叉流再生器性能试验研究

搭建叉流再生器性能试验台,利用Celdek规整填料作为气液接触介质,再生剂选用LiCl-H2O溶液,选取再生量和再生效率作为再生性能的评价指标。试验分析空气、溶液进口参数对再生性能的影响,并利用试验数据建立适用于LiCl-H2O溶液的再生效率和传质系数的试验关联式。最后将试验结果与文献中的相关结果进行比较,结果表明:不同的再生剂对再生性能的影响基本相同;当溶液浓度较低时(LiCl-H2O溶液≤32%),使用LiCl-H2O溶液比使用LiBr-H2O溶液的再生量大,而溶液浓度较高时,情况反之。     

深度冷冻吸收制冷系统的实验研究

针对ACAR循环,设计建立了该循环的实验台,以R32 R134a/DMF作为工质,对不同配比的R32与R134a进行了一系列实验,测定了循环的制冷温度以及相关参数数据.实验结果表明ACAR循环能够在发生温度不高的情况下获得较低的蒸发温度,在利用低品位热能进行深度冷冻方面有一定潜力.     

Experimental study on mechanical behavior of laminates at low temperature

A series of tensile tests were conducted to research the mechanical behavior of the glass fiber and the carbon fiber reinforced epoxy laminates at low temperature (77 K). The specimens of laminates contained various stacking sequences (angle-ply) and notch geometry (central and edge notch). The curves of loading vs displacement of cross-head were recorded and the curves of stress-strain were got. The strengths of the various laminates were given too. Using a microscope-CCD imaging system, the growth of damage area was imaged. The concept of the energy dissipation density of laminates was presented and the data of the energy dissipation density for some laminates were got. The results showed that the strength and the energy dissipation density of laminates at 77 K are higher than those at 296 K.     

冻土试验低温恒温箱温度均匀性试验研究

冻土低温恒温箱内的温度均匀性对试验精度至关重要。为改善冻土试验低温恒温箱的温度均匀性,该文对放置试样情况下的低温恒温箱进行设有不同形式导流板的多组试验,分析试验结果表明:在低温恒温箱内放置试样会对箱内温度均匀性产生较大影响,具体表现为上热下冷、前热后冷;而在低温恒温箱内设置温度导流板可以有效提升箱内温度均匀性。通过对比分析不同形式导流板对箱体内气流流向的影响,得到一种能够强制箱体内气流在试样周围均匀分布的导流板形式。试验结果显示:该导流板能够将不同温度监测点温度差异控制在温度均值的±0.2℃以内,能够满足冻土试验的温度均匀性要求。     

脉管制冷机回热器填加紫铜丝网的影响

在回热器中加入紫铜丝网增加径向导热有利于抑制大功率脉冲管制冷机回热器中的温度不均现象,但紫铜丝网也可能对制冷机性能产生其它的影响。通过数值模拟考察了在没有温度分布不均时,不同的紫铜丝网目数、分布方式、丝网厚度等对制冷机性能的影响。结果表明,在假设回热器温度均匀的情况下,不论如何填充定量的紫铜丝网,总会引起制冷机的效率降低;如果总的紫铜丝网数量一定并且均匀地分布在回热器中,整机制冷性能不会因填充层数的不同而有明显变化;采用与回热器不锈钢丝网目数接近的紫铜丝网要比目数相差较大的丝网可以获得更好的效果。     

Comparative evaluation of erbium and lead regenerator materials for low temperature cryocoolers

A new erbium-based alloy has been tested as an environmentally benign replacement for lead in the second stage regenerator of low temperature (8-16 K) cryocoolers. This work focuses on obtaining improved performance of a Gifford-McMahon cooler by material modification in the second stage regenerator. Properties and experimental results for an improved second stage regenerator using erbium-based alloys are presented. A slight improvement in performance was observed using the erbium regenerator material over lead.     

行波热声发动机中平板与丝网回热器的对比实验研究

制作出了一个平板回热器,将其置入行波热声发动机中与丝网回热器进行对比实验研究.实验结果表明,平板回热器能够有效提高行波热声发动机的输出声功,但是其热效率有所降低.     

Heat capacity of potential regenerator ABO3 materials at low temperature

Several samples of rare-earth oxide of perovskite structure were developed and investigated between 5 and 50 K. For this purpose several samples of rare-earth magnetic materials were developed by systematically changing A- and B-sites in the general formula of a perovskite ABO₃. In this formula A is a rare-earth ion and B is a metal ion. The heat capacities of the samples were measured with the thermal relaxation method. We discussed the possibility of using these materials as regenerator material. TbCoO₃ and GdMnO₃ have demonstrated interesting results. Both materials have large specific heat between 5 and 10 K compared to other conventional regenerator materials.     

