Measurement of Thermal Physical Properties of PCM and Other Reactive Materials and Development of the ASTM E2584 Standard

Abstract

The ASTM Standard Test Method E2584 “Standard Practice for Thermal Conductivity of Materials Using a Thermal Capacitance (Slug) Calorimeter†was developed by NIST to measure thermal conductivity of fire resistive and reactive materials during monotonic heating and cooling that can model real fire processes. The heating regime adopted in ASTM E2584 is very reasonable because the change in materials’ composition and structure during fire can depend on kinetic factors and thermal history of materials. Investigation of thermal physical properties of materials during chemical, phase and structural transformations remains one of the modern scientific and technical problems when evaluating heat transfer processes in materials used in various industrial fields, such as fire materials research, investigation of thermal processes in chemical technology, heat transfer problems in Phase Change Materials (PCM), in moist building envelopes, during designing thermal protection systems for spacecraft to deal with reentry heating, etc. The main problem in experimental measurements of thermophysical properties is the impossibility of using standard steady state methods during time-dependent physical and chemical processes in the materials. Only the methods of monotonous heating/cooling, representing the real transient processes, allow measurement of thermal physical properties during phase and chemical transformations. The ASTM