天空辐射制冷技术发展现状与展望

天空辐射制冷技术是指地球表面物体通过“大气窗口”波段(主要在8～13μm)向宇宙发射红外辐射以实现自身降温的过程。作为一种无需能量输入的制冷技术,天空辐射制冷可为应对能源危机及全球变暖提供一种新的思路。从发展历程看,传统的辐射制冷技术应用仅限于夜间。近年来,随着纳米光子学及超材料领域的发展,日间辐射制冷技术的优势已经得到验证。本文对天空辐射制冷技术的发展现状进行了回顾,涉及基本原理、材料与结构,分析了其潜在应用前景,并重点讨论了该技术当前研究与应用中面临的挑战。在能源形势与环境问题日益严峻的今天,探索天空辐射制冷技术在不同场景的应用,如建筑节能、减轻城市热岛效应、缓解水资源短缺、提高光伏发电效率等,有望助力我国的碳达峰、碳中和事业发展。     

空间辐射制冷技术的应用与发展

介绍了辐射制冷技术的应用历史与现状，列举了多种国外飞行任务使用的辐射制冷器的性能指标与简图，此基础上分析了当前辐射制冷技术的发展特点与趋势，提出了将来一段时期内辐射制冷技术的研究重点。     

航天器制冷机的发展概况

随着空间技术的发展，使得各种遥感仪广泛用于航天器上。如红外探测器、Ｘ射线、γ射线和亚毫米波探测器等须在低温下工作才能提高灵敏度，降低热噪声。因此，制冷系统是空间技术不可缺少的重要组成部分。目前采用的制冷系统有：被动制冷包括辐射制冷和低温制冷剂贮存系统；机械制冷机。主要介绍了空间制冷机分类、特点，在航天器上已经和即将使用的制冷机。     

几种材料的辐射制冷实验效果研究

对4种可以用于辐射制冷的化合物进行了辐射制冷效果的对比试验,并测定了其吸收比和法向发射比.结果表明,4种化合物都具有很高的辐射率,且与其辐射制冷实验结果表现出一致.首次提出CaF2用于辐射制冷,实现了制冷空间温度比环境温度低8～11℃的结果.     

航天器上的氦制冷

综合介绍了氦制冷在航天器中的应用状况。氦制冷的温度低于４Ｋ。８０年代以来，氦制冷在红外天文卫星、空间实验室、空间站、航天飞机所进行的许多与液氦温区有关的实验中得到了成功的应用。介绍了应用状况、低温系统的特性。展望了９０年代航天器中氦制冷的应用前景。     

弹热制冷技术的发展现状与展望

弹热制冷是由应力场驱动弹热材料相变而产生制冷效应的固态制冷技术,特点是无任何环境破坏作用,具有较高的理论制冷效率和制冷功率密度。近年来,欧美多个研究机构对弹热制冷技术进行了持续性研究,使该技术得到快速发展,已有多个可实际工作的弹热制冷原型机。本文从热力学理论基础、弹热工质、原型机开发和系统性能仿真等方面展开分析与讨论,为国内同行开展弹热制冷相关领域的研究提供参考。根据文献资料,现阶段弹热制冷机的制冷效率可达14%的热力完善度(外部参数),且有潜力在未来达到30%的热力完善度,从长远来看,材料层面的热力完善度可达80%,在系统层面还有较大性能提升空间。因此,可以持谨慎乐观的态度认为,弹热制冷技术在今后将得到更快、更广泛的发展和应用。     

空间环境模拟设备用G—M制冷机的研制

介绍了一台以磁性蓄冷材料Ｅｒ３Ｎｉ为第二级蓄冷器填料的大制冷功率两级Ｇ－Ｍ制冷机。该制冷机可作为空间环境模拟设备冷背景冷源，满足了辐射制冷器空间环境热模拟试验的要求。通过优化制冷机结构参数，使制冷机在转速为４０ｒ／ｍｉｎ时，二级最低制冷温度达５．５Ｋ、２０Ｋ时取得１５．４Ｗ的有效制冷量。证明了应用磁性蓄冷材料改善Ｇ－Ｍ制冷机性能的有效性。     

首个工商制冷空调设备维修行业标准--《制冷空调设备维修保养技术规范》进入征求意见阶段

随着制冷空调设备与系统在我国得到越来越广泛的应用，制冷空调产品的保有量规模也在不断扩展，但从另一方面看，随着使用年限的增加，设备和系统的老化和故障率也明显增多，市场对制冷空调设备维修保养的需求日益增加。然而，国内从事制冷空调维修的企业虽然众多，但在工商制冷空调领域，管理、技术等方面参差不齐，维修保养行业市场、技术等亟待规范。     

空间吸附制冷技术的研究进展

吸附制冷机具有工作寿命长、无运动部件、不会产生振动、可靠性较高、无电磁干扰的特点,是未来空间制冷技术中最重要的制冷技术之一.介绍了美国和欧洲空间吸附式制冷技术的发展和研究热点,结合中国深空探测对低温制冷技术的需求提出了发展空间吸附制冷技术的建议.     

