们的研究表明，在液氮温区，采用氮加碳氢化合物或者氟利昂作工质，比采…     

转反义ACS基因番茄和普通番茄果实中锌含量和钠钾比与抗病性的关系研究

植物激素与矿质元素吸收以及与植物抗性的关系研究是近年来人们关注的热点。实验采用电感耦合等离子体原子发射光谱法(ICP-AES)测定转反义ACS基因耐贮番茄(乙烯的生物合成被抑制)及同品种普通番茄果实(对照)中Zn,Na,K元素的含量及Na/K比例的差异,并对其与果实抗病原菌侵染能力的关系进行讨论。结果表明：乙烯生物合成受阻的转反义ACS番茄果实抗病原菌侵染的能力高于对照果实,其Zn元素的含量是普通番茄果实的1.5倍;K元素含量在两种果实中无明显差异,但Na元素含量显著高于对照,Na/K比值是对照的2.0倍。说明Zn元素含量和Na和K元素的比例关系可能在转反义ACS番茄果实抗病原菌侵染的过程中起到一定作用。     

Phase separation in Na–K liquid alloy

The quasi-chemical expression for weakly interacting binary alloy has been applied to obtain energy parameters and their temperature derivatives for Na–K liquid alloy at 384?K. These energy parameters have then been used to calculate thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing and microscopic functions, such as concentration fluctuation in long wavelength limit, Warren–Cowley short-range order parameter, ratio of mutual and self-diffusion coefficients. The analysis reveals that the energy parameters are temperature dependent and the Na–K liquid alloy at 384?K is a weakly interacting homocoordination system. The observed thermodynamic properties of Na–K alloy in molten state have successfully been explained by assuming Na₂K complex on the basis of the quasi-chemical formalism for a weakly interacting system.     

氩气/甲烷/空气介质阻挡放电等离子体的发射光谱诊断

为了获得可燃气体的放电及等离子体发射光谱特性,进一步揭示等离子体助燃作用下燃料在稀燃状态的点火与燃烧特性,在常压下以氩气作为载气对预混的甲烷和空气进行放电研究。实验基于平行板电极射频(13.56 MHz)介质阻挡放电的等离子体发生装置,首先在常压下对体积分数为90%氩气/10%空气的混合气体开展放电研究;再在90%氩气含量不变的情况下,调节空气含量并加入与之能形成燃烧化学当量比Φ＝1的甲烷,氩气/甲烷/空气的混合气体同样能实现稳定而均匀的放电;最后分别在90%氩气含量不变,甲烷和空气在当量比为Φ＝0.4～1.9六种情况下进行放电实验。由光谱仪记录不同放电工况下的发射光谱信息,诊断反应产物类型,利用观测到的氮分子第二正带系(0-2)380.4 nm和(1-3)375.4 nm处的发射谱线,与自编程序计算的模拟谱线拟合,得出分子转动温度(即气体温度)。研究结果表明：通过拟合模拟光谱与实验所测发射光谱的方法推测分子转动温度,进而获得气体的平动温度,氩气/空气放电的气体温度可达到1 150 K,氩气/甲烷/空气Φ＝1时放电气体温度升高到1 390 K;甲烷与空气形成不同当量比时,所测等离子体气体温度相对于90%氩气/10%空气混合气体温度的温升在70～240 K范围变化;由光谱信息观测到CH,H,OH和CH₂O等活性粒子的存在以及气体温度的升高,表明可燃成分混合气在射频电场放电作用下发生等离子体燃烧化学反应并释放出化学热。     

T1系单相超导材料的高氧压合成及压力对超导性的影响

 系统地研究了在0~3 MPa氧压下T1系超导材料的制备过程及其超导性质。结果表明：0.25~0.90 MPa氧压下所制备的样品为纯2223相，T_c0最高可达125.3 K；1.45~3.00 MPa氧压下样品为纯2212相，T_c0在95~100 K之间；0.90~1.45 MPa氧压下样品为2223及2212两相共存。对两种单相样品的高压研究结果表明，2223相样品比2212相样品有着较强的压力效应，在0~0.52 GPa压力下分别为4.0 K/GPa及2.0 K/GPa。     

Pressure and temperature induced modification of luminescence from tetracene single crystals

Fluorescence spectra of crystalline tetracene have been recorded in the temperature range 120 to 300 K under hydrostatic pressure up to 600 MPa. From discontinuities in both emission spectra and spectral intensities it is concluded that two phase transitions occur. The room temperature phase is transformed to a low temperature phase/high pressure phase I at T^I_t (p = 0) = 182 K, the temperature coefficient being dT^I_t/dp = 0.395 K/MPa. The phase transition is induced by a decrease of the specific volume under pressure and/or upon cooling. Lack of a significant shift of the origin of the fluorescence band near T^I_t at constant pressure is an artifact resulting from the neglect of reabsorption effects. The Stokes shift is 260 cm^-1, independent of temperature and crystal modification. In accord with previous Raman data a second phase transition occurs at T^II_t (p) = 143 K, the pressure shift being dT^II_t/dp = 0.088 K/MPa.In addition, the shift of the triplet energy as a function of pressure as well as the pressure-dependence of the rate constants governing fission of a singlet exciton into a pair of triplets is discussed utilizing their magnetic field dependences.     

