新型制冷机冷凝器壳侧的传热强化研究

针对现行制冷机冷凝器的不足 ,设计了适用于冷凝传热的新型折流杆冷凝器的壳程内部结构 ,并分析了其传热强化机理。在重力控制条件下 ,对不同内部支承结构与管束组合的冷凝器进行了传热实验研究 ,得到了水蒸汽在冷凝器壳侧的冷凝传热特性曲线。采用冷凝传热强化因子的概念 ,建立了预测该种折流杆冷凝器壳侧冷凝传热膜系数的计算公式 ,为折流杆冷疑器在制冷系统中的设计应用提供了理论依据。     

轻离子反射系数的标度公式

最近发现，轻离子输运行为具有显著的标度特性，可用一个称为标度输运截面的参数来标定。本文利用这个重要的性质，给出了以标度输运截面为自变量的轻离子粒子数反射系数和能量反射系数的普适拟合公式。此公式具有非常好的单值对应关系，相比之下，经常应用的约化能ε作为标度参数的反射公式，因其分散度大而相形见绌。 关键词：     

热声制冷机微热力学循环的火用经济性能优化

用有限时间热力学方法分析存在传热损失时,热声制冷机微热力学循环模型的火用经济性能,导出循环利润率与工质振荡温度,以及利润率与制冷系数的特性关系,并数值分析了价格比、横向温度梯度等参数对火用经济性能的影响。     

Manifolds for which the heat kernel is given in terms of geodesic lengths

We exhibit some classes of Riemannian manifolds and of Lie groups where the heat kernel is given in an exact way by formulae essentially involving only the spectrum of geodesic lengths.     

由相对不确定度研究气体比热容比的测量仪器选择

该实验利用测量气体比热容比的经典装置,证明小球装置中做简谐振动,并依据周期推导气体比热容比理论公式,分析了测定气体比热容比的误差来源采用计算机实时测量技术获得气体在任意时刻的压强,利用比热容比的相对不确定度确定了测量仪器,从而利用精确的测量量求得气体比热容比值,利用确定的仪器测量,最终实验相对百分误差控制在0.5％.     

Validation of hard tooth tissue thermal diffusivity measurements applying an infrared camera

The problem concerns investigations of thermophysical properties of small biological specimens. Results of experimental verification of some thermal diffusivity data of hard tooth tissue are presented and discussed. The measurements have been performed on two sliced tooth specimens of different thicknesses. The temperature changes of one flat surface have been recorded applying an infrared camera while the opposite surface has been monotonously heated. The results of measurements have been analysed in order to identify the differences related to variations in thermal properties of hard tooth tissues. Distinct differences between heated enamel, crown dentine and root dentine structures have been revealed. Lack of analytical heat transfer formulae restricted the analysis to qualitative aspects of the problem. Conclusions concerning possible quantitative calculations and the methodology of such an analysis have been formulated.     

Improvements to formulae for the ensemble relative variance of random noise in a reverberation room

In this paper possible improvements to the formulae previously developed by the author for predicting the ensemble relative variance of the intensity of a frequency band of random noise which has been passed through a reverberation room are investigated. First the experimentally deduced values of the factor in the formulae which depends on the modal spatial functions are considered. It is shown that these values do not always agree well with theoretically deduced values. Better empirical values for the factor are suggested. Then the assumptions behind the different formulae in the literature for the ensemble relative variance of random noise are considered. These different formulae are then applied to the case when random noise is passed through a reverberation room. In Appendix A the different definitions of filter bandwidth are discussed, while in Appendix B the derivations of the different ensemble variance formulae are presented.     

