低于液氮温度的泡沫塑料吸湿增重

为减少火箭上液氢/液氧燃料蒸发损失,要求绝热材料热导率小,附加质量轻,并有好的抗应力强度。泡沫塑料因其密度低、绝热性能及机械强度好等优点,是国内外最广泛使用的火箭上深低温系统绝热材料。但泡沫塑料长时间存在大温度梯度时,将强化吸湿增重,从而增加火箭起飞附加质量,也恶化绝热效果。因此,获得可靠的泡沫塑料吸湿增重数据对大推力火箭推力设计有重要意义。报告了用脉管制冷机冷却的泡沫塑料吸湿增值实验装置及实验结果。利用两台自行研制的GM型单级脉管制冷机提供冷量,样本一面被冷却到约45 K温度,同时另一面暴露在30℃恒温及95%的相对湿度环境。设计了一种波纹管结构来减少环境对真空低温系统的漏热。总共测试了4组8个样本,测试时间为7 h。测试结果与液氮温度的测试结果进行对比和分析,结果发现两者吸湿增重相同,即温度梯度降低引起的低温泵增强效应在该温区可忽略不计。同时发现样本搭接结构对吸湿增重没有影响。     

基于CFD及FEM的聚氨酯泡沫塑料低温绝热结构优化设计

针对某低温风洞压缩机转子系统轴承箱,选取聚氨酯泡沫塑料作为绝热材料,并辅以电加热作为热防护手段。采用计算流体力学(CFD)方法对轴承箱内润滑油流动以及传热过程做分析模拟计算,并通过缩比实验结果验证计算方法可靠性。结果表明,绝热层厚度100 mm、电加热功率250 W/m~2工况,运行48 h后润滑油温度高于278 K,加热面最高温度约341 K,可以满足轴承箱使用条件,避免了绝热层厚度及加热功率经验性设计取值可能带来的加热面局部超出绝热材料安全使用温度、寿命缩短问题;同时降低所需绝热层厚度,降低轴承箱内空间狭小所带来的工艺实施难度。绝热结构选取分层泡沫预制块工艺方案,采用有限元分析方法 (FEM)对预制块强度校核,并依据传热计算结果设置边界条件以提升校核准确性。结果显示,预制块内部应力水平小于材料许用应力。该模拟计算方法对聚氨酯泡沫塑料绝热产品应用和工艺设计具有一定的参考意义。     

用于液化天然气冷量回收的冷脉管发动机

脉管制冷机是一种主要应用于卫星上冷却探测器的低温制冷机。具有室温推移活塞的脉管制冷机是一种可逆脉管制冷机。其逆向循环为冷脉管发动机,是一种新的可用于液化天然气冷量发电的装置。用数值分析的方法阐述了其工作原理,分析了最佳扫气容积比与脉管长度的关系,讨论了扫气容积对功率的调节。     

10~30K温区纯不锈钢丝网与混填磁性填料制冷性能对比

低温回热材料的性能是制约深低温制冷机发展的关键因素之一。在10~30K温区,对比低温段回热器采用不锈钢丝网（SS）和SS与HoCu₂混合填充两种方式的回热器损失、能量流分布及制冷性能。数值模拟表明,回热器采用纯SS填充时存在较大换热损失,而混填时流阻损失影响显著增大,随着制冷温度提高,回热器换热损失均能减小,而流阻损失有所增加。低温级脉管内能量流模拟结果表明,HoCu₂填充时,回热器焓流较小,传输到冷端的PV功也较小。最后在主动调相的热耦合两级脉管上开展实验测试,结果显示,SS与HoCu₂混合填充的低温级脉管无负荷温度到9.56K,当制冷温度为25K及以下时,制冷效率高于纯SS填充;制冷温度高于28K时,纯SS填充的制冷效率更高。通过常规不锈钢材料和磁性材料填充回热器制冷性能对比,为液氢温区高效回热器设计提供参考。     

聚氨酯在建筑业上的开发应用

随着生活水平的提高 ,居住条件不断改善 ,在寒冷的冬天 ,房屋需加热以取暖 ;在炎热的夏季 ,房屋又需冷却以降温 ,住宅的加热与冷却都要消耗能量。同时 ,建筑物的设计与建造必须考虑绝热保温 ,提高能源效率 ,降低能量消耗。聚氨酯是最好的绝热材料 ,由于其良好的加工性能 ,可以制成泡沫、软、硬等各种不同类型的材料 ,可以极大地降低各类建筑物的能量消耗。相同条件下使用各种不同绝热材料的相对厚度如下 :聚氨酯 5 0ｍｍ ;聚苯乙烯 80ｍｍ ;矿棉 90ｍｍ ;软木 1 0 0ｍｍ ;纤维板 1 30ｍｍ ;软质木材2 80ｍｍ。聚氨酯硬质泡沫塑料重量轻、比…     