Measurement of neutral gas temperature in inductively coupled plasmas

Dependence of the neutral gas temperature on the gas pressure and discharge power in an inductively coupled plasma source has been investigated using optical emission spectroscopy. Both nitrogen and argon plasmas have been studied separately. In the case of argon plasma, about 5% nitrogen was added to the total gas flow as an actinometer. The maximum temperature was found to be as high as 1850 K at 1 Torr working pressure and 600 W radiofrequency power. The temperature increases almost linearly with the logarithm of the gas pressure, but changes only slightly with the discharge power in the range of 100–600 W. In a nitrogen plasma, a sudden increase in the neutral gas temperature occurs when the gas pressure is increased at a given discharge power. This suggests a discharge-mode transition from the H-mode (high plasma density) to the E-mode (low plasma density). In the H-mode, the gas temperature is proportional to the logarithm of the gas pressure, as in the argon plasma. However, the gas temperature increases almost linearly with the discharge power, which is in contrast to the case of argon plasma. The electron density in the nitrogen plasma is about 10% of that in the argon plasma. This may explain the observation that the nitrogen neutral temperature is always lower than the argon neutral temperature under the same discharge power and gas pressure.     

Fluorescence spectroscopy of 1,2,4-trimethylbenzene at high temperatures and pressures: application to temperature measurements

Fluorescence of the S₁→S₀ transition of 1,2,4-trimethylbenzene vapour after laser excitation at 266 nm was investigated in a heated cell. Experiments were performed for temperature between 350 and 900 K, at pressure between 0.1 and 3.0 MPa and for oxygen molar fraction between 0 and 21%. The absorption cross section was found to reduce by about 20% between 350 and 900 K. 1,2,4-trimethylbenzene fluorescence exponentially decreased by three orders of magnitude as temperature increased. A similar behaviour was observed with pressure, although fluorescence reduced only by a factor of 2.5 between 0.1 and 3.0 MPa. Additionally, Stern–Volmer plots were found to be linear for temperatures between 450 and 750 K. Using the dependence of 1,2,4-trimethylbenzene fluorescence on temperature, potential use of this molecule for temperature measurements in turbulent flows is suggested.     

The Hydrogen Dissociator

A performance analysis is presented for the hydrogen dissociator used in hydrogen masers to provide a beam of atomic hydrogen. An analysis of the discharge characteristics yields relations for electron temperature as a function of vessel size and gas pressure and for plasma density as a function of power input. Also a relation between ion impact energy at the wall and electron temperature is derived. For a typical dissociator (2" diameter, 0.1 Torr hydrogen pressure, and 4 watt input power) these relationships yield an electron temperature of 39,000°K, a plasma density of 1011 cm-3 and an ion impact energy of 20 volts. The dissociation rate is calculated using published cross-sections. Assuming a recombination rate of 4 × 10-3, the analysis yields an atomic hydrogen density of about 1014 cm-3, a degree of dissociation of 2%, and an atomic beam flux of 1.3 × 1018 cm-2 × sec-1 for the example quoted. This beam flux is in good agreement with estimated values for hydrogen masers. A coefficient for performance ? is derived for the hydrogen dissociator, defined as the ratio of atomic beam flux to discharge power consumption. It is shown that ? is a function of the electron temperature and has a maximum at 87,000°K. It is concluded from this analysis that the discharge in presently used hydrogen dissociators is well optimized given the pressure constraints of the system.     

Experimental study of pressure and density of saturated and superheated vapor of refrigerant R-236ea from 20 to 150 °C

The saturation pressure, pressure and density of superheated vapor of 1,1,1,2,3,3-hexafluoropropane (HFC-236ea, R-236ea) were studied by an isochoric piezometer within the temperature range of 294–423 K up to the pressure of 4.0 MPa. The uncertainties of temperature, pressure, and density measurements were estimated as ±20 mK, ±1.5 kPa, ±(0.1–0.2) %, and ±(0.1–0.2) %, correspondingly. The purity of studied samples was 99.68 mass %. The obtained experimental data are shown as tables and analytical equations. Coefficients of the virial state equation were calculated for R-236ea on the basis of these data. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 04-02-16355).