1.1 该试验方法包括根据驻点传热和驻点压力的实验测量值，根据驻点焓的传热理论计算。 1.2 优势: 1.2.1 可以在模型试验的溪流位置获得滞止焓值。该值为烧蚀计算提供了一组一致的数据，以及传热和停滞压力。 1.2.2 这种滞止焓的计算不需要测量任何电弧加热器参数。 1.3 限制和注意事项- 使用这种方法计算滞止焓时，有许多因素可能导致误差，包括: 1.3.1 湍流- 向气流中添加能量所产生的湍流可能会偏离层流平衡传热理论。 1.3.2 气体的平衡、非平衡或冻结状态- 反应速率和膨胀可能使气体远离热力学平衡。 1.3.3 非催化作用- 表面复合速率和金属量热计的特性可能会使传热偏离平衡理论。 1.3.4 自由电流- 电弧加热气流可能具有自由电流，这将有助于测量实验传热率。 1.3.5 非均匀压力剖面- 在传热测量点处，气流区域的非均匀压力分布可能会扭曲驻点速度梯度。 1.3.6 马赫数效应- 无量纲驻点速度梯度是马赫数的函数。此外，马赫数是焓和压力的函数，因此需要迭代过程。 1.3.7 模型形状- 无量纲驻点速度梯度是模型形状的函数。 1.3.8 辐射效应- 热气流可能会对传热速率产生辐射成分。 1.3.9 传热速率测量- 传热测量可能会出错（参见方法 E469型 和试验方法 E422型 , E457型 , E459型 和 E511型 ). 1.3.10 污染- 电极材料可能具有足够大的质量流率百分比，以有助于传热率测量。 1.4 单位- 以国际单位表示的数值视为标准值。本标准不包括其他计量单位。 1.4.1 例外情况- 括号中给出的值仅供参考。 1.5 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。 1.6 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 本试验方法的目的是利用传热理论和驻点传热和压力的测量值，对气动模拟装置的驻点焓进行标准计算。通过该试验方法获得的滞止焓给出了一组一致的数据，以及用于烧蚀计算的传热和滞止压力。

1.1 This test method covers the calculation from heat transfer theory of the stagnation enthalpy from experimental measurements of the stagnation-point heat transfer and stagnation pressure. 1.2 Advantages: 1.2.1 A value of stagnation enthalpy can be obtained at the location in the stream where the model is tested. This value gives a consistent set of data, along with heat transfer and stagnation pressure, for ablation computations. 1.2.2 This computation of stagnation enthalpy does not require the measurement of any arc heater parameters. 1.3 Limitations and Considerations— There are many factors that may contribute to an error using this type of approach to calculate stagnation enthalpy, including: 1.3.1 Turbulence— The turbulence generated by adding energy to the stream may cause deviation from the laminar equilibrium heat transfer theory. 1.3.2 Equilibrium, Nonequilibrium, or Frozen State of Gas— The reaction rates and expansions may be such that the gas is far from thermodynamic equilibrium. 1.3.3 Noncatalytic Effects— The surface recombination rates and the characteristics of the metallic calorimeter may give a heat transfer deviation from the equilibrium theory. 1.3.4 Free Electric Currents— The arc-heated gas stream may have free electric currents that will contribute to measured experimental heat transfer rates. 1.3.5 Nonuniform Pressure Profile— A nonuniform pressure profile in the region of the stream at the point of the heat transfer measurement could distort the stagnation point velocity gradient. 1.3.6 Mach Number Effects— The nondimensional stagnation-point velocity gradient is a function of the Mach number. In addition, the Mach number is a function of enthalpy and pressure such that an iterative process is necessary. 1.3.7 Model Shape— The nondimensional stagnation-point velocity gradient is a function of model shape. 1.3.8 Radiation Effects— The hot gas stream may contribute a radiative component to the heat transfer rate. 1.3.9 Heat Transfer Rate Measurement— An error may be made in the heat transfer measurement (see Method E469 and Test Methods E422 , E457 , E459 , and E511 ). 1.3.10 Contamination— The electrode material may be of a large enough percentage of the mass flow rate to contribute to the heat transfer rate measurement. 1.4 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4.1 Exception— The values given in parentheses are for information only. 1.5 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. 1.6 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 The purpose of this test method is to provide a standard calculation of the stagnation enthalpy of an aerodynamic simulation device using the heat transfer theory and measured values of stagnation point heat transfer and pressure. A stagnation enthalpy obtained by this test method gives a consistent set of data, along with heat transfer and stagnation pressure for ablation computations.