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首页> 外文学位 >Fabrication, assembly, and characterization of a hollow-core fiber-based micro cryogenic cooler.
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Fabrication, assembly, and characterization of a hollow-core fiber-based micro cryogenic cooler.

机译：基于中空纤维的微型低温冷却器的制造，组装和表征。

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摘要

One of the world smallest Joule-Thomson (JT) micro cryogenic cooler (MCC) aimed at cooling low power-consumption electronics or high temperature superconductors, is demonstrated. The MCC is composed of a hollow-core fiber-based micro heat exchanger (HX) and silicon micro machined JT expansion valve. The heat exchanger is 25 mm long and 0.61 mm in outer diameter, with six hollow-core fibers of 125 mum O.D./76 mum I.D. bundled internally; the cold head is built with a stack of 2 mm square silicon chip.;To fabricate and assemble the MCC, a controlled etching process has been established to fabricate a multi-layer silicon structure for a heat exchanger-to-cold head assembly. Metals are selectively coated on the silicon structure and ends of fibers to facilitate fluxless solder jointing and bonding process to avoid adhesives clogging in the micro channels. One of the main features of the assembly was the 700 nm gap between the silicon structure and a glass cover; the gap was the expansion valve for the cooler. Another feature was the hermetic coupling for the high and low pressure (e.g. 16:1 atm ratio) micro-fluidic channels using 6 hollow fibers enclosed by a glass capillary tube. The capillary tube was covered by a segmental metal coating for minimizing radiation and conduction heat leakage from the room temperature surrounding to the cooler. The heat exchanger-to-cold head assembly was connected to an existing macro-scaled compressor through a coupler, which consisted of three micro-machined silicon structures bonded by a self-patterned SU8 film.;To achieve the temperature at which we aimed, and to provide required refrigeration power, the MCC is well thermally isolated to minimize heat loads from the environment. Thermal isolation analysis, designs, and measurements of MCCs are investigated. In a 77 K cold head under a 300 K shielding temperature, the glass capillary based test vehicle, the hollow-core fiber-based MCC with segmental low emissivity metal coating, and the hollow-core fiber-based MCC without segmental coating enclosed by an enhanced low emissivity shielding are tested to achieve a heat leak of 5.1 mW, 9.6 mW, and 3.8 mW, respectively. By cooling the enhanced low emissivity shielding to 240 K from 300 K, the MCC without metal coating reached a heat leak of 1.9 mW, and a thermal isolation up to 85,000 K/W is achieved. The enhanced low emissivity shielding has been proven to provide a better thermal isolation by reducing the radiation around the cold head and minimize the conduction by avoiding metal coatings on the heat exchanger.;Two different optimized mixed refrigerants (three-component mixture and five-component mixture) are designed to enhance the efficiency in the MCC, to minimize required flow and pressure ratio. With 1.6:0.087 MPa pressure ratio and 38 mumol/s flow, the cold head achieved a 112 K temperature by using three-component mixture. With 1.4:0.07 MPa and 11 imol/s flow, a 140 K stable temperature is achieved by using five-component mixture. A 76 K temperature in transient can also be observed in the five-component mixture cooling. In this thesis, the concept, designs, fabrication, assembly and test results are reported and discussed in detail.
机译：演示了世界上最小的焦耳-汤姆森（JT）微型低温冷却器（MCC），该冷却器旨在冷却低功耗电子设备或高温超导体。 MCC由空心纤维基微型热交换器（HX）和硅微加工JT膨胀阀组成。热交换器的长度为25毫米，外径为0.61毫米，带有六根外径为125毫米/内径为76毫米的空心纤维。内部捆绑；冷头由2平方毫米的硅芯片堆叠构成；要制造和组装MCC，已经建立了可控的蚀刻工艺，以制造用于热交换器至冷头组件的多层硅结构。将金属选择性地涂覆在硅结构和纤维末端上，以促进无助焊剂的焊接和粘合过程，从而避免粘合剂堵塞微通道。该组件的主要特征之一是硅结构和玻璃盖之间的700 nm间隙；间隙是冷却器的膨胀阀。另一个功能是使用玻璃毛细管包围的6条空心纤维对高压和低压（例如16：1 atm比）微流体通道进行气密耦合。毛细管上覆盖有分段金属涂层，以最大程度地减少从室温到冷却器的辐射和传导热泄漏。热交换器-冷头组件通过耦合器连接到现有的大型压缩机，该耦合器由三个微加工的硅结构组成，这些结构通过自图案化的SU8膜粘结在一起；为了达到目标温度，为了提供所需的制冷功率，MCC进行了良好的热隔离，以最大程度地降低环境的热负荷。对MCC的热隔离分析，设计和测量进行了研究。在屏蔽温度为300 K的77 K冷头中，玻璃毛细管基测试车，带有分段低辐射率金属涂层的中空纤维基MCC和不带有分段涂层的中空纤维基MCC被外壳包围经过测试的增强型低辐射屏蔽层分别实现了5.1 mW，9.6 mW和3.8 mW的热泄漏。通过将增强的低发射率屏蔽从300 K冷却到240 K，无金属涂层的MCC的热泄漏达到1.9 mW，并且达到了85,000 K / W的热隔离。事实证明，增强的低发射率屏蔽层可通过减少冷头周围的辐射来提供更好的热隔离，并通过避免在热交换器上形成金属涂层来最大程度地减少热传导。两种不同的优化混合制冷剂（三组分混合物和五组分混合物）混合物）旨在提高MCC的效率，以最小化所需的流量和压力比。在1.6：0.087 MPa的压力比和38 mumol / s的流量下，冷头通过使用三组分混合物达到112 K的温度。在1.4：0.07 MPa和11 imol / s的流量下，使用五组分混合物可实现140 K的稳定温度。在五组分混合物冷却中，也可以观察到瞬态温度为76K。本文对概念，设计，制造，组装和测试结果进行了报道和讨论。

著录项

  • 作者

    Lin, Mu-Hong.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Engineering Electronics and Electrical.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 210 p.
  • 总页数 210
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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