Analysis of directional radiative behavior and heating efficiency for a gas-fired radiant burner

For the purpose of energy conservation and uniform heating of object surface, a gas-fired porous radiant burner with a bundle of reflecting tubes is developed. A physical model is developed to simulate the directional radiative behavior of this heating device, in which the Monte Carlo method based on the concept of radiation distribution factor is used to compute the directional radiative behavior. The effects of relating parameters on the directional behavior of radiative heating and the heating efficiency are analyzed. With the increase of the length-to-radius ratio of tube, the radiation heating efficiency decreases, but the radiation energy incident on the object surface is more collimated. The radiation heating efficiency increases with the specular reflectivity. With the increase in length of tube segment with specular reflective surface, the radiation heating efficiency increases, but the extent of concentration and collimation of radiative energy decreases. For real design of the heating device, some trade-offs are needed to balance the radiation heating efficiency and the uniformity of radiative heating of object surface.     

CT-6B托卡马克的电子迴旋波加热实验

分别使用频率为34.34GHz和20.1GHz的迴旋管系统从外侧和顶端注入微波,对CT-6B托卡马克等离子体加热,均观察到明显的加热效果。分析表明两者有不同的加热机制。前者主要属于O模的共振加热;后者为X模的非共振-高密度加热,其机制可能来源于高密度截止层附近的非线性现象。在两种实验中,都观测到称为二次加热的非线性加热现象。它们可能分别来自不同的物理机制。     

微波加热技术的应用与研究进展

文章简述了微波加热的发展概况，阐述了微波加热的介电损耗机理和微波加热的特性．从微波加热与解冻、微波干燥、微波改性、微波烧结、微波杀菌等方面，介绍了微波加热技术在国内的研究与应用情况，指出微波加热技术具有广阔的发展前景，今后应重点加强微波与物料问相互作用理论、微波场中物料的传热和传质机制、微波加热工艺与设备、微波加热技术和其他技术的有机结合等方面的研究．     

相变材料蓄能式低温热水采暖地板热性能模拟

提出了一种采用定形相变材料蓄能的低温热水采暖地板形式。为了研究定形相变材料蓄能式低温热水采暖地板的传热性能,建立了该地板的传热分析模型。分析了相变材料的相变温度对地板表面平均热流密度和蓄能比的影响;比较了相变材料潜热蓄能地板与混凝土显热蓄能地板的热性能差异。结果表明:定形相变材料地板停止加热后仍可以在较长时间内保持稳定的热流密度。同时定形相变材料地板具有较大的蓄能比,使其夜间蓄存的热量可被更多地用于日间供热。     

短脉冲激光加热模型的遴选原则

 利用推导出的1维半空间光致热弹性应力响应的精确解，对激光与材料相互作用的加热模型的选取进行了研究。理论分析和计算结果表明：常用的表面加热模型只有在热穿透深度远大于光吸收长度时有效，若将其应用于超短脉冲激光（ps以下量级）加热的情况，可能会导致较大的误差；皮秒和飞秒激光辐照的热效应须用体加热模型计算。     

加热方式对真空冷冻干燥过程的影响

以平板状饱和牛肉为对象，对不同供热方法下冷冻干燥过程的传热传质进行了数值计算与实验研究，分析比较了表面加热与微波加热两种供热方式对冻干过程的影响，为冻干过程中供热方式的选择提供了理论依据及分析方法。     

一种新型的多孔太阳墙采暖房

长江中下游地区很多建筑没有安装专门的供暖设备,传统的空调采暖增加了建筑能耗。利用太阳能和建筑物自身进行采暖,具有重要的意义和价值。本文提出了一种新型的多孔太阳墙采暖房,其核心部分多孔太阳墙是由多孔陶瓷构成。在晴朗的冬季,对多孔太阳墙采暖房的采暖性能进行了实验研究;研究重点检测了不同外界环境(主要是指太阳辐射照度和环境温度)下,多孔太阳墙采暖房的采暖及储热性能。研究表明:多孔太阳墙采暖房在白天大部分时间都具有较好的采暖效果,且采暖房内的温差较小;同时具有较好的储热性能。以实验测得的武汉地区1月某天的实验数据为例,相比环境温度,当天采暖房内最高温升为19.9℃。在07:00～16:00之间,采暖房的平均温升为11.5℃;在辐射强度较弱的16:00～18:00,采暖房的平均温升为6.6℃。在07:00～18:00之间,采暖房内最大温差为1.37℃,出现在12:40。     

Mode of turbulent heating of plasma by hot and cold ions

Turbulent heating of plasma particles in the mode of strong heating by hot ions and weak heating by cold ions, where the turbulent state lifetime is not limited as in the case of heating by ions with equal temperatures, is discussed.     