Current views on thermal conductivity and diffusivity measurements of oxide melts at high temperature

There have been various attempts to measure thermal conductivity of relatively low conductive materials such as oxides and nitrides, at high temperature. However, their accuracy was not sufficient to allow quantitative discussion mainly because of experimental difficulties, particularly at sample temperature above 1000 K, for several reasons. For example, the radiative heat flow is known to play a significant role at higher temperature, but the separation of such a component from the measured heat flows has only been established recently. An attempt will be made in this paper to review current information on thermal conductivity measurement of oxide melts at high temperature above 1000 K. Thus, this review is primarily concerned with the several methods for determining thermal conductivity of high temperature melts including their respective merits and demerits. A new laser-flash method proposed in the early 1960's has received much attention for determining thermal conductivity of high temperature melts and is an even better technique than the conventional techniques such as the hot-wire method. Although some advantages of the laser-flash method are readily apparent, major progress has been obtained only in the last few years and new information is now available. Therefore, it will be the authors' intention to provide the principle and the new data processing for the laser-flash method, including some selected examples of its application to determining thermal conductivity of oxide melts at high temperature. The relevant significant quantities such as the radiative heat transfer coefficient are also discussed, in order to facilitate the understanding of the present status of fundamentals and the powerful link between physical constants such as the reflective index of sample material and the required formulae for determining thermal conductivity of high temperature melts by the laser-flash method.     

非线性对称平板光波导TE模色散特性的近似计算

本文利用微扰法,导出了克尔型非线性对称平板光波导TE模传播常数的近似计算公式。结果表明,本文公式得到的结果与精确结果吻合得很好。     

The influence of the behaviour of the load on the frequencies and critical loads of arches with flexibly supported ends

In this work, exact and approximate formulae for determining the lowest natural frequencies and critical loads for arches with flexibly supported ends have been obtained in three cases of load behaviour during the deformation process. The influence of the manner of loading on the frequencies and on the critical load has been shown as a function of the opening angle of the arch and the rigidity of the end supports.     

A Ubiquitous Thermal Conductivity Formula for Liquids,Polymer Glass,and Amorphous Solids

The microscopic mechanism of thermal transport in liquids and amorphous solids has been an outstanding problem for a long time.There have been several approaches to explain the thermal conductivities in these systems, for example, Bridgman's formula for simple liquids, the concept of the minimum thermal conductivity for amorphous solids, and the thermal resistance network model for amorphous polymers.Here, we present a ubiquitous formula to calculate the thermal conductivities of liquids and amorphous solids in a unified way, and compare it with previous ones.The calculated thermal conductivities using this formula without fitting parameters are in excellent agreement with the experimental data.Our formula not only provides a detailed microscopic mechanism of heat transfer in these systems, but also resolves the discrepancies between existing formulae and experimental data.     

热电发电机驱动热电制冷机联合系统最优性能

用非平衡热力学与有限时间热力学相结合的方法,考虑装置内部的Seebeck效应、Peltier效应、焦耳热效应、傅立叶效应及装置与热源间传热损失,建立了牛顿传热规律下热电发电机驱动热电制冷机联合系统的有限时间热力学模型,得到装置制冷率和制冷系数的解析式.在装置热电单元总数和换热器总换热面积一定的条件下,优化热电单元和换热面积的分配,获得装置的最大制冷率和制冷系数,并着重分析了热电发电机高温热源温度和热电制冷机制冷空间温度对装置最优性能的影响.结果表明,优化可以有效地提高装置制冷率和制冷系数,增大装置极限制冷温差,拓宽装置工作范围.     

Analysis of dispersion characteristics of groove guides with mode-matching method

Groove guide is widely recognized as one of the most promising millimeter wave transmission structures. In this paper, the mode-matching method is used to analyse the dispersion characteristics of single and asymmetrical double groove guides, and the unified formulae of Nth-order approximation dispersion equations are presented. Based on this analysis, a general program for calculating the dispersion characteristrics of single and asymmetrical double groove guides has been completed. Some comparisons between the results obtained by present method and published data show that very good agreement has been seen. The effectiveness and the reliability of the given formulae and program are thus verified.     

