1.1 本试验方法描述了使用安装在表面上的平板测量仪测量垂直于表面的净热流。导热通量不是本标准的重点。测试方法涵盖了与绝缘材料相关的导电应用 C518型 和实践 C1041 和 C1046 . 本试验方法涵盖的传感器均使用垂直于表面的两个平行平面之间的温差测量，以根据傅立叶定律确定与表面交换的热量。仪表在两个方向上的传热原理相同。 1.2 该测试方法在应用、尺寸和结构方面相当广泛。作为测量垂直于表面的温度梯度的热流的一般方法的示例，在后面的章节中详细描述了不同的传感器类型( 1. ). 2. 应用包括辐射和对流传热。测量范围从0.01到50 kW/m，在航空航天到生物医学工程中有着广泛的应用 2. . 量规通常为方形或矩形，其尺寸从1 mm到10 cm或更大不等。厚度范围为0.05至3 mm。 1.3 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。 1.4 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和健康实践，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 该试验方法将为测量进出表面位置的净热通量提供指导。为了确定辐射能成分，需要测量表面涂层的发射率或吸收率，并应与周围表面匹配。应尽量减少和表征由于量规的存在而对表面造成的潜在物理和热破坏。 对于对流和低源温度辐射进出表面的情况，重要的是考虑量规的存在如何改变表面热流。所需的量通常是在没有量规的情况下表面位置的热流。 5.1.1 温度限制由量规材料特性和表面应用方法决定。可测量的热通量范围和时间响应受到量规设计和构造细节的限制。从10瓦/米开始测量 2. 至100 kW/m以上 2. 使用电流传感器很容易获得。时间常数可能低至10毫秒，而较厚的传感器的响应时间可能大于1秒。选择传感器类型和特性以匹配所需应用的范围和时间响应非常重要。 5.2 测量的热流基于一维分析，在量规表面上具有均匀的热流。由于在表面上放置量规会导致热破坏，这可能不是真的。卫斯理( 3. )Baba等人( 4. )分析了量规对表面基板内热场和传热的影响，并确定一维假设在以下情况下有效: 哪里: k s = 基材的导热系数， R = 量规的有效半径， δ = 组合厚度，以及 k = 量规和粘合层的有效导热系数。 5.3 对流热通量的测量对表面温度的扰动特别敏感。 由于传热系数也受表面温度的任何不均匀性的影响，如Moffat等人所解释的，随着位置的微小温度变化的影响进一步放大( 2. )还有Diller( 5. ). 此外，计量表面积越小，任何表面温度不均匀性对传热系数的影响越大。因此，仪表引起的表面温度扰动应保持在远小于引起热通量的表面与环境温差的范围内。这需要在量规和其安装表面之间有一个良好的热路径。 5.3.1 图2 显示了安装在板上的热流计，其表面温度为 T s 和周围板的表面温度 T p . 目标是使仪表表面温度尽可能接近板温度，以最大限度地减少仪表的热破坏。这要求沿热通道将量规和粘合剂的热阻降至最低 T s 和 T p . 图2 安装的表面安装热流计示意图 5.3.2 另一种避免表面温度中断问题的方法是用热流计材料覆盖整个表面。这有效地确保了通过量规的热阻与周围板的热阻相匹配。独立测量基板表面温度和仪表表面温度很重要。 表盘表面温度必须用于定义传热系数的值。当压力计材料未覆盖整个表面时，需要进行温度测量，以确保压力计确实能提供较小的热破坏。 5.4 如果热电阻层的热特性已知，则可以通过分析估算热流计的时间响应。98%响应阶跃输入所需的时间( 6. )基于一维分析: 其中α是TRL的热扩散率。分析中还必须包括覆盖层或封装层。量规尺寸和特性的不确定性需要对时间响应进行直接实验验证。如果测量仪设计用于吸收辐射，则可以使用脉冲激光或光开关布拉格池来产生小于1μs的上升时间( 7. , 8. ). 然而，带狭缝的机械轮可以与灯一起使用，以产生约1毫秒的上升时间( 9 )，这通常就足够了。 5.4.1 由于这些传感器的响应接近指数上升，因此可以通过将对热流阶跃变化的实验响应与指数曲线匹配来获得传感器时间常数τ的测量值。 施加热通量的阶跃变化值由以下公式表示: q 不锈钢 . 由此产生的时间常数表征了一阶传感器响应。

1.1 This test method describes the measurement of the net heat flux normal to a surface using flat gages mounted onto the surface. Conduction heat flux is not the focus of this standard. Conduction applications related to insulation materials are covered by Test Method C518 and Practices C1041 and C1046 . The sensors covered by this test method all use a measurement of the temperature difference between two parallel planes normal to the surface to determine the heat that is exchanged to or from the surface in keeping with Fourier’s Law. The gages operate by the same principles for heat transfer in either direction. 1.2 This test method is quite broad in its field of application, size and construction. Different sensor types are described in detail in later sections as examples of the general method for measuring heat flux from the temperature gradient normal to a surface ( 1 ). 2 Applications include both radiation and convection heat transfer. The gages have broad application from aerospace to biomedical engineering with measurements ranging form 0.01 to 50 kW/m 2 . The gages are usually square or rectangular and vary in size from 1 mm to 10 cm or more on a side. The thicknesses range from 0.05 to 3 mm. 1.3 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are provided for information only. 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 and health 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 This test method will provide guidance for the measurement of the net heat flux to or from a surface location. To determine the radiant energy component the emissivity or absorptivity of the gage surface coating is required and should be matched with the surrounding surface. The potential physical and thermal disruptions of the surface due to the presence of the gage should be minimized and characterized. For the case of convection and low source temperature radiation to or from the surface it is important to consider how the presence of the gage alters the surface heat flux. The desired quantity is usually the heat flux at the surface location without the presence of the gage. 5.1.1 Temperature limitations are determined by the gage material properties and the method of application to the surface. The range of heat flux that can be measured and the time response are limited by the gage design and construction details. Measurements from 10 W/m 2 to above 100 kW/m 2 are easily obtained with current sensors. Time constants as low as 10 ms are possible, while thicker sensors may have response times greater than 1 s. It is important to choose the sensor style and characteristics to match the range and time response of the required application. 