氩气微槽道焦-汤效应制冷器实验研究

汉普逊型J-T效应制冷器结构不紧凑,其支撑芯轴占据较大空间,换热效率低。为提高其换热性能,将换热效率高的微槽道技术应用于J-T效应制冷器,设计出一种新型的多层微槽道J-T效应制冷器试件,并搭建实验台对其进行性能测试与分析。实验以进口温度7.5℃和10.5℃,进口压力4 MPa至8 MPa的氩气为冷源,对各测点的温度进行采集,并完成冷端温度的性能测试与分析。实验表明,在相同的进气温度下,随着进气压力增高,冷端温度降低,在进气温度为10.5℃、压力为8MPa时冷端温度最低可达-41.1℃。同时,在相同的进气压力下,冷端温度随进气温度的降低而降低,在进气压力7 MPa下,进口温度7.5℃比10.5℃的冷端温度低6.1℃。     

基于正交试验的JT节流制冷器换热器热力性能研究

J-T节流制冷器在红外制导领域有着广泛的应用,针对以氩气为工质的Hampson型J-T节流制冷器,建立了稳态数理模型,并采用正交设计试验法研究了肋高、肋间距以及肋厚对J-T节流制冷器换热器热力性能的影响。通过极差分析的方法研究了各因素影响换热器换热量和效能的主次顺序,以及各因素水平变化对试验指标的影响,得到了使两项指标最优的各因素水平组合。与原尺寸对比,优化后换热器的换热量提升了7.31%,效能提升了5.77%,为J-T节流制冷器的优化提供了新的思路和方法。     

氮气多层微槽道J-T效应制冷器性能实验研究

本文将多层矩形微槽道与焦汤制冷器两种结构结合制作了多层微槽道J-T效应制冷器,回热段设置高低压矩形通道各三层交叉叠放。以氮气为制冷剂,采集其在多层微槽道J-T节流制冷器各测点温度,分析氮气在制冷系统各阶段的降温特性,对比氮气与氩气在微槽道J-T效应制冷器中的实验结果。结果表明:当进口压力为4~8 MPa时,随着压力的增大,氮气冷端温度越低,达到稳定冷端温度的时间越短;当进口压力为8 MPa时,氮气冷端在200 s左右趋于稳定温度约1.7℃;在相同进口压力下,氩气冷端温度低于氮气,但氮气达到冷端温度的时间比氩气更短;进口压力为7 MPa时,氮气冷端温度稳定时间比氩气提前约450 s;进口压力8 MPa的氮气与4~5 MPa的氩气温降相近,且氮气的降温时间更短,可以考虑用氮气代替氩气以减少制冷成本。     

微型压缩机驱动的微型混合工质J-T制冷器实验研究

为研究微型混合工质节流制冷器的降温性能,搭建了微型压缩机驱动微型混合工质节流制冷器的制冷系统,并得到了初步实验研究结果。采用Aspen微型压缩机驱动微型J-T节流制冷器,应用混合制冷剂实现深度制冷。微型J-T节流制冷器采用微小通径的不锈钢毛细管制作,其通道特征尺寸为0.3mm。初步实验表明,微型J-T节流制冷器达到了180K温区。由于采用微型压缩机驱动,系统结构紧凑,可在便携生物储存设备、低温医疗以及电子器件冷却等领域应用。     

一种复合制冷系统的空间使用可行性分析

半导体制冷器由于材料限制,主要应用于２００ Ｋ 左右的中低温领域。通过低温热管将半导体制冷器热端与辐射制冷器相连,使其热量直接辐射到宇宙空间中,维持２００ Ｋ 温度,将可能使冷端达到接近１００ Ｋ 的空间实用化低温。作者将对这种半导体制冷器／ 热管／ 辐射制冷器的复合制冷系统空间使用的可行性作出简单分析。     

一种空间复合制冷系统的可行性分析--半导体制冷器/热管/辐射制冷器

半导体制冷器由于材料限制,主要应用于２００Ｋ左右的中低温领域。通过低温热管相连,利用辐射制冷器冷却半导体制冷器热端,将其热量直接辐射到宇宙空间中,使其维持在２００Ｋ温度,将可能使冷端达到接近１００Ｋ的空间实用化低温。对这种半导体制冷器／辐射制冷器的复合制冷系统,空间使用的可行性做出简单分析。     