迷宫精馏型溶液除湿空调机组的试验分析

机组选用自主研发的迷宫精馏型溶液除湿（再生）器,通过改善空气流动方向,增加溶液与空气的接触时间,提高溶液的吸收能力。分别测试机组在名义除湿工况、名义制冷工况和全新风工况下的除湿能力,测试结果表明机组在全新风工况下的除湿能力最好。     

钢结构角焊缝低温抗剪疲劳性能的试验研究

为分析构件应力集中区域裂纹对磁记忆信号的影响,分别对Q345钢材有裂纹和无裂纹两类菱形缺陷试件开展逐级加载拉伸试验,采集卸载后试件表面磁记忆信号,通过ABAQUS有限元模拟得出试件卸载后等效残余应力分布,对比分析磁记忆信号分布和演变规律,提取了4个反映磁记忆信号畸变程度的特征参数。结果表明：磁记忆信号可以反映残余应力扩展的演变过程;由于裂纹的存在,磁记忆信号的分布特征会发生改变;对磁记忆信号特征参数定量分析发现,裂纹的存在不会改变磁记忆信号畸变程度随外加荷载变化的整体规律,但是磁记忆信号畸变程度和其随荷载增大的速率都会增加。

     

Experimental study of the flow rectification performance of conical diffuser valves

Flow rectification performance of conical diffuser valves has been investigated experimentally. In order to quantify the valving capability of the diffuser, a diffuser performance test cell is designed. The main feature of the test cell is that the volume change of the pumping chamber is independent of the diffuser geometry and actuation frequency. Experiments have been carried out over a range of diffuser angles varying from 10° to 35° and Roshko numbers (based on diffuser throat diameter and actuation frequency) from 25 to 300. Results show that the valving performance of the diffuser is significantly affected by the tapered angle and Roshko number. The diffuser valve with diverging angle of 10° exhibits the best performance. This is consistent with our recent simulations. The maximum flow rectification efficiency that has been attained at condition of zero backpressure is around 48%. In addition, we have simultaneously measured the time-dependent pressure inside the actuation chamber. It is found that the variations of the pressure amplitude with the Roshko number are qualitatively similar to those of the valving efficiency; high rectification efficiencies are always associated with large actuation pressures. However, for a large actuation volume, the valve performance declines, even though the actuation pressure increases. A possible explanation for this phenomenon is also provided.     

Experimental investigation on refrigeration performance of a reciprocating active magnetic regenerator of room temperature magnetic refrigeration

Room temperature magnetic refrigeration has been proved to be a feasible refrigerating technology and has a prosperous application potential. In this research, magnetocaloric effect (MCE) of metal gadolinium is measured and the metal is prepared from ingot to granular state by method of hydriding–ball milling–dehydriding. The other compound, Gd₅Si₂Ge₂ alloy, is also prepared into grains by mechanical comminuting and its magnetocaloric property is obtained. An experimental system of room temperature magnetic refrigeration is established, and three kinds of magnetic refrigerant (MR I: 0.3 mm mean diameter gadolinium particle, MR II: 0.55 mm mean diameter gadolinium particle and MR III: 0.3–0.75 mm Gd₅Si₂Ge₂ alloy particle) are employed in AMR. Performance experiments of AMR system under various temperature range, temperature span, flow rate, and flow period conditions are investigated. The results indicate that AMR adopting MR I, II, III can generate a maximum refrigerating capacity of 18.7 W, 17.8 W, and 10.3 W, respectively, under a 3 K temperature span. With the increasing temperature span, the capacity decreases. MR I and MR II have an equivalent refrigerating ability higher than MR III.     

基于并联回热器模型的大功率斯特林脉管制冷机回热器温度不均匀性研究

基于流体网络理论,建立了两个并联的回热器模型来解释回热器内温度不均匀产生机理.通过对回热器内部环流的计算,首次提出了预测回热器最大径向温差的数学模型.最后,还对回热器径向温度不均匀引起的损失进行了定量分析,并提出了抑制大功率斯特林型脉管制冷机回热器内温度不均匀的方法.     