日间辐射制冷材料研究进展

辐射制冷是一种备受关注的新型降温方式,该方式利用大气透明窗口(ATW)向外太空辐射传热,实现被动降温.一般日间辐射制冷材料应在8～13μm波段内具有高发射率,在太阳光谱波段吸收率低于5％.辐射制冷研究可以绿色低耗的方式为建筑节能、服饰降温、冷藏冷凝、电池降温等提供方案,有着广阔的应用前景.如何使辐射材料较好地匹配理想辐射光谱是目前最主要的问题.近年来研究者多从辐射材料结构入手,在提高8～13μm窗口波段发射率的同时,通过构建具备光子带隙或发生Mie散射的结构等方式,减少太阳辐射吸收,并取得了显著成果.通过高聚物掺杂纳米粒子、不同折射率材料堆叠等结构设计,使辐射制冷材料的红外选择性得到了显著提升.一些高聚物在8～13μm波段内具有高发射率,同时可有效隔绝体系外的热量输入.将高聚物与发射光谱互补的掺杂纳米粒子相结合,可覆盖整个目标波段,提高其制冷性能.层堆叠模式参考了光子晶体阻断特定波长电磁波传播的特性,设计了不同折射率层交替排列,在不影响高发射层向外辐射红外能量的同时降低了材料对太阳光的吸收.本文主要综述了近年日间辐射制冷材料的研究进展,按其结构形态,将前沿辐射制冷材料分为薄膜类、涂层类、织物类和块材类,并阐述了辐射制冷器在建筑、电池降温等方面的实际应用.     

空间斯特林制冷机的可靠性筛选

介绍了中国国内空间斯特林制冷机的早期失效模式及其对应的筛选试验方法,研究了长寿命制冷机的寿命筛选方法,采用温度循环为模拟应力,试验内容包括两部分:制冷机的开关机试验和连续工作试验,总试验时间约500 h.按照给定的筛选程序,可在短期内发现制冷机内部潜在的薄弱环节,诱发其早期失效,剔除不良产品,经过筛选之后的制冷机可有一个长期稳定的工作期,从而提高了制冷机的使用可靠性,推动了自研制冷机在空间任务中的应用.     

Sorption cooling: A valid extension to passive cooling

Passive cooling has shown to be a very dependable cryogenic cooling method for space missions. Several missions employ passive radiators to cool down their delicate sensor systems for many years, without consuming power, without exporting vibrations or producing electromagnetic interference. So for a number of applications, passive cooling is a good choice. At lower temperatures, the passive coolers run into limitations that prohibit accommodation on a spacecraft. The approach to this issue has been to find a technology able to supplement passive cooling for lower temperatures, which maintains as much as possible of the advantages of passive coolers.Sorption cooling employs a closed cycle Joule–Thomson expansion process to achieve the cooling effect. Sorption cells perform the compression phase in this cycle. At a low temperature and pressure, these cells adsorb the working fluid. At a higher temperature they desorb the fluid and thus produce a high-pressure flow to the expander in the cold stage. The sorption process selected for this application is of the physical type, which is completely reversible. It does not suffer from degradation as is the case with chemical sorption of, e.g., hydrogen in metal hydrides. Sorption coolers include no moving parts except for some check valves, they export neither mechanical vibrations nor electromagnetic interference, and are potentially very dependable due to their simplicity. The required cooling temperature determines the type of working fluid to be applied. Sorption coolers can be used in conjunction with passive cooling for heat rejection at different levels.This paper starts with a brief discussion on applications of passive coolers in different types of orbits and on the limitations of passive cooling for lower cooling temperatures.Next, the working principle of sorption cooling is summarized. The DARWIN mission is chosen as an example application of sorption and passive cooling and special attention is paid to the reduction of the radiator area needed by the sorption cooler.The application field of this type of sorption cooling in space missions is currently being expanded by examining the performance of alternative working fluids, suitable for different cooling temperatures.     

Northrop Grumman Aerospace Systems cryocooler overview

Mechanical long life cryocoolers are an enabling technology used to cool a wide variety of detectors in space applications. These coolers provide cooling over a range of temperatures from 2 K to 200 K, cooling powers from tens of mW to tens of watts. Typical applications are missile warning, Earth and climate sciences, astronomy and cryogenic propellant management. Northrop Grumman Aerospace Systems (NGAS) has delivered many of the US flight cooler systems and has 12 long life pulse tube and Stirling coolers on orbit with two having over 11 years of continuous operation. This paper will provide an overview of the NGAS cryocooler capabilities.     