聚碳酸酯微孔泡沫塑料力学性能的研究

采用超临界微孔发泡技术制备出一系列聚碳酸酯(PC)微孔泡沫塑料,通过扫描电镜、力学性能测试等方法研究了超临界流体温度对发泡剂(CO2)含量的影响,及发泡温度、发泡时间和超临界流体温度对PC微孔泡沫塑料力学性能的影响。结果表明:在测试范围内,随超临界CO2流体温度的升高,CO2含量降低;升高发泡温度或延长发泡时间均使PC微孔泡沫塑料的拉伸强度和冲击强度降低;随超临界CO2流体温度的升高,PC微孔泡沫塑料的拉伸强度增加,冲击强度降低。     

一种逼近卡诺制冷效率的级联脉管法及其两级验证

理论分析表明,通过多级级联脉管组成的新结构,其理论制冷效率有望达到卡诺效率。给出了这样一种具有传输管声功回收装置的级联型脉管制冷机,传输管能将主级制冷机脉管热端压力波领先质量流的相位扭转为质量流领先压力波,同时实现能量最大化的传输,用以驱动次级制冷机。实验结果表明,两级级联型脉管制冷机在233 K工作时,制冷效率比单级结构提高了33%。     

矿物纤维胶粘剂——苏联发明公报号597695

本发明涉及制取绝热材料时所用矿物、玻璃等纤维的粘接用胶组份问题.已有的矿物纤维绝热和隔音材料的粘接用胶组份含有水溶性的酚醛齐聚物和水.该胶粘剂水溶性好,而且使用时产品的热处理温度低、时间短.但强度提高不大.发明的目的是为了增加材料的强度和耐水性.为此目的,在含有水溶性酚醛及水的组份中添加细     

含硅聚氨酯泡沫稳定剂

前言由于聚氨酯泡沫塑料具有密度小、强度高、弹性好和绝热绝缘以及化学稳定性好等优良性能,所以得到了迅速的发展和广泛应用。而泡沫稳定剂在其制造过程中却是一个关键性助剂,它对各类聚氨酯泡沫塑料的通用性较小,故品种众多,并已逐渐形成系列。     

主动调相方式对脉管制冷机性能的影响

通过实验研究了主动调相脉管制冷机的性能,采用锁相器调节主动调相压缩机（APC）的电压幅值和相位角,实现对活塞运动的调节,旨在考察APC对冷指的调相能力。当调相压缩机和主压缩机驱动电压之间的相位角,即电压相位角（调相压缩机落后主压缩机）为210°和240°时,测试了两台压缩机活塞的位移相位角为90°～130°时制冷机的性能。结果表明,不同电压相位角时,制冷机在相同的位移相位角下,其性能仍会出现差异。对比发现,主动调相方式下制冷机的最佳性能优于惯性管调相方式,当制冷量为30 W,系统输入电功减小了8.1%。最后,从相位调节及冷指与压缩机匹配两方面,解释了脉管制冷机在不同的调相方式下性能出现差异的原因,表明了APC能够替代惯性管对脉管制冷机进行调相。     

运载火箭共底贮箱加注过程非稳态温度分布数值模拟

以液氧和煤油为推进剂的新一代运载火箭，承力式共底贮箱结构一方面可以缩短整个运载器长度，改善运载器长径比，二能取消液氧贮箱与煤油贮箱间的箱间段，减轻结构质量。但要求共底夹层需要良好的隔热性能，同时承受煤油箱和液氧箱双向压力载荷。获得加注过程共底夹层的温度非稳态分布是分析夹层隔热和应力性能的基础。基于CFD方法，模拟了液氮加注过程，共底贮箱包括液氮贮箱和煤油贮箱以及共底夹层，从室温到加注完成的非稳态温度分布。数值模型考虑了贮箱表面可能结冰时的热边界条件变化以及由于壁面漏热导致的液氮/氮蒸气相变蒸发。为了防止煤油局部温度过低，重点分析了叉形环处包裹或未包裹PMI绝热材料对煤油温度场和液氮蒸发率的影响。计算结果表明，叉形环处包裹绝热材料时在自然蒸发阶段煤油局部最低温度小于240 K，而未包裹绝热材料时局部最低温度大于260 K，满足设计要求。仿真结果为液氧和煤油共底贮箱的优化设计提供参考。     

