一种燃料热沉标准物质候选物的纯度定值及不确定度分析

一种多环烃化合物作为超声速飞行器用燃料热沉标准物质候选物,对于燃料的热沉准确计量具有十分重要的意义.通过采用质量平衡和核磁定量两种不同测量原理的方法,对这种热沉标准物质候选物的纯度进行了定值,并进行了不确定度分析和评定.在此过程中,采用气相色谱法(GC-FID)对候选物的分装样品进行了均匀性检验和稳定性考察.研究结果表...     

高超声速飞行器综合热管理系统方案探讨

高超声速飞行器是当今世界航空航天领域研究的热点,由于其在飞行中遭受的热环境极其严酷,因 而可靠的综合热管理系统是安全飞行的保证。针对不同飞行任务的高超声速飞行器,分别提出了综合热管理系 统方案;对飞行时间短,飞行速度和高度变化快的飞行器,提出了以液氢燃料为主要热沉、相变蓄热材料为辅 助热沉的热管理方案;对飞行时间长,飞行马赫数高的飞行器,提出了以吸热型碳氢燃料为热沉的热管理方案; 分别探讨了两套方案涉及的关键技术,指出了未来研究工作的方向。     

固体生物质燃料中碳氢元素测量结果不确定度评定

基于三节炉测定固体生物质燃料的方法建立测量模型,分析三节炉法测定固体生物质燃料碳和氢测定结果的不确定度来源:所测试样按照文中方法评定的煤中碳氢测量结果为C_(ad)=(45.91±0.21)%,k=2;H_(ad)=(4.76±0.05)%,k=2;测量重复性是固体生物质燃料碳氢测量结果不确定度的主要来源。因此,严格控制重复性测定的条件,确保样品的均匀一致性、提高人员操作熟练程度,是提高三节炉法测定生物质燃料中碳氢结果精密度,降低测量重复性引入不确定度分量的关键环节。     

校准实验室中的不确定度

<正>在ISO等国际组织1993年联合颁布《测量不确定度表示指南(GUM)》以前,我国计量系统在计量检定规程和检定系统表制定、计量基标准建立、标准物质定值、计量标准考核等工作中广泛应用的是测量误差理论。GUM的颁布为全球测量不确定度评定与表示提出了通用方法,后来又推出包括蒙特卡洛法(MCM)等补充性文件。实验室认可尤其是校准实验室的要求推动了测量不确定度的应用。实验室认可要求校准实验室评估开展项目的不确定度、校     

标准物质定值与不确定度评定软件系统的研究与开发

标准物质定值与不确定评定是标准物质研制过程中的一个非常重要的阶段,涉及大量的数据处理与统计分析.在进行数据处理时,Excel功能相对薄弱,Matlab、SAS、SPSS等软件的使用则太过复杂.以ISO 35及相关技术规范为指导,研究完成了标准物质常用定值模式下的数据处理,包括均匀性检验及不均匀性带来的不确定度评定,稳定性检验及其不确定度的评定,定值不确定度评定以及总不确定度合成计算.以理论研究为基础,采用最新的软件开发技术,开发出了稳定可靠具有良好扩展性的标准物质定值与不确定度评定软件系统.     

WR-42功率基准系统有效效率不确定度评定

WR-42功率基准是一套微量热计系统,利用直流替代及量热技术对被测热敏电阻型功率座的有效效率进行定标。对WR-42功率基准系统中有效效率不确定度评定的过程进行了介绍,并给出了有效效率的测量结果与不确定度的评定结果。该基准的研制成功,填补了18～26.5GHz频段的空白,结合其它功率基准,使我国射频与微波功率计量基准频段从10MHz连续覆盖到了220GHz。     

氧弹热量计测量苯甲酸热值及其示值误差的不确定度评定

以苯甲酸标准物质为例,根据热值和热值示值误差的数学模型,逐步评定了热量计热容量、热值和热值示值误差的不确定度。研究了热量计温升不确定对热值不确定度的影响;探讨了标准物质热值不确定度对热值示值误差不确定度的影响。苯甲酸热值不确定度U（Q）为40J/g（k＝2）,苯甲酸热值示值误差的不确定度U（ΔQ）为30J/g（ k＝2）。评定结果对于煤炭等燃料热值不确定度评定,氧弹热量计仪器准确度评定和计量检定规程的修订具有指导意义。     

新版《通用计量术语及定义》系列讲座 第二讲 测量仪器的特性(一)