Lifetime test and heritage on orbit of coolers for space use

This report describes the results and operating status of ground lifetime testing and achievements on orbit of coolers for space use. Ground lifetime tests of coolers of three types were conducted to demonstrate their long life and reliability. Three single-stage Stirling coolers were tested for 89,016, 71,871 and 68,273 h from 1998, a two-stage Stirling cooler was tested for 72,906 h, and a 4-K class cooler with a two-stage Stirling cooler and a Joule–Thomson cooler was tested for over 2.5 years. After lifetime tests were completed, a few coolers were investigated to determine the cause of the cooling performance degradation. Additionally, the filled gas of the coolers was analyzed. These coolers have shown good results on orbit. Three single-stage Stirling coolers were carried on the X-ray astronomical satellite “SUZAKU” (launched in July 2005), Japanese lunar polar orbiter “KAGUYA” (launched in September 2007), and the Japanese Venus Climate Orbiter “AKATSUKI” (launched in June 2010). Two units of a two-stage Stirling cooler were carried on the infrared astronomical satellite “AKARI” launched in February 2006. A 4-K class cooler was carried on the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) aboard the Japanese Experiment Module (JEM) of the International Space Station (ISS). SMILES was launched in September 2009.     

多元红外三通道辐射制冷器研究

研制了一台用于冷却红外多光谱扫描仪中多元红外探测器列阵的星载辐射制冷器。空间红外遥感器需要制冷系统,而辐射制冷器非常适合空间遥感器的需求。简要介绍了它的研制情况,方案设计思路,辐射制冷器基本构成,理论计算方法,做过的模拟试验及其结果,并对在轨使用情况作了简介。     

改进的蒙特卡洛法加快空间辐射制冷器耦合因子的计算速度

耦合因子的计算是空间辐射制冷器热分析的基础,蒙特卡洛法是满足抛物面W型辐射制冷器耦合因子计算的有效方法.基于统计原理,蒙特卡洛法计算空间辐射制冷器耦合因子的缺点是计算时间较长.通过避免传统的迭代计算,加快了蒙特卡洛法计算速度.同时,采用改进辐射能束概率分布算法的蒙特卡洛计算精度同传统方法相当,并也随随机能束数的增加而提高精度.     

空间辐冷器耦合因子计算软件的开发

介绍了空间辐冷器耦合因子计算软件的开发原理、相应流程及运行结果，对于具有复杂表面的辐冷器，蒙特卡洛法是进行耦合因子计算的有效方法。基于上述原理所开发的计算软件，具有收敛快、精度高的优点，达到了实用要求。     

Cryogenic system design of the next generation infrared space telescope SPICA

The Japanese infrared space telescope SPICA mission, following the successful Akari mission, has been studied at the concept design phase in international collaboration with ESA under the framework of the ESA Cosmic Vision 2015-2025. The SPICA spacecraft is to be launched in 2018 and transferred into a halo orbit around the Sun-Earth L2 to obtain a stable thermal environment where the IR space telescope’s large mirror of 3 m-class in diameter can be cooled to <5.5 K with mechanical coolers and effective radiative cooling with no use of stored cryogen. The SPICA’s large and cold telescope is expected to provide unprecedented scientific observation optimized for mid-IR and far-IR astronomy with ultra-high sensitivity and excellent spatial resolution during a nominal mission life of 3 years (goal 5 years). Thermal and structural analyses show that the obtained design of the SPICA cryogenic system satisfies the mission requirement. Mechanical coolers for the 4.5 K stage and the 1.7 K stage, which have been continuously developed, have a sufficient cooling capacity with low power consumption to lift the heat loads from instruments and parasitic heat loads. As a result, it is concluded that the concept design of the SPICA cryogenic system is confirmed for the initial cooling mode after launch and the nominal operation mode.     

Construction and tests of a heart scanner based on superconducting sensors cooled by small stirling cryocoolers

At the University of Twente, a heart scanner has been designed and constructed that uses superconducting devices (superconducting quantum interference devices (SQUIDs)) to measure the magnetic field of the heart. A key feature is the elimination of liquid cryogens by incorporating cryocoolers. In the design, two coolers are operated in counter-phase to reduce the mechanical interference. In addition to the application of ferromagnetic shields around the compressors, the magnetic cooler interference is reduced by placing the SQUID magnetometers coplanar with respect to the coolers. In this way, the cooler noise was reduced to a level below the intrinsic sensor noise: 0.16 pT/√Hz. A temperature of 60 K was realised with a cool-down time of about 2 h. The corresponding heat load to the coolers is roughly 0.9 W. Magnetocardiograms were recorded inside a magnetically shielded room.