共查询到18条相似文献,搜索用时 125 毫秒
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为分析再生混凝土导热系数变化机理,进行了再生混凝土导热系数理论模型研究。在细观尺度上,将再生混凝土看作由新硬化砂浆、天然骨料、界面过渡区、孔隙相组成的四相复合材料。采用等效化方法,建立了界面过渡区导热系数模型并进行了验证,同时定义了等效界面过渡区(NITZ)影响系数η,η与再生混凝土导热系数有显著的线性关系。基于复合材料导热系数计算模型,利用η建立再生混凝土导热系数理论模型,计算结果与测试结果吻合较好,误差小于6%。在此基础上,根据该模型分析了各相组分导热系数、水灰比、骨料取代率、孔隙饱和度等因素对再生混凝土导热系数的影响,揭示了再生混凝土与普通混凝土传热差异,为再生混凝土传热机理的进一步研究提供了理论基础。 相似文献
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导热系数测量系统的数值模拟 总被引:1,自引:0,他引:1
对中国计量科学研究院的稳态保护热平板导热系数测量系统的温度场分布进行数值计算,并在此基础上对实验材料内测温点的选择进行了分析.结果表明,测温点复盖了实验材料内温度的最低和最高点,且呈线性分布,满足实验材料导热系数测量所需温度梯度测量的要求.此外,对热流密度测量的探讨发现,热流密度测量范围的确定是实现精密测量导热系数的关键. 相似文献
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根据金属纵向直接电加热的卡里劳希法则,利用Gleeble-2000热力学动态模拟试验机,通过通电加热细长棒试样时的功率能耗及两端长度上湿度的变化,测试金属材料的导热系数。对SM490YB H型钢进行了导热系数测试,结果表明,卡里劳希法则是可行的,试验方法便捷,试验数值准确,拓宽了Gleeble-2000型热模拟试验机的应用范围和领域。 相似文献
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M. Dell’Isola F. R. d’Ambrosio Alfano G. Giovinco E. Ianniello 《International Journal of Thermophysics》2012,33(8-9):1674-1685
The presence of moisture in building envelopes can have many causes and may lead to deterioration of useful thermophysical characteristics of the materials, to weakening of the building structure, and to facilitating growth of mold. The International Standard ISO 13788 establishes a calculation procedure for the determination of hygrometric characteristics of building components and materials, assuming that the influence of moisture content on the thermal field across walls, ceilings, and roofs may be neglected. However, condensed water increases the effective thermal conductivity of building materials, thus modifying the temperature profiles across the building envelope. This effect is analogous to the one due to the material aging. In this paper, the authors show the results of effective thermal-conductivity measurements in some commonly adopted building materials as a function of moisture content, in order to assess the potential significance of interstitial condensation on thermal losses and to verify if the maximum allowed moisture content reported is useful to prevent the decay of the thermal properties of building materials. 相似文献
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导热系数测试仪校准方法研究 总被引:1,自引:0,他引:1
根据防护热板法导热系数测试仪的原理和特点,在理论研究和实践测试的基础上,提出了一种通过精密表面温度计和导热系数参比板来校准其基本示值误差的方法.该方法测量简便,测量值稳定可靠,可溯源至国家计量基准,同时根据传热方程导出了基本误差的计算公式,对实际校准工作具有一定的参考价值. 相似文献
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L. Risegari M. Barucci E. Olivieri G. Ventura 《Journal of Low Temperature Physics》2006,144(1-3):49-59
At very low temperatures, the tunnelling theory for amorphous solids predicts a thermal conductivity κ α Tm, with m = 2. However, most of the data in the literature in the temperature range 0.1–1 K report an m < 2. We want to show that this discrepancy often disappears for T→ 0 K. Here we report the case of Polyvinyl Chloride (PVC) whose thermal conductivity is known in the 0.2–100 K temperature range. A new technique is described which makes the measurement of the exponent m of the thermal conductivity independent of the spurious thermal power. Such technique is particularly useful for measurements of κ when working with a low power refrigerator. We carried out measurements down to 50 mK, obtaining a thermal conductivity W/cm K for our PVC sample below 120 mK. 相似文献
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Zbyšek Pavlík Eva Vejmelková Lukáš Fiala Robert Černý 《International Journal of Thermophysics》2009,30(6):1999-2014
The effect of moisture content on the thermal conductivity of lime-based composites is investigated both experimentally and
theoretically. Experimental measurements of thermal conductivity as a function of moisture content from a dry state to a fully
water saturated state are performed using an impulse technique. The obtained experimental data are analyzed at first with
fundamental theoretical models, and it is found that they conform to both Wiener’s and Hashin–Shtrikman’s bounds. The thermal
conductivity of wet lime-based composites is then analyzed using several homogenization techniques, among them, Lichtenecker’s,
Polder and van Santen’s, and Dobson’s formulas. The validity of applied effective-media treatments is assessed comparing the
measured and calculated data. Lichtenecker’s equation is found to achieve the best agreement with experimental measurements. 相似文献
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P. Stachowiak V. V. Sumarokov J. Mucha A. Jeżowski 《Journal of Low Temperature Physics》1998,111(3-4):379-385
Thermal conductivity of solid CO was investigated over the temperature range 1.3–37 K by steady state flow method. The thermal conductivity coefficient reaches its maximum value 28 mW/cm K at about 6 K. Problem of the dipolar ordering at low temperatures has been discussed. 相似文献
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以保护热平板法测量保温材料导热率的测量装置为基础,采用数值模拟方法,对冷、热板上开设测温孔前后两种情况的温度分布进行了三维模拟计算,对其截面上的温度梯度进行了对比分析.结果显示,开设测温孔前、后计算得到温度梯度的相对偏差仅为0.16%,远小于保护热板法测量材料导热率1%相对标准不确定度.这一结果表明,测温孔的开设,对材料导热率测量的影响很小. 相似文献