微小型焦-汤效应节流制冷器发展与研究

本文综述了微小型焦耳-汤姆逊(J-T)效应节流制冷器近年来的发展情况,从制冷器的结构型式演变以及理论研究两方面对现有技术和研究成果进行了总结,在分析有关文献的基础上对微小型J-T效应节流制冷器的发展方向做了进一步的展望。随着应用领域的拓展及加工工艺的进步,制冷器的结构型式越来越趋于小型化、多样化,借助微刻蚀技术制作的多级、多层、多通道微小型J-T节流效应制冷器具有很大的发展空间;在理论研究方面,由于微小型J-T节流制冷器的运行机理较复杂,目前的理论模型多是基于不同程度的假设,因此,对于微小型J-T效应节流制冷器的理论研究,不仅需建立并求解更切实际的理论模型,还需关注与及时应用相关的基础研究成果。     

液氦温区小型节流制冷机发展现状及趋势

随着国际空间与地面制冷技术的不断发展,对液氦温区甚至超流氦温区的冷环境需求场合越来越广.针对目前国外在深低温超小型节流制冷器方面的研究已经开展并取得可观成果,介绍了有关J-T节流的原理、J-T节流制冷机的结构等有关知识,概述了当前国外10 K以下温区J-T节流制冷机的应用情况,对液氦温区J-T节流制冷机的发展前景进行了...     

不同节距肋片管节流制冷器启动时间的研究

节流制冷器的启动属于非稳态过程,目前的仿真计算仍然存在较大的误差。通过建立不同节距肋片管节流制冷器的实验模型,验证对节流制冷器启动时间的影响。实验结果表明,肋片管换热器翅片节距的变化,对节流制冷器的启动时间影响较大,该影响不是线性关系存在拐点。在设计模型时,肋片管的最佳节距为0.2 mm,该研究对J-T制冷器的设计有指导意义。     

高压氩气节流型低温探针的实验研究

设计制作了直径5 mm的基于高压氩气节流制冷的低温探针,并通过实验测试了探针的冷冻性能。在进气压力20 MPa时,1 min内探针尖端在296.3 K空气中最低温度可以达到112.9 K。在进气压力18 MPa时,探针在291 K的水中5 min内能够形成尺寸4.9×2.8 cm的椭圆形冰球。预冷进气使温度从290.4 K降到274.3 K,能够使探头冷量输出增加约24%。     

多元混合物节流制冷工质最佳配比计算

混合物作为节流工质能大大提高制冷机的热力性能。然而即使采用相同组元组成的混合物在配比不同的情况下,节流制冷机的性能也会不同。报道了针对应用于Ｊ－Ｔ节流制冷机的混合物工质配比的优化计算。以热力学完善度为目标函数,采用复合形优化算法,设计了一套混合物最佳配比优化计算程序。计算结果对实际混合物制冷循环设计有一定指导意义。     

120 K～150 K温区混合工质内复叠节流制冷机的实验研究

混合工质节流制冷机在许多方面获得越来越广泛的应用,本文提出了利用内复叠节流制冷系统获得120K－150K温区的制冷方安分析了它的应用前景,建立了相应的单级油润滑制冷压缩驱动的实验系统。无热负荷时最低温度达到112K,在130K时获得了60W的制冷量,135K时获得了74W的制冷量。     

一种快速降温的J-T制冷器

介绍了一种快速降温Ｊ－Ｔ制冷器的工作流程和试验。采用预冷及锥形换热结构,氮气工作制冷温度７８Ｋ,制冷量为３５０－ｍＷ,降温时间２ｓ。     

Joule-Thomson cryocooler for space applications

A J-T cryocooler is being developed for space applications. It is under laboratory testing and will be flight-tested aboard the Space Shuttle in middle to late 1997. A seal-ability study confirmed that the EDM design is robust and can accommodate a wide range of heat loads while maintaining the development heritage.     

