1.1 本试验方法确定了当平坦均匀试样的表面与使用防护热板装置保持在恒定温度下的固体平行边界接触时，实验室测量其稳态热通量的标准。 1.2 为此目的设计的测试设备称为防护热板设备，是一种主要（或绝对）方法。该试验方法与ISO 8302相似，但不完全相同。 1.3 本试验方法规定了建造和运行令人满意的防护装置所需的一般设计要求- 热板装置。它涵盖了各种各样的设备结构、测试条件和操作条件。未给出符合本试验方法的详细设计，但必须在一般要求的约束下进行设计。参考文献中给出了防护热板装置设计、构造、校准和操作中使用的分析工具、概念和程序的示例 ( 1- 41 ) . 2. 1.4 该测试方法包括单面和双面测量模式。允许采用分布式和线源防护加热板设计。 用户应参考单面操作模式的标准实践，实践 第1044页 和在线源设备，练习 第1043页 ，了解这些加热器设计的更多详情。 1.5 防护热板装置可在垂直或水平热流下运行。但是，用户需要注意，因为如果试样内发生对流热流，两个方向的测试结果可能不同。 1.6 尽管对于在防护装置上可测量的样本电导的大小，没有明确的上限- 热板，出于实际原因，试样电导应小于16W/（m 2. K） 。 1.7 本试验方法适用于各种样品的测量，从不透明固体到多孔或透明材料，以及各种环境条件，包括在极端温度和各种气体和压力下进行的测量。 1.8 使用该测试方法可以成功地评估垂直于热通量方向的不均匀性，例如层状结构。然而，在热通量方向上具有不均匀性的测试样品，例如具有热桥的绝缘系统，可能会产生特定位置的结果，不应尝试使用此类设备。 参见测试方法 第363页 以获得测试这些系统的指导。 1.9 根据使用该方法的测量结果计算热传输财产应符合实践 第1045页 . 1.10 为了确保预期的精度和准确度，应用本标准的人员必须具备热测量和测试实践的要求以及与隔热材料和系统相关的传热理论的实际应用知识。应为每个设备提供详细的操作程序，包括设计原理图和电气图纸，以确保测试符合本测试方法。 此外，必须验证与设备连接的自动数据收集和处理系统的准确性。这可以通过校准和将具有已知结果的数据集输入计算机程序来实现。 1.11 对于这种类型的测试方法来说，建立设计和施工细节以及涵盖所有可能给不具备热流理论、温度测量和一般测试实践技术知识的人员带来困难的意外情况的程序是不可行的。用户还可能发现，在维修或修改设备时，有必要成为一名设计师或建设者，或两者兼而有之，对他们的基本理解和仔细的实验技术要求更高。 本试验方法的标准化无意以任何方式限制新的或改进的仪器或程序的未来开发。 1.12 本试验方法未规定设备操作所需的所有细节。取样、试样选择、预处理、试样安装和定位、试验条件选择和试验数据评估的决定应遵循适用的ASTM试验方法、指南、实践或产品规范或政府法规。如果没有适用的标准，则必须使用并记录反映公认传热原理的合理工程判断。 1.13 该测试方法允许使用广泛的设备设计和设计精度，以满足特定测量问题的要求。符合本试验方法要求对报告中每个报告变量的不确定性进行陈述。其中包括对所涉及的重大误差因素的讨论。 1.14 本试验方法中的主要部分安排如下: 部分 部分 范围 1. 参考文件 2. 术语 3. 试验方法总结 4. 意义和用途 5. 仪器 6. 试样制备和调节 7. 程序 8. 结果的计算 9 汇报 10 精度和偏差 11 关键词 12 数字 防护热板装置机械部件的总体布置 图1 防护热板装置中的热流图示 图2 报告表单示例 图3 附件 厚度的重要性 第1.1节 测量厚度 第1.2条 仪器的限制 第1.3条 温度限制 第1.4条 试样的限制 第1.5条 随机和系统误差分量 第1.6节 变量的错误组件 第1.7条 导热或热阻误差分析 第1.8条 热导率或热阻误差分析 第1.9条 不确定性验证 2010年10月 1.15 以国际单位制表示的值应视为标准值。本标准不包括其他测量单位。 1.16 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 具体的预防说明见 注释22 . 1.17 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《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 本试验方法包括平板试样的热通量测量和相关试验条件。防护热板装置通常用于测量通过具有“低”导热率的材料的稳态热通量，通常表示为“绝热体”。 “可接受的测量精度要求试样几何形状具有较大的面积与厚度比。 5.2 选择厚度、面积和密度尽可能相同的两个试样，并将一个试样放置在防护热板的每一侧。与防护热板和主防护板相对的试样表面与冷表面组件的表面接触。 5.3 即使在室温下，也不容易测量通过热绝缘体的稳态传热。这是因为通过试样的热传递是通过三种不同的传热模式（辐射、传导和对流）中的任何一种或全部进行的。 试样中的任何不均匀性或各向异性都可能需要特殊的实验预防措施来测量热流。在某些情况下，可能需要数小时甚至数天才能达到热稳定状态。不得建造防护系统，以迫使计量的热量仅通过被测绝缘试样的测试区域。材料中的水分含量可能会导致瞬态行为。随着时间或环境条件的变化，材料的物理或化学变化也可能永久性地改变试样。 5.4 将该测试方法应用于不同的测试绝缘要求设计者在设计选择建筑材料和测量和控制系统时做出选择。因此，当在环境温度与低温或高温下使用时，保护热板装置可能有不同的设计。设计阶段还必须选择测试厚度、温度范围、温差范围、环境条件和其他系统参数。 附件A1 其解决了设备的限制、厚度测量考虑因素和测量不确定性等问题，所有这些都必须在设备的设计和操作中考虑。 5.5 根据本试验方法制造和操作的仪器应能够准确测量其设计应用范围。由于该试验方法适用于广泛的试样特性、试验条件和仪器设计，因此，对试验方法的精度和偏差进行全面说明是不切实际的。需要对所使用的特定仪器进行分析，以指定报告结果的精度和偏差。因此，符合测试方法要求用户必须在报告的测试条件下估计并报告结果的不确定性。 5.6 新设备的鉴定。当开发新的或修改后的设计时，应至少对两种已知热稳定性的材料进行测试，并验证或校准可追溯到国家标准实验室的财产。应在至少两组温度条件下进行试验，这些温度条件应涵盖设备的工作范围。如果测试结果与国家标准实验室特征之间的差异被确定为显著，则应尽可能确定误差来源。 只有在与经认证的样品成功比较后，仪器才能声称符合本测试方法。建议定期继续检查，以确认设备的持续一致性。 5.7 由于以下因素，材料试样的热传递财产可能受到影响: （a） 材料成分 （b） 湿度或其他环境条件 （c） 时间或温度暴露 （d） 厚 （e） 试样上的温差 （f） 平均温度。因此，必须认识到，材料热传递财产代表值的选择必须基于对这些因素的考虑和足够的测试信息。 5.8 由于热通量及其不确定性可能取决于环境和仪器试验条件以及试样的固有特性，因此该试验方法的报告应包括对试样和试验条件的全面描述。 5.9 比较试验方法（如试验方法）的结果 第518页 取决于热通量参考标准的质量。本试验方法中的仪器是用于生成参考标准的绝对方法之一。任何比较方法的准确度都不会比参考程序的准确度好。 虽然比较方法（如试验方法）的精度可能 第518页 将与本试验方法（试验方法 第518页 不能更准确。如有争议，建议采用该测试方法。

