共查询到20条相似文献,搜索用时 203 毫秒
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声制冷机是一种新型制冷机,具有无机械运动部件,可靠性高寿命长,采用惰性气体为工质无污染等优点.驻波型热声制冷机的声功泵热效应是不可逆过程,内部不可逆损失导致热声制冷机效率偏低,制约了热声制冷机的发展和应用.本文研究了线性范围内驻波型制冷机换热器和回热器内的可压缩振荡流动与传热过程的熵产,分析了板间距,振荡频率和温度梯度对熵产的影响。 相似文献
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《工程热物理学报》2016,(3)
优化匹配出口阻抗是热声制冷机获得最佳性能的关键点之一。本文提出了一种电机调相式热声制冷机方案,它利用直线发电机提供热声制冷机高效工作所需的相位,同时回收制冷机出口膨胀功并转换成电能,提高整机效率。与现有技术相比,本方案的热声制冷机具有制冷效率较高、结构简单的优点,适用于冷量比较大、制冷温度较高、膨胀功相对较多的情形。此外,还可满足热驱动热声冷电联产的应用需求。本文基于经典热声理论,先计算分析了直线发电机入口阻抗、制冷机入口压比对制冷性能的影响。在此基础上搭建实验台进行了初步实验,在平均压力3 MPa、工作频率55 Hz下,获得了110 K制冷量158.3 W,制冷机相对卡诺效率为16.1%,将回收的电功计入后整机效率达到了31.4%。 相似文献
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简要介绍了热声制冷机的发展,特别介绍了Husam El—Gendy等人小型热声制冷机的优化的工作。结果表明:优化的高频微型热声制冷机能达到每平方厘米数百瓦的制冷功率密度,可完全用于激光制冷、电子制冷和其它需要热控制的器械。 相似文献
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Tijani ME Zeegers JC de Waele AT 《The Journal of the Acoustical Society of America》2002,112(1):128-133
The characteristic pore dimension in the stack is an important parameter in the design of thermoacoustic refrigerators. A quantitative experimental investigation into the effect of the pore dimensions on the performance of thermoacoustic devices is reported. Parallel-plate stacks with a plate spacing varying between 0.15 and 0.7 mm are manufactured and measured. The performance measurements show that a plate spacing in the stack of 0.25 mm (2.5 deltak) is optimum for the cooling power. A spacing of 0.4 mm (4 deltak) leads to the lowest temperature. The optimum spacing for the performance is about 0.3 mm (3 deltak). It is concluded that a plate spacing in the stack of about three times the penetration depth should be optimal (3 deltak) for thermoacoustic refrigeration. 相似文献
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K.W. LipsøK.K. Nielsen D.V. Christensen C.R.H. BahlK. Engelbrecht L. Theil KuhnA. Smith 《Journal of magnetism and magnetic materials》2011,323(23):3027-3032
The effect of demagnetization in a stack of gadolinium plates is determined experimentally by using spatially resolved measurements of the adiabatic temperature change due to the magnetocaloric effect. The number of plates in the stack, the spacing between them and the position of the plate on which the temperature is measured are varied. The orientation of the magnetic field is also varied. The measurements are compared to a magnetostatic model previously described. The results show that the magnetocaloric effect, due to the change in the internal field, is sensitive to the stack configuration and the orientation of the applied field. This may have significant implications for the construction of a magnetic cooling device. 相似文献
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A weakly nonlinear theory of the thermoacoustic instability in gas-filled tubes is developed in the time domain by exploiting the difference between the instability time scale and the period of standing waves. By carrying the expansion to fourth order in the perturbation parameter, explicit results for the initial growth, nonlinear evolution, and final saturation are obtained. The dependence of the saturation amplitude upon the temperature difference in the stack, the tube geometry, stack plate spacing, Prandtl number, and other parameters is illustrated. 相似文献
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Thermoacoustic engines convert heat energy into high amplitude sound waves, which is used to drive thermoacoustic refrigerator or pulse tube cryocoolers by replacing the mechanical pistons such as compressors. The increasing interest in thermoacoustic technology is of its potentiality of no exotic materials, low cost and high reliability compared to vapor compression refrigeration systems. The experimental setup has been built based on the linear thermoacoustic model and some simple design parameters. The engines produce acoustic energy at the temperature difference of 325–450 K imposed along the stack of the system. This work illustrates the influence of stack parameters such as plate thickness (PT) and plate spacing (PS) with resonator length on the performance of thermoacoustic engine, which are measured in terms of onset temperature difference, resonance frequency and pressure amplitude using air as a working fluid. The results obtained from the experiments are in good agreement with the theoretical results from DeltaEc. 相似文献
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Thermoacoustic engines are the devices that convert thermal energy into acoustic energy without moving parts. The main objective of this study is to analyze the performance of a thermoacoustic prime mover measured in terms of onset temperature difference, frequency, and pressure amplitude by varying resonator, stack length, and plate thickness. From the experiments, it is observed that onset temperature difference and pressure amplitude increases with increase in resonator and stack length with minimum plate thickness, whereas the frequency increases with decrease in resonator and stack length with higher plate thickness. The experimental results are compared with simulated results via Design Environment for Low Amplitude Thermoacoustic Energy Conversion software (Los Alamos National Laboratory, Los Alamos, New Mexico, USA). 相似文献