Estimation of performance of a J-T refrigerators operating with nitrogen-hydrocarbon mixtures and a coiled tubes-in-tube heat exchanger

The exergy efficiency of Joule-Thomson (J-T) refrigerators operating with mixtures (MRC systems) strongly depends on the choice of refrigerant mixture and the performance of the heat exchanger used. Helically coiled, multiple tubes-in-tube heat exchangers with an effectiveness of over 96% are widely used in these types of systems. All the current studies focus only on the different heat transfer correlations and the uncertainty in predicting performance of the heat exchanger alone. The main focus of this work is to estimate the uncertainty in cooling capacity when the homogenous model is used by comparing the theoretical and experimental studies. The comparisons have been extended to some two-phase models present in the literature as well.Experiments have been carried out on a J-T refrigerator at a fixed heat load of 10 W with different nitrogen-hydrocarbon mixtures in the evaporator temperature range of 100–120 K. Different heat transfer models have been used to predict the temperature profiles as well as the cooling capacity of the refrigerator. The results show that the homogenous two-phase flow model is probably the most suitable model for rating the cooling capacity of a J-T refrigerator operating with nitrogen-hydrocarbon mixtures.     

丙酮污染对微型机械制冷机性能影响的实验研究

设计微型高压阀直接向机械制冷机内在线、连续地添加污染杂质,提出了制冷机丙酮污染的强化加速实验方案,从量化角度深入研究了污染对回热式机械制冷机性能影响的规律.实验分析表明,随着丙酮添加量的增加,制冷能力首先稍微增强,然后在42 mg和121 mg时分别出现了性能衰变的拐点.在间歇性开机时还发现了制冷机污染效应的时延现象.结合传热、流阻等理论对实验规律进行了分析讨论,为机械制冷机的可靠性技术和寿命预测研究奠定了基础.     

A study on the transient characteristics of a self-regulating Joule-Thomson cryocooler

An experimental and numerical study of transient characteristics for the self-regulating Joule-Thomson (J-T) cryocooler is developed in the present work. The modelling of the bellows control mechanism and the simulation of the cooler system are developed. It is proved by experiment that the most important transient behaviours can be accurately predicted by the present numerical simulation. In order to rectify the instability problem of the bellows controlled J-T cooler, this study also proposes a revised design to improve temperature stability. The revised dual-orifice J-T cooler can effectively reduce the phenomena of unstable temperature and mass flow rate, but sacrifices the expected gas consumption rise by approximately 5 percent. Through experimental evaluation, it becomes obvious that this revised type cooler would be a better design.     

CFD analysis of a diaphragm free-piston Stirling cryocooler

This paper presents a Computational Fluid Dynamics (CFD) analysis of a novel free-piston Stirling cryocooler that uses a pair of metal diaphragms to seal and suspend the displacer. The diaphragms allow the displacer to move without rubbing or moving seals. When coupled to a metal diaphragm pressure wave generator, the system produces a complete Stirling cryocooler with no rubbing parts in the working gas space. Initial modelling of this concept using the Sage modelling tool indicated the potential for a useful cryocooler. A proof-of-concept prototype was constructed and achieved cryogenic temperatures. A second prototype was designed and constructed using the experience gained from the first. The prototype produced 29 W of cooling at 77 K and reached a no-load temperature of 56 K. The diaphragm’s large diameter and short stroke produces a significant radial component to the oscillating flow fields inside the cryocooler which were not modelled in the one-dimensional analysis tool Sage that was used to design the prototypes. Compared with standard pistons, the diaphragm geometry increases the gas-to-wall heat transfer due to the higher velocities and smaller hydraulic diameters. A Computational Fluid Dynamics (CFD) model of the cryocooler was constructed to understand the underlying fluid-dynamics and heat transfer mechanisms with the aim of further improving performance. The CFD modelling of the heat transfer in the radial flow fields created by the diaphragms shows the possibility of utilizing the flat geometry for heat transfer, reducing the need for, and the size of, expensive heat exchangers. This paper presents details of a CFD analysis used to model the flow and gas-to-wall heat transfer inside the second prototype cryocooler, including experimental validation of the CFD to produce a robust analysis.     

Performance optimization of a miniature Joule–Thomson cryocooler using numerical model

The performance of a miniature Joule–Thomson cryocooler depends on the effectiveness of the heat exchanger. The heat exchanger used in such cryocooler is Hampson-type recuperative heat exchanger. The design of the efficient heat exchanger is crucial for the optimum performance of the cryocooler.In the present work, the heat exchanger is numerically simulated for the steady state conditions and the results are validated against the experimental data available from the literature. The area correction factor is identified for the calculation of effective heat transfer area which takes into account the effect of helical geometry. In order to get an optimum performance of the cryocoolers, operating parameters like mass flow rate, pressure and design parameters like heat exchanger length, helical diameter of coil, fin dimensions, fin density have to be identified. The present work systematically addresses this aspect of design for miniature J–T cryocooler.