四热源吸收式制冷机的传热面积优化

本文提出了一种不可逆的四热源四温度位吸收式制冷机模型，研究其最佳制冷率，性能系数和传热面积之间的优化关系，并进行了讨论，获得了一些有意义的新结论；可以为四热源吸收式制冷机的优化设计和最佳运行工况的选择提供理论指导．     

电动声源热声致冷机声学和计算实例

我们将各种热声致机简化为一包括声学终端在内的声管道系统，并通过实例讨论了致冷机的声学特性，该管道系统与一般声管道不同：１．在热声堆中热波和粘滞波不可不计。２．在热声堆与声管连接时，必需考虑合成波的体积流；而热声堆内只需考虑传播波的体积流。本文对此提出了阻抗连接条件的修正。实例使用电动扬声器为声源，给出了热声行波和驻波致冷的声学计算方法以及它们的声学特性，所用扬声器的标称伏安为１００ＶＡ，可为热声致     

Transition edge sensor system for material analysis using transmission electron microscope

We have developed a Transition Edge Sensor (TES) – Energy Dispersive Spectroscopy (EDS) for Transmission Electron Microscope (TEM) based on a dilution refrigerator. The dilution refrigerator was cooled by liquid helium (L-He), which was supplied from an L-He container separated from the dilution refrigerator. We adopted the hybrid magnetic shields combining a permalloy shield and a NbTi/Nb/Cu superconducting shield to operate the TEM–TES system under a magnetic field of 200 mT. The permalloy shield was used to prevent the ambient magnetic field until the NbTi superconducting shield cooled from room temperature (RT) to 2 K. The critical magnetic field was 220 mT for the TES change from a superconducting state to a normal state. The SQUID – current vs. bias current curve, under the condition that the snout was inserted in the TEM, was equal to the curve of the snout that was out of the TEM. The C (0 0 2) planes could be observed at 120 kV under the condition the snout was inserted in the TEM.     

Acoustic pressure losses in woven screen regenerators

In thermoacoustic travelling-wave engines and other Stirling cycle devices, good performance depends on the material of a regenerator being in intimate contact with the gas inside it, so that each particle of gas oscillates in temperature following the adjacent material as it is acoustically displaced. This requires that the passages are small enough for temperature waves to penetrate across the gas path with the frequencies of interest. One type of ‘regenerator’ that is commonly used for this purpose is composed of multiple layers of woven stainless steel mesh, laid on top of one another in random registration. Associated with the thermal penetration is a viscous loss of pressure and this must be quantified if efficient engines are to be designed.In the literature, reliance has been placed on the correlation of steady-flow loss data for these meshes, but for the coarser ones operating at frequencies greater than 28 Hz, the assumption of quasi steady-flow is dubious and direct acoustic measurements must be made. This paper reports acoustic pressure loss data for meshes with 34 and 75 wires per inch taken in two configurations of impedance tube, and finds that the dependence on velocity is the same as in steady-flow, but that there is indeed some enhancement of loss for frequencies above 40 Hz. (Separation of the mesh layers is probably responsible for the anomalously low loss coefficients that were recorded in one set of data.) It is shown that the acoustic pressure losses can be correlated in terms that give the acoustic impedance more directly than the friction factor correlations.     

蓄冷器空体积对脉冲管制冷机性能的影响

基于理想气体与蓄冷器的假设,运用热力学第一、二定律对蓄冷器进行热力学分析,研究工质温度在蓄冷器单元内的变化,以及脉管制冷机运行频率对工质温度的影响,并运用Matlab软件,对蓄冷器单元内温度进行模拟。研究表明:对于理想蓄冷器,同等压力波幅下,增大频率和蓄冷器空体积,都会增大气体的温度波动幅值。     

斯特林制冷机间隙密封冷量损失实验研究

传统的斯特林制冷机回热器使用接触式滑动密封,存在磨损,限制斯特林制冷机的使用寿命。间隙密封的应用则可以在完成密封作用的同时消除接触磨损和因此而产生的污染。但由于间隙内气体的泄漏,引起了冷量损失,使制冷量减少。设计了一套模拟实验装置,通过实验验证了回热器与气缸壁间隙内气体泄漏率及泄漏引起的冷量损失理论分析的正确性。     

直线压缩机驱动热声型低温热声制冷机研究

直线压缩机驱动的热声型低温热声制冷机是获得低温的一种重要制冷技术,它利用直线压缩机往复运动产生的声波驱动脉管产生热声制冷效应而工作。文中报道了由中国科学院理化所和深圳市中科力函热声技术工程研究中心联合研制的系列液氮温区低温热声制冷机,其效率达到22%,为目前国际上所有公开报道的各类热声制冷机中的最高效率。该系列低温热声制冷机在低温下无运动部件、可靠性高,在红外探测器、高温超导滤波器等低温电子器件冷却方面具有重要应用前景。此外,还将对下一步的研究进行简单的介绍。     

Thermoacoustic oscillations in ducted domestic heating systems

Thermoacoustic oscillation is a significant problem in ducted domestic heating systems fitted with fully premixing burners as well as in combustion systems of industrial scale. This paper reports experiments using a burner closely representative of practical designs in which high-intensity free-field sound has been used to simulate the feedback which may be excited naturally in installations with different acoustic properties. This experimental approach facilitates study of the non-linear response of the burner/flame sub-system to feedback of different frequencies and direct measurement of the acoustic impedance of the burner under operational conditions. A function proportional to the Rayleigh integral has been evaluated directly from the experimental results. It is found that the head of this type of burner divides the typical installation into a quarter-wave tube and a Helmholtz resonator which must couple unstably for thermoacoustic oscillations to be autoexciting. It is further found that there is a strong interaction between the acoustic field and the mean flow which modifies significantly the behaviour of the burner as a Helmholtz resonator and thus the stability of the whole system.     

脉冲管制冷机蓄冷器的热力学循环数值分析

脉冲管制冷机内部工质气体热力学循环是理解脉冲管制冷机制冷机理的一个重要方面。本文采用拉格朗日方法对制冷机蓄冷器内部气体微团热力学循环进行了数值统计分析,结果表明,对于变频率和充气压力工况,蓄冷器内单位质量气体单位时间内循环换热量和制冷机能达到的最低制冷温度紧密相关。