1.1 本试验方法描述了使用与表面齐平的量规测量垂直于表面的净热流。几何形状与试验方法涵盖的热流计相同 E511 ，但测量原理不同。本标准涵盖的量规均使用垂直于表面的温度梯度测量来确定与表面交换的热量。尽管在大多数情况下，净热通量是到表面的，但仪表在两个方向上的传热原理相同。 1.2 这种通用测试方法在应用、尺寸和结构方面相当广泛。作为示例，在后面的章节中详细描述了商用的两种不同的量规类型。Diller总结了常用的热流计( 1. ). 2. 应用包括辐射和对流传热。用于航空航天应用的量规通常较小（0。 直径155至1.27 cm），具有快速的时间响应（10μs至1s），用于测量0.1至10000 kW/m范围内的热流水平 2. . 工业应用有时满足于物理尺寸较大的仪表。 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 本试验方法的目的是测量进出表面位置的净热通量。为了测量辐射能成分，需要测量仪表面涂层的发射率或吸收率。在测量对流能量成分时，必须将表面的潜在物理和热破坏降至最低，并对其进行表征。必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、传感元件的安装方法以及引线的连接方式决定。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。1千瓦/米分数的测量 2. 达到10兆瓦/米以上 2. 使用电流表很容易获得。薄膜传感器的时间响应可能小于10μs，而较厚的传感器的响应时间可能约为1s。选择量规类型和特性以匹配所需应用的范围和时间响应非常重要。 5.1.2 当差分热电偶传感器按照一维热通量的规定在相应的时间响应限制内运行时，电压输出与热通量成正比。然而，灵敏度可能是仪表温度的函数。 5.2 测量的热流基于一维分析，在量规表面具有均匀的热流。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，随着位置的微小温度变化的影响进一步放大。 ( 2. )还有Diller( 3. ). 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比驱动热流的表面与环境温差小得多的范围内。这需要在传感器和安装表面之间有一个良好的热通道。如果压力表不是水冷的，那么通往系统散热器的良好热通道很重要。量规的有效导热系数应大于或等于周围材料。它还应具有良好的物理接触，通过在孔中紧密配合和将量规拧紧到表面的方法来确保。用于将量规拧紧至表面材料的示例方法如所示 图2 . 表壳有一个法兰和一个拧入表面材料的单独紧固螺母。 图2 安装的插入式热流计示意图 5.2.1 如果压力表是水冷的，那么通往板的热通道就不那么重要了。热量传递到计量器，作为散热器而不是周围的板进入水中。因此，仪表和板之间的热阻甚至可能会增加，以阻止从板到冷却水的热传递。不幸的是，这也可能增加量规和周围表面之间的热失配。 5.2.2 图2 显示了安装在板中的热流计，其表面温度为 T s 和周围板的表面温度 T p . 如前所述，仪表和板之间的温差也可能会增加仪表上的局部传热系数。这会放大测量误差。因此，一个设计良好的热流计将使量规表面和板之间的温差保持在最小值，尤其是在测量任何对流的情况下。 5.2.3 在瞬态或非稳态传热条件下，与周围材料不同的量规热容也可能导致温差，从而影响测量的热流。基板和仪表表面温度的独立测量有利于定义传热系数，并确保仪表热破坏小到可以接受的程度。 5.3 此处描述的热流计也可以水冷，以提高其在高温环境中的生存能力。然而，通过限制表温的升高，可能会导致测量热流的大幅中断，尤其是在存在对流的情况下。为了使对流测量与周围表面经历的热流相匹配，表盘温度必须与该表面的温度相匹配。这通常需要对周围表面进行水冷。 5.4 如果热电阻层的热特性已知，则可以解析地估计热流传感器的时间响应。98%响应阶跃输入所需的时间( 4. )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。校准仪表灵敏度 等式3 仅在稳态条件下适用。 5.4.1 对于薄膜传感器，TRL材料的特性可能与大块材料的特性大不相同。因此，需要对时间响应进行直接的实验验证。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( 5. , 6. ). 在带有激波风洞的对流中，可以提供5μs左右的上升时间( 7. ). 5.4.2 由于这些测量仪的响应接近指数上升，因此第一个- 通过将热通量阶跃变化的实验响应与指数曲线匹配，可以获得量规的阶跃时间常数τ。 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。 5.4.3 通过使用简单的数据处理例程，压力计的时间响应可以提高28倍 ( 8. ) . 它结合了传感器的时间和空间温度测量。这是测量和记录温度信号以及热通量的另一个原因。

1.1 This test method describes the measurement of the net heat flux normal to a surface using gages inserted flush with the surface. The geometry is the same as heat-flux gages covered by Test Method E511 , but the measurement principle is different. The gages covered by this standard all use a measurement of the temperature gradient normal to the surface to determine the heat that is exchanged to or from the surface. Although in a majority of cases the net heat flux is to the surface, the gages operate by the same principles for heat transfer in either direction. 1.2 This general test method is quite broad in its field of application, size and construction. Two different gage types that are commercially available are described in detail in later sections as examples. A summary of common heat-flux gages is given by Diller ( 1 ). 2 Applications include both radiation and convection heat transfer. The gages used for aerospace applications are generally small (0.155 to 1.27 cm diameter), have a fast time response (10 μs to 1 s), and are used to measure heat flux levels in the range 0.1 to 10 000 kW/m 2 . Industrial applications are sometimes satisfied with physically larger gages. 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 The purpose of this test method is to measure the net heat flux to or from a surface location. For measurement of the radiant energy component the emissivity or absorptivity of the surface coating of the gage is required. When measuring the convective energy component the potential physical and thermal disruptions of the surface must be minimized and characterized. Requisite is 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, the method of mounting the sensing element, and how the lead wires are attached. The range of heat flux that can be measured and the time response are limited by the gage design and construction details. Measurements of a fraction of 1 kW/m 2 to above 10 MW/m 2 are easily obtained with current gages. With thin film sensors a time response of less than 10 μs is possible, while thicker sensors may have response times on the order of 1 s. It is important to choose the gage style and characteristics to match the range and time response of the required application. 