1.1 本试验方法描述了使用传感元件的传感器测量辐射热流 ( 1. , 2. ) 2. 是一种薄的圆形金属箔。这些传感器通常被称为Gardon仪表。 1.2 以国际单位制表示的数值应视为标准。括号中的数值仅供参考。 1.3 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。 1.4 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====== 3.1 图1 是示例圆形箔片热流传感器的剖面图。它由一个圆形康铜箔组成，通过金属键合工艺连接到无氧高导电铜（OFHC）的散热器上，铜线连接在圆形箔的中心和散热器上的任何点- 水槽主体。传感器阻抗通常小于1V。为了最大限度地减少电流，数据采集系统（DAS）应为电位测量系统或具有至少100000Ω的输入阻抗。 3.2 如中所述 2.3 ，当传感器的主体和中心线由铜制成且圆形箔为康铜时，会产生近似线性输出（相对于热流）。其他金属组合可用于更高温度，但大多数 ( 4. ) 是非线性的。 3.3 由于箔片边缘的热电偶接头是中心热电偶的基准，因此该仪器不需要冷接头补偿。 用于将信号从传感器传输到读出装置的导线通常由多股镀锡铜制成，用TFE氟碳化合物绝缘，并用同样覆盖TFE氟碳化合物的编织物屏蔽。 3.4 带有散热器热电偶的传感器可用于指示箔片中心温度。已知边缘温度后，可直接从铜-康铜（T型）热电偶表中读取箔边缘到中心的温差。然后将该温差添加到体温中，表示箔片中心温度。 3.5 水冷式传感器: 3.5.1 水冷式传感器应用于铜散热器将上升到235以上的任何应用中 °C（450 °F）无冷却。冷却传感器示例如所示 图2 . 冷却液流量必须足以防止传感器体内的冷却液局部沸腾，其出口流量的特征脉动（“咯咯”）表明正在发生沸腾。水冷式传感器可以使用黄铜水管和侧面，以获得更好的可加工性和机械强度。 图2 水冷式热流计的横截面图 3.5.2 给定传感器设计和加热所需的水压- 通量水平取决于流动阻力和内部通道的形状。传感器每分钟需要的水量很少超过几升水。大多数情况下每分钟只需要几升。 3.5.3 热通量超过3400 W/cm 2. （3000英热单位/英尺 2. /s） 可能需要具有薄内壳的传感器，以便将热量从箔片/散热器有效转移到高速水道中。水在3.4至6.9 MPa（500至1000 psi）的压力下产生15至30 m/s（49至98 ft/s）的速度。对于这种薄壳，锆铜可用于其强度和高导热性的组合。 注1: 将散热器从纯铜改为锆铜可能会改变灵敏度和响应线性。 3.6 箔片涂层: 3.6.1 测量辐射能时，使用高吸收率涂层。理想情况下，高吸收率涂层应提供几乎漫反射的吸收表面，其中吸收与涂层上的辐射入射角无关。这种涂层被称为朗伯涂层，传感器输出与入射角相对于法线的余弦成正比。理想的涂层也不依赖于吸收波长，近似于灰体。只有少数涂层接近这些理想特性。 3.6.2 当暴露在半球形环境中时，大多数高吸收率涂层具有不同的吸收率- 入射或更窄角度，入射辐射。对于五种涂层，Alpert等人的测量表明，接近正常的吸收率为3到5 % 高于半球形吸收率 ( 5. ) . 这项工作还表明，商用热流计涂层通常在偏离法线60°至70º的入射角外保持朗伯（余弦定律）行为。 3.6.3 乙炔烟尘（总吸收率α T = 0.99）和樟脑烟尘（α T = 0.98）有缺点 ( 4. ) 抗氧化性低，与传感器表面的附着力差。从丙酮或乙醇溶液中干燥的胶体石墨涂层（α T =  0.83），因为它们在较宽的温度范围内很好地粘附在传感器表面。 喷涂黑漆（α T = 0.94至0.98），其中一些可能需要烘烤。它们在抗氧化性和胶态石墨与烟灰之间的粘附性方面居中。胶体石墨通常用作其他高吸收涂层的底漆。 3.6.4 低吸收率金属涂层，如高度抛光的金或镍，可用于降低传感器对辐射热的响应。由于这些涂层有效地增加了箔片厚度，因此降低了传感器灵敏度。镀金也使传感器响应非线性，因为这种金属的热导率随温度的变化比康铜或镍的热导率变化更快； 涂层必须很薄，以避免改变塞贝克系数。 3.6.5 箔表面发生的放热反应将导致传感器额外加热。这种影响可能在很大程度上取决于箔表面的催化性能。催化作用可以通过表面涂层来控制 ( 3. ) .

