热声制冷的实验研究

自行研制了热声驱动脉管制冷机实验台,着重研究了加热温度、平均工作压力、小孔开度、工质各类等因素对脉管制冷机性能的影响。初步实验表明,以氮、氦及氦和氩混合物（氦占94％）作工质,分别获得了234.5K、179K及165K的无负荷制冷温度,此外,本文还指出了进一步改进方向,具有一定参考价值。     

驻波型热声制冷机的搭建及理论验证

基于驻波特性和换热基本理论设计并搭建了一台驻波型热声制冷样机,并对利用压力声学和线性热声理论分析热声效应的方法分别进行了验证.系列控制变量实验表明,当扬声器的驱动电压为7 V,驱动频率为315 Hz,无量纲化的热声堆位置为0.27时,样机冷端可获得2.16 K的理想降温;且扬声器的驱动电压在测定范围内对制冷量的影响呈现明显的正相关.采用该实验装置的物理参数值,利用DeltaEC程序和线性热声学理论的计算较好地吻合了实验结果,验证了这种分析方法的可行性.     

热声制冷的研究现状

本在介绍热声制冷各研究方向的基础上，对其发展现状进行了详细的综述，并对今后的发展进行了展望。     

扬声器驱动热声制冷机的研究进展

热声制冷技术是一项新型的制冷技术,它具有运动部件少、运行可靠、振动小、寿命长、对环境无污染等优点,在航天、超导、低温电子、低温生物等众多领域有着十分广阔的应用前景。本文阐述热声制冷效应的基本原理和热声制冷循环之后,系统介绍了热声制冷机中共振管、板毪、换热器、动力源(扬声器)等部件和制冷工质的研究情况。同时,指出了扬声器驱动热声制冷存在的问题,并对热声制冷的发展进行了展望。     

热声热机场方程的改进计算

本文讨论热声热机于二种热力学媒质组成的热声变换堆内外，温度、速度和压力场所应满足的改进的场方程．以PI和dP_1／dx等作为待定参数时，速度u_1和温度T_1的解式．并讨论了解式的含意与实验结果的对照．     

热驱动室温行波热声制冷机的实验研究

本文报道了热声驱动的室温行波热声制冷机的实验研究。以氦气为工质研究了平均充气压力、工作频率等参数对制冷性能的影响。实验达到的最好结果为:最低温度为-47℃,在-20℃的制冷量为80W,按输入制冷机的P-V功计算,相应的制冷系数COP达到1.6左右。     

扬声器驱动热声制冷机设计研究

热声制冷机主要由声驱动器、共振管、板叠、高低温端换热器、声容等部件组成。它具有运动部件少、运行可靠、振动小和寿命长等优点 ,在军事、航天、微电子、低温物理等领域有着十分诱人的应用前景。文中运用经典线性热声理论对热声制冷机各个组成部件设计进行了介绍 ,在此基础上设计了一台扬声器驱动热声制冷机 ,并用专业计算软件进行了数值模拟验证 ,为热声制冷机进一步优化与发展提供了一个解决方案。     

开式循环热声制冷

早在１００多年前，欧洲的吹玻璃工匠就发现了由温度梯度驱动的声振荡现象．随着液Ｈｅ在科学实验中的广泛应用，人们又发现，当一段上端封闭、下端开口的不锈钢管插入到液Ｈｅ杜瓦瓶内时，也会有气柱的纵向振荡被激发，即所谓热声振荡．对热声现象的定性解释最早（１２０...     

基于DeltaE的驻波型热声发动机设计方法

在消化和吸收目前普遍接受的热声系统计算软件DeltaE(Design Environment for Low Amplitude Thermoacoustic Engines)的基础上,发展了驻波型热声发动机的结构设计方法;提出引入双参数评估法对发动机性能进行评估,以获取较高的热声转化效率。     

Piezo-driven thermoacoustic refrigerators with dynamic magnifiers

Thermoacoustic refrigeration is an emerging cooling technology which does not rely for in its operation on the use of any moving parts or harmful refrigerants. This technology uses acoustic waves to pump heat across a temperature gradient. The temperature gradient forms across the ends of a porous body, called the stack, enclosed in a resonator. The vast majority of thermoacoustic refrigerators to date have used electromagnetic loudspeakers to generate the acoustic input. In this paper, the design, construction, operation, and modeling of a piezo-driven thermoacoustic refrigerator are detailed. The performance of the refrigerator is significantly enhanced by coupling the acoustic driver with an elastic structure, referred to as a dynamic magnifier. Proper selection of the magnifier parameters can increase the magnitude of the pressure oscillations across the stack, and consequently the temperature difference. The magnified refrigerator demonstrates the effectiveness of piezoelectric actuation in moving 0.3 W of heat across a 10 °C temperature difference with an input power of 7 W. All the theoretical predictions are validated against data from experimental prototypes. The developed theoretical and experimental tools can serve as invaluable means for the design and testing of piezo-driven thermoacoustic refrigerator configurations.     

