数据机房用热管复合式空调节能性试验研究

为改进现有数据中心制冷空调系统耗能大、运行成本高等不足,设计了一套分离式热管与蒸气压缩式空调复合使用的机房空调系统,试验研究了其在不同环境温度下的制冷量和能效比,并对该复合空调系统节能性进行了分析。试验结果表明:当室外侧环境温度为7℃时,分离式热管制冷量达到最大值4575W,EER高达17.99。因此在冬季或春秋过度季节,仅运行热管工况,就可以满足机房制冷需求。综合全年空调运行工况分析,在哈尔滨、北京和广州地区全年分别至少有67%、52%和19%的时间不需要开启压缩机制冷,这可以大大降低机房制冷系统的能耗。     

压缩空气蓄能系统应用于低温制冷性能分析

压缩空气蓄能系统(compressed air energy storage,CAES)是一种新型的蓄能系统,利用储存的高压空气的膨胀功和膨胀后的低温空气进行制冷.常规的空气制冷系统在制取-50～-100℃的制冷温度时具有较好的经济性能,本文提出将这种常规的空气制冷系统与压缩空气蓄能系统相结合形成一种新型低温制冷系统.文章讨论了此种低温制冷系统的组成形式和运行方式,并计算其运行性能,且与常规的空气制冷系统和蒸气压缩制冷系统进行了对比.结果显示该新型低温制冷系统在-50～-100℃制冷温度时,性能优于常规系统.     

数据中心制冷系统冷源选择及能效分析

本文针对我国不同气候区的气候特点,以某中等规模数据中心为例,对风冷式直接蒸发系统和水冷式冷水机组系统两种常用的数据中心制冷系统进行了能效分析,量化给出了季节性和区域性气候差异对数据中心制冷系统的能效影响,分析了风冷式和水冷式系统在不同气候区的应用优势。对一种将热管循环与蒸气压缩制冷循环相结合的复合型自然冷源系统进行了运行测试,计算给出了不同气候区自然冷源的可用时间和节能潜力,分析结果可用于数据中心选址以及其制冷系统的优化设计。     

热管与蒸气压缩式复合机房空调系统实验研究

搭建了高效利用室外环境空气冷能的分离式热管与蒸气压缩式复合机房空调系统实验台,对系统在热管工况和蒸气压缩式工况的性能进行了实验研究。结果表明:复合空调系统在热管工况下换热量随换热温差、高差、风量的增大而增大;当换热温差进风温差从11.6℃增加到17.4℃,换热量增加了14.4%;风量由2937.4m3/h增加到4196.3m3/h,换热量增加了5.4%;高差由1.1m增大到2.0m,换热量增加了8.3%;该系统的最佳制冷剂充注量为5.4kg。该系统在蒸气压缩式制冷工况下也具有良好的运行效果,且可实现两种模式的灵活切换,表明该复合空调系统是一种的高效可靠机房空调系统。     

动力型分离式热管在机房空调中研究与应用

针对数据机房全天候空气调节需求,设计30k W动力型分离式热管模块,在标准焓差法实验室进行动力型分离式热管性能实验,结果表明:(1)屏蔽泵能够为热管系统持续提供足够驱动力,保证热管系统稳定、可靠的运行;(2)当热管系统回气温度与室外环境温度差≥ΔT时,热管系统制冷性能在设定工况下达到设计指标,验证了动力型分离式热管系统合理性和适用性;(3)动力型分离式热管系统的制冷量、COP随着室内外温差近似线性增长,在外界环境温度≤10℃的较宽的温度范围内使用热管系统替代蒸汽压缩式制冷系统,实现数据机房和通讯基站空调系统的低成本运行,大幅度节能减排;(4)针对机房负荷多变情况设计快速精确调节流量控制装置,实现对整个系统实施流量调节和能量控制,为热管系统控制策略设计提供了有价值的数据。     

两级复叠蒸气压缩制冷系统研究进展

复叠制冷系统耦合两套制冷系统运行,解决大温差工况下单级蒸气压缩制冷系统能效比低、压缩机排气温度高等问题,在制冷系统和热泵系统中应用广泛。与多级压缩制冷系统相比,复叠制冷系统可灵活选用高、低温级制冷剂,提升系统运行效率。两套制冷系统的耦合,使得影响复叠系统性能因素增多,保持系统高效运行的控制方案更加复杂。概述了两级复叠蒸气压缩制冷系统现状,指出了高低温循环制冷剂的合理选取、复叠系统热力循环的优化及高效的控制策略是目前提升复叠制冷系统性能的三种有效手段。采用CO_2二氧化碳作为低温级制冷剂优选最优的高温级制冷剂,基于控制策略优化运行能效比是当前研究热点。     

准三级蒸气压缩式制冷系统与两级压缩制冷系统的比较

对普通的双极压缩制冷系统进行改进,提出了一种准三级蒸汽压缩式制冷系统,在普通双极压缩制冷系统的基础上,在其低压压缩部分增加了由闪蒸器构成的补气系统,通过理论计算得出结论,与普通的两级压缩制冷系统相比,准三级蒸气压缩式制冷系统的制冷量及制冷COP,得到了明显的提高。     

分离式热管蒸气压缩复合式空调的实验研究

因为基站机房内部的热流密度非常高,需要空调全年运行,导致用电量很大。为此,设计了一套分离式重力热管蒸气压缩复合式空调。它可以根据机房的工况在热管模式、空调模式和热管空调复合模式之间自由切换,从而降低系统的全年总能耗。实验结果表明:在室外温度为15℃、进风温度为35℃时,新系统制冷量达18.5kW,能效比为4.4;当室外温度为15℃、进风温度为25℃时,制冷量达14.6kW,能效比为3.5;与传统的空调相比,新系统的年节能率在20%到55%之间。     

平行流冷凝器的传热计算与应用研究

针对数据中心用蒸汽压缩/热管复合型环控机组系列产品研发的需要,在分析国内外学者相关研究成果的基础上,建立了平行流换热器的计算模型,设计了外侧为热管冷凝器、内侧为制冷冷凝器的组合式平行流换热器,建立了30kW热管复合型制冷模块实验系统,进行了室外侧环境温度为35℃、10℃和16℃的压缩式制冷、热管制冷和热管复合制冷的工作性能实验。结果表明,所设计的组合式冷凝器达到预期指标,验证了设计计算模型的可靠性,为平行流冷凝器在大型热管复合环控机组中的工程应用提供了依据。     

制冷参数测量仪的设计

针对蒸气压缩式制冷循环的特点,提出了制冷参数测量仪的设计方案。通过测量制冷系统的蒸发温度、蒸发压力、冷凝温度、冷凝压力这四个参数,并结合饱和蒸汽表或压焓图、热力学基本性质和马丁-侯方程,可获得制冷系统性能参数和热力学参数;为满足高精度的参数测量,设计了可靠的恒流源电路;为解决压力传感器的温度漂移设计了二元曲线拟合的方法,补偿后的最大相对误差为0.53%。仪表具有制冷、制热、自动、真空度、气密性多种测量模式,可通过USB与上位机通讯,可用于空调、冰箱等单工质制冷系统测量,支持30余种冷媒。该仪表的研制填补了国内制冷领域专业数字式测量仪表的空白。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.