Investigation on regenerator temperature inhomogeneity in Stirling-type pulse tube cooler

Regenerator is one of the most crucial components to pulse tube cooler (PTC) and thermoacoustic engine. As such regenerator is scaled up to high-power, the thermal and hydrodynamic communication transverse to the acoustic axis gets weaker and weaker. Under this condition, any unsymmetric factor could cause serious instability to the cooler or engine, which degrades their performance. Investigation has been carried out on a high-power two-stage thermal-coupled U-shape Stirling-type PTC. By detailed circumferential temperature measurements along the middle heat exchanger and second stage regen-erator, a kind of temperature inhomogeneity caused by unsymmetric pre-cooling effect of inter-stage thermal bridge was found in the lower part of the regenerator of the PTC. The temperature inhomoge-neity originating from the middle heat exchanger of the second stage regenerator amplified itself in the lower part of the regenerator and then internal streaming formed. The maximal radial temperature dif-ference could reach 30―40 K. Experimental results show that the temperature inhomogeneity intensi-fies with increased pre-cooling power and its direction can be reversed by changing the pre-cooling effect of the first stage PTC to heating effect by using external thermal load. This research shows that it is important to maintain the heating or cooling effects of heat exchangers uniform in high-power re-generative coolers and engines.     

13 K thermally coupled two-stage Stirling-type pulse tube refrigerator

A pulse tube refrigerator (PTR), without moving com-ponents in low temperature region, occupies a number of advantages, such as simplicity, reliability, long-life, low vibration and so on. This novel refrigerator is a potential substitute for the common cryocoolers (e.g. G-M coolers and Stirling coolers), capable of cooling infrared detectors and superconductive devices and liquefying cryogenic fluids. Multi-stage PTRs have been developed to attain a cooling temperature below 20 K and to s…     

A 300 Hz high frequency thermoacoustically driven pulse tube cooler

This article introduces the latest progress of a 300 Hz thermoacousUcally driven pulse tube cooler. Based on the experience of former experiments, improvements have been made in the standing-wave engine, pulse tube cooler and their coupling mechanism. An inlet pressure ratio of 1.248 was obtained with the mean pressure and heating power of 4.13 MPa and 1760 W, respectively. A lowest no-load temperature of 69.5 K has been reached under this condition. This is the first time for thermoacoustically driven pulse tube coolers to reach the temperature below 70 K with such a high frequency.     

A heat-driven thermoacoustic cryocooler capable of reaching below liquid hydrogen temperature

A "double-gas acoustic amplifier" is introduced to couple a thermoacoustic heat engine and a two-stage pulse tube cooler in this paper. Compared with previous acoustic amplifiers, this new acoustic amplifier maintains the function of amplification for pressure amplitude. In particular, the novel acoustic amplifier with a reservoir makes it possible to install an acoustic transparent but gas blocking elastic membrane between the engine and the cooler. Thus, the engine can use nitrogen as the working gas to work at low frequency; and meanwhile, the cooler can still use helium as the working gas to maintain its high performance. With this new amplifier, the cooling temperature of a two-stage pulse tube cooler driven by an energy-focused thermoacoustic engine reached 18.7 K.     

A novel coupling configuration for thermoacoustically-driven pulse tube coolers： Acoustic amplifier

A thermoacoustically-driven pulse tube cooler has re-cently reached temperatures below 77 K[1] by modifying the resonance tube of the thermoacoustic engine and the hot end phase adjuster of the pulse tube cooler. Normally, the pulse tube cooler is directly connected with the ther-moacoustic engine so that pressure ratio available to the pulse tube cooler is limited by what the thermoacoustic engine can provide[1,2]. To obtain temperatures below 70 K, the high frequency pulse tube cooler genera…     

Performance of cryogenic regenerator with <Superscript>3</Superscript>He as working fluid

Almost all experimental and theoretical studies on regenerative cryocoolers at temperatures below 20 K mention the use of 4He as working fluid.A preliminary qualitative evaluation indicates that because of the superfluid phase transition,a working fluid of 3 He would overcome the cooling temperature limitation set by 4He.Starting with a comparison of the thermophysical properties of 3He and 4He,cryogenic regenerator simulations applied to the third/last stage of a pulse tube refrigerator,with 3He and 4He separately,were implemented to quantitatively analyze performance differences of the regenerator with respect to regenerator loss, cooling power and COP.Results conclude that 3He could significantly improve the performance of a regenerative cryocooler.     