5.2 The measured heat flux is based on one-dimensional analysis with a uniform heat flux over the surface of the gage surface. Because of the thermal disruption caused by the placement of the gage on the surface, this may not be true. Wesley ( 3 ) and Baba et al. ( 4 ) have analyzed the effect of the gage on the thermal field and heat transfer within the surface substrate and determined that the one-dimensional assumption is valid when: where: k s = the thermal conductivity of the substrate material, R = the effective radius of the gage, δ = the combined thickness, and k = the effective thermal conductivity of the gage and adhesive layers. 5.3 Measurements of convective heat flux are particularly sensitive to disturbances of the temperature of the surface. Because the heat transfer coefficient is also affected by any non-uniformities of the surface temperature, the effect of a small temperature change with location is further amplified, as explained by Moffat et al. ( 2 ) and Diller ( 5 ). Moreover, the smaller the gage surface area, the larger is the effect on the heat-transfer coefficient of any surface temperature non-uniformity. Therefore, surface temperature disruptions caused by the gage should be kept much smaller than the surface to environment temperature difference causing the heat flux. This necessitates a good thermal path between the gage and the surface onto which it is mounted. 5.3.1 Fig. 2 shows a heat-flux gage mounted onto a plate with the surface temperature of the gage of T s and the surface temperature of the surrounding plate of T p . The goal is to keep the gage surface temperature as close as possible to the plate temperature to minimize the thermal disruption of the gage. This requires the thermal resistance of the gage and adhesive to be minimized along the thermal pathway from T s and T p . FIG. 2 Diagram of an Installed Surface-Mounted Heat-Flux Gage 5.3.2 Another method to avoid the surface temperature disruption problem is to cover the entire surface with the heat-flux gage material. This effectively ensures that the thermal resistance through the gage is matched with that of the surrounding plate. It is important to have independent measures of the substrate surface temperature and the surface temperature of the gage. The gage surface temperature must be used for defining the value of the heat-transfer coefficient. When the gage material does not cover the entire surface, the temperature measurements are needed to ensure that the gage does indeed provide a small thermal disruption. 5.4 The time response of the heat-flux gage can be estimated analytically if the thermal properties of the thermal-resistance layer are well known. The time required for 98 % response to a step input ( 6 ) based on a one-dimensional analysis is: where α is the thermal diffusivity of the TRL. Covering or encapsulation layers must also be included in the analysis. Uncertainties in the gage dimensions and properties require a direct experimental verification of the time response. If the gage is designed to absorb radiation, a pulsed laser or optically switched Bragg cell can be used to give rise times of less than 1 μs ( 7 , 8 ). However, a mechanical wheel with slits can be used with a light to give rise times on the order of 1 ms ( 9 ), which is generally sufficient. 5.4.1 Because the response of these sensors is close to an exponential rise, a measure of the time constant τ for the sensor can be obtained by matching the experimental response to step changes in heat flux with exponential curves. The value of the step change in imposed heat flux is represented by q ss . The resulting time constant characterizes the first-order sensor response.