1.1 本规程涵盖了根据试验方法使用的圆线热源防护热板的设计 C177 . 注1: 试验方法 C177 介绍了保护式热板装置及其在平板试件传热性能测定中的应用。原则上，试验方法包括设计有防护热板的设备，防护热板具有分布式或线性热源。 1.2 具有圆形线热源的防护热板是一种设计，其中仪表和防护板是具有相对较少数量的加热器的圆形板，每个加热器沿着固定半径的圆形路径嵌入。在操作中，来自每条线热源的热量径向流入板中，并通过试样轴向传递。 1.3 仪表和防护板由连续的导热材料制成。 板的厚度足够厚，对于典型的试样热导率，防护热板的径向和轴向温度变化非常小。通过线路热源的适当位置，使仪表板边缘的温度等于仪表板的平均温度，从而便于温度测量和热防护。 1.4 线路热源保护的热板已在平均温度范围内成功使用，从 − 10到 + 65°C，圆形金属板和仪表板中的单线热源。参考文献中给出了仪表板中具有单线热源的圆线热源防护热板设计的时间发展 ( 1. 9 ) . 2. 1.5 对于高温应用，线热源保护的热板已成功使用，平均温度为7-160°C，带有圆形金属板和多条线- 仪表板中的热源。参考文献中给出了仪表板中具有多个线热源的圆线热源防护热板的时间发展 ( 10- 14 ) . 注2: 附件中提供了双线热源防护热板装置的施工详图和说明。 3. 1.6 这种做法并不排除( 1. )更低或更高的温度；( 2. )圆形以外的板几何形状；( 3. )除圆形以外的线形热源几何形状；或 4. )使用由陶瓷、复合材料或其他材料制成的板材。 1.7 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.8 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。 1.9 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 4.1 本规程描述了带圆线热源的防护热板的设计，并为确定仪表板的平均温度提供了指导。它提供了以下信息和计算程序:( 1. )边缘热损失或增益的控制( 附件A1 ); ( 2. )线路热源的位置和安装( 附件A2 ); ( 3. )仪表与护板间隙的设计( 附录X1 ); 和 4. )仪表板加热器引线的位置( 附录X2 ). 4.2 带有一条或多条线的圆形防护热板- 热源易于进行数学分析，从而根据测量的功率输入和在一个或多个已知位置的测量温度来计算平均表面温度。此外，圆板几何形状简化了对试样边缘热增益或热损失引起的误差的数学分析（参见参考文献 ( 15 , 16 ) ). 4.3 线热源以规定的半径放置在仪表板中，使得仪表板外缘的温度等于仪表区域的平均表面温度。因此，仪表板的平均温度的确定是通过放置在间隙附近的少量温度传感器来完成的。 4.4 具有一个或多个线路热源的防护热板将具有径向温度变化，与试样的平均温度降相比，最大温差非常小。 只要防护措施足够，只有仪表板的平均表面温度才能进入热传输特性的计算。 4.5 应注意设计圆线热源保护的热板，以使通向每个加热器的电流不会显著改变仪表和保护板中的温度分布，或者以已知的方式影响这些温度分布，从而进行适当的校正。 4.6 在防护热板中使用一个或几个圆形线热源简化了结构和维修。对于室温操作，板通常为一体式金属结构，因此易于制造到所需的厚度和平面度。相对于分布式热源热板的间隙设计，间隙的设计也被简化。 4.7 在单面操作模式下（参见实践 C1044 )，线热源设计在轴向方向上的对称性最大限度地减少了由于穿过间隙的不希望的热流而引起的误差。

1.1 This practice covers the design of a circular line-heat-source guarded hot plate for use in accordance with Test Method C177 . Note 1: Test Method C177 describes the guarded-hot-plate apparatus and the application of such equipment for determining thermal transmission properties of flat-slab specimens. In principle, the test method includes apparatus designed with guarded hot plates having either distributed- or line-heat sources. 1.2 The guarded hot plate with circular line-heat sources is a design in which the meter and guard plates are circular plates having a relatively small number of heaters, each embedded along a circular path at a fixed radius. In operation, the heat from each line-heat source flows radially into the plate and is transmitted axially through the test specimens. 1.3 The meter and guard plates are fabricated from a continuous piece of thermally conductive material. The plates are made sufficiently thick that, for typical specimen thermal conductances, the radial and axial temperature variations in the guarded hot plate are quite small. By proper location of the line-heat source(s), the temperature at the edge of the meter plate is made equal to the mean temperature of the meter plate, thus facilitating temperature measurements and thermal guarding. 1.4 The line-heat-source guarded hot plate has been used successfully over a mean temperature range from − 10 to + 65°C, with circular metal plates and a single line-heat source in the meter plate. The chronological development of the design for circular line-heat-source guarded hot plates having a single line-heat source in the meter plate is given in Refs ( 1- 9 ) . 2 1.5 For high-temperature applications, the line-heat-source guarded hot plate has been used successfully over a mean temperature from 7 to 160°C, with circular metal plates and multiple line-heat sources in the meter plate. The chronological development for circular line-heat-source guarded hot plates having multiple line-heat sources in the meter plate is given in Refs ( 10- 14 ) . Note 2: Detailed drawings and descriptions for the construction of two line-heat-source guarded-hot-plate apparatuses are available in the adjunct. 3 1.6 This practice does not preclude ( 1 ) lower or higher temperatures; ( 2 ) plate geometries other than circular; ( 3 ) line-heat-source geometries other than circular; or ( 4 ) the use of plates fabricated from ceramics, composites, or other materials. 1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.8 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. 1.9 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 practice describes the design of a guarded hot plate with circular line-heat sources and provides guidance in determining the mean temperature of the meter plate. It provides information and calculation procedures for: ( 1 ) control of edge heat loss or gain ( Annex A1 ); ( 2 ) location and installation of line-heat sources ( Annex A2 ); ( 3 ) design of the gap between the meter and guard plates ( Appendix X1 ); and ( 4 ) location of heater leads for the meter plate ( Appendix X2 ). 4.2 A circular guarded hot plate with one or more line-heat sources is amenable to mathematical analysis so that the mean surface temperature is calculated from the measured power input and the measured temperature(s) at one or more known locations. Further, a circular plate geometry simplifies the mathematical analysis of errors resulting from heat gains or losses at the edges of the specimens (see Refs ( 15 , 16 ) ). 4.3 The line-heat source(s) is (are) placed in the meter plate at a prescribed radius (radii) such that the temperature at the outer edge of the meter plate is equal to the mean surface temperature over the meter area. Thus, the determination of the mean temperature of the meter plate is accomplished with a small number of temperature sensors placed near the gap. 4.4 A guarded hot plate with one or more line-heat sources will have a radial temperature variation, with the maximum temperature differences being quite small compared to the average temperature drop across the specimens. Provided guarding is adequate, only the mean surface temperature of the meter plate enters into calculations of thermal transmission properties. 4.5 Care shall be taken to design a circular line-heat-source guarded hot plate so that the electric-current leads to each heater either do not significantly alter the temperature distributions in the meter and guard plates or else affect these temperature distributions in a known way so that appropriate corrections are applied. 4.6 The use of one or a few circular line-heat sources in a guarded hot plate simplifies construction and repair. For room-temperature operation, the plates are typically of one-piece metal construction and thus are easily fabricated to the required thickness and flatness. The design of the gap is also simplified, relative to gap designs for distributed-heat-source hot plates. 4.7 In the single-sided mode of operation (see Practice C1044 ), the symmetry of the line-heat-source design in the axial direction minimizes errors due to undesired heat flow across the gap.