液氦温区双级G—M制冷机循环的数值模拟分析

提出了适用于液氦温区的双级Ｇ－Ｍ制冷机的数值模拟方法．模型中考虑了实际气体性质,磁性填料的变物性,阀门的配气特性,回热器的空容积及气体和填料的耦合换热,一、二级的相互影响等因素,综合模拟了双级Ｇ－Ｍ制冷机的工作过程．计算所得的参数变化规律合理,与实验相比,计算结果比较满意．分析了主要参数对制冷性能的影响．     

前置烧焦罐式高效再生器催化裂化装置催化剂藏量稳定性分析

催化裂化装置的稳定性分析对反应再生系统操作分析、设计与控制有重要的意义，其中催化剂藏量系统的稳定是反应再生系统稳定的必要条件。对于前置烧焦罐式高效再生器催化裂化装置，由压力平衡导出了待生、再生催化剂的循环速率和二密相床至烧焦罐的催化剂内循环速率表达式。在此基础上，建立了催化剂藏量系统的动态模型及其简化的线性模型。由线性模型和控制系统稳定性理论证明，不作任何控制时催化剂藏量的稳定性是有条件的。给出了该系统的催化剂藏量稳定性判据，并用反应再生系统仿真实验验证了这一判据     

脉管制冷机的热力学第一定律和第二定律分析

采用热力学第一定律和第二定律分别对小孔型和双向进气型脉管制冷机进行了热力学分析，揭示了制冷机内部的流动和传热过程的动态特性．用数值模拟方法得到了制冷机内部各点的压力、温度、质量流率等参数的瞬时变化情况及整机的制冷系数，并得到了制冷机各部件的yōng损失及整机的yōng效率．计算结果表明：针对所研究的脉管制冷机从小孔型到双向进气型的改进使得制冷机的制冷系数从0．091提高到了0．108，yōng效率从25．04％提高到了29．95％；回热器和小孔阀是制冷机中产生yōng损失的主要部件．分析结果为脉管制冷机的进一步优化指明了改进途径．     

超高频微型脉冲管制冷机回热器优化设计

为了指导超高频回热器设计过程中运行参数的选取,基于准确度较高的回热器设计软件REGEN3.3开展了超高频1W@80K脉冲管制冷机回热器优化设计工作,总结了运行参数对于超高频回热器结构尺寸的影响。研究表明:冷端压比越高,回热器最优长度越短,直径越小;频率对回热器最优直径影响较小,进一步提高频率,回热器长度可适当变短;充气压力对回热器最优长度和直径影响均较小。最后总结出了超高频回热器运行参数选取方法,在保证回热器高效前提下进一步减小回热器尺寸,并将显著减少设计计算量。     

直管套管内超临界二氧化碳热力性能研究

为了解决气冷器内不可逆损失对换热性能的影响问题,提高直管套管式气冷器的热力性能,对超临界二氧化碳套管式气冷器内二氧化碳与冷却水之间的热量传递过程进行了研究.采用Fluent数值模拟软件与熵产分析方法,通过改变操作压力、二氧化碳质量流量及冷却水的质量流量和进口温度进行数值计算,得出气冷器中二氧化碳和冷却水沿管长的温度分布...     

相变蓄热器多温位释热特性模拟研究

针对翅片管式相变蓄热器多温位释热过程进行数值模拟,分析其多温位相变传热过程的放热特性。结果表明,蓄热器低温级相变材料温度的变化速率高于高温级相变材料温度的变化速率,这是因为蓄热器低温级制冷剂流量高于高温级制冷剂流量,且低温级制冷剂出口温度与相变材料的温差高于高温级。采用热焓法对单管蓄热器模型在第一类边界条件下的融化和凝固过程进行数值模拟,并与实验测得的数据进行对比,模拟分析蓄热器高、低温级液相率及温度变化情况,综合分析相变传热过程的蓄放热特性,为进一步优化蓄能除霜过程高、低温级能量分配提供理论基础。     

SCR废催化剂中钒和钨常温常压浸出新工艺

基于SEM-EDS，XPS，获得常温常压下SCR废催化剂二段式浸出新工艺，采用Box-Behnken试验设计(BBD)方法分段研究了各因素及其交互作用对钒和钨浸出影响，得到了最佳工艺参数，并分析了浸出机理.结果表明，采用二段式浸出工艺，各因素影响顺序为:第一阶段提钒，反应温度＞浸出时间＞浸出剂浓度;第二阶段提钨，反应温度＞浸出剂浓度＞浸出时间.第一段当NaOH浓度0.5mol·L^-1，60℃下反应10min时，钒浸出率为(61.40±0.24)%;第二段当NaOH浓度2.5mol·L^-1，90℃下反应50min时，钨浸出率为(55.73±0.22)%.废催化剂中钒以V₂O₃，VOSO₄和V₂O₅形式存在，与NaOH反应生成可溶性钒酸盐，少部分V₂O₃和V₂O₅在反应过程中生成VOSO₄后溶解.     