1.1 This test method establishes the criteria for the laboratory measurement of the steady-state heat flux through flat, homogeneous specimen(s) when their surfaces are in contact with solid, parallel boundaries held at constant temperatures using the guarded-hot-plate apparatus. 1.2 The test apparatus designed for this purpose is known as a guarded-hot-plate apparatus and is a primary (or absolute) method. This test method is comparable, but not identical, to ISO 8302. 1.3 This test method sets forth the general design requirements necessary to construct and operate a satisfactory guarded-hot-plate apparatus. It covers a wide variety of apparatus constructions, test conditions, and operating conditions. Detailed designs conforming to this test method are not given but must be developed within the constraints of the general requirements. Examples of analysis tools, concepts and procedures used in the design, construction, calibration and operation of a guarded-hot-plate apparatus are given in Refs ( 1- 41 ) . 2 1.4 This test method encompasses both the single-sided and the double-sided modes of measurement. Both distributed and line source guarded heating plate designs are permitted. The user should consult the standard practices on the single-sided mode of operation, Practice C1044 , and on the line source apparatus, Practice C1043 , for further details on these heater designs. 1.5 The guarded-hot-plate apparatus can be operated with either vertical or horizontal heat flow. The user is cautioned however, since the test results from the two orientations may be different if convective heat flow occurs within the specimens. 1.6 Although no definitive upper limit can be given for the magnitude of specimen conductance that is measurable on a guarded-hot-plate, for practical reasons the specimen conductance should be less than 16 W/(m 2 K). 1.7 This test method is applicable to the measurement of a wide variety of specimens, ranging from opaque solids to porous or transparent materials, and a wide range of environmental conditions including measurements conducted at extremes of temperature and with various gases and pressures. 1.8 Inhomogeneities normal to the heat flux direction, such as layered structures, can be successfully evaluated using this test method. However, testing specimens with inhomogeneities in the heat flux direction, such as an insulation system with thermal bridges, can yield results that are location specific and shall not be attempted with this type of apparatus. See Test Method C1363 for guidance in testing these systems. 1.9 Calculations of thermal transmission properties based upon measurements using this method shall be performed in conformance with Practice C1045 . 1.10 In order to ensure the level of precision and accuracy expected, persons applying this standard must possess a knowledge of the requirements of thermal measurements and testing practice and of the practical application of heat transfer theory relating to thermal insulation materials and systems. Detailed operating procedures, including design schematics and electrical drawings, should be available for each apparatus to ensure that tests are in accordance with this test method. In addition, automated data collecting and handling systems connected to the apparatus must be verified as to their accuracy. This can be done by calibration and inputting data sets, which have known results associated with them, into computer programs. 1.11 It is not practical for a test method of this type to establish details of design and construction and the procedures to cover all contingencies that might offer difficulties to a person without technical knowledge concerning theory of heat flow, temperature measurements and general testing practices. The user may also find it necessary, when repairing or modifying the apparatus, to become a designer or builder, or both, on whom the demands for fundamental understanding and careful experimental technique are even greater. Standardization of this test method is not intended to restrict in any way the future development of new or improved apparatus or procedures. 