正一、准确度等级准确度等级是指"在规定工作条件下,符合规定的计量要求、使测量误差或仪器不确定度保持在规定极限内的测量仪器或测量系统的等别或级别"。测量仪器的使用一般可归纳为两种形式:第一,经评定合格后直接使用示值,这时测量仪器存在示值误差,但实际误差不超出最大允许误差的要求;第二,经评定得出示值误差后对测量仪器的示值进行修正或者定值,这时虽然部分地消除了测量仪器的偏移误差,但测量仪器的示值误差或实际值仍然存在不确定度。对前一种情况,测量仪器的准确度评定根据最大允许误差进行;后一种情况,以实际值的测量不确定度评定测量仪器的准确度。     

中国计量出版社新书推介

测量不确定度评定与表示实例———本书是全国计量标准、计量检定人员考核委员会为配合ＪＪＦ１０５９—１９９９测量不确定度评定与表示计量技术规范的宣贯而选编的 ,书中列举了测量不确定度评定与表示实例８０个 ,每个实例包括有关量值的测量方法、数学模型、方差和灵敏系统的计算、不确定度的评定、表示与报告等内容 ,对掌握测量不确定度评定和表示方法具有示范和指导作用。本书可供科研单位、检测／校准机构及工矿企业从事计量检定、检测／校准、产品检验、精密测试及科学实验的人员使用 ,也可供高等院校有关专业师生参考。定价 :６０．…     

富燃料推进剂燃烧热值测试不确定度分析

采用氧弹式量热计测定了某富燃料推进剂的燃烧热值,讨论了测定过程中量热系统热容量、内筒温升测量偏差、点火系统放热量、富燃料推进剂质量称量等因素引入的不确定度分量,计算出了氧弹式量热计测定某富燃料推进剂的燃烧热值的合成标准不确定度为19 J/g,扩展不确定度为38 J/g。     

A design method of thermoelectric coolerConception d'un refroidisseur thermoélectrique

A system design method of thermoelectric cooler is developed in the present study. The design calculation utilizes the performance curve of the thermoelectric module that is determined experimentally. An automatic test apparatus was designed and built to illustrate the testing. The performance test results of the module are used to determine the physical properties and derive an empirical relation for the performance of thermoelectric module. These results are then used in the system analysis of a thermoelectric cooler using a thermal network model. The thermal resistance of heat sink is chosen as one of the key parameters in the design of a thermoelectric cooler. The system simulation shows that there exists a cheapest heat sink for the design of a thermoelectric cooler. It is also shown that the system simulation coincides with experimental data of a thermoelectric cooler using an air-cooled heat sink with thermal resistance 0.2515°C/W. An optimal design of thermoelectric cooler at the conditions of optimal COP is also studied. The optimal design can be made either on the basis of the maximum value of the optimal cooling capacity, or on the basis of the best heat sink technology available.     

The Uncertainty in SCHF‐DT Thermal Conductivity Measurements of Lotus‐Type Porous Copper

Lotus‐type porous metals with many straight pores are attractive for use as heat‐sinks because a large heat‐transfer capacity can be obtained, due to the small diameter of the pores. In order to use lotus‐type porous copper effectively as a heat sink, it is important to know the effective thermal conductivity considering the effect of pores on heat conduction in the material. Since these metals have anisotropic pores, a steady‐state comparative longitudinal heat‐flow method for measuring thermal conductivity, referring to an ASTM standard, is better than other methods. So far, the effective thermal conductivity of lotus‐type porous copper has been measured by using specimens of different thickness (the SCHF‐DT method). In this paper, the uncertainty in the effective thermal conductivity of a specimen measured using this method was evaluated by comparison between numerical analysis and current experimental data. The following conclusions were drawn: 1) The uncertainty showed good agreement with the uncertainty analysis; 2) The contribution of the thermal grease thickness was large, based on a combined standard uncertainty analysis; and, 3) The effective thermal conductivity perpendicular to the pores of lotus copper can be measured within 10% uncertainty by this method.     

