热声制冷中的工质选择

在分析热声工作机理，探讨混合工质在热声制冷机中的作用机理的基础上，从工作频率及效率的角度出发，指出了低Ｐｒ数的混合工质对热声效应的积极作用，有利于提高热声驱动器及热声制冷的工作效率，低声速则有利于增强热声转换强度，为选用合适的工作介质提供了依据。     

低温制冷机的最新研究进展

回顾了间壁式与回热式低温制冷机的最新进展和未来发展趋势，介绍了它们的应用，大多数应用要求较高可靠性和代成本，而空间应用更要求高效率和低重量。最新的发展包括采用气体混合工质改善Ｊ－Ｔ制冷机效率；采用挠性气体轴承来减少在压缩机和排出央的摩擦；采用吸附式压缩机和热声驱动器来取代机械压缩机和压力波发生器。     

CFC12工质替代后冰箱压缩机气阀的重新设计

以ＱＤ６７Ａ型冰箱压缩机为研究对象，从理论上分析和预测了以ＨＦＣ１５２ａ／ＨＣＦＣ２２混合工质替代ＣＦＣ１２后压缩机气阀的性能，并进行了使气阀适应替代工特征的重新设计和实验研究。研究结果表明，使用替代工质后，改进后压缩机的性能系数和制冷能力双改进前分别高出１０．３％和２１．７％。     

氦氢混合工质G-M单级脉管制冷机性能研究

对G-M型单级脉管制冷机采用氦氢混合工质在30 K温区进行实验研究,从制冷量、COP、压降特性、压缩机耗功、制冷温度的稳定性等方面进行了讨论和分析,同时给出了在最优状态下加载热负荷的温度变化情况.实验结果表明,采用适当配比的氦氢混合工质有助于提高脉管制冷性能.     

在冰箱中用混合制冷剂替代CFC12的研究

为了保护大气臭氧层,将在不远的将来禁止使用CFC12。混合工质是CFC12的替代物之一。由于混合工质的热物理性质与CFC12不同,应用混合工质后必须调整制冷系统。本文提出了调整的法则。用这一法则重新设计或重新选择了冰箱BC—132中的压缩机、冷凝器及其它一些零件,取得了良好的结果。     

R410A与R22制冷压缩机性能试验装置的对比

对制冷剂R410A与R22的热物性进行比较,并对分别以R410A和R22为工质的制冷压缩机性能试验装置进行对比分析,为建立以R410A为工质的制冷压缩机性能试验装置提供技术支持。     

混合冷剂压缩机热物性及热动力学计算

讨论了混合冷剂工质热物性,给出了其熵焓平衡计算的Newton--Raphson快速算法;同时,给出了混合冷剂压缩机整机压比分配算法。数值实验表明,该计算方法能够用于混合冷剂压缩机初步设计,且具有较高的计算效率。     

非共沸混合工质单级压缩回热循环实验研究

针对非共沸混合制冷工质单级压缩回热制冷循环,分析了LHR循环的特点及主要研究问题。根据非共沸混合制冷工质的特性,讨论并选取了适合于-70℃低温冷柜的混合制冷工质R23和R600a。利用制冷工质物性分析软件NIST Refprop 8.0初步研究了不同配比时制冷系统的特性,然后通过实验方法从不同角度分析混合制冷工质的配比对系统性能的影响,最终得到比较合理的混合制冷工质R23/R600a组分比例3:7。同时分析了该配比下制冷压缩机排气温度、压比、低温冷柜内温度等的变化特点,最后对蒸发器的温度变化特性和回热器的温度变化特性进行了总结。     

驻波型热声压缩机驱动脉管的最新结果

热声驱动脉管制冷机中由于完全无运动部件,具有运行稳定、寿命长等优点,经过对先前已经达到138K的热声驱动脉管制冷机进行系统的改进,在国内首次使该类型的制冷机进入低温温区,以氦气为工质获得了119.7K的制冷温度,这一温度已经能够液化一个大气压表压下的天然气（主要成分：甲烷）,显示出该制冷方式广阔的应用前景,此外,研究了混合工质对热声驱动脉管制冷系统性能的影响情况,并获得了117.6K的最低制冷温度。     

R417a在热泵热水系统中替代R22的实验研究

在热泵热水系统中,对新混合工质R417a进行了理论制冷循环分析和灌注式替代R22的循环性能对比试验研究,结果表明混合工质R417a的制热量稍低于R22,但性能系数COP、压缩机排气温度和功耗等循环性能指标均优于R22,实验过程中R417a工质性能稳定,运行正常,不需更换润滑油。     

冷指尺寸对超高频微型脉冲管制冷机性能的影响分析

冷指是脉冲管制冷机的重要部件,其尺寸大小决定压缩机乃至制冷机整机的尺寸,其内部的功热转换效率和损失等会对制冷机的性能产生显著的影响.为满足脉冲管制冷机微型化的需求,必须提高制冷机频率、减小冷指尺寸,而冷指尺寸的缩小又会影响制冷机的性能.为了掌握冷指尺寸对制冷机性能的影响规律,利用SAGE软件对运行频率为130 Hz,直...     

