基于内外场合算的垂直埋管换热器传热模型

该文建立了垂直地埋管换热器传热理论模型,该模型能考虑钻孔内比热容和地埋管内循环液体沿竖直方向的对流换热。基于该理论模型编制了相应的计算软件,分析了竖直地埋管换热器钻孔内材料参数对其换热效率的影响。计算结果表明:当钻孔内回填料的导热系数较大、U形管两臂较近时,两臂之间会发生明显的热短路现象;U形管两臂间距越大,换热效率越高;U形管管径越大,换热效率越高;回填料的比热容对地埋管的换热效率在短期内有一定影响,当地埋管地源热泵系统长期运行时,回填料比热容的影响可以忽略;钻孔内回填料的导热系数对地埋管的换热效率有较大影响,当其小于岩土层导热系数时,地埋管的换热效率会随回填料导热系数的增大而较快提高;但当其大于岩土层导热系数时,由于两臂间的热短路增强,地埋管的换热效率随回填料导热系数的增加而趋于平缓。     

U型地埋管换热器热短路特性研究

针对竖直U型埋管地热换热器管间热短路问题,建立了U型埋地换热器三维传热模型,对地源热泵竖直型埋管地热换热器的热短路现象进行了量化分析,并对影响热短路的主要参数进行了模拟分析。研究表明,增大支管间距可减小热短路现象,但在加大钻井直径困难的条件下,增大管间距受限,所以效果不显著;但不同回填材料的导热系数对热短路的影响较大。因此,减小U型管地热换热器支管间热短路的有效措施是合理选择回填材料的导热系数。     

基于地下水流动地埋管热作用距离分析研究

地埋管换热器周围温度场随着运行时间变长不断向远处扩散,地下水流动使得埋管热作用距离沿流动方向大大增加。通过饱和含水层内地埋管换热模型,得到了地下水流动作用下埋管热作用距离的近似表达式,分析了地下水流速、土壤导热系数和孔隙率对热作用距离的影响。借助于地埋管热作用测试平台,分析了地下水流动作用下埋管热作用距离和热恢复特性,结果表明：地下水流动使得埋管热作用距离远大于纯导热模式,且热作用距离在埋管轴向不同埋深处大小不一,建议在地下水流速大于1×10-6m/s的地质区域,沿地下水流动方向设置埋管间距为8~10m。     

地下水流动对地埋管热作用距离影响的研究

地埋管换热器周围温度场随着运行时间变长不断向远处扩散,地下水流动使得埋管热作用距离沿流动方向大大增加。通过饱和含水层内地埋管换热模型,得到了地下水流动作用下埋管热作用距离的近似表达式,分析了地下水流速、土壤导热系数和孔隙率对热作用距离的影响。借助于地埋管热作用测试平台,分析了地下水流动作用下埋管热作用距离和热恢复特性,结果表明:地下水流动使得埋管热作用距离远大于纯导热模式,且热作用距离在埋管轴向不同埋深处大小不一,建议在地下水流速大于1×10-6m/s的地质区域,沿地下水流动方向设置埋管间距为8~10 m。     

成都某综合交通枢纽浅层地源热泵地埋管热物性分析与系统评价

基于成都某综合交通枢纽南北场咽喉区开展地质勘察数据,并对其开展岩土热响应试验分析与评价。地勘结果表明,工程区地下水类型主要为基岩裂隙承压水,地下水的渗流作用加强了热量交换速率,使测试得到的岩土体的综合热换功率值偏大,地下水对地埋管式地源热泵系统的运行较为有利。工程区的岩土体双U平均导热系数平均值为：2.45～2.78W/(m·K),所在地的岩土体（深度110m内）初始平均温度为18.32℃。各试验孔中,双U形式的地埋管换热功率均大于单U形式的热换功率,换热功率提高约22%。从测试效果和经济角度出发,结合四孔联合测试工况,建议选用双U25地埋管,夏季标准工况释热能力为42.89W/m,冬季标准工况取热能力为-42.66W/m。全年动态负荷计算分析结果表明,站房部分由可再生能源提供的空调冷热负荷比例可达32.1%,枢纽部分由地源热泵系统提供的空调冷热负荷比例可达21.5%。该研究成果可为在轨道交通领域推进浅层地热能利用提供可靠的技术路线及理论依据。     

银川市地埋管换热器不同深度换热能力分析

结合银川市地层特征及地源热泵以冬季供暖为主的特点,为提高地埋管换热器的换热能力,保证系统冬季取热量与夏季排热量基本平衡,维持系统长期稳定运行,提出适当增加垂直地埋管钻孔深度的方案。对银川市某地埋管地源热泵项目2组不同深度试验孔进行现场热响应试验,得到岩土体地埋管深度范围内的初始平均温度、综合导热系数和单位孔深取热能力随钻孔深度增加而增加的结论。研究结果可为该地区地埋管地源热泵项目可行性研究、工程设计提供参考。     

地源热泵系统的热响应实验方法研究

土壤的平均导热系数与热阻是影响地下埋管换热器传热性能及地源热泵系统节能性与经济性的重要因素。利用线热源理论,通过地源热泵的工作试验过程,得到系统进出口水温等参数,并通过最小二乘法对所得数据进行拟合,得到地埋管换热器钻孔的导热系数及土壤热物性参数,测试结论对于指导土壤热交换器设计与施工具有一定的参考价值。     

地源热泵岩土导热系数测试影响因素分析

建立了地源热泵岩土导热系数现场测试系统的三维数值模型,基于所建数值模型分析了测试时间、舍弃初始小时数、钻孔半径、岩土体初始温度、加热器输入功率等因素对岩土导热系数测试结果的影响。研究结果表明:热响应测试时间应大于70h;对于柱热源模型,随着钻孔尺寸的增大,辨识得到的导热系数逐渐减小;岩土初始温度对岩土导热系数辨识结果没有影响,但采用参数估计法作为辨识方法时,岩土初始温度的测试精度对辨识结果有较大影响;对于纯导热模型,加热器输入功率对岩土导热系数辨识结果没有影响。     

热探针测定装置参数实验研究

针对线热源理论自制的热探针在实际测定导热系数过程中所得结果受实验参数影响显著的问题,该文对加热时间、电压、试样直径3个实验参数展开研究,在不同的装置参数下测定乙二醇的导热系数,以探究三者对导热系数测定结果的影响及参数选取的最优区间。实验结果表明:热探针的最佳加热时间为40~60 s,最佳电压为1~2 V;电压2 V时可忽略试样直径对测定结果的影响;实验过程温度变化5℃时可显著降低试样对流引起的实验误差。研究结果可为热探针测定导热系数参数的选取提供可靠的数据参考,所得规律能有效降低热探针测定导热系数的误差。     

并联和串联连接的竖直双U型埋管地热换热器热短路的分析

利用地热换热器准三维传热模型,采用数值计算的方法对并联和串联布置竖直双U型埋管地热换热器支管间的热短路进行了分析;讨论了不同支管间距、不同回灌材料导热系数、不同深度,不同管内流量情况下的热短路。结果表明：并联连接的要比串联连接的热短路影响小。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。