1.1 本试验方法包括使用热流计装置测量通过平板试样的稳态热传导。 1.2 热流计装置因其概念相对简单、快速且适用于广泛的试样而被广泛使用。如果在预期热流范围内进行校准，则热流计装置的精度和偏差可以很好。这意味着应使用类似类型的材料、类似的热导率、类似的厚度、平均温度和温度梯度进行校准，如试样预期的那样。 1.3 这是一种比较或二次测量方法，因为应使用具有已知热传导特性的样本来校准仪器。 校准样品的特性必须可追溯到绝对测量方法。校准样品应从公认的国家标准实验室获得。 1.4 热流计装置在恒定但不同的温度下通过两个平行板之间的试样建立稳态一维热流。通过使用校准标准对热流传感器进行适当校准，并通过测量板温度和板分离。傅立叶导热定律用于计算热导率、热阻或热阻和热导率。 1.5 本试验方法应结合实践使用 C1045 . 热工技术在测量技术和提高对材料热流原理的理解方面取得了许多进展。 这些进展促使对热传输特性测量的概念方法进行了修订 ( 1- 4. ) . 2. 该测试方法的所有用户都应该了解这些概念。 1.6 本试验方法适用于通过各种试样特性和环境条件测量热传导。该方法已在10至40°C的环境条件下使用，厚度约为250 mm，板材温度为-195°C至540°C，厚度为25 mm ( 5. , 6. ) . 1.7 本试验方法可用于表征材料特性，其可能代表也可能不代表实际使用条件。其他测试方法，如测试方法 C236 或 C976 如果需要，应使用。 1.8 为了满足本试验方法的要求，试样的热阻应大于0。 10米 2. · K/W 在热流方向上，应使用边缘绝缘或防护加热器或两者来控制边缘热损失。 1.9 在这种类型的测试方法中，试图建立结构和程序的细节，以涵盖可能给缺乏相关技术知识的人带来困难的所有意外情况，是不现实的。因此，本试验方法的使用者应具有足够的知识，以满意地满足其需求。例如，需要了解传热原理、低水平电气测量和一般测试程序。 1.10 该方法的用户必须熟悉并理解附录。本附录对解决设备设计和误差分析至关重要。 1.11 本试验方法的标准化无意以任何方式限制研究人员改进或新方法或程序的未来发展。 1.12 由于热流计装置的设计不是一件简单的事情，因此，本文给出了证明装置性能的程序 附录X3 . 1.13 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.14 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、健康和环境实践，并确定监管限制的适用性。 1.15 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 本试验方法提供了一种快速测定隔热材料和其他材料稳态传热性能的方法，在适当校准仪器后，具有高精度。 4.2 正确校准热流计装置需要使用具有先前通过试验方法确定的热传导特性的样品进行校准 C177 或 C1114 . 注1: 仪器的校准通常需要与试样预期的材料类型、热导率、厚度、平均温度和温度梯度相似的试样。 4.3 给定材料或产品试样的热传导特性可能因材料成分的变化而变化； 受湿气或其他条件影响；随时间变化；随平均温度和温差变化；并取决于之前的热历史。因此，必须认识到，在特定应用中代表材料的热传输特性的典型值的选择应基于对这些因素的考虑，并且在不修改所有使用条件的情况下不一定适用。 4.3.1 例如，本试验方法规定，应在不含任何游离水分的试样上获得热性能，尽管在使用中可能无法实现此类条件。更基本的是热特性对变量的依赖性，例如平均温度和温差。 这些相关性应在典型使用条件下进行测量或测试。 4.4 在测量过程中，应特别注意表现出明显不均匀性、各向异性、刚度或特别高或低的热流阻力的试样（见实践） C1045 ). 当试样中存在热桥时，使用热流计装置可能会产生非常不可靠的结果。如果存在热桥并与热流平行，则所得结果可能毫无意义。当在高温或低温、高于或低于大气压的环境压力或惰性或危险的特殊环境气体中进行测量时，也需要特别注意。 4.5 任何给定测试方法准确性的确定是仪器设计、相关仪器和受试样品类型的函数（见第节） 10 )，但该试验方法能够在±2℃范围内测定热传导特性 % 通过试验方法确定的 C177 当环境温度接近试验的平均温度时( T （环境）= T （平均值）±1°C），并且在10到40°C的范围内。在所有情况下，热流计装置的精度永远不会优于用于校准装置的主要标准的精度。 4.5.1 当本试验方法用于产品认证试验时，仪器应具有 A1.7 应遵循以下程序之一: 4.5.1.1 在认证试验之前或之后的24小时内，应使用可追溯至认证日期前不超过五年的公认国家标准实验室的二级转移标准或校准标准对仪器进行校准检查。 应将两次校准的平均值用作校准因子，并用该平均值认证样品。当校准系数的变化大于1时 %, 应重新测试标准试样，并计算新的平均值。如果校准系数的变化仍然大于1 % 应使用第节中的程序校准仪器 6. . 4.5.1.2 其中，仪器的短期和长期稳定性均已被证明优于1 % 读数（参见第节 10 )，仪器可以不太频繁的间隔进行校准，不超过30天。只有在测试后的校准测试之后，并且只有在先前校准测试的校准系数变化小于1时，才能对如此测试的样本进行认证 %. 当校准变化大于1时 %, 该间隔的试验结果应视为无效，并根据 4.5.1.1 . 4.5.2 按照第节校准的热流计装置进行测量的精度（重复性） 6.6 通常比±1好得多 % 的平均值。该精度用于识别校准中的变化，在质量控制应用中是可取的。

1.1 This test method covers the measurement of steady state thermal transmission through flat slab specimens using a heat flow meter apparatus. 1.2 The heat flow meter apparatus is used widely because it is relatively simple in concept, rapid, and applicable to a wide range of test specimens. The precision and bias of the heat flow meter apparatus can be excellent provided calibration is carried out within the range of heat flows expected. This means calibration shall be carried out with similar types of materials, of similar thermal conductances, at similar thicknesses, mean temperatures, and temperature gradients, as expected for the test specimens. 1.3 This a comparative, or secondary, method of measurement since specimens of known thermal transmission properties shall be used to calibrate the apparatus. Properties of the calibration specimens must be traceable to an absolute measurement method. The calibration specimens should be obtained from a recognized national standards laboratory. 1.4 The heat flow meter apparatus establishes steady state one-dimensional heat flux through a test specimen between two parallel plates at constant but different temperatures. By appropriate calibration of the heat flux transducer(s) with calibration standards and by measurement of the plate temperatures and plate separation. Fourier’s law of heat conduction is used to calculate thermal conductivity, and thermal resistivity or thermal resistance and thermal conductance. 