面向LNG的高效大冷量串联型脉管制冷机理研究

The high reliability, large cooling capacity refrigerator technology is the key supporting approach to liquefy the natural gas. The pulse tube cryocooler technology could be a potential method that is qualified for the Liquid Natural Gas (LNG) field due to its compact, long time operating and low vibration characteristics. However, the pulse tube cryocooler has an inherent low efficiency problem owing to the fact that it does not recover the expansion work at the cold end to generate more cooling power. This project targets to develop a high cooling capacity and high efficiency pulse tube cryocooler at LNG temperature range by adding another pulse tube cooler after the first stage with a transmission tube. Also, a thermoacoustic power amplifier connects this transmission tube with the second cryocooler which aims to amplify the acoustic power delivered to the second stage. The configuration of this transmission tube with the thermoacoustic power amplifier could reuse and promote the expansion work at the cold end of first stage therefore generating more cooling capacity on the second stage. The research will focus on the following subjects: 1) Explore the thermoacoustic loss inside the acoustic power transmission tube therefore decrease the acoustic power loss and increase the useful work supplying to the second stage pulse tube cryocooler. 2) Study on the heat transfer characteristics of the micro bare tube heat exchanger as the heater in the thermoacoustic amplifier therefore discover the high thermoacoustic transition efficiency. 3) Discover the mechanism of the thermoacoustic amplifier and increase the acoustic power transferring to the second stage. The project could provide a reference for the pulse tube cryocooler working at high temperature range and the possibility of this refrigeration technology working at different temperature range.

大冷量高效可靠的低温制冷技术是液化天然气（LNG）应用中亟需解决的关键支撑技术。脉管制冷机具有可靠、长寿、低振动等优势，在LNG领域具有较大的应用潜力。然而由于脉管制冷机冷端膨胀功未回收，导致其本征制冷效率低，这一缺陷在LNG温区更加明显。本项目旨在研发面向LNG的大冷量高效的脉管制冷技术。通过串联驱动方式实现脉管冷端膨胀功的回收，并探索管式微通道换热器强化交变流换热，以及采用余热驱动的热声放大器增加系统输入声功的可行性，以此提高串联型脉管整机制冷性能。拟开展以下研究：1）揭示级间传输管的阻抗匹配和损失机制，提高声功传输效率；2）研究微通道换热器的高效传热特性，强化换热性能；3）探索热声放大器对次级声功的放大效应，将余热转化为次级声功，提高次级声功的输入性能。本项目的研制将为脉管技术在LNG温区的制冷提供借鉴，也可探索这一技术同时在不同温区制冷的可能性。

大冷量高效可靠的低温制冷技术是液化天然气（LNG）应用中亟需解决的关键支撑技术。脉管制冷机具有可靠、长寿、低振动等优势，在LNG领域具有较大的应用潜力。本项目通过减小串联式脉管制冷机的各级漏热损失，并探索圆管式微通道换热器的高效换热性能。主要研究内容包括：1. 通过对多级串联型脉管制冷机的级间传输管的阻抗匹配和损失机制，提出采用多级真空罩绝热的方法替换传统的珠光沙绝热方案，进而减小15%的漏热损失，提高6%以上的制冷量。2. 基于热力学与传热学理论，论证圆管微通道换热器的换热特性，得到了实验验证。研究提出了一种通过引入微型圆管微通道换热器作为冷凝器和蒸发器来减少制冷系统充注量的潜在方法。3. 基于已有的实验装置，测试微通道换热器的基本性能，为微通道换热器应用于串联型斯特林制冷机提供理论支撑。采用简化的ε-NTU方法预测"I型"和"N型"圆管微通道换热器的性能。改装后的微通道制冷系统最低温度为-25°C，改进系统的冷却时间为140分钟。微通道圆管蒸发器可节省88%的蒸发器制冷剂空隙体积和77%的铜材料。4 进一步验证微通道圆管换热器的换热性能。研究制冷系统中安装有圆管微通道换热器和正温系数（PTC）加热器的除霜性能。实验证明，采用微通道圆管换热器和PTC加热器组件的除霜效率为65.19%，其优于传统的除霜装置效率。5. 探索水冷型微通道圆管换热器的换热性能。设计了微通道水冷板，通过Fluent仿真，将现有市面上的水冷板与本次设计的微通道水冷板进行对比研究，表明微通道水冷板具有更好的冷却效果。