共查询到20条相似文献,搜索用时 31 毫秒
1.
B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2018,126(4):446-456
A method is presented for evaluation the radiation flux produced by a gas layer near a heated surface, where the gas temperature depends on a distance from the surface. This method refers to small temperature gradients and operates with an effective radiation temperature for each frequency, as well as with the width of the gas absorption band. These parameters are determined by the absorption spectrum of atoms or gas molecules, and also by the shape of the spectral line for the radiative transition between certain states of atomic particles of a gas. The possibilities of this method are demonstrated by examples of emission of photons from the solar photosphere, as well as emission of CO2 molecules in the atmospheres of the Earth and Venus. 相似文献
2.
V. V. Kuznetsov O. V. Vitovsky S. V. Dimov S. A. Safonov S. P. Kozlov 《Journal of Engineering Thermophysics》2007,16(2):99-106
In this paper, experimental and numerical investigations of the hydrodynamics and heat transfer in a disk slot heat exchanger-reactor
for a radial flow of a gas mixture reacting on the channel walls are described. Data for the coefficients of heat transfer
from the wall being heated to the gas flowing inside the reactor are presented. The temperature field of a catalytically active
reactor plate at heat release on it has been investigated experimentally. Calculations of the flow and heat transfer in a
slot reactor element for a catalytic reaction with heat release have been performed. Partial oxidation of methane in an oxygen
medium with the formation of a hydrogen-containing synthesis gas in a two-dimensional microchannel has been investigated numerically.
Data for the extent of the chemical conversion of methane versus the initial mixture consumption and reaction temperature
are presented. 相似文献
3.
Andrew V. Nowak John L. Lyman 《Journal of Quantitative Spectroscopy & Radiative Transfer》1975,15(10):945-961
Mixtures of SF6 diluted by argon were heated behind an incident shock front in the range 400 to 1500K. Absorption measurements at 11 wavelengths near 10·6 μm were made on the post-shock, equilibrated gas using a CO2 laser. A band contour model, which makes use of known spectroscopic constantd and the experimental results, satisfactorily accounts for the observed temperature dependence of the absorption coefficient. We are able to estimate the identity of the transitions responsible for absorption of the laser radiation. 相似文献
4.
Nongray molecular gas radiation can be formulated in terms of slab band absorptance, which can be calculated from correlations of laboratory-measured values of band absorption. Slab-band absorptance is not only useful for obtaining the emissivity or mean beam length but also for the formulation of the radiant flux in a nonisothermal gas. Effects of nongray self-absorption by cold boundary layers can then be readily estimated. Illustrative results are presented for gas in a channel with simple straight-line boundary layer profiles at the walls and constant temperature in the center. 相似文献
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光声(光热)效应是由于物质吸收一强度随时间变化的光束而被时变加热时所引起的一系列热效应和声效应,研究了这些热效应和声效应,可以获得物质的热学和学学性质,光声技术正是探测由于吸收光辐射后样品的微小温度变化所引起的周围气体压力变化,具有灵敏度高、操作方便、应用广泛等独特的优点,已成为研究物质光谱特性、热学性质等的独特有力手段,文章主要介绍了光声技术在固体热扩散率测量中的原理及常规应用方法。 相似文献
7.
Radiative Effects on Mixed Convection in a Uniformly Heated Vertical Convergent Channel with an Unheated Moving Plate 下载免费PDF全文
Assunta Andreozzi Nicola Bianco & Vincenzo Naso 《advances in applied mathematics and mechanics.》2011,3(3):280-296
Fluids engineering is extremely important in a wide variety of materials processing
systems, such as soldering, welding, extrusion of plastics and other polymeric
materials, Chemical Vapor Deposition (CVD), composite materials manufacturing.
In particular, mixed convection due to moving surfaces is very important in
these applications. Mixed convection in a channel, as a result of buoyancy
and motion of one of its walls has received little research attention and few
guidelines are available for choosing the best performing channel configuration,
particularly when radiative effects are significant.
In this study a numerical investigation of the effect of radiation on
mixed convection in air due to the interaction between a buoyancy flow
and an unheated moving plate induced flow in a uniformly heated convergent
vertical channel is carried out. The moving plate has a constant velocity
and moves in the buoyancy force direction. The principal walls of the
channel are heated at uniform heat flux. The numerical analysis is
accomplished by means of the commercial code Fluent. The effects of
the wall emissivity, the minimum channel spacing, the converging angle
and the moving plate velocity are investigated and results in terms of
air velocity and temperature fields inside the channel and wall temperature
profiles, both of the moving and the heated plates, are given. Nusselt numbers,
both accounting and not for the radiative contribution to heat removal,
are also presented. 相似文献
8.