1.12 This test method does not specify all details necessary for the operation of the apparatus. Decisions on sampling, specimen selection, preconditioning, specimen mounting and positioning, the choice of test conditions, and the evaluation of test data shall follow applicable ASTM Test Methods, Guides, Practices or Product Specifications or governmental regulations. If no applicable standard exists, sound engineering judgment that reflects accepted heat transfer principles must be used and documented. 1.13 This test method allows a wide range of apparatus design and design accuracy to be used in order to satisfy the requirements of specific measurement problems. Compliance with this test method requires a statement of the uncertainty of each reported variable in the report. A discussion of the significant error factors involved is included. 1.14 Major sections within this test method are arranged as follows: Section Section Scope 1 Referenced Documents 2 Terminology 3 Summary of Test Method 4 Significance and Use 5 Apparatus 6 Specimen Preparation and Conditioning 7 Procedure 8 Calculation of Results 9 Report 10 Precision and Bias 11 Keywords 12 Figures General Arrangement of the Mechanical Components of the Guarded-Hot-Plate Apparatus Fig. 1 Illustration of Heat Flow in the Guarded-Hot-Plate Apparatus Fig.2 Example Report Form Fig. 3 Annexes Importance of Thickness A1.1 Measuring Thickness A1.2 Limitations Due to Apparatus A1.3 Limitations Due to Temperature A1.4 Limitations Due to Specimen A1.5 Random and Systematic Error Components A1.6 Error Components for Variables A1.7 Thermal Conductance or Thermal Resistance Error Analysis A1.8 Thermal Conductivity or Thermal Resistivity Error Analysis A1.9 Uncertainty Verification A1.10 1.15 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.16 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. Specific precautionary statements are given in Note 22 . 1.17 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 This test method covers the measurement of heat flux and associated test conditions for flat specimens. The guarded-hot-plate apparatus is generally used to measure steady-state heat flux through materials having a “low” thermal conductivity and commonly denoted as “thermal insulators.” Acceptable measurement accuracy requires a specimen geometry with a large ratio of area to thickness. 5.2 Two specimens are selected with their thickness, areas, and densities as identical as possible, and one specimen is placed on each side of the guarded-hot-plate. The faces of the specimens opposite the guarded-hot-plate and primary guard are placed in contact with the surfaces of the cold surface assemblies. 5.3 Steady-state heat transmission through thermal insulators is not easily measured, even at room temperature. This is due to the fact heat transmission through a specimen occurs by any or all of three separate modes of heat transfer (radiation, conduction, and convection). It is possible that any inhomogeneity or anisotropy in the specimen will require special experimental precautions to measure that flow of heat. In some cases it is possible that hours or even days will be required to achieve the thermal steady-state. No guarding system can be constructed to force the metered heat to pass only through the test area of insulation specimen being measured. It is possible that moisture content within the material will cause transient behavior. It is also possible that and physical or chemical change in the material with time or environmental condition will permanently alter the specimen. 