1.1 该试验方法涉及根据质量密度、导热系数和恒压比热的测量值计算热扩散率。它适用于任何可以确定这些数据的材料。本试验方法涵盖的温度范围为293至573K。本试验方法与用于获取密度、比热和导热系数原始数据的整体试验程序密切相关。它不能用作“独立”测试方法，因为通过该测试方法计算的热扩散率值取决于原始数据库的性质。该试验方法提供了计算热扩散率的一般指南，但不能被视为涵盖了与密度、比热和热导率相关的所有问题 注1: 通过本试验方法确定的扩散率为体积平均值，平均体积为 ≥ 2. × 10 −5. m 3. （20厘米 3. ). 这一要求要求必须使用体积大于最小平均体积的试样，并禁止使用闪光法测量热扩散率，如激光脉冲技术。 1.2 以国际单位制表示的数值应视为标准。本标准不包括其他测量单位。 1.3 本试验方法适用于各向同性样品；也就是说，热传输特性不取决于热流方向的样品。如果热导率取决于热流方向，则通过该测试方法得出的扩散率必须与电导率测量中使用的方向相同。 1.4 必须使用成分和含水量尽可能相同的试样进行导热系数、比热和质量密度测量。 1.5 地质构造的一般不均匀性排除了表征整个岩层或土层的热扩散系数的独特规范。地质介质的性质变化很大，不可能指定一种适用于所有可能情况的扩散率测定试验方法。一些最重要的限制来自以下因素: 1.5.1 可变矿物学- 如果所研究地层的矿物学随距离变化很大，其顺序与切割电导率、比热和密度样本的样本大小相同，则给定样本集的计算扩散率将取决于获得这些样本的精确位置。 1.5.2 可变孔隙度- 多孔岩石或土壤的热特性在很大程度上取决于孔隙度的数量和性质。空间变化的孔隙度引入了与空间变化成分遇到的问题类似的性质问题。此外，孔隙的特性可能阻止通过烘箱干燥完全脱水。 1.6 所有观察值和计算值应符合实践中确定的有效数字和舍入准则 D6026 . 1.6.1 本标准中用于规定如何收集/记录或计算数据的程序被视为行业标准。此外，它们代表了通常应保留的有效数字。使用的程序不考虑材料变化、获取数据的目的、特殊目的研究或用户目标的任何考虑因素； 通常的做法是增加或减少报告数据的有效位数，以与这些考虑因素相称。考虑工程设计分析方法中使用的有效数字超出了本标准的范围。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 热扩散系数是在求解瞬态热传导问题时产生的一个参数。它通常表征热脉冲在固体材料中扩散的速率。 5.2 求解瞬态热传导问题所需的参数数量取决于几何形状和施加的边界条件。在少数特殊情况下，只需要材料的热扩散率。在大多数情况下 k ，ρ，和 c p 除α外，还需要。该测试方法为与岩石热传输相关的数值或分析热传导计算提供了一组一致的参数。 5.3 为了使用本试验方法测定热扩散率，参数( k , ρ, c p )必须在尽可能接近相同的试样条件下测定。 5.4 通过本试验方法确定的扩散率只能用于分析岩石在与现有岩石相同的热条件下的热传输 k ，ρ，和 c p 测量。 注2: 本标准产生的结果的质量取决于执行该标准的人员的能力，以及所用设备和设施的适用性。符合实践标准的机构 D3740 通常认为能够胜任和客观的测试/采样/检查等。本标准的用户应注意遵守惯例 D3740 本身并不能保证可靠的结果。可靠的结果取决于许多因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 This test method involves calculation of the thermal diffusivity from measured values of the mass density, thermal conductivity, and specific heat at constant pressure. It is applicable for any materials where these data can be determined. The temperature range covered by this test method is 293 to 573 K. This test method is closely linked to the overall test procedure used in obtaining the primary data on density, specific heat, and thermal conductivity. It cannot be used as a “stand alone” test method because the thermal diffusivity values calculated by this test method are dependent on the nature of the primary data base. The test method furnishes general guidelines to calculate the thermal diffusivity but cannot be considered to be all-inclusive to capture issues related to the density, specific heat, and thermal conductivity Note 1: The diffusivity, as determined by this test method, is intended to be a volume average value, with the averaging volume being ≥ 2 × 10 −5 m 3 (20 cm 3 ). This requirement necessitates the use of specimens with volumes greater than the minimum averaging volume and precludes use of flash methods of measuring thermal diffusivity, such as the laser pulse technique. 1.2 The values stated in SI units are to be regarded as the standard. No other units of measurements are included in this standard. 1.3 This test method is intended to apply to isotropic samples; that is, samples in which the thermal transport properties do not depend on the direction of heat flow. If the thermal conductivity depends on the direction of heat flow, then the diffusivity derived by this test method must be associated with the same direction as that utilized in the conductivity measurement. 1.4 The thermal conductivity, specific heat, and mass density measurements must be made with specimens that are as near identical in composition and water content as possible. 1.5 The generally inhomogeneous nature of geologic formations precludes the unique specification of a thermal diffusivity characterizing an entire rock formation or soil layer. Geologic media are highly variable in character, and it is impossible to specify a test method for diffusivity determination that will be suitable for all possible cases. Some of the most important limitations arise from the following factors: 1.5.1 Variable Mineralogy— If the mineralogy of the formation under study is highly variable over distances on the same order as the size of the sample from which the conductivity, specific heat, and density specimens are cut, then the calculated diffusivity for a given set of specimens will be dependent on the precise locations from which these specimens were obtained. 1.5.2 Variable Porosity— The thermal properties of porous rock or soil are highly dependent on the amount and nature of the porosity. A spatially varying porosity introduces problems of a nature similar to those encountered with a spatially varying composition. In addition, the character of the porosity may preclude complete dehydration by oven drying. 1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.6.1 The procedure used to specify how data are collected/recorded or calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analytical methods for engineering design. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== 5.1 The thermal diffusivity is a parameter that arises in the solution of transient heat conduction problems. It generally characterizes the rate at which a heat pulse will diffuse through a solid material. 5.2 The number of parameters required for solution of a transient heat conduction problem depends on both the geometry and imposed boundary conditions. In a few special cases, only the thermal diffusivity of the material is required. In most cases, separate values of k , ρ, and c p are required in addition to α. This test method provides a consistent set of parameters for numerical or analytical heat conduction calculations related to heat transport through rocks. 5.3 In order to use this test method for determination of the thermal diffusivity, the parameters ( k , ρ, c p ) must be determined under as near identical specimen conditions as possible. 5.4 The diffusivity determined by this test method can only be used to analyze heat transport in rock under thermal conditions identical to those existing for the k , ρ, and c p measurements. Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.