替代制冷剂管内蒸发研究进展

替代制冷剂的传热性能研究对合理设计使用这些制冷剂的制冷系统十分关键。介绍了国外在替代制冷剂管内蒸发换热方面的研究进展,讨论比较了制冷系统传统制冷工质与新工质间在换热及压降方面的差异,并探讨了润滑油对换热及压降的影响。     

汽车空调系统工质替代研究现状及未来

提出了汽车空调工质替代原则,指出制冷剂R134a已成为汽车空调的主流替代工质,但R134a只能作为过渡性替代物,最终将使用自然工质作为制冷剂。同时,讨论了采用自然工质作为制冷剂的其它循环方式,认为固体吸附式制冷系统是一种有潜力的汽车空调制冷系统。     

碳氢制冷剂应用于汽车空调的可行性分析

本文分析了碳氢制冷剂作为汽车空调制冷工质的优势和汽车空调中使用碳氢制冷剂的危险性,综合国内外的研究,得出汽车空调中使用碳氢制冷剂有很高的安全性,对比了R290、R600a的混合物和R12的性能,从理论上验证了用碳氢制冷剂替代R12作为汽车空调循环工质的可行性,计算了一些品牌汽车的空调系统碳氢制冷剂的理论充灌量,为碳氢制冷剂在汽车空调中的应用提供了参考.     

CFC22应用于螺杆式制冷机

欧美的空调制冷工程师们已重新认识到,基于螺杆式压缩机使用对环境安全的制冷剂HCFC22的机组的优越性,越来越多的制冷机制造商正向这一市场进军。制冷剂生产商们正在探索可以替代R11、R12的新工质,然而,任何其它新的代用品都将使造价昂贵,而效率比所替代工质要低,且应用于现有机器上并不是一拍即合。颇有吸引力的代用品就是R22,一种广泛应用于民用建筑及商业空调达数十年之久的     

汽车空调系统采用工质R407C的性能结构探讨

提出了汽车空调制冷剂对环境的污染问题,并对此具体论述了制冷系统采用混合工质R407C替代氟利昂-22的必要性和可行性,从而根据新工质特性,研究探讨出满足公交车空调冷量要求的空调系统.     

基于R600/R290混合制冷剂的立式冷冻箱的降温能力试验研究

为优化以混合制冷剂为工质的立式冷冻箱制冷系统降温能力,对使用R600/R290混合制冷剂的立式冷冻箱在32℃环境温度下进行降温能力试验,研究混合制冷剂充注量、制冷剂各组分配比、毛细管流量及风机转速对其性能的影响.结果 表明:混合制冷剂充注量过大会削弱制冷系统降温能力,并使压缩机功率增加;增大毛细管流量、风机转速及混合制...     

TEWI及制冷剂的替代

制冷工质对大气温室效应的影响过去采用GWP作为评判标准,它不能充分反映制冷工质及使用它的制冷装置在运行的过程中对温室效应的综合影响情况,而TEWI则综合考虑了这些因素。本文介绍了TEWI的有关计算,并分析了考虑TEWI的情况下制冷剂的替代。     

关注制冷剂的环境影响

臭氧层的耗损和全球变暖,是当今举世瞩目的环境问题。由制冷剂产生的影响,自然备受关注。 自从1834年第1台以乙醚作制冷剂的蒸气压缩式制冷机问世以来,人们一直不懈地努力寻求“理想”的工质,到本世纪初,氨(R717)、二氧化碳(R744)、二氧化硫(R-     

进口超低温箱混合工质替代特性的计算及实验分析

在我国超低温箱采用的制冷剂一般为，高温级是R12／R22／R502，低温级是R13。近年来，国内部分单位和部门先后进口了不少的超低温箱，大都使用共沸混合制冷剂，如R500和R503，由于市场上没有或者很少销售这些工质，目前普遍出现超低温箱不能进行正常维修、使用等现状。为此针对进口超低温箱所存在的这类主要问题，结合国内实际情况，进行了制冷剂特性计算和替代工质的实验分析，同时也成功地为国内有关单位进行了进口超低温箱混合工质的替代工作。     