1.5 This test method shall be used in conjunction with Practice C1045 . Many advances have been made in thermal technology, both in measurement techniques and in improved understanding of the principles of heat flow through materials. These advances have prompted revisions in the conceptual approaches to the measurement of the thermal transmission properties ( 1- 4 ) . 2 All users of this test method should be aware of these concepts. 1.6 This test method is applicable to the measurement of thermal transmission through a wide range of specimen properties and environmental conditions. The method has been used at ambient conditions of 10 to 40°C with thicknesses up to approximately 250 mm, and with plate temperatures from –195°C to 540°C at 25-mm thickness ( 5 , 6 ) . 1.7 This test method may be used to characterize material properties, which may or may not be representative of actual conditions of use. Other test methods, such as Test Methods C236 or C976 should be used if needed. 1.8 To meet the requirements of this test method the thermal resistance of the test specimen shall be greater than 0.10 m 2 · K/W in the direction of the heat flow and edge heat losses shall be controlled, using edge insulation, or a guard heater, or both. 1.9 It is not practical in a test method of this type to try to establish details of construction and procedures to cover all contingencies that might offer difficulties to a person without pertinent technical knowledge. Thus users of this test method shall have sufficient knowledge to satisfactorily fulfill their needs. For example, knowledge of heat transfer principles, low level electrical measurements, and general test procedures is required. 1.10 The user of this method must be familiar with and understand the Annex. The Annex is critically important in addressing equipment design and error analysis. 1.11 Standardization of this test method is not intended to restrict in any way the future development of improved or new methods or procedures by research workers. 1.12 Since the design of a heat flow meter apparatus is not a simple matter, a procedure for proving the performance of an apparatus is given in Appendix X3 . 1.13 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.14 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.15 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 This test method provides a rapid means of determining the steady-state thermal transmission properties of thermal insulations and other materials with a high level of accuracy when the apparatus has been calibrated appropriately. 4.2 Proper calibration of the heat flow meter apparatus requires that it be calibrated using specimen(s) having thermal transmission properties determined previously by Test Methods C177 , or C1114 . Note 1: Calibration of the apparatus typically requires specimens that are similar to the types of materials, thermal conductances, thicknesses, mean temperatures, and temperature gradients as expected for the test specimens. 4.3 The thermal transmission properties of specimens of a given material or product may vary due to variability of the composition of the material; be affected by moisture or other conditions; change with time; change with mean temperature and temperature difference; and depend upon the prior thermal history. It must be recognized, therefore, that the selection of typical values of thermal transmission properties representative of a material in a particular application should be based on a consideration of these factors and will not apply necessarily without modification to all service conditions. 