基于连续辐射理论,得到连续辐射能量与等离子体电子温度的关系式。依据青海地区一次强地闪回击过程的光谱,从中分离出连续辐射强度,对其吸收特征进行分析以减小吸收带来的计算误差。通过对连续谱强度的曲线拟合得到闪电放电通道电子温度,温度峰值为29 800 K,温度下限为16 200 K,由同一波段光谱中的O Ⅰ线和N Ⅱ线分别拟合了电子温度。比较结果发现:由连续辐射得到的闪电通道电子温度从高温向低温过渡,高温值与离子线信息获得的闪电核心电流通道处的温度符合较好,而低温则与原子线计算的结果接近,反映了外围电晕发光通道的温度。所以,依据连续谱得到的结果能更全面地反映温度沿通道径向的分布。对于闪电热等离子体通道,连续谱法提供了一种计算闪电放电通道电子温度的新途径,对地闪回击研究有一定的意义。 相似文献
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为了对电厂脱硝过程中逃逸的微量氨气进行在线检测,实验室采用可调谐激光吸收光谱技术对常温常压下以及不同温度下的低浓度氨气进行了测量试验,其中电厂逃逸氨气检测处温度约为650 K。通过分析近红外波段的氨气吸收谱线,并考虑实际测量环境H2O和CO2等浓度很大的气体吸收谱线的干扰,实验选取2.25 μm附近的ν2+ν3谱线作为浓度检测谱线。为了验证所选谱线对低浓度NH3的测量能力,实验对H2O,CO2和NH3的吸收谱线进行模拟,发现低浓度NH3受较大浓度的H2O和CO2谱线的干扰较小,尤其是CO2谱线的干扰可以忽略不计,且2.25 μm处谱线强度远远大于通讯波段1.53 μm处的谱线。基于新型Herriott池以及高温管式炉,结合可调谐激光吸收光谱中的直接吸收技术和波长调制技术,实现了对不同温度下超低浓度NH3的高分辨率快速检测。常温常压下其线型函数可以利用洛伦兹线型来近似描述,直接吸收测量技术可以使探测极限降低到0.225×10-6。通过采用简单降噪处理技术如多次平均、简单小波分析等,得到不同温度下的谐波信号与浓度具有良好的线性关系,为采用可调谐激光吸收光谱技术进行现场低浓度逃逸氨气检测提供了很好的依据。 相似文献
11.
B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2018,127(1):48-57
An analogy is shown for broadening the spectral line of atoms in the case of competition between the short-range Doppler broadening mechanism and the long-range impact mechanism in atomic gases, as well as for the absorption band of a molecular gas in the infrared (IR) region of the spectrum, where the longrange part of the spectrum is also determined by the impact mechanism of the broadening. The long-range part in the pedestal region of the absorption band is associated with the distribution of molecules over the rotational states, and, in the range of wings of the absorption band, it is due to a finite time of collisions between emitting and perturbed molecules. The flux of resonant radiation produced by an excited atomic gas is estimated using the concepts of the spectral absorption band and a large optical thickness of the gas. These concepts are used for a molecular gas where, in the framework of the regular model (the Elsasser model), expressions are given for the absorption coefficient related to a specific spectral absorption band, separately in the pedestal region and for wings of the absorption band. As a demonstration of the possibilities of these concepts, the IR flux is calculated on the surface of Venus from its atmosphere, which includes seven vibrational transitions of the carbon dioxide molecule and amounts to 26% of the total flux of IR radiation emitted by the Venus surface. An analysis of the Venus energy balance leads to the conclusion that the main part of IR radiation of the Venus atmosphere falling on its surface is formed by a microscopic dust in the Venus atmosphere. This channel of the Venus energy balance is realized if the mass of a microscopic dust in the Venus atmosphere is seven orders of magnitude less than the mass of atmospheric carbon dioxide. 相似文献
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By varying the substrate temperature in the range of 800-1000 °C, the conditions for the synthesis of AlN nanowires were optimized. Al powders were heated under flowing ammonia gas. The samples were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence (PL) spectroscopy. Based on the absence of tip particles, the growth mechanism of AlN nanowires was considered to follow a vapor-solid process. The overall intensity of the PL spectra was increased by increasing the synthesis temperature, whereas their shapes were changed by varying the synthesis temperature. The associated emission mechanisms are discussed. 相似文献
14.