HFO-1234ze在空气源热泵热水器中 替代R417A、R22的研究

首先从热物性、ODP、GWP、工质毒性、可燃性方面对HFO-1234ze、R417A、R22三种制冷剂进行对比,并进行理论计算,初步分析HFO-1234ze制冷剂运用在空气源热泵热水器上的可行性。然后,在焓差法实验室内,对分别采用HFO-1234ze,R417A和R22作为制冷工质的空气源热泵热水器进行名义工况下的性能测试,对三种制冷剂的吸排气温度,吸排气压力,压缩机输入功率、制热量、性能系数进行对比分析。本文研究结果显示HFO-1234ze可以作为R417a与R22在热泵热水器中的替代制冷剂。此次研究为热泵热水器的工质选择提供参考。     

基于CFD技术的气流温度传感器数值校准虚拟风洞初探

在气流温度传感器风洞校准试验中,由于试验成本高、校准试验环境与实际使用环境差距大等原因,有必要构建气流温度传感器数值校准虚拟风洞,实现极限非常规校准工况的气流温度传感器误差修正及虚拟校准,并通过气流温度传感器的虚拟校准数值风洞获取仿真结果,尽可能地减少实物校准的工况数量,同时也从理论层面为气流温度传感器的设计与校准提供...     

Development of an air cushioning material based on a novel idea

The air cushioning material introduced in this paper as a new packaging material represents a new steadying and cushioning system using air pressures. The material is a two‐layer structure consisting of an airtight chamber (air chamber) filled with air and a urethane chamber holding flexible and resilient urethane that permits free air passage. Ordinary air cushioning materials have drawbacks in that they repeat expansion and contraction according to changes in atmospheric pressure and temperature during long storage or transportation to remote destinations. While their expansion may damage the case or the packaged object, their contraction may cause a drop in steadying pressures, so that the contents may move about inside and eventually sustain damage. The two‐layer structure of the new material rectifies the shortcoming of ordinary air cushioning materials that they may be affected greatly by temperature changes. Also, the greatly improved flexibility of the packaging material opens up possibilities for far wider applications in packaging precision devices and machinery. The airtight chamber to be filled with air is provided with an air charge port and an air discharge port, which may be used to control the charged air pressure. The desirable air pressure is such that the urethane in the urethane chamber is compressed to about half the ordinary size. Since it can be checked visually or tactually, the charging of air, which used to be a delicate and rather difficult operation, is easy. Conventionally, most of the packaging materials were of throw‐away type and thus handled as waste materials. The new air cushioning material, which is surfaced with a strong wear‐resistant cloth, is designed for repetitive use, so that it will contribute greatly to the reduction of wastes if systematic recovery is carried out. Copyright © 1999 John Wiley & Sons, Ltd.     

The effect of water vapor in increasing growth stresses in the oxide scale on martensitic steam plant alloys

Abstract

Investigation of the oxidation behavior of 9% Cr steels at 650°C in dry air and air + 10% H₂O have shown that oxide scale growth stresses may play a significant role in breakaway. For this reason, preliminary studies on the development and characteristics of growth stresses in oxides on these materials have begun. These studies include in situ acoustic emission (AE) for monitoring scale cracking, deflection testing in monofacial oxidation (DTMO) and in situ X–ray measurements. The measurements were complemented by detailed post-experimental metallographic investigations.

From the DTMO measurements the stresses in the oxide on the specimens tested in humid environment are increased by about a factor of 5 compared to dry air at the beginning of oxidation for P91. In a humid environment the stresses decrease with oxidation time while in dry air they remain almost constant. Significant acoustic emission (AE) occurs in humid air for oxidation coupons while virtually no AE is observed for thin foils in a humid environment and for coupons in dry air. These first results seem to be in good agreement with weight gain data characterizing the breakaway behavior in these environments, indicating that, indeed, oxide growth stresses play a key role for oxidation resistance and, thus, component lifetimes of such steels.

The first X–ray results indicate that for E911 the scale structure and composition changes completely between the two environments. Furthermore, in humid air, a breakaway effect is observed with a change from protective spinel type oxide to locally non-protective Fe–rich oxide.     