高效再生器催化剂循环速率的计算

提出了计算催化裂化高效再生器催化剂内循环速率的两种方法:烧焦罐底部热平衡法和稀相管压力降法.对实际工业装置标定数据进行计算表明.用热平衡法计算得到的催化剂循环比值(催化剂内循环速率与两器循环速率之比.)在10以上,不符合实际情况,主要是由于烧焦罐内存在轴向返混。实测的烧焦罐底部温度高于待生剂、再生剂和主风的混合温度.因此,推荐采用稀相管压力降法计算催化剂内循环速率.该法计算简单,结果可靠.还考察了催化剂循环比对烧焦罐再生效果的影响,提高循环比可以提高再生温度,但降低了催化剂混合时平均碳含量.总的再生效果有一最优循环比,在所考察的工业条件下为1.0～1.5.     

两级压缩高温热泵木材干燥的研究

研制出可以实现单级、双级两级压缩的木材高温热泵干燥试验装置,介绍了两级压缩木材高温热泵干燥试验装置的设备组成及工作原理,用马尾松进行了木材干燥试验.结果表明:该试验装置的节能效果显著,平均能量回收率可达28%以上;采用该装置进行的木材干燥过程中的含水率、温度、湿度变化与常规干燥趋势一致.     

斯特林制冷机性能改进的实验研究

对斯特林制冷机用于制冷温区进行了探讨，提出一种复合型的低温制冷机型式－脉管型斯特林制冷机，并从理论上分析了其制冷机理和性能，同时展开了实验研究，与单一的斯特林制冷机进行了性能对比，得出了有益的结果，脉管型斯特林制冷机用于２４５Ｋ以上温区较单一的斯特林制冷机具有优势。     

基于泛化傅里叶描述子的运动目标检测

提出了一种两层运动目标检测算法.基于普通模型的第一层检测从当前帧中粗略地分割出运动目标.第二层检测包括两部分:首先,从粗略分割和所有历史分割中提取运动目标的泛化傅里叶描述子,然后基于描述子相似性度量,从历史分割中提取和粗略分割相似程度较高的部分组成新模型,并基于新模型得到第二层检测结果.普通模型与新模型均使用概率建模方法,两层检测均使用图分割技术.实验结果表明了该方法的有效性.     

Phase-locked oscillator at 3 mm waveband using high Tc superconductor mixer mounted on pulse tube crycooler

DUE TO ITS HIGH NON-LINEARITY, JOSEPHSON JUNCTION MIXER POSSESSES THE ADVANTAGES OF HIGH HARMONIC NUMBER, HIGH CONVERSION EFFICIENCY, LOW EQUIVALENT NOISE TEMPERATURE, ETC. AS THE MIXING ELEMENT, A HIGH TEMPERATURE SUPERCONDUCTOR (HTS) JUNCTION MIXES THE …     

太阳能斯特林机热交换器动态 流阻损失数值分析

建立了太阳能斯特林机热交换器流阻损失方程,确定了其内工质流速和质量流率与转角的内在联系,开展了热交换器动态流阻损失数值计算,得到了回热器、加热器和冷却器动态流阻损失特性及其与热交换器参数的关系.研究表明:回热器、冷却器、加热器流阻功率损失比例分别为65.5%,19%和15.5%.回热器内流阻损失随丝网目数的增加而增大,随丝网孔隙率的增加而减小;冷却器内正、反向流阻损失峰值分别出现在转角100°和270°附近,且反向峰值更大;加热器内流阻损失曲线在横轴两侧不对称,正、反向峰值分别在转角144°和300°位置取得,且正向峰值大于反向峰值;同时在加热器和冷却器中,管径对流阻损失的影响均更显著.     

原料预热温度对催化裂化装置动态和定态特性的影响

利用前置烧焦罐式高效再生器催化裂化装置动态机理数学模型及其仿真软件平台,考察了原料预热温度对反应再生系统动态和定态特性的影响。在控制汽提段和二密相床藏量的条件下,当同时控制或不控制沉降器压力和反应温度时,反应再生系统是稳定的;否则是不稳定的。在控制再生器压力、沉降器压力和提升管反应器出口温度的条件下,提高原料预热温度,反应深度（以反应热表征）降低,气体、汽油和焦炭产率均下降,但柴油产率下降很少,再生剂含碳量降低。因此,应适当提高反应温度设定值,以改善产品分布。在再生器压力、沉降器压力和提升管出口温度均不被控制时,提高原料预热温度,气体、汽油和焦炭产率及反应深度变化很小。由于再生温度提高较大,再生效果得到改善。