Effect of magnetic field decay on the chemical heating of cooling neutron stars

The effect of magnetic field decay on the chemical heating and thermal evolution of neutron stars is discussed in this paper. Our main goal is to study how the chemical heating mechanism and thermal evolution are changed by the field decay and how the magnetic field decay is modified by the thermal evolution. We compare stars cooling with chemical heating with one without chemical heating and find that the decay of the magnetic field is delayed significantly by the chemical heating. We find that the effect of chemical heating has been suppressed through the decaying magnetic field by the spin-down of the stars at a later stage. Compared with typical chemical heating, we find the decay of the magnetic field can even cause the surface temperature to turn down at an older age. When we discuss the cooling of neutron stars, we should consider the coupling effect of the magnetic field and the rotational evolution of neutron stars on the heating mechanisms.     

Cathode Heating by Vacuum Arcs: A Survey

Theoretical predictions about heat sources, power dissipation and heating time scales are compared with available experimental data. It is concluded that the heating process must have a much faster time scale than quasi-stationary heat conduction. This can be achieved only by ion impact heating. A special model is discussed (thin layer heating) which explains the high power dissipation within the cathode as well as the short heating times.     

端部周期加热下管内气温奇异分布的实验研究

设计搭建了端部周期加热时管内气体热声对流的实验平台,对端部周期加热引起的气体热声对流作用下管内气体的温度分布进行了实验研究。该实验以氩气为工质,利用三极管控制加热电路实现周期性加热;测量了不同加热频率下管内的气体温度,并与常热流加热时的温度分布进行对比,结果表明端部周期加热时管内气体的温度分布与同功率下常热流加热时存在明显的差异,并且在某些测点出现了温度的奇异分布。本实验验证了超温现象的存在,为管内气体热声对流现象的进一步研究奠定了基础。     

电子器件制造过程中的一种均匀化加热法的数值研究

本文提出了喷嘴沿被加热物体宽度方向往复移动式射流冲击加热方法,该加热方法可提高被加热物体的等温性。通过进行数值模拟,得到了在任意时刻,被加热物体的温度分布及全体计算时间内被加热物体表面平均温度分布,进而得到了喷嘴移动周期与被加热物体的等温性的关系。     

ECR等离子体的磁电加热研究

在ECR等离子体装置上进行了磁电加热研究,利用离子灵敏探针(ISP)测量了磁电加热前后离子温度的变化,研究了电极环偏压、磁场强度、气压等参数对磁电加热过程以及加热效率的影响.结果表明:等离子体的整体加热是通过离子在电极环鞘层中的磁电加热及被加热的离子沿径向的输运来完成的.轴心处离子温度随电极环偏压的升高呈非线性增加.磁电加热效率随偏压的增大而增大,在电极环偏压为1000 V时,磁电加热效率为2%-2.5%,ECR等离子体中的离子温度能够提高20 eV以上.磁场强度在磁电加热过程中对离子的限制和加热起到重要作用,当磁场强度在6.3×10^-2-8.7×10^-2T之间变化时,磁电加热的效率随磁场强度的增大而增大.气压在0.02-0.8 Pa范围内,磁电加热的效率随气压的减小而增大. 关键词： ECR等离子体 磁电加热 离子温度     

Preparation of activated carbons by microwave heating KOH activation

Activated carbons with high surface areas were prepared via KOH activation process by microwave (MW) heating. As a comparison, activated carbons were also prepared by conventional heating (EF) method. The influences of KOH/Mesocarbon microbeads (MCMB) weight ratio and activation time on the pore properties of the activated carbons were investigated. For both MW and EF heating methods, the surface area and pore volume increase to a maximum and then decrease with the KOH/MCMB ratio increasing. The effects of activation time on the pore properties depend on the KOH/MCMB ratio. The activated carbons prepared by MW heating have higher surface area and larger pore volume than those by EF heating when KOH/MCMB ratio is the same. The MW heating method shortens the activation time considerably. Activated carbons prepared by MW heating show low content of oxygen containing groups.     

