1.1 本试验方法包括使用功率密度均匀、横向热流低的薄加热器测定隔热平板试样的稳态传热性能。具有低横向热导率的薄加热器可以减少不必要的横向热流，并避免需要主动边缘防护。 1.2 这种热传导测量的主要测试方法描述了一种原理，而不是一种特定的设备。该原理涉及确定穿过已知厚度试样的热流密度以及试样热表面和冷表面的温度。 1.3 在本试验方法中，给了仪器设计者相当大的自由度；由于各种设计都是可能的，因此中给出了设备的鉴定程序 5.3 . 1.4 如果要用本试验方法测定试样的热阻或热导率，则试样必须满足以下条件 2. : 1.4.1 试样在加热器等温区域上的部分必须准确代表整个试样。 1.4.2 样本的其余部分不应扭曲中定义的样本部分的热流 1.4.1 . 1.4.3 试样应具有热均匀性，以便热导率不是样品内位置的函数，而是方向、时间和温度的函数。试样应无孔洞、高密度体积以及试验表面或试样边缘之间的热桥。 1.4.4 试验方法 C177 描述了可以帮助确定以下情况的测试: 1.4 都很满意。在本试验方法中，测量值的差异小于2 % 可能被认为无关紧要，并且满足了要求。 1.5 除以下要求外，试样还应满足以下要求之一: 1.4 . 1.5.1 如果是术语中定义的均质材料 C168 然后通过该测试方法确定热阻率和热导率。 1.5.2 如果对层状或其他热不均匀材料进行测试，则可以通过该测试方法确定热阻和热导率。 1.6 使用本标准相同原理的薄加热器装置的两个版本如所述 附件A1 和 附件A2 . 它们在概念上相似，但在尺寸和构造上不同，因此保证对每种设计进行单独描述。该测试方法绝不会限制薄加热器元件的尺寸。所述装置之一使用薄金属箔，而另一个使用金属屏作为热源。较小的箔片装置设计用于快速测量薄至0.5 cm、厚至2 cm试样的热传递；然而，如果需要，可以设计使用箔片加热器的装置来测量更厚的材料。 更大的屏幕仪器设计用于测量厚度在3到15 cm之间的试样，其中精确极限取决于试样的热阻。两种仪器都使用热电偶测量温度，但也可以使用其他温度传感系统。 1.7 本测试方法涵盖了测量技术的理论和原理。除了说明满足规定要求的两个装置所需的施工细节外，本文件未提供其他施工细节。详细信息见参考文献 ( 1- 23 ) 3. 和附属物。 1.8 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。 1.9 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。 1.10 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====== 5.1 实践中描述了可能影响材料试样热传导特性的因素 C1045 以及测试方法的精度和偏差部分 C177 . 5.2 由于本试验方法规定的所需试验条件，应认识到获得的热性能不一定适用于所有服务条件，无需修改。例如，本试验方法通常规定，应在不含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（如平均温度和温差）的依赖性。 5.3 当开发出新的或改进的仪器设计时，应在至少两组已知长期热稳定性的不同材料上进行试验。在每种材料的工作范围内，应在至少两种不同的平均温度下对每种材料进行试验。应仔细研究结果中的任何差异，以确定原因，然后采取适当措施予以消除。 只有在对具有可追溯到公认国家标准实验室的已知热性能的材料进行成功验证研究后，才应认为使用该仪器获得的试验结果符合本试验方法。建议定期检查设备性能。 5.4 许多材料的热传导特性取决于先前的热历史。在多种条件下测试此类样本时，必须小心，以便按照限制对结果影响的顺序进行测试。 5.5 薄加热器装置的典型用途包括: 5.5.1 产品开发和质量控制应用。 5.5.2 在所需平均温度下测量热导率。 5.5.3 潮湿或接近熔点或其他临界温度的试样的热性能（见 注1 ). 注1: 由于使用了较小的温差和热源的低热容量，本试验方法所涵盖类型的仪器适用于研究含水分样品的热性能。 5.5.4 测定相对较高的 R 使用大型仪器对绝缘样品进行估价。对于金属网加热器装置，可以测量厚度高达15 cm的样品。

1.1 This test method covers the determination of the steady-state thermal transmission properties of flat-slab specimens of thermal insulation using a thin heater of uniform power density having low lateral heat flow. A thin heater with low lateral thermal conductance can reduce unwanted lateral heat flow and avoid the need for active-edge guarding. 1.2 This primary test method of thermal-transmission measurement describes a principle, rather than a particular apparatus. The principle involves determination of the thermal flux across a specimen of known thickness and the temperatures of the hot and cold faces of the specimen. 1.3 Considerable latitude is given to the designer of the apparatus in this test method; since a variety of designs is possible, a procedure for qualifying an apparatus is given in 5.3 . 1.4 The specimens must meet the following conditions if thermal resistance or thermal conductance of the specimen is to be determined by this test method 2 : 1.4.1 The portion of the specimen over the isothermal area of the heater must accurately represent the whole specimen. 1.4.2 The remainder of the specimen should not distort the heat flow in that part of the specimen defined in 1.4.1 . 1.4.3 The specimen shall be thermally homogeneous such that the thermal conductivity is not a function of the position within the sample, but rather may be a function of direction, time, and temperature. The specimen shall be free of holes, of high-density volumes, and of thermal bridges between the test surfaces or the specimen edges. 1.4.4 Test Method C177 describes tests that can help ascertain whether conditions of 1.4 are satisfied. For the purposes of this test method, differences in the measurements of less than 2 % may be considered insignificant, and the requirements fulfilled. 1.5 The specimens shall meet one of the following requirements, in addition to those of 1.4 . 1.5.1 If homogeneous materials as defined in Terminology C168 are tested, then the thermal resistivity and thermal conductivity can be determined by this test method. 