聚苯乙烯蜂窝状多孔膜的制备及应用

以线性聚苯乙烯(PS)为膜材料,采用Breath Figures法制备了高度规整的蜂窝状结构多孔膜.研究了溶液浓度、环境湿度、气体吹扫速度及不同溶剂对多孔膜结构的影响.结果表明,相比于苯和二氯甲烷,氯仿作为溶剂因其挥发度适宜,PS浓度在20～80mg/mL的铸膜溶液可形成规整的蜂窝状结构多孔膜,且膜孔分布均匀、大小均一;制膜的湿度需高于环境湿度,但随着湿度的增加孔径增大;气体吹扫速度可在400～1000mL/min范围,但吹扫速度较大时孔径略有降低.该膜可作为固定诸如辣根过氧化酶等活性酶的载体,用于酶催化反应.     

运用统计能量分析法预示空空导弹舱内动力学环境

空空导弹在挂飞过程中会遇到多种冲击和振动环境的作用，对导弹结构及其内部设备的性能影响不可忽视。针对某型空空导弹，利用稳态统计能量分析法对其包含机动抖振的随机振动环境进行预示，同时采用基于冲击响应谱的瞬态统计能量分析法预示导弹设备舱内的高频冲击环境。计算仿真与实测结果比较表明，统计能量分析法能够较为准确地预示动力学环境。     

一个空调房间气流组织的数值模拟

本文针对相同室内条件，不同气流组织型式下的各种模型，运用计算流体力学的方法，对室内速度场、温度场进行数值模拟。分析不同的速度场、温度场，预测最优化的气流组织方案，供设计时参考选用。     

基于奶牛健康状况的最佳产奶性能的空调探索

本研究是探索符合奶牛健康状况及产奶性能的空调，而奶牛所产牛奶的性能是否良好也是奶牛健康与否的重要表现形式，空调的作用在于调节环境的温湿度来提高空气的质量，以达到人们所预期的环境状态。因此，探索符合奶牛健康状况及产奶性能的的空调归根结底就是探索奶牛产奶性能与温湿度的关系，我们用THI来表示温湿度，THI：0．72（Td＋Tw）＋40．6，其中Td、Tw分别为干湿球温度计的干湿球温度。奶牛产奶性能通过产奶量、乳成分和乳中体细胞数表现，这三者在THI小于70左右时趋于稳定，没有明显地偏差。而在THI大于70时随rHI的增加产奶量、乳成分减少，而体细胞数量增多。且THI在60-65之间时奶牛产奶性能最佳，健康状况良好。这也就是我们探索的符合奶牛健康状况及产奶性能的空调。     

遥感综合技术在城市环境监测中的应用

在城市飞速发展的今天,城市环境也越来越受到重视.本文在简单介绍了城市环境后,阐述了遥感技术的整体特点与应用和简单分析了GIS和GPS的特点及三者之间的关系,然后再针对具体的城市环境问题（城市大气污染、水污染、地面污染、固体废物堆场污染和热污染等）,探讨了遥感技术在城市环境监测方面的具体应用.最后,在总结了遥感综合技术在环境监测方面的作用的基础上,提出了今后可以发展的新方面.     

Determination of correction factors for alpha activity measurements in the environment (conditions of high dust loading)

Within the framework of a French national monitoring program to survey the man-made radioactivity in the environment, several power plants and research facilities on the territory use environmental air monitors for unwanted releases of radioactive aerosols. High sensitivity and lack of false alarms are all important for environmental air monitors. The project aims to conduct investigations to improve operation of environmental air monitors, particularly under conditions where a lot of non-radioactive dust may be deposited on the filters (conditions of high dust loading). The dust may increase the frequency with which filters must be changed and can lead to an underestimation of the real activity. This underestimation is due to deteriorated alpha energy resolution and response specificity to the radionuclides of interest. In this study, our objective was to find experimental correction factors for the degraded activity measurements taking into account the alpha absorption in the dust loading.     

室内环境的多级模糊综合评价方法

通过对影响室内环境（热环境、光环境、声环境和空气品质）各因素的分析,建立了评价指标体系;引入模糊数学理论,确定隶属度函数,建立模糊评价矩阵,利用多级模糊变换方法对室内环境进行综合评价;引入实例来验证评价的合理性。