THE ENERGY ASPECT OF THE RECIPROCAL INTERACTIONS OF PAIRS OF TWO DIFFERENT VIBRATION MODES OF A CLAMPED ANNULAR PLATE

The standardized mutual active and reactive sound power of a clamped plate, representing the energy aspect of the reciprocal interactions of two different in vacuo modes, has been computed. It was assumed that the vibrations are axisymmetric, elastic and time harmonic, the plate's transverse deflection is small as compared with the plate's size, and that the vibration velocity is small as compared with the acoustic wavenumber generated. The Kirchhoff-Love theory of a perfectly elastic plate was used. The integral formulae for the mutual sound power were transformed into their Hankel representations which made possible their subsequent computation. A closed path integral was used to express the integral in its Hankel representation to compute the mutual active sound power. The asymptotic stationary phase method was used to compute the two magnitudes, i.e., the mutual active and reactive sound power. The results obtained are the asymptotic formulae valid for the acoustically fast waves. The oscillating as well as the non-oscillating terms have been identified in the formulae to make possible their further separate analysis. The availability of the asymptotic formulae makes possible some fast numerical computations of the mutual sound power. Moreover, the formulae presented herein, together with those for the individual modes known from the literature, make a complete basis for further computations of the total sound power of the plate's damped and forced vibrations in fluid.     

半导体器件HPM损伤脉宽效应机理分析

 HPM能量在半导体器件损伤缺陷区的热量沉积以及向周围材料的热量扩散,是造成半导体器件损伤脉宽效应的机理;分别得到了全脉宽段、长脉宽段和短脉宽段的损伤经验公式,该损伤经验公式能较好地对实验和理论模拟效应数据进行拟合。     

Importance of the kinetic-energy expression for a bound electron in classical theory

Electron-impact ionization cross-sections of alkali-metal atoms and noble-gas atoms have been calculated using Gryzinski's, Vriens' and Burgess' formulae. The kinetic energy of the bound electron has been estimated by using Slater's rule. Comparisons have been made with experimental results.     

Prediction of total loss factors of structures,I: Theory and experiments

A method for calculating the total loss factors of a complex structure has been derived by using Statistical Energy Analysis (SEA). The derived formulae have been simplified on the assumption that coupling between substructures except for the measured substructure is very weak. In two limiting situations, “damping addition” formulae have been obtained. The formula has been applied to predict the total loss factors of a steel box and these results are compared with actual experimental measurements. The agreement between estimated and measured values was in most cases quite good.     

NMR spin-lattice relaxation time T1 calculation for molecular reorientation through inequivalent potential barriers in the case of n-fold (n = 2, 3, 4, 6) symmetry axis

It has been shown that if reorientational jumps of molecules or their parts take place through inequivalent potential barriers, it is possible to draw information on the multiplicity of the axis of reorientation from the spin-lattice T ₁ time measurements in the NMR experiment. For the model of n potential wells of which one is deeper than the others, for n = 2, 3, 4, 6 the analytical formulae have been derived for the T ₁ relaxation time as a function of the correlation time and n. The recurrent form of the formulae for the conditional probability of the well population has been obtained, which permits calculation of the relaxation time for any n.     

Thermodynamic coefficients of ideal Fermi gas

We present analytical formulae for the first and second derivatives of the Helmholtz free energy of non-relativistic ideal Fermi gas. Important thermodynamic quantities such as heat capacity, sound velocity, heat capacity ratio, and others are explicitly expressed through the derivatives. We demonstrate correct ideal Boltzmann gas and low-temperature Fermi gas asymptotes and derive corrections to thermodynamic functions for these limiting cases. Numerical computations of thermodynamic properties of ideal Fermi gas can be accurately performed using the developed freely available Python module ifg .     

Determination of the refractive index of fibres using the modified area method: I. Homogeneous fibres

The mathematical formulae for determining the mean refractive indices and birefringence of homogeneous fibres are modified. This modification depends on calculating the area under the fringe shift and cross-sectional area of homogeneous fibres having nearly circular cross-sectional area taking the refraction of the incident light beam by the fibre into consideration. The mathematical analysis for two-beam and multiple-beam interferometric techniques is dealt with. These formulae are applied to polypropylene fibres with draw ratios of 3.5 and 4 using the two techniques. A comparison between the results when using the new formulae and when neglecting the refraction has been studied. The diffraction of a He–Ne laser beam is used for determining the shape of the cross-sectional area of these fibres. Microinterferograms are given for illustration.