Mechanical,acoustic, and thermal performances of shear thickening fluid–filled rigid polyurethane foam composites: Effects of content of shear thickening fluid and particle size of silica

Shear thickening fluid (STF) features a rheological property, and rigid polyurethane (PU) foams feature low thermal conductivity and excellent acoustic insulation. In this study, an STF/PU rigid foam composite sandwich structure was designed using different contents (0, 0.5, 1, or 1.5 wt %) of STF that contained 14 nm, 40 nm, or 75 nm silicon dioxide (SiO₂). The effects of STF content and silica size on the cell structure, mechanical performance, acoustic absorption, and thermal performance of the STF/PU foam were explored. The test results show that STF/PU foam exhibited three characteristic acoustic absorption peaks, and the maximum acoustic absorption coefficient reached 0.841. STF addition increased compression, bending strength, and maximum acoustic coefficient, as well as initial mass loss temperature. STF-filled PU foam composites containing 14 nm and 40 nm SiO₂ had a mild rise in thermal insulation. The rigid STF/PU foam composites with a cell structure had the maximum thermal conductivity of 0.22 W m⁻¹ K⁻¹ and sound absorption coefficient of 0.841, which confirm that they are a good candidate for sound-absorbing energy conservation materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47359.     

Effect of insulation layer for thermal shock in cryogenic composite laminates

The structural weight of a cryogenic propellant tank for reusable launch vehicles (RLVs) can be effectively reduced by the use of advanced composite materials. However, microscopic damage such as transverse matrix cracks (TMC) and delaminations are prone to develop in composites well below the load levels that would result in mechanical failure. This microscopic damage leads to a leakage path for the fuel. The leakage is influenced by many factors including connectivity of the cracks, residual and service‐induced stresses, and composite stacking sequence. This article is concerned with the effect of thermal gradients due to sudden exposure to a cryogenic temperature with and without insulation layer. An investigation of the insulation layer for sudden exposure to cryogenic temperatures is conducted numerically. The exposure of the harsh environment could make the damages such as delaminations, TMC, and leakage path. The defects from manufacturing could be formed, and they are critical parts under sudden exposure to cryogenic temperature. Therefore, the qualitative analysis for insulation technique is needed. The results from this article are very important because the stress levels which cause damages can be predicted and also controlled using the insulating techniques. The insulation skill which can suppress the stress levels is newly introduced in this article for RLV cryogenic fuel tank. Moreover, the effect of lay‐ups is also investigated in this article. The thermal gradient can be controlled by using different lay‐ups. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Glass bubble reinforced polyurethane foams with high mechanical strength for cryogenic temperature insulation

In this study, glass bubble (GB) is added to polyurethane (PU) foams at different weight ratios—0, 0.25, 0.5, 0.75, and 1 wt% —to investigate the changes in the mechanical and thermal properties of the foam. By conducting several tests and measurements, the density, cell morphology, compressive strength, and thermal conductivity of the foam are studied. In particular, the effect of GB additives is examined by conducting compression tests at various temperatures (−163, −100, −40, and 20°C). Scanning electron microscopy and X-ray microscope reveal that the foams exhibit higher stability below 0.5 wt%, which improves the thermal performance. On the other hand, the compressive strength of the foams increases for all weight ratios of GB, and it increases sharply at 0.75 wt%. In addition, the chemical interactions and the dispersion of additives in the PU matrix are investigated through Fourier transform infrared and X-ray diffractions analysis. It is found that the synthesis of PU foams with GB nanoparticles is an efficient method for improving the mechanical properties and insulation performance of the foam for LNG insulation technology.     