1.1 This test method describes the measurement of radiative heat flux using a transducer whose sensing element ( 1 , 2 ) 2 is a thin circular metal foil. These sensors are often called Gardon Gauges. 1.2 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are provided for information only. 1.3 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. 1.4 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 ====== 3.1 Fig. 1 is a sectional view of an example circular foil heat-flux transducer. It consists of a circular Constantan foil attached by a metallic bonding process to a heat sink of oxygen-free high conductivity copper (OFHC), with copper leads attached at the center of the circular foil and at any point on the heat-sink body. The transducer impedance is usually less than 1 V. To minimize current flow, the data acquisition system (DAS) should be a potentiometric system or have an input impedance of at least 100 000 Ω. 3.2 As noted in 2.3 , an approximately linear output (versus heat flux) is produced when the body and center wire of the transducer are constructed of copper and the circular foil is constantan. Other metal combinations may be employed for use at higher temperatures, but most ( 4 ) are nonlinear. 3.3 Because the thermocouple junction at the edge of the foil is the reference for the center thermocouple, no cold junction compensation is required with this instrument. The wire leads used to convey the signal from the transducer to the readout device are normally made of stranded, tinned copper, insulated with TFE-fluorocarbon and shielded with a braid over-wrap that is also TFE-fluorocarbon-covered. 3.4 Transducers with a heat-sink thermocouple can be used to indicate the foil center temperature. Once the edge temperature is known, the temperature difference from the foil edge to its center may be directly read from the copper-constantan (Type T) thermocouple table. This temperature difference then is added to the body temperature, indicating the foil center temperature. 3.5 Water-Cooled Transducer: 3.5.1 A water-cooled transducer should be used in any application where the copper heat-sink would rise above 235 °C (450 °F) without cooling. Examples of cooled transducers are shown in Fig. 2 . The coolant flow must be sufficient to prevent local boiling of the coolant inside the transducer body, with its characteristic pulsations (“chugging”) of the exit flow indicating that boiling is occurring. Water-cooled transducers can use brass water tubes and sides for better machinability and mechanical strength. FIG. 2 Cross-Sectional View of Water-Cooled Heat-Flux Gages 3.5.2 The water pressure required for a given transducer design and heat-flux level depends on the flow resistance and the shape of the internal passages. Rarely will a transducer require more than a few litres of water per minute. Most require only a fraction of litres per minute. 3.5.3 Heat fluxes in excess of 3400 W/cm 2 (3000 Btu/ft 2 /s) may require transducers with thin internal shells for efficient transfer of heat from the foil/heat sink into a high-velocity water channel. Velocities of 15 to 30 m/s (49 to 98 ft/s) are produced by water at 3.4 to 6.9 MPa (500 to 1000 psi). For such thin shells, zirconium-copper may be used for its combination of strength and high thermal conductivity. Note 1: Changing the heat sink from pure copper to zirconium copper may change the sensitivity and the linearity of the response. 3.6 Foil Coating: 3.6.1 High-absorptance coatings are used when radiant energy is to be measured. Ideally, the high-absorptance coating should provide a nearly diffuse absorbing surface, where absorption is independent of the angle of incidence of radiation on the coating. Such a coating is said to be Lambertian and the sensor output is proportional to the cosine of the angle of incidence with respect to normal. An ideal coating also would have no dependency of absorption with wavelength, approximating a gray-body. Only a few coatings approach these ideal characteristics. 3.6.2 Most high absorptivity coatings have different absorptivities when exposed to hemispherically-incident or narrower-angle, incident radiation. For five coatings, measurements by Alpert, et al, showed the near-normal absorptivity was 3 to 5 % higher than the hemispherical absorptivity ( 5 ) . This work also showed that commercial heat flux gauge coatings generally maintain Lambertian (Cosine Law) behavior out to incidence angles 60° to 70º off-normal. 3.6.3 Acetylene soot (total absorptance α T = 0.99) and camphor soot (α T = 0.98) have the disadvantages ( 4 ) of low oxidation resistance and poor adhesion to the transducer surface. Colloidal graphite coatings dried from acetone or alcohol solutions (α T =  0.83) are commonly used because they adhere well to the transducer surface over a wide temperature range. Spray black lacquer paints (α T = 0.94 to 0.98), some of which may require baking, also are used. They are intermediate in oxidation resistance and adhesion between the colloidal graphites and soots. Colloidal graphite is commonly used as a primer for other, higher-absorptance coatings. 3.6.4 Low-absorptance metallic coatings, such as highly polished gold or nickel, may be used to reduce a transducer's response to radiant heat. Because these coatings effectively increase the foil thickness, they reduce the transducer sensitivity. Gold coating also makes the transducer response nonlinear because the thermal conductivity of this metal changes more rapidly with temperature than that of constantan or nickel; the coating must be thin to avoid changing the Seebeck Coefficient. 3.6.5 Exothermic reactions occurring at the foil surface will cause additional heating of the transducer. This effect may be highly dependent on the catalytic properties of the foil surface. Catalysis can be controlled by surface coatings ( 3 ) .