ASTM E598 Standard Test Method for Measuring Extreme Heat-Transfer Rates from High-Energy Environments Using a Transient, Null-Point Calorimeter

ASTM E598 Introduction

ASTM E598 provides the means for determining the heat transfer rate or heat flux to the surface of a solid body (test sample) employing the measured transient temperature rise of a thermocouple situated at the null point of a calorimeter installed in the body and arranged to simulate a semi-infinite solid. By definition, the null point is a unique position on the axial centreline of a disturbed body with the same transient temperature history as on the surface of a solid body when there is no hole in the physical structure through which heat flux is input. 

ASTM E598 Test Method

ASTM E598 Equipment and Sample Preparation

ASTM E598 Results and Interpretation 

This standard provides a numerical heat flux for a sample surface based on the transient temperature rise at the thermocouple null point. It is employed to back-calculate the heat transfer rate to the surface and the thermal performance of the sample under such conditions.

Tests Related to ASTM E598

ASTM E598 is related to tests, including ASTM E422 for using a water-cooled calorimeter to measure heat flux and ASTM E511 for using copper constant circular foil for measuring heat flux.

Use of ASTM E598 Testing in Various Industries

ASTM E598 testing is used in many industries that require knowledge about heat transfer to optimize products’ performance and ensure safety. In aerospace and defense, it is used to determine the properties of the material that comes into contact with high temperatures and guarantee the resultant thermal protection of components like the skins of aircraft panels and heat shields. In the electronics industry, it is applied to assess materials for application in devices that produce large amounts of heat, and the outcome is that parts like microchips and circuit boards should be able to shed heat well.

Materials Commonly Tested with ASTM E598 

Substances that are usually subjected to this test are those that need assessment of thermal conductivity and thermal insulating properties. These include aerospace alloys, ceramics, and composites that require high-temperature stability in aerospace and defense. Semiconductor materials, circuit board substrates, and thermal interface materials are examined in the electronics industry for their application of heat dissipation.

Safety and Best Practices in ASTM E598 Testing

In ASTM E598 testing, safety, and best practice guidelines are important to achieve accurate results for heat flux and temperature rise. The place of the thermocouples should be handled carefully by the operators since even slight displacement affects the heat transfer rate measurements. Appropriate heat-protective gloves and goggles should be worn particularly when testing high-heat materials. 

Importance of ASTM E598

The majority of applications of null-point calorimeters have been in the determination of heat transfer rates at the stagnation zone of a solid body that is placed in a high-pressure, high enthalpy, flowing gas stream, the body axis being parallel to the flow axis (angle of attack = 0). Thus, the utilization of null-point calorimeters at off-stagnation point stations or when angle of attack measurements are to be made may present special difficulties in calorimeter construction and data analysis.