煤油贮箱冷氦鼓泡增压过程数值研究

火箭飞行过程中，约90 K的低温氦气用以加压室温下的煤油贮箱使煤油流出，保障发动机燃料供应。为尽可能减少氦气用量，设计低温氦气从液相中喷入，使得氦气在贮箱内上升过程先和液态煤油充分换热升温，再进入气相空间增压。但该过程可能引起两个不利的结果，首先浸没在煤油中的低温氦气管路表面可能结冰，结冰沉底或可能堵塞发动机滤网；其次氦气可能被煤油携带，从而排出口位置可能出现气液两相流。这两种情况都对火箭发动机稳定运行造成负面影响，因此是不允许的。对低温氦气在贮箱中心喷入和环向多孔喷入两种结构的气液两相流过程进行了数值研究，构建了基于Euler-Euler模型的两相传热非稳态模型，数值结果与地面实验观察到的现象进行了定性对比，定性验证了模型的准确性。重点考察了煤油排出过程两种喷入结构的气液两相流分布以及煤油结冰可能性。研究结果从机理上解释了实验现象，并为煤油贮箱增压排出方案设计提供了参考。     

Processing‐structure‐property relationship in rigid polyurethane foams

Rigid polyurethane (PU) foam is used as a thermal insulating and supporting material in domestic refrigerator/freezers and it is produced by reaction injection molding (RIM) process. There is a need to improve the thermal property of rigid PU foam but this is still a challenging problem. Accordingly, this work investigates the RIM process parameters to evaluate their effects on rigid PU foam's structure and hence property. It has been found that mold temperature is a key parameter whereas curing time has negligible effect on structure of PU foam. Cell size, strut thickness, and foam density have been found very critical in controlling the thermal and mechanical properties. Upper and lower values of 30 to 32 kg/m³ density are critical to observe contribution of radiation and solid conductivity separately. Finally, PU foam with 160 µm average cell size, 16 µm strut thickness, below 10% open cell content, and 30 to 32 kg/m³ density allow obtaining better thermal insulation without significant reducing in the compressive strength. The presented work provides a better understanding of processing‐structure‐property relationship to gain knowledge on producing high‐quality rigid PU foams with improved properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44870.     

Manufacture and use of pulverized flexible polyester polyurethane foam particles

Crucial process modifications were shown necessary to improve the economics of cryogenic grinding of flexible polyurethane (PU) foam. It is concluded that foam densification prior to cryogenic processing was essential to reduce insulation effects. In comparative studies of foam and densified foam, increasing the density to ～800 kg/m³ resulted in dramatically reduced cryogen use and vastly improved output. Results indicated that cryogenic pulverization presents a significantly more economic solution than previously recognized. Particles produced by this method were added to foam formulations and effects of particle size and structure on compression properties and cell structure of resultant foams were studied. Particle sizes <100 μm gave similar compression properties and cell size to virgin foam at up to 10 parts by weight on 100 parts of polyol, but cell structure and compressive properties showed increasing divergence as particle size and addition concentration increased. Studies of alternative uses showed that the PU particles showed promise as fillers in rigid PU foam formulations and suggested an extending or reinforcing action in natural rubber vulcanizates.     

Preliminary evaluation of the performance of an adsorption‐based hydrogen storage system

Using modeling and thermal simulations, the feasibility of an adsorption‐based hydrogen storage system for vehicles is evaluated. The storage capacity of a 150 L tank filled with a high surface‐area activated carbon is mapped for temperatures from 60 to 298 K and pressures up to 35 MPa. The thermal simulations are verified using experiments. For a storage capacity target of 5 kg, the adsorption‐based storage system will offer a storage advantage over the cryogenic gas storage if the residual mass of hydrogen in the tank is retrieved by heating. For a discharge rate of 1.8 g/s, the required heat is of the order of 500 W. The net energy requirements for the refueling has contributions from compression, precooling and tank cooling and can approach that for liquid hydrogen storage. With a good insulation and a maximum tank pressure of 35 MPa, the dormancy period can be extended to several weeks. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

LNG低温储罐绝热性能的验证

LNG低温储罐的保冷性能直接影响到BOG压缩机的能耗,本文通过探讨LNG低温储罐的绝热性能,详细分析影响LNG低温储罐自然漏热的各种因素,并通过计算方法求得以满罐为基准、在最热气象条件下的蒸发气的量,来验证宁夏哈纳斯液化天然气有限公司LNG储罐的绝热性能。     

保温隔热墙体材料的研究现状

保温隔热材料近年来发展迅速,目前已在墙体方面得到大量应用。本文主要概述了有机、无机以及复合保温隔热墙体材料的研究现状,国内有机保温隔热材料主要采用聚苯乙烯泡沫板(EPS)、聚氨酯材料(PU)、挤塑聚苯乙烯泡沫板(XPS)等,无机保温材料主要有泡沫玻璃、泡沫混凝土、岩棉和无机保温砂浆等,有机保温材料和无机保温材料各有优缺点,对比分析表明：复合保温隔热墙体材料将成为一种发展趋势。最后分析了我国保温隔热墙体材料的应用现状。