ICRF Heating Theory

The fundamental aspects of plasma heating in the Ion Cyclotron Range of Frequencies (ICRF) are presented, with an emphasis on heating tokamak devices. Topics include wave propagation, minority heating, ion-ion hybrid mode conversion, second harmonic heating, evolution of the ion velocity distribution, and ICRF antenna design.     

Convergence of electron kinetic,two-temperature,and one-temperature models for laser short-pulse heating

The laser short-pulse heating of metallic workpieces initiates the non-equilibrium heating in the surface vicinity of the substrate. The material response to the non-equilibrium heating cannot be predicted accurately by the one-temperature model. Consequently, new models pertinent to laser short-pulse heating are needed. In the present study, laser short-pulse heating of gold, copper, and lead is considered. The material responses to the laser short-pulse due to the electron kinetic theory and the two-temperature and the one-temperature models are examined in detail. The differences between the collisional and diffusional heating mechanisms are presented. The conditions for the convergence of conduction mechanisms are discussed. The electron kinetic theory, the two-temperature, and the one-temperature predictions are compared for three substrates. It is found that the electron kinetic theory predictions differ from the predictions of the one-temperature model in the surface vicinity of the substrate during the early heating duration. As the heating progresses, both models predict similar temperature profiles. The electron kinetic theory and the two-temperature model predictions are in good agreement. PACS 44.10.+i; 42.62.-b     

Investigation of practical high repetition rate copper vapour lasers with external heating

The characteristics of high repetition rate CVL devices incorporating passive external heating have been investigated. Pre-heating of the CVL plasma tube using external heating has been shown to significantly reduce CVL warm-up time, while supplementary heating of the CVL plasma tube using external heating allows efficient CVL operation with reduced discharge power input without any degradation in output power.     

Enhancement of ohmic and stochastic heating by resonance effects in capacitive radio frequency discharges: a theoretical approach

In low-pressure capacitive radio frequency discharges, two mechanisms of electron heating are dominant: (i) Ohmic heating due to collisions of electrons with neutrals of the background gas and (ii) stochastic heating due to momentum transfer from the oscillating boundary sheath. In this work we show by means of a nonlinear global model that the self-excitation of the plasma series resonance which arises in asymmetric capacitive discharges due to nonlinear interaction of plasma bulk and sheath significantly affects both Ohmic heating and stochastic heating. We observe that the series resonance effect increases the dissipation by factors of 2-5. We conclude that the nonlinear plasma dynamics should be taken into account in order to describe quantitatively correct electron heating in asymmetric capacitive radio frequency discharges.     

Research on pyrolysis of toluene under microwave heating by using ReaxFF molecular dynamics simulations

ReaxFF molecular dynamics (MD) simulations are performed to study high-temperature pyrolysis of toluene under microwave heating. It is observed that the temperature of the reaction system under microwave heating has a rapidly rising stage, which is similar to the phenomenon of thermal runaway often appeared in reactions under microwave heating. Simulations indicate that the consumption rate of toluene and generating rates of H₂ and CH₄ obtained under microwave heating are always lower than those obtained under conventional heating at the early stage. Analyses of the pyrolysis of toluene show that ReaxFF MD simulations can provide an efficient way to study chemical reactions under microwave heating.     

Laser heating: an electron-kinetic theory approach and induced thermal stresses

Laser heating offers considerable advantages for laser treatment of mechanical parts. The laser heating initiates the thermal stresses and expansion of the substrate. In the present study, laser heating of steel substrate is considered. Three-dimensional electron-kinetic theory approach is introduced when simulating the heating process. A moving laser source is taken into account provided that the laser scans the surface at a constant speed. Thermal stresses due to laser heating are computed and thermal expansion along the laser beam axis is predicted. It is found that the thermal stress increases considerably as the heating progresses. Moreover, the expansion of the free surface reaches a value of the order of a nanometer.