Theoretical and experimental investigation of onset characteristics of standing-wave thermoacoustic engines based on thermodynamic analysis

A simplified physical model for calculating the onset temperature ratio and the frequency of a standing wave thermoacoustic engine (SWTE) in the time domain is built based on thermodynamic analysis. Coefficients of transient pressure drop and heat transfer are first deduced from linear thermoacoustic theory. By numerical computation, the evolutions of the pressure amplitude and the spectrum characteristics during the onset process are presented. Furthermore, the effects of stack spacing, charge pressure, and resonator length on the onset temperature ratio and the frequency are calculated. Relatively good agreement between the computational and the experimental results has been achieved, which validates the model for calculating the onset characteristics.     

热声制冷机回热器的数值研究

以驻波型热声制冷机的回热器作为研究对象,通过对二维可压缩形式的连续性方程、N-S方程、能量方程和理想气体状态方程的数值求解,得到了热声核区域内工作介质的能流密度矢量和能量迹线云图.结果表明:在轴向方向上影响能量传递的主要因素为气体的热传导项.     

热声热机起振过程中回热器内气体的温度分布

文中研究了驻波型热声发动机回热器内的气体,研究时段为从加热到起振前的过程,对气体在此时段内建立数学模型并加以分析。通过求解该模型,得出了回热器内不同时间和位置点的温度变化,其计算结果与实验数据相吻合。最后对模型简化导致的误差进行了分析修正。     

驻波热声系统的自激振荡机理

热声发动机的起振过程是一个产生并维持自激振荡的过程, 研究热声自激振荡机理有助于进一步了解热声效应的实质. 根据热声网络理论, 建立了驻波热声发动机的整机网络. 将热声网络比拟成电网络, 利用厄米特式计算了输入热声网络的视在功流, 功流平衡对应自激, 在角频率虚部为零的情况下计算了热声发动机的阈值温度和运行频率. 结果表明, 计算值与实验值符合得较好, 充气压力与阈值温度和运行频率的耦合关系大致相同. 所得结论有助于进一步探究热声效应机理以及热声发动机系统的优化设计.     

Condensation in a steady-flow thermoacoustic refrigerator

Condensation may occur in an open-flow thermoacoustic cooler with stack temperatures below the saturation temperature of the flowing gas. In the experimental device described here the flowing gas, which is also the acoustic medium, is humid air, so the device acts as a flow-through dehumidifier. The humid air stream flows through an acoustic resonator. Sound energy generated by electrodynamic drivers produces a high-amplitude standing wave inside of the resonator, which causes cooling on a thermoacoustic stack. Condensation of water occurs as the humid air passes through the stack and is cooled below its dew point, with the condensate appearing on the walls of the stack. The dry, cool air passes out of the resonator, while the condensate is wicked away from the end of the stack. Thermoacoustic heat pumping is strongly affected by the form of the condensate inside of the stack, whether condensed mostly on the stack plates, or largely in the form of droplets in the gas stream. Two simple models of the effect of the condensate are matched to a measured stack temperature profile; the results suggest that the thermoacoustic effect of droplets inside the stack is small.     

串级热声发动机的机理分析及数值模拟

简要综述了热声发动机的发展历程,把三种典型的发动机形式作了比较分析,在此基础上,对国际上最近提出的串级型发动机进行了定性讨论,并结合一定的几何结构,运用线性热声理论对该类型热声机进行了数值模拟。     

Thermal-relaxation dissipation in thermoacoustic systems

Pressure oscillations in a sound wave are accompanied by temperature oscillations. In the presence of a solid boundary, the heat transfer from the oscillating gas to the solid boundary causes dissipation of the acoustic energy. This results in the attenuation of the sound wave. This thermal-relaxation dissipation process has a negative effect on the performance of thermoacoustic heat pumps and engines. A simple analytical model describing the interaction between an acoustic wave and a solid boundary is presented. The effect of the solid material and gas type on thermal-relaxation dissipation is analysed. The main result of this model is that the choice of a solid material with the smallest possible heat capacity per unit area in combination with a gas with the largest possible heat capacity per unit area minimises the thermal-relaxation dissipation. From the different combinations solid-gas used in the calculations, the combination cork-helium leads to the lowest thermal attenuation of the sound wave. In this case, the heat transfer from the gas to the wall less damps the temperature oscillations. However, because of the porosity of cork that may cause some problems, it is suggested that the combination polyester-helium can be used in practice to minimise the thermal-relaxation losses.