Influence of the connecting tube at the cold end in a U-shaped pulse tube cryocooler

In some special applications, the pulse tube cryocooler must be designed as U-shape; however, the connecting tube at the cold end will influence the cooling performance. Although lots of U-shape pulse tubes have been developed, the mechanism of the influence of the connecting tube on the performance has not been well demonstrated. Based on thermoacoustic theory, this paper discusses the influence of the length and diameter of the connecting tube, transition structure, flow straightener, impedance of the inertance tube, etc. on the cooling performance. Primary experiments were carried out in two in-line shape pulse tube cryocoolers to verify the analysis. The two cryocoolers shared the same regenerator, heat exchangers, inertance tube and straightener, and the pulse tube, so the influence of these components could be eliminated. With the same electric power, the pulse tube cryocooler without connecting parts obtained 31 W cooling power at 77 K; meanwhile, the other pulse tube cryocooler with the connecting parts only obtained 27 W, so the connecting tube induced more than a 12.9% decrease on the cooling performance, which agrees with the calculation quite well.     

分离型二级脉管制冷机的实验研究第一部分20～40 K温区单级大功率脉管制冷机

为了满足液氦温区分离型二级脉管制冷机第二级预冷的需要,设计制作了1台20～40K温区单级大功率脉管制冷机.采用额定功率为6 kW的压缩机驱动该制冷机,最低制冷温度达13.8K,刷新了单级脉管制冷机最低制冷温度纪录.该制冷机在40 K可获得高达55.9 W的制冷量,基本可以满足15～40 K温区超导磁体等冷却的需要.着重分析了频率、充气压力和不同压缩机对系统制冷性能的影响,测试了长时间运行中系统性能的变化情况.     

Experimental study on the design of orifice pulse tube refrigerator

An experimental study on the design of a single-stage orifice pulse tube refrigerator (OPTR) was carried out. It was shown experimentally that there exists an optimum operating frequency which increases with decreasing pulse tube volume. For a fixed pulse tube volume, increasing the pulse tube diameter will improve the performance. The experimental results are used to derive a correlation for the performance of OPTR which correlates the net cooling capacity with the operating conditions and the dimensions of the OPTR.     

Characterization of a 300 Hz thermoacoustically-driven pulse tube cooler

This article introduces our recent experimental advances on a 300 Hz pulse tube cooler driven by a thermoacoustic standing-wave engine. After some modifications on the engine, the integral system performance is improved, which leads to a better cooling performance of the high frequency pulse tube cooler compared with that in former reports. Cooling powers of the pulse tube cooler with different operating conditions have been measured in detail for the first time. So far, a lowest no-load temperature of 68 K and a maximum cooling power of 1.16 W at 80 K have been obtained with the mean pressure and the heating power being 4.1 MPa and 1 kW, respectively.     

Experimental study on the coupling characteristics of 100 Hz inertance tube pulse tube cryocooler working under optimal frequcency

Miniature pulse tube cryocooler is one of the main developing trends of pulse tube cryocooler. Four pulse tube cold fingers, two compressors and a series of inerance tube assemblies are employed to carry out the experimental investigation of coupling characteristic of miniature pulse tube cryocooler. It is concluded that the cooling performance of miniature pulse tube cryocooler is determined by the match conditions among its compressor, cold finger and inertance tube. If the three parts of cooler match well, the cold finger can achieve nearly same cooling performance under two totally different working conditions.     

Intermediate cooling from pulse tube and regenerator in a 4 K pulse tube cryocooler

This paper introduces intermediate cooling by thermally attaching heat exchangers on the second stage pulse tube and regenerator in a commercial 4 K pulse tube cryocooler. Due to the large enthalpy flow in the 2nd stage pulse tube and regenerator, both intermediate heat exchangers on the pulse tube and regenerator can provide cooling capacities in the temperature range of 5–15 K without or with minor effect on the performance of the 4 K stage. Extracting cooling capacity from the pulse tube or regenerator reduces the 1st stage cooling performance in the present study. The joint intermediate heat exchanger on the pulse tube and regenerator has demonstrated promising results for applications.     

Effects of reservoir volume on performance of pulse tube cooler

A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.     

Experimental research of high frequency tapered pulse tube cooler

Tapered pulse tube, corresponding to traditional cylinder tube, is a special design of pulse tube coolers. In this paper, different types of tapered pulse tube arrangements with different angles are tested based on our optimized high frequency PTC. Experiments show that PTCs with tapered PTCs, either to hot or cold end, degrade the performance of PTC in comparison to the cylinder tube. This paper proposes and tests for the first time CD tapered pulse tube. This special tapered pulse tube from two directions, with big diameter at two ends and small diameter in the middle, is similar to converging–diverging nozzle. It improves the performance of PTC over the optimized cylinder tube, though the improvement is only about 1–2 K in minimum temperature.     

80K脉管制冷机惯性管调相机理及优化研究

液氮温区脉冲管制冷机在高温超导等领域的应用越来越广泛。基于热声理论,本文采用Delta EC软件对纯惯性管及惯性管加气库的调相能力进行模拟研究,建立了80 K温区制冷机整机数值模型,分析了不同惯性管及气库组合方式对制冷机性能的影响。结果表明:纯惯性管结构和单段惯性管加气库两种方式可以达到较为接近的调相能力,采用双段惯性管接气库方式可以提高制冷机性能,最低温度可以达到48.8 K。最后搭建制冷机整机性能测试实验台对模拟结果进行了验证。