V. P. Zharov V. S. Letokhov E. A. Ryabov 《Applied Physics A: Materials Science & Processing》1977,12(1):15-17
A new detection method for absorption from excited vibrational states is suggested, based on optoacoustic detection of weak
absorption in a heated gas. Using this method CO2 laser radiation (λ=9.6 μm) absorption was investigated from excited vibrational states of CO2, BCl3, and BF3 molecules. 相似文献
15.
基于氧气A吸收带的baseline拟合距离反演算法 总被引:1,自引:0,他引:1
目标红外被动测距的实现同气体及其波段的选取密切相关。氧气A吸收带具有独特的谱线结构,对于火箭羽流或者高温辐射体的距离探测,氧气A吸收带是最佳的距离反演通道。利用该特点,详细研究了逐线积分算法(LBLRTM),并设计了氧气A带吸收系数及标准光谱计算软件;利用A吸收带吸收光谱带外数据,采用多项式拟合方法,实现基线(baseline)拟合,进而得到带平均透过率;在不同的距离条件下,将两种带平均透过率进行对比,误差在1.9%左右,拟合精度较高,该方法为后续距离的精确反演提供了理论依据。 相似文献
16.
激光加热物体的三维模型计算 总被引:5,自引:4,他引:1
将物体的热传导系数、比热容、密度、物体对激光的吸收系数考虑成温度的函数,并考虑到物体向周围空间有热辐射和对流换热交换能量等情况下,用控制容积法对激光加热物体作三维真实边界的计算分析.这一结果在激光加热物体温度场的计算上有广泛的实用性. 相似文献
17.
The efficiency of thermoelectric conversion of heat from gas combustion was evaluated in a small-scale system consisting of two channels with opposing gas flows and thermocouples located in the separating wall. Combustion occurred in the chamber fed with fresh mixture heated by combustion products through heat-conducting walls of the channel. In the channel walls, there were thermoelectric converters. It has been shown that in this system, the maximum conversion efficiency of heat from gas combustion may be close to the maximum efficiency of thermoelectric conversion calculated by the maximum acceptable working temperature of the hot side of the converter. This conclusion is valid in the case when the adiabatic combustion temperature of the gas mixture is below the maximum allowable operating temperature of the hot side of the thermoelectric converter. The considered system is promising for the burning of low-calorific gas mixtures and does not require additional energy for cooling the cold side of the thermoelectric converter. 相似文献
18.
二代加百万千万级核电站严重事故下卸压过程中高温流体流经卸压阀,可能造成流道变形,甚至造成阀杆下落使得排放流道封闭,造成卸压失败。对严重事故专用卸压阀在卸压过程中可能经历的高温流体状态进行谱分析,获得了不同卸压能力下阀门经受的高温流体状态。开展了高温可能引起的阀门流道变形对卸压效果的影响分析。第二类阀门虽然存在阀门流道变形的可能,但能够获得较长严重事故处置时间,从优化严重事故对策的角度,严重事故专用卸压阀推荐采用第二类阀门排放能力450~600 t/h范围。 相似文献
19.
An engineering method for calculating the parameters and characteristics of pulse detonation engines 总被引:1,自引:0,他引:1
Theoretical fundamentals for calculating the thermodynamic cycle of engines with fuel detonation (FD cycle), which is realized in the thrust units of pulse detonation engines (PDE), are presented. A system of equations for calculating the parameters of the detonation waves under various conditions of their initiation is derived. These equations were used to examine how various factors influence the parameters of detonation waves and, consequently, the work of the cycle, thermal efficiency, and the specific parameters of the PDE. It was demonstrated that the maximum thermal efficiency of the FD cycle virtually coincides with the minimum losses caused by the irreversibility of heat input into the detonation wave. It was established that the losses are substantially dependent on the temperature of the working substance (compressed air or heated gas) supplied into the thrust units, more specifically, they decrease with increasing temperature. 相似文献
20.
Classification and performance capability of electric are linear plasmatrons are presented. The results of investigation into convective and radiative heat transfer in the discharge channel of a plasmatron are reported. The radiative heat transfer dominates both in the structure of heat losses and in the formation of discharge volt-ampere characteristic at the initial region of the flow. Relations to calculate heat losses by radiation are given. Radiative convective interaction at the arc boundary is shown to play a substantial role for high-current discharges stabilized by axial vortex gas flow. It is shown that the calculation of convective heat transfer at the turbulent region of the flow may be carried out by flow averaged parameters. 相似文献