机械泵驱动冷却回路在模拟航天温度边界下散热能力分析

 对机械泵驱动两相冷却系统在模拟太空工作的边界问题条件下散热能力和工作特性进行实验研究,从而得到结论：当系统的热负荷较小而边界温度较低时,放热量变大使系统平均温度降低,造成蒸发段温度无法控制,冷凝器的温度也可能会降到低于工质的凝固点冻结,冷凝段管路也将因固态工质堵塞而无法循环,此时需采取降低储液器设定温度的方法来减小系统的放热量。当系统的热负荷较大而边界温度较高时,系统在冷凝器的放热量较小而使得热负荷无法完全释放时,系统的平均温度上升,造成泵的入口温度达到工质的饱和温度,产生的气泡有可能会对机械泵内的部件产生气蚀,并引起机械泵工作不稳定,无法保证设定的流量循环。实验结论为该类系统的设计与应用提供了可靠的依据。     

机械泵驱动冷却回路在模拟航天温度边界下散热能力分析

对机械泵驱动两相冷却系统在模拟太空工作的边界问题条件下散热能力和工作特性进行实验研究,从而得到结论:当系统的热负荷较小而边界温度较低时,放热量变大使系统平均温度降低,造成蒸发段温度无法控制,冷凝器的温度也可能会降到低于工质的凝固点冻结,冷凝段管路也将因固态工质堵塞而无法循环,此时需采取降低储液器设定温度的方法来减小系统的放热量.当系统的热负荷较大而边界温度较高时,系统在冷凝器的放热量较小而使得热负荷无法完全释放时,系统的平均温度上升,造成泵的入口温度达到工质的饱和温度,产生的气泡有可能会对机械泵内的部件产生气蚀,并引起机械泵工作不稳定,无法保证设定的流量循环.实验结论为该类系统的设计与应用提供了可靠的依据.     

机械泵两相冷却系统过热现象的实验研究

机械泵驱动两相冷却系统是一种以机械泵为驱动力的封闭式相变传热设备。在对该系统进行研究过程中发现,当启动蒸发器热负荷时,在蒸发段出口将产生明显的过热现象,并且有较大的压力脉。通过对大量实验对与过热度有关的启动温度、流量和启动热负荷进行比较分析,得出启动温度越低,产生的过热度越大的结论:启动温度越低,启动需要的过热度相对要大;其次,热流密度越大,过热时间维持的越短;最后,从过热状态到两相状态的闪蒸过程将系统的阻力发生较大变化,流量越大压力脉冲越高。     

并行蒸发器两相冷却系统支路散热不平衡性的实验研究

 对并行蒸发器机械泵驱动两相流冷却系统各个支路散热量不平衡条件下散热特性进行实验研究,结果表明并行蒸发段各支路的流量分配同管路的阻力有关,当上下两侧蒸发器的热量不平衡时,质量流量的分配始终是一个动态的变化过程,其中,热负荷较大的一侧,阻力不断增加,流量逐渐减小,而热负荷较小的一侧流量在不断变大,并且热量差越大,流量差变化越快;当减小并行支路的热量差有利于蒸发段的散热平衡,热量差越小,系统散热稳定性越强。同毛细泵驱动的两相冷却系统相比,机械泵驱动的两相流冷却系统的散热性好,等温性高,热不平衡处理能力强,并行支路热负荷之差可以达到100多倍,并且能够保持较长的稳定运行。     

毛细抽吸两相环系统稳定性的实验研究

为了研究毛细抽吸两相环回路（ＣＰＬ）运行的稳定性特性,对ＣＰＬ－Ⅲ工程模型系统进行了实验研究。总结了ＣＰＬ系统运行稳定性的各种影响因素,包括蒸发器功率、储液器温度、冷却液温度及蒸发器之间的相互影响等,并且对以上因素进行了理论上定性的解释。增大毛细抽吸力,提高储液器温度、保持储液器温度恒定,降低蒸发器功率、减小蒸发器功率的扰动,降低冷却液温度,使储液器的注入点远离蒸发器等可以提高系统稳定性,两个蒸发器之间的相互作用也对ＣＰＬ系统稳定性有影响。在已有实验数据的基础上,给出了系统运行的稳定区域图,并拟合出了不稳定区域的边界线方程。     