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Local heat transfer coefficients from a flat plate to a pair of circular air impinging jets are investigated experimentally, A pair of well-controlled, fully developed circular air impinging jets at room temperature are used in the experiments. The experimental method in this investigation is the transient liquid-crystal technique. During the experiments, the surface liquid-crystal color distribution of the test plate is recorded using a video imaging acquisition system, and the color information is translated into a surface temperature distribution through a digital color image processing unit. Local heat transfer coefficients art obtained using a surface transient heat conduction analysis. The flow Reynolds number of the jet is kept at 23,000. The jet-to-plate distance and the jet-to-jet spacing are varied in the experiment. Detailed radial heat transfer distributions at different radial directions are obtained and analyzed for L/D = 2, 4, 6, 8, and 10. The effect of jet spacing distance (S/D =1.75, 3.5,5.25, 7.0) is analyzed by comparing to data obtained from a single jet with similar flow configurations. 相似文献
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As a basic form of the equivalent source method (ESM) that is used to nearfield acoustical holography (NAH) problems, discrete monopoles are utilized to represent the sound field of interest. When setting up the virtual source distribution, it is vital to maintain a "retreat distance" between the virtual sources and the actual source surface such that reconstruction would not suffer from singularity problems. However, one cannot increase the distance without bound because of the ill-posedness inherent in the reconstruction process with large distance. In prior research, 1-2 times lattice spacing, or the inter-element distance of microphones, is generally recommended as retreat distance in using the ESM-based NAH. While this rule has shown to yield good results in many cases, the optimal choice is a complicated issue that depends on frequency, geometry of the physical source, content of evanescent waves, distribution of sensors and virtual sources, etc. This paper deals about attaining the best compromise between the reconstruction errors induced by the point source singularity; the reconstruction ill-posedness is an interesting problem in its own right. The paper revisits this issue, with the aid of an optimization algorithm based on the golden section search and parabolic interpolation. Numerical simulations were conducted for a baffled planar piston source and a spherically baffled piston source. The results revealed that the retreat distance appropriate for the ESM ranged from 0.4 to 0.5 times the spacing for the planar piston, while from 0.8 to 1.7 times average spacing for the spherical piston. Experiments carried out for a vibrating aluminum plate also revealed that the retreat distance with 0.5 times the spacing yielded better reconstructed velocity than those with 1/20 and 1 times the spacing. 相似文献
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Lin TR 《The Journal of the Acoustical Society of America》2008,123(2):729-737
An analytical solution is presented in this paper to investigate the control mechanism and modal characteristics of finite periodic and irregular ribbed plates. Peak responses of a finite periodic ribbed plate were examined where they were grouped into two sets of propagation zones according to the coupling mechanism at beam/plate interfaces. Details of modal characteristics in pass bands of the periodic ribbed plate were elucidated and the control mechanism was discussed. Modes in each pass band that are governed by shear force couplings were characterized by one of the beam flexural modes whose modal responses could be represented approximately by those of the corresponding orthotropic plate modes. Modes in the second set of pass bands were found to retain the resonance frequencies of the corresponding modes of the unribbed base plate. Higher order orthotropic plate modes were also identified, which could not be grouped into any pass bands defined by the classical periodic theory. The control mechanism leading to vibration confinement in disordered and irregular ribbed plates was also discussed. It was found that beam spacing irregularity attributes to localization of the group of modes associated with flexural wave couplings but not the group of modes associated with moment couplings. 相似文献
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The flow field and the energy transport near thermoacoustic couples are simulated using a 2D full Navier-Stokes solver. The thermoacoustic couple plate is maintained at a constant temperature; plate lengths, which are "short" and "long" compared with the particle displacement lengths of the acoustic standing waves, are tested. Also investigated are the effects of plate spacing and the amplitude of the standing wave. Results are examined in the form of energy vectors, particle paths, and overall entropy generation rates. These show that a net heat-pumping effect appears only near the edges of thermoacoustic couple plates, within about a particle displacement distance from the ends. A heat-pumping effect can be seen even on the shortest plates tested when the plate spacing exceeds the thermal penetration depth. It is observed that energy dissipation near the plate increases quadratically as the plate spacing is reduced. The results also indicate that there may be a larger scale vortical motion outside the plates which disappears as the plate spacing is reduced. 相似文献