1.5.2 If materials which are layered or otherwise thermally inhomogeneous are tested, thermal resistance and thermal conductance can be determined by this test method. 1.6 Two versions of thin-heater apparatus using the same principle of the standard are described in Annex A1 and Annex A2 . They are similar in concept but differ in size and construction, and hence warrant separate descriptions for each design. This test method in no way limits the size of the thin-heater element. One of the units described uses a thin metal foil, while the other uses a metal screen as the heat source. The smaller, foil apparatus is designed to make rapid measurements of heat transmission through specimens as thin as 0.5 cm and as thick as 2 cm; however, an apparatus using a foil heater could be designed to measure much thicker materials, if desired. The larger, screen apparatus is designed to measure specimens with thicknesses between 3 and 15 cm, where the exact limits depend on the thermal resistance of the specimens. Both apparatuses use thermocouples for measuring temperature, but other temperature-sensing systems can be used. 1.7 This test method covers the theory and principles of the measurement technique. It does not provide details of construction other than those required to illustrate two devices which meet the prescribed requirements. Detailed information is available in References ( 1- 23 ) 3 and the Adjunct. 1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.9 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. 1.10 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 ====== 5.1 Factors that may influence the thermal-transmission properties of a specimen of material are described in Practice C1045 and the Precision and Bias section of Test Method C177 . 5.2 Because of the required test conditions prescribed by this test method, it shall be recognized that the thermal properties obtained will not necessarily apply without modification to all conditions of service. As an example, this test method normally provides that the thermal properties shall be obtained on specimens that do not contain 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. 5.3 When a new or modified design of apparatus is evolved, tests shall be made on at least two sets of differing material of known long-term thermal stability. Tests shall be made for each material at a minimum of two different mean temperatures within the operating range of each. Any differences in results should be carefully studied to determine the cause and then be removed by appropriate action. Only after a successful verification study on materials having known thermal properties traceable to a recognized national standards laboratory shall test results obtained with this apparatus be considered to conform with this test method. Periodic checks of apparatus performance are recommended. 5.4 The thermal transmission properties of many materials depend upon the prior thermal history. Care must be exercised when testing such specimens at a number of conditions so that tests are performed in a sequence that limits such effects on the results. 5.5 Typical uses for the thin-heater apparatus include the following: 5.5.1 Product development and quality control applications. 5.5.2 Measurement of thermal conductivity at desired mean temperatures. 5.5.3 Thermal properties of specimens that are moist or close to melting point or other critical temperature (see Note 1 ). Note 1: Apparatus of the type covered by this test method apply to the study of thermal properties of specimens containing moisture because of the use of small temperature differences and the low thermal capacity of the heat source. 5.5.4 Determination of thermal properties of relatively high R value insulation samples with large apparatuses. In the case of the metal-screen heater apparatus, samples with thicknesses up to 15 cm can be measured.