5.4 Application of this test method on different test insulations requires that the designer make choices in the design selection of materials of construction and measurement and control systems. Thus it is possible that there will be different designs for the guarded-hot-plate apparatus when used at ambient versus cryogenic or high temperatures. Test thickness, temperature range, temperature difference range, ambient conditions and other system parameters must also be selected during the design phase. Annex A1 is referenced to the user, which addresses such issues as limitations of the apparatus, thickness measurement considerations and measurement uncertainties, all of which must be considered in the design and operation of the apparatus. 5.5 Apparatus constructed and operated in accordance with this test method should be capable of accurate measurements for its design range of application. Since this test method is applicable to a wide range of specimen characteristics, test conditions, and apparatus design, it is impractical to give an all-inclusive statement of precision and bias for the test method. Analysis of the specific apparatus used is required to specify a precision and bias for the reported results. For this reason, conformance with the test method requires that the user must estimate and report the uncertainty of the results under the reported test conditions. 5.6 Qualification of a new apparatus. When a new or modified design is developed, tests shall be conducted on at least two materials of known thermal stability and having verified or calibrated properties traceable to a national standards laboratory. Tests shall be conducted for at least two sets of temperature conditions that cover the operating range for the apparatus. If the differences between the test results and the national standards laboratory characterization are determined to be significant, then the source of the error shall, if possible, be identified. Only after successful comparison with the certified samples, can the apparatus claim conformance with this test method. It is recommended that checks be continued on a periodic basis to confirm continued conformance of the apparatus. 5.7 The thermal transmission properties of a specimen of material have the potential to be affected due to the following factors: (a) composition of the material (b) moisture or other environmental conditions (c) time or temperature exposure (d) thickness (e) temperature difference across the specimen (f) mean temperature. It must be recognized, therefore, that the selection of a representative value of thermal transmission properties for a material must be based upon a consideration of these factors and an adequate amount of test information. 5.8 Since both heat flux and its uncertainty may be dependent upon environmental and apparatus test conditions, as well as intrinsic characteristics of the specimen, the report for this test method shall include a thorough description of the specimen and of the test conditions. 5.9 The results of comparative test methods such as Test Method C518 depend on the quality of the heat flux reference standards. The apparatus in this test method is one of the absolute methods used for generation of the reference standards. The accuracy of any comparative method can be no better than that of the referenced procedure. While it is possible that the precision of a comparative method such as Test Method C518 will be comparable with that of this test method, Test Method C518 cannot be more accurate. In cases of dispute, this test method is the recommended procedure.