4.3.1 As an example, this test method provides that the thermal properties shall be obtained on specimens that do not contain any free moisture although in service such conditions may not be realized. Even more basic is the dependence of the thermal properties on variables, such as mean temperature and temperature difference. These dependencies should be measured or the test made at conditions typical of use. 4.4 Special care shall be taken in the measurement procedure for specimens exhibiting appreciable inhomogeneities, anisotropies, rigidity, or especially high or low resistance to heat flow (see Practice C1045 ). The use of a heat flow meter apparatus when there are thermal bridges present in the specimen may yield very unreliable results. If the thermal bridge is present and parallel to the heat flow the results obtained may well have no meaning. Special considerations also are necessary when the measurements are conducted at either high or low temperatures, in ambient pressures above or below atmospheric pressure, or in special ambient gases that are inert or hazardous. 4.5 The determination of the accuracy of the method for any given test is a function of the apparatus design, of the related instrumentation, and of the type of specimens under test (see Section 10 ), but this test method is capable of determining thermal transmission properties within ± 2 % of those determined by Test Method C177 when the ambient temperature is near the mean temperature of the test ( T (ambient) = T (mean) ± 1°C), and in the range of 10 to 40°C. In all cases the accuracy of the heat flow meter apparatus can never be better than the accuracy of the primary standards used to calibrate the apparatus. 4.5.1 When this test method is to be used for certification testing of products, the apparatus shall have the capabilities required in A1.7 and one of the following procedures shall be followed: 4.5.1.1 The apparatus shall have its calibration checked within 24 h before or after a certification test using either secondary transfer standards traceable to, or calibration standards whose values have been established by, a recognized national standards laboratory not more than five years prior to the certification date. The average of two calibrations shall be used as the calibration factor and the specimen(s) certified with this average value. When the change in calibration factor is greater than 1 %, the standard specimen shall be retested and a new average calculated. If the change in calibration factor is still greater than 1 % the apparatus shall be calibrated using the procedure in Section 6 . 4.5.1.2 Where both the short and long term stability of the apparatus have been proven to be better than 1 % of the reading (see Section 10 ), the apparatus may be calibrated at less frequent intervals, not exceeding 30 days. The specimens so tested cannot be certified until after the calibration test following the test and then only if the change in calibration factor from the previous calibration test is less than 1 %. When the change in calibration is greater than 1 %, test results from this interval shall be considered void and the tests repeated in accordance with 4.5.1.1 . 4.5.2 The precision (repeatability) of measurements made by the heat flow meter apparatus calibrated as in Section 6.6 normally are much better than ±1 % of the mean value. This precision is required to identify changes in calibration and is desirable in quality control applications.