新型涡轮-泵驱动式回路热管设计及热力学分析

针对热管在逆重力条件下工作时冷凝液回流驱动力不足的问题,提出了一种全新的涡轮-泵驱动回路热管系统.该系统利用蒸汽驱动涡轮和与之连在一起的机械泵,机械泵直接驱动冷凝液返回到蒸发器而实现系统循环,其传热能力由蒸发段的沸腾极限确定,极限热流密度可达到70~80W.cm-2以上,大大超过了毛细泵回路热管由毛细力所确定的传热能力.热力学分析表明,蒸发段和冷凝段的温差达到10℃以上,涡轮-泵装置即可为冷凝液提供足够的回流驱动力.对于高热流密度耗能设备的热传输问题,该回路热管系统是一种很好的解决方式.     

机械泵驱动两相冷却系统工作点温度控制

对系统的控温原理和主要方法进行理论阐述,从而确定采用对储液器温度的主动式控温方法实现对蒸发段工作温度的控制思路.提出"回路直接冷却"和"半导体制冷片--系统回路协同工作"这2种储液器温度控制方法,并且对其控温精度和降温速度等技术进行实验研究.结果表明,改进前,采用"冷回路"向储液器漏热并结合加热器实现温度控制的设计方案控温精度仅为±0.4℃,且在需要快速降低蒸发段工作温度时较难实现;改进后,采用半导体制冷片同系统管路协同运行的方法不仅可控性大大增加,而且降温速度从原来的0.12℃/min提高到0.36℃/min.在模拟外太空边界温度波动幅度的条件下,改进前、后温度控制方法蒸发段的控制精度分别为±0.4℃和±0.1℃,从而克服了该类系统在工作温度控制中降温速度慢、控温精度低的缺点,并可推广到热管、毛细泵驱动回路等类似的航空航天两相冷却系统中.     

HCPV用平板式环路热管实验研究

设计了一种用于高倍聚光光伏太阳能电池(HCPV)散热的混合烧结芯平板式环路热管,并实验研究了负荷、倾角、冷凝器参数等对热管启动和运行性能的影响.实验表明,该热管基本可满足HCPV负荷及安装角度要求,热面温度100℃内的最大负荷可达320 W(热流密度为40 W/cm2).蒸发器和储液器、蒸发器和冷凝器相对位置对热管性能影响很大.当储液器在蒸发器下方时启动更容易;冷凝器在蒸发器上方时低负荷启动温度下降.可通过减少冷凝器内冷却水流量,提升热管反重力运行的启动能力.     

R41跨临界单级压缩带回热器热泵系统研究

建立了跨临界单级压缩带回热器热泵系统的理论模型,并对R41(一氟甲烷)与CO2的循环特性进行了热力性能和火用的分析比较.结果表明:两种工质在常温下进行跨临界循环,R41系统的整体性能优于CO2系统.在选定工况下,R41系统比CO2系统的最优高压侧压力平均降低40.6%以上,系统性能系数平均提高14.2%以上,系统火用效率平均提高14.3%,且R41系统在单位质量制热量和压缩机排气温度方面均优于CO2系统.最后提出了通过减小气体冷却器传热温差、降低节流压差,以及合理利用蒸发器冷量来提高系统火用效率的观点.     

CO2蒸气固体颗粒制冷系统

压缩式制冷装置通常利用液体汽化吸热来获得冷量,由于CO2在三相点-56℃以下时产生固体,故不能用它作为制冷剂来获得-56℃以下的低温环境.提出一种利用CO2蒸气固体颗粒作为制冷剂的制冷系统,可以以CO2为工质获得三相点以下的温度.在该系统中,采用可调喷嘴、升华器、高、低压流量调节阀代替原系统中的蒸发器,并对该系统进行了理论循环分析.结果表明,理想情况下该系统COP比现有的制冷系统高约50%.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-