A numerical study on the unsteady heat transfer in active regenerator with multi-layer refrigerants of rotary magnetic refrigerator near room temperature

As the temperature span(△T) of a refrigerator with an active magnetic regenerator(AMR) of single magneto-caloric material is limited, in the current investigation, the multi-layer AMR consisting of Gd and Gd_0.73Tb_0.27 is studied to improve the refrigeration performance at a larger △T with the numerical method, where the experimental magneto-caloric properties are adopted for a better precision. Effects of Gd_0.73Tb_0.27 content (φ) and fluid flowrate (q_V) on refrigeration capacity (q_ref,V) and coefficient of performance (COP), together with those of hot and cold reservoir temperatures (T_c and T_h), are investigated. Besides, temperature contours of fluid and solid matrix are presented for discussions. The present study demonstrates that compared with AMR of pure Gd, the multi-layer AMR improves the q_ref,V and COP by ～167% and 57% at △T = 28K, respectively. Moreover, it is observed that q_ref,V of multi-layer AMR has a convex variation tendency with φ, and the maximum at T_c of 268K equals 874.7 kW/m³. As a contrast, COP has two peaks, and the optimal φ is almost independent of T_c, while it decreases with a rising T_h. In addition, current investigation indicates that q_ref,V takes a lager value at a larger q_V, while a smaller q_V facilitates a good COP.     

Experimental investigation on the packed bed of rodlike particles

Rodlike particles have been usually found in industrial applications, such as the straw and needle catalyst in energy and chemical engineering. Compared to spherical particles, rodlike particles exhibit different behaviour in the packing structure due to their rotational movement. In this work, we have experimentally explored the packing structure and its friction factor for fluid flow. The porosity of packing structure generated by two packing methods is measured for four kinds of rodlike particles. The experimental results show that the porosity of bed of rodlike particles in the poured packing is not a monotonic function of the aspect ratio of particles. This is due to the competition between the “self-fitting” effect and excluded effect. The porosity of bed of rodlike particles is more sensitive to the packing method than that of spherical particles. To describe the pressure drop of fluid flow through the packing structure, the Ergun equation is further modified by introducing the modified Reynolds number and Galileo number. By combing the experimental data for packed bed generated by the fluidised packing method, and other experimental work in current literature, a new empirical equation is proposed to predict the friction factor of the packing structure of rodlike particles, in which the effects of the particle orientation and particle shape are both considered by the equivalent sphericity. These experimental results would be of interest from applied standpoints as well as revealing fundamental effects of the aspect ratio of rodlike particles on the packing structure.     

旋转填充床中合成微细晶须碳酸钙的试验研究

通过试验研究筛选出MgCl2与H3PO4两种在旋转填充床(RPB)中促使微细晶须碳酸钙合成的晶形控制剂,单因素试验探明了各晶形控制剂条件下合成微细晶须碳酸钙的较佳工艺条件,正交试验研究了各因素对粒子长径比影响的显著性.研究表明:与常重力场中合成晶须碳酸钙的方法相比,RPB产生的超重力场中合成晶须碳酸钙反应温度降低约20℃、合成等物质的量晶须碳酸钙所需时间约为其他方法的1/36～1/18、粒子短轴直径达到80～250 nm微细程度;使用MgCl2时只有反应温度对粒子长径比有显著影响,而使用H3PO4时反应温度、RPB转速和气体体积流量对产品粒子长径比均有显著影响.     

Experimental study on a new internally cooled/heated dehumidifier/regenerator of liquid desiccant systems

For providing good performance of dehumidifier and regenerator with certain dimensions, a new type of internally cooled/heated dehumidifier/regenerator based on the plate–fin heat exchanger (PFHE) was designed. To investigate the behavior of the new equipment, an experimental setup was established in an environment chamber with regulable temperature and humidity air. By the internally cooled dehumidification testing, effects of the cooling water temperature, the air flow rate and the desiccant temperature on the dehumidification performance and the cooling efficiency were presented. The behavior of internally cooled dehumidification process was compared with that of the adiabatic dehumidification process. The results suggested that the cooling efficiency decreased with the increasing of the cooling water temperature and desiccant with low temperature could bring more mass transfer coefficients. There is an optimal air flow rate to achieve the maximum absolute humidity decrease of the air. By the internally heated regeneration testing, effects of the air flow rate and the desiccant inlet temperature on the regeneration performance and air outlet parameters were discussed and also compared with those of the adiabatic regeneration process. It was concluded that the regeneration efficiency of internally heated regeneration was more than that of the adiabatic regeneration, and the internally heated regenerator could offer better thermal performance.     

低温条件下压缩机油位控制的实验研究

在低温条件下,为了保证直流变频多练空调的正常启动和运行,压缩机油池内的油位控制是非常重要的.压缩机启动控制对比实验研究结果表明,在启动阶段,延长回油平台时长以及增加回油循环和除霜循环有利于油位保持在安全油位之上.单台室内机开机启动时,相应的电子膨胀阀开度必须在350步以上,才能确保机组正常启动成功及油位安全.