ASTM E459-22

5.1?This test method may be used to measure the net heat transfer rate to a metallic or coated metallic surface for a variety of applications, including:

5.2?The thin-skin calorimeter is one of many concepts used to measure heat transfer rates. It may be used to measure convective, radiative, or combinations of convective and radiative (usually called mixed or total) heat transfer rates. However, when the calorimeter is used to measure radiative or mixed heat transfer rates, the absorptivity and reflectivity of the surface should be measured over the expected radiation wavelength region of the source, and as functions of temperature if possible.

5.3?In 6.6 and 6.7, it is demonstrated that lateral heat conduction effects on a local measurement can be minimized by using a calorimeter material with a low thermal conductivity. Alternatively, a distribution of the heat transfer rate may be obtained by placing a number of thermocouples along the back surface of the calorimeter.

5.4?In high temperature or high heat transfer rate applications, the principal drawback to the use of thin-skin calorimeters is the short exposure time necessary to ensure survival of the calorimeter such that repeat measurements can be made with the same sensor. When operation to burnout is necessary to obtain the desired heat flux measurements, thin-skin calorimeters are often a good choice because they are relatively inexpensive to fabricate.

5.5?It is important to understand that the calorimeter design (that is, that shown in Fig. 1) will measure the net heat flux into the thin-skin calorimeter. This configuration may or may not be the same as the test specimen of interest. If it is the same configuration, then the results from use of Eq 1 can be used directly. But if the configuration is different, then some additional analysis should be performed. For example, if the actual test specimen has an insulated layer on the inside surface of the thin-skin, but the thin-skin calorimeter does not, then the net heat flux from Eq 1 will not be the same as the response of the test specimen. Refer to Appendix X1 for further discussion of this topic.

1.1?This test method covers the design and use of a thin metallic calorimeter for measuring heat transfer rate (also called heat flux). Thermocouples are attached to the unexposed surface of the calorimeter. A one-dimensional heat flow analysis is used for calculating the heat transfer rate from the temperature measurements. Applications include aerodynamic heating, laser and radiation power measurements, and fire safety testing.

1.2?Advantages:?

1.3?Limitations:?

1.4?UnitsThe values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

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.