5.1.2 When differential thermocouple sensors are operated as specified for one-dimensional heat flux and within the corresponding time response limitations, the voltage output is directly proportional to the heat flux. The sensitivity, however, may be a function of the gage temperature. 5.2 The measured heat flux is based on one-dimensional analysis with a uniform heat flux over the surface of the gage. 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 in the surface temperature, the effect of a small temperature change with location is further amplified as explained by Moffat et al. ( 2 ) and Diller ( 3 ). 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 driving the heat flux. This necessitates a good thermal path between the sensor and the surface into which it is mounted. If the gage is not water cooled, a good thermal pathway to the system’s heat sink is important. The gage should have an effective thermal conductivity as great or greater than the surrounding material. It should also have good physical contact insured by a tight fit in the hole and a method to tighten the gage into the surface. An example method used to tighten the gage to the surface material is illustrated in Fig. 2 . The gage housing has a flange and a separate tightening nut tapped into the surface material. FIG. 2 Diagram of an Installed Insert Heat-Flux Gage 5.2.1 If the gage is water cooled, the thermal pathway to the plate is less important. The heat transfer to the gage enters the water as the heat sink instead of the surrounding plate. Consequently, the thermal resistance between the gage and plate may even be increased to discourage heat transfer from the plate to the cooling water. Unfortunately, this may also increase the thermal mismatch between the gage and surrounding surface. 5.2.2 Fig. 2 shows a heat flux gage mounted into a plate with the surface temperature of the gage of T s and the surface temperature of the surrounding plate of T p . As previously discussed, a difference in temperature between the gage and plate may also increase the local heat transfer coefficient over the gage. This amplifies the measurement error. Consequently, a well designed heat flux gage will keep the temperature difference between the gage surface and the plate to a minimum, particularly if any convection is being measured. 5.2.3 Under transient or unsteady heat transfer conditions a different thermal capacitance of the gage than the surrounding material may also cause a temperature difference that affects the measured heat flux. Independent measures of the substrate and the gage surface temperatures are advantageous for defining the heat transfer coefficient and ensuring that the gage thermal disruption is acceptably small. 5.3 The heat flux gages described here may also be water cooled to increase their survivability when introduced into high temperature environments. By limiting the rise in gage temperature, however, a large disruption of the measured heat flux may result, particularly if convection is present. For convection measurements to match the heat flux experienced by the surrounding surface, the gage temperature must match the temperature of that surface. This will usually require the surrounding surface to also be water cooled. 5.4 The time response of the heat flux sensor 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 ( 4 ) 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. The calibrated gage sensitivity in Eq 3 applies only under steady-state conditions. 5.4.1 For thin-film sensors the TRL material properties may be much different from those of bulk materials. Therefore, a direct experimental verification of the time response is desirable. 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 ( 5 , 6 ). A rise time on the order of 5 μs can be provided in a convective flow with a shock tunnel ( 7 ). 5.4.2 Because the response of these gages is close to an exponential rise, a measure of the first-order time constant, τ, for the gage 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. 5.4.3 The time response of the gage can be improved by up to a factor of 28 by using a simple data processing routine ( 8 ) . It uses a combination of the temporal and spatial temperature measurements of the sensor. This is another reason for measuring and recording temperature signals along with the heat flux.