液体比热容实验系统的研制

基于流动型绝热量热法搭建了一套高温高压液体比热容实验系统,系统主要包括:流动型量热器、电加热控温系统以及内外绝热屏。该实验系统的温度范围为293~453 K,压力范围为0.1~20 MPa。为了检验实验系统的漏热损失,采用纯水在不同温度下进行标定;为了进一步检验实验系统的准确性,测量了甲苯和环己烷2种参考物质在不同温度和不同压力下的比定压热容,新实验系统的不确定性评定结果,比定压热容的扩展不确定度为1.41%（k=2）。     

Experimental studies on air-cooled NH3-H2O based modified gax absorption cooling system

An experimental investigation on the performance of an air-cooled modified generator absorber heat exchange (GAX) absorption cooling system has been carried out and presented in this paper. The conventional system is modified by incorporating high pressure GAX, low pressure GAX, a solution cooler and an additional solution heat exchanger to reduce the heat input to the system. The system is designed for a cooling capacity of 10.5 kW using ammonia-water (NH₃-H₂O) as the working fluid. The performance of the system in terms of the circulation ratio, internal heat recovery and coefficient of performance (COP) has been obtained. The system is capable of producing a low evaporator temperature of −5 °C, at a sink temperature of 35 °C, under no load conditions. The results indicate that at a generator and evaporator temperature of 120 °C and 2 °C respectively, the system delivers a maximum cooling capacity of about 9.5 kW with a fuel and total COP of 0.61 and 0.57 respectively.     

CCD芯片热电制冷的非稳态传热研究

针对散热受限热电制冷系统中温度非稳态变化过程,建立了一个简单的分析模型,基于该模型对CCD芯片热电制冷进行了仿真分析和实验研究.仿真和实验结果均表明:在散热受限条件下,热电制冷系统的热传过程长时间处于非稳态;存在一个最优制冷电流I_(max),当I_c相似文献   

Experimental study of a miniature vapor compression refrigeration system with two heat sink evaporators connected in series or in parallel

A miniature vapor compression refrigeration system included two heat sinks connected in series (indicated as series system) or in parallel (indicated as parallel system) was built. The performance of the series system was studied and compared with that of the parallel system. The results indicate that the largest cooling capacity of the two systems is about 160 W and the optimal refrigerant charge is about 0.6 M_total in the miniature vapor compress refrigeration (VCR) system. There is no relation between the optimal refrigerant charge and the arrangement of the heat sinks. The coefficient of performance (COP) of the series system ranged from 1.81 to 3.22, while the COP of the parallel system was in the range of 1.51–2.92 under the cooling capacity of 100 W. The cooling of the heat sink 2 lag behind that of the heat sink 1 in the serial system, while the refrigerant is difficult to equally distribute in the parallel system.     

Analysis and simulation of high-power LED arraywith microchannel heat sink

The high power light emitting diode (LED) array integrated with the microchannel heat sink is designed in this paper, and then optimal analysis and simulation have been carried out. According to the theory of heat transfer and fluid mechanics, the calculation of the thermal resistance for the microchannel heat sink is obtained, and the thermal resistance is minimized. Finally the simulation with FLUENT software is developed to verify the theoretical analysis.
Established analysis and simulation show that the width of the cooling channel is 0.1 mm, and the cooling water flow rate is 1 m/s. On the other hand, the system acquires the best heat dissipation effect, and the minimum of thermal resistance is 0.019 W/℃.     

大型空间环模器热沉仿真研究

用分布参数方法，建立了热沉动态数学模型，运用MATRIXx仿真平台，建立了仿真模型，并进行了动，静态工况仿真计算。得出了热沉在稳定工况下的温度场，流量与最大温差的关系及温度动态特性，为热沉的优化设计，温度控制提供了重要依据，也为调温系统的动态仿真奠定了基础。     

Ideal-Gas Heat Capacity for 2,3,3,3-Tetrafluoropropene (HFO-1234yf) Determined from Speed-of-Sound Measurements

The isobaric ideal-gas heat capacity for HFO-1234yf, which is expected to be one of the best alternative refrigerants for HFC-134a, was determined on the basis of speed-of-sound measurements in the gaseous phase. The speed of sound was measured by means of the acoustic resonance method using a spherical cavity. The resonance frequency in the spherical cavity containing the sample gas was measured to determine the speed of sound. After correcting for some effects such as the thermal boundary layer and deformation of the cavity on the resonance frequency, the speed of sound was obtained with a relative uncertainty of 0.01 %. Using the measured speed-of-sound data, the acoustic-virial equation was formulated and the isobaric ideal-gas heat capacity was determined with a relative uncertainty of 0.1 %. A temperature correlation function of the isobaric ideal-gas heat capacity for HFO-1234yf was also developed.