高频微型非金属脉冲管制冷机轴向导热损失的计算分析

针对所开发的高频微型同轴非金属脉冲管制冷机进行了轴向导热损失的计算与分析,并与相同几何尺寸的金属脉冲管制冷机进行了比较。仅从降低轴向导热损失的角度讲,使用低导热率的非金属材料制作制冷机部件对制冷性能有较大的积极作用。对于2台实验样机而言,通过蓄冷器和脉冲管内的气体的轴向导热损失已经超出通过各自管壁的轴向导热而成为最大的导热损失项,但通过蓄冷填料的轴向导热损失却成为三项损失中一个可以忽略的小量,这是非金属脉冲管制冷机区别于相同几何尺寸的常规金属脉冲管制冷机的显著特点。     

热端温度对直线型脉冲管制冷机的影响分析

基于一台单级直线型脉冲管制冷机,研究分析了热端温度变化对制冷机性能的影响关系.建立了一维数值模型,分析了高频脉冲管制冷机内部相关热力学参数随热端温度变化的关系,从而揭示了热端温度变化影响整机性能的作用机理.最后通过实验数据和模拟值的比较研究,验证了模型的准确性.     

三级同轴型脉冲管制冷机温度分布对回热器损失影响的数值研究

采用数值模拟方法研究三级同轴脉冲管制冷机,比较分析了同截面回热器和脉冲管的温度差异,并由此研究探讨了回热器各项损失与温度分布的相关性。结果表明,同一级回热器里不同形状的蓄冷材料之间的温度梯度会有较大的变化,导致轴向导热损失的明显增加。     

同轴型脉冲管制冷机中蓄冷器与脉冲管热耦合对性能影响的研究

同轴型脉冲管制冷机的特点是蓄冷器和脉冲管共用一个不锈钢壁面形成同轴结构,这样使其在结构上最为紧凑,但同轴结构会不可避免地形成蓄冷器和脉冲管内部气体之间的热耦合。借助一台U型脉冲管制冷机对脉冲管制冷机中蓄冷器和脉冲管热耦合的形成及其影响进行了初步的实验研究和分析。通过实验研究得到了蓄冷器和脉冲管壁面轴向温度变化曲线。在此基础上进行了热耦合的实验研究,以此来考察热耦合对整机性能的影响。初步的整机性能实验结果显示这种热耦合对改善制冷机性能是有益的。     

行波型热声发动机与脉冲管配合的实验研究

采用热声发动机驱动脉冲管制冷机，使彻底消除低温制冷机中的运动部件成为可能。作者研制了行波型热声发动机驱动脉中管制冷机实验台。进行三个脉冲管与行波型热声发动机的配合实验，着重研究了热端气体温度、冷端温降和压力振幅的变化规律。     

行波型热声制冷机及混合工质的实验研究

行波型热声制冷机,因采用热声发动机驱动脉冲管制冷机,使消除低温制冷机中的运动部件成为可能.作者建立了行波型热声制冷机实验装置,采用氮气、氦气及其混合气进行了行波型热声发动机与脉冲管制冷机的配合实验,获得73.8℃的最大温降.着重研究了热端气体温度、压力振幅和冷端温降的变化规律.     

脉冲管制冷机系统Gedeon直流的损失评估

指出现有文献中对Gedeon直流损失评估的不正确性,利用建立在线性热声理论基础上的数值模型对1台微型脉冲管制冷机中的Gedeon直流损失作出分析和评估.计算结果显示,占交变质量流幅度0.1%～0.3%的直流分量即足以对制冷机效果产生严重影响.在此范围内,现有文献中的评估公式过高地估计了直流分量造成的冷量损失,尤其当直流分量小于0.1%时与实际造成的冷量损失存在量级上的差别.正方向或负方向的直流对系统的影响在一定范围内大致相当,但超出这一范围时,负方向直流(由脉冲管热端流向脉冲管冷端)的影响明显加剧.     

脉冲管制冷机内部的物理机制

在对脉冲管制冷机的内部过程进行分析之后指出：热力学非对称效应和热声效应是这种制冷机中同时存在的两种重要的物理机制,其中热端调相造成的脉冲管冷端热力学非对称效应是产生制冷效应的主要,而气体和固体相互作用产生的热声效应实现了热量的输运,两种效应综合起来决定了脉冲管制冷机的性能。     

谐振子耦合型热声驱动脉管制冷机研究

热声驱动脉管制冷机通常采用直接或者长管耦合的方式,但是因为耦合后的发动机和制冷机难以达到最佳的工作状态,耦合长管的损失也比较大,因此整体效率较低。本文提出一种热声驱动脉管制冷机结构,利用谐振子耦合热声发动机和脉管制冷机,能够显著减小声功传递损失,提升整机效率。全文针对在900 K加热温度、80 K空气液化温区下的热声驱动脉管制冷机展开理论研究,首先分析了谐振子耦合机理,并对谐振子参数进行了优化设计;其次,研究了加热温度、制冷温度和机械阻尼对系统性能影响;最后,将谐振子耦合型与长管耦合型两种方式的热声驱动制冷机进行了对比分析。结果表明:在平均压力为3MPa,加热温度为900 K,制冷温度为80 K时,谐振子耦合的热声驱动制冷机可获得整机22.5%的效率,而长管耦合的热声驱动脉管制冷机获得11.6%的效率。     

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...     

