1.1 本试验方法包括使用安装在物体中并配置为模拟半无限固体的热量计零点处的热电偶的测量瞬态温升，测量固体（试样）表面的传热速率或热通量。根据定义，零点是受扰物体轴向中心线上的唯一位置，在相同热流输入下，在没有物理扰动（孔）的情况下，受扰物体的瞬态温度历史与固体表面上的瞬态温度历史相同。 1.2 零点量热计已用于测量浸入空气、氮气、二氧化碳、氦气、氢气以及这些气体和其他气体的混合物的流动和静态环境中的物体的高对流或辐射传热率。 流速范围从零（静态）到亚音速到高超音速，总流动焓从1.16到大于4.65 × 10 1. MJ/kg（5 × 10 2. 大于2 × 10 4. Btu/lb.），身体压力为10 5. 大于1.5 × 10 7. Pa（大气压力大于1.5 × 10 2. atm）。测量的传热速率范围为5.68至2.84 × 10 2. 兆瓦/米 2. (5 × 10 2. 至2.5 × 10 4. 英制热量单位/英尺 2. -秒）。 1.3 零点量热计最常见的用途是测量浸入高压、高焓流动气流中的固体驻点处的传热速率，其中体轴通常平行于流动轴（零攻角）。在非驻点位置和角度使用零点量热计- 攻击测试可能会对热量计设计和数据解释造成特殊问题。 1.4 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。 1.5 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 本试验方法的目的是测量浸入静态环境或高速流体中的物体的极高传热率。这通常是在测量期间多次曝光时保持测量装置的结构完整性的情况下实现的。传热速率高达2.84 × 10 2. 兆瓦/米 2. (2.5 × 10 4. 英制热量单位/英尺 2. -秒） ( 7. ) 已使用零点量热计测量。使用铜零点量热计提供了一个测量系统，具有良好的响应时间和传感器烧坏（或烧蚀）的最大运行时间。零点量热计的传感器体直径通常为2.36毫米（0.093英寸）压入轴对称模型的机头。 5.2 参考文献中广泛讨论了高热流测量应用中涉及零点量热计的误差来源 ( 3- 7. ) . 特别是，分析和实验表明，零点空腔上方的铜厚度至关重要。如果厚度太大，仪器的时间响应将不够快，无法提取重要的流动特性。另一方面，如果厚度太小，零点量热计将显示比输入或入射热通量大得多（且随时间变化）的值。因此，在使用之前，应通过实验检查所有零点量热计是否具有适当的时间响应和校准。尽管校准装置的制造并不困难或昂贵，但目前只有一个已知系统 ( 6. 和 7. ) . 零点量热计的设计可以根据本文件中的数据完成。然而，这些传感器的制造是一项困难的任务。由于零点热量计目前没有大的市场，这些传感器的商业来源很少。制造细节通常被视为专有信息。一些用户已经开发出制造自己传感器的方法 ( 7. ) . 通常建议客户要求供应商提供每个零点量热计的瞬态实验时间响应和校准数据。否则，最终用户无法假设传感器会给出准确的结果。 5.3 通常，零点量热计的结果解释与其他热量计的结果相同- 基于半无限固体原理运行的通量传感器，如同轴表面热电偶和铂薄膜测量仪。也就是说，表面化学反应的影响、局部流场和能量场的梯度、热辐射以及相对于流场矢量的模型对齐将产生与其他类型热流传感器相同的定性结果。此外，信号调节和数据处理可以显著影响零点量热计数据的解释。

1.1 This test method covers the measurement of the heat-transfer rate or the heat flux to the surface of a solid body (test sample) using the measured transient temperature rise of a thermocouple located at the null point of a calorimeter that is installed in the body and is configured to simulate a semi-infinite solid. By definition the null point is a unique position on the axial centerline of a disturbed body which experiences the same transient temperature history as that on the surface of a solid body in the absence of the physical disturbance (hole) for the same heat-flux input. 1.2 Null-point calorimeters have been used to measure high convective or radiant heat-transfer rates to bodies immersed in both flowing and static environments of air, nitrogen, carbon dioxide, helium, hydrogen, and mixtures of these and other gases. Flow velocities have ranged from zero (static) through subsonic to hypersonic, total flow enthalpies from 1.16 to greater than 4.65 × 10 1 MJ/kg (5 × 10 2 to greater than 2 × 10 4 Btu/lb.), and body pressures from 10 5 to greater than 1.5 × 10 7 Pa (atmospheric to greater than 1.5 × 10 2 atm). Measured heat-transfer rates have ranged from 5.68 to 2.84 × 10 2 MW/m 2 (5 × 10 2 to 2.5 × 10 4 Btu/ft 2 -sec). 1.3 The most common use of null-point calorimeters is to measure heat-transfer rates at the stagnation point of a solid body that is immersed in a high pressure, high enthalpy flowing gas stream, with the body axis usually oriented parallel to the flow axis (zero angle-of-attack). Use of null-point calorimeters at off-stagnation point locations and for angle-of-attack testing may pose special problems of calorimeter design and data interpretation. 1.4 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. 1.5 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 The purpose of this test method is to measure extremely high heat-transfer rates to a body immersed in either a static environment or in a high velocity fluid stream. This is usually accomplished while preserving the structural integrity of the measurement device for multiple exposures during the measurement period. Heat-transfer rates ranging up to 2.84 × 10 2 MW/m 2 (2.5 × 10 4 Btu/ft 2 -sec) ( 7 ) have been measured using null-point calorimeters. Use of copper null-point calorimeters provides a measuring system with good response time and maximum run time to sensor burnout (or ablation). Null-point calorimeters are normally made with sensor body diameters of 2.36 mm (0.093 in.) press-fitted into the nose of an axisymmetric model. 5.2 Sources of error involving the null-point calorimeter in high heat-flux measurement applications are extensively discussed in Refs ( 3- 7 ) . In particular, it has been shown both analytically and experimentally that the thickness of the copper above the null-point cavity is critical. If the thickness is too great, the time response of the instrument will not be fast enough to pick up important flow characteristics. On the other hand, if the thickness is too small, the null-point calorimeter will indicate significantly larger (and time dependent) values than the input or incident heat flux. Therefore, all null-point calorimeters should be experimentally checked for proper time response and calibration before they are used. Although a calibration apparatus is not very difficult or expensive to fabricate, there is only one known system presently in existence ( 6 and 7 ) . The design of null-point calorimeters can be accomplished from the data in this documentation. However, fabrication of these sensors is a difficult task. Since there is not presently a significant market for null-point calorimeters, commercial sources of these sensors are few. Fabrication details are generally regarded as proprietary information. Some users have developed methods to fabricate their own sensors ( 7 ) . It is generally recommended that the customer should request the supplier to provide both transient experimental time response and calibration data with each null-point calorimeter. Otherwise, the end user cannot assume the sensor will give accurate results. 5.3 Interpretation of results from null-point calorimeters will, in general, be the same as for other heat-flux sensors operating on the semi-infinite solid principle such as coaxial surface thermocouples and platinum thin-film gages. That is, the effects of surface chemical reactions, gradients in the local flow and energy fields, thermal radiation, and model alignment relative to the flow field vector will produce the same qualitative results as would be experienced with other types of heat flux sensors. In addition, signal conditioning and data processing can significantly influence the interpretation of null-point calorimeter data.