声功回收型脉管制冷机的分析与研究

对所有的回热式低温制冷机,压力小与质量流之间的相位控制是达到制冷效果的关键。在斯特林制冷机中,这一相位是由压缩活塞和冷头排出器的相对运动来提供来;而在脉管制冷机中,这一相角是由构成脉管制冷机的各个部件：回热器、换热器、脉管、小孔,气库,连管等在几何空间上的合理拓扑结构来实现达到适宜的热声网络阻抗,从而最终实现压力波与质量流之间的适配相角。脉管制冷机的这一结构上的简化及由此带来的寿命长,可靠性高等优     

A thermodynamic model based on exergy flow for analysis and optimization of pulse tube refrigerators

A thermodynamic model based on exergy flow through pulse tube refrigerators (PTRs) is developed. An exergetic efficiency parameter representing the losses in the pulse tube itself is proposed. The effects of control parameters representing a general phase shifter and their effect on the system performance are discussed. Analytical solutions representing important parameters in the design of PTRs such as the load curve, cooling power and efficiency in terms of basic system input parameters are developed. It is shown that the analytical model is powerful and convenient for optimization of PTRs and in quantifying its operational bound and important losses. Results indicating a compromise between cooling power and efficiency in PTRs under certain conditions are presented and discussed.     

Enthalpy flow rate of a pulse tube in pulse tube refrigerator

An integration formula of enthalpy flow rate along a pulse tube in pulse tube refrigerators is described on the assumption of sinusoidal mass flow rate and sinusoidal pressure fluctuation. For ideal double inlet and ideal orifice pulse tube with helium as working medium, it is simplified to a polynomial formula. Polynomial formulas for roughly evaluating the volume of the pulse tube in ideal double inlet and ideal orifice pulse tube refrigerators are also given.     

Development and experimental investigation of Stirling-type pulse tube refrigerator (PTR) below 20 K; cold compressor and colder expander

This research paper focuses on the experimental investigation of the Stirling-type pulse tube refrigerator with cold compression concept. Due to this innovative feature, the pulse tube refrigerator can reach lower temperature effectively other typical single-stage Stirling-type pulse tube refrigerators. The experiment as a proof of concept is carried out to demonstrate the capability of the pulse tube refrigerator operating between 80 K and 20 K. The cold linear compressor, which is submerged in a liquid nitrogen bath, produces cold mass flow with the efficiency of 85% for all the frequencies. At the lowest temperature part of the pulse tube refrigerator, the no-load temperature of 18.7 K is recorded and the cooling power of 0.4 W is measured at 20 K. The experimental results are analyzed in dynamic and thermal aspects by using the numerical model. The model can well explain how much losses are distributed in the system.     

Numerical method of inertance tube pulse tube refrigerator

A nodal analysis method for simulating inertance tube pulse tube refrigerators is introduced. The energy equation, continuity equation, momentum equation of gas, energy equation of solid are included in this model. Boundary condition can be easily changed to enable the numerical program calculate thermal acoustic engines, inertance tube pulse tube refrigerators, double inlet pulse tube refrigerators, and others. Implicit control volume method is used to solve these equations. In order to increase the calculation speed, the continuity equation is changed to pressure equation with ideal gas assumption, and merged with momentum equation. Then the algebraic equation group from continuity and momentum equation becomes one group. With this numerical method, an example calculation of a large scale inertance tube pulse tube refrigerator is shown.     

不可逆回热铁电斯特林制冷循环的优化分析

研究以铁电体为工质的斯特林制冷循环,探讨热阻和回热损失对其性能的影响。可为铁电制冷器的研制和设计提供些新理论指导。     

Integration of superconducting magnets with cryogen-free dilution refrigerator systems

There has been much recent research interest into “cryogen-free” dilution refrigerators. Cryogen-free systems have some advantages from a safety and convenience point of view as liquid cryogens are unnecessary. However, this also makes integrating the low-temperature system with a high magnetic field environment much more challenging. Here we shall describe recent successes of integrating superconducting magnets and dilution refrigerators into one system requiring a single pulse tube cooler. The resulting environment provides experimental temperatures between 7 mK and 30 K and magnetic fields up to 12 T. We shall describe the effects of AC loss heating in such systems on the pulse tube refrigerator when the field is ramped and also the effects of eddy current heating on the mixing chamber in sweeping fields.     

热声驱动脉管制冷机的压力特性

自行研制了热声驱动脉管制冷机实验台,着重研究了热声驱动脉管制冷机的压力特性,明确了充气压力对超振温度、加热温度、制冷温度、压比及夺力振幅等的影响,实验表明,自行研制的热声压缩机在驱动脉管制冷机的情况下,仍可获１．０７以上的压比,基本可以满足驱动无阀型脉管制冷机的需要,在最近进行的实验中,以氮和氦作工质,分别获得了１９６Ｋ和１３８Ｋ的无负荷制冷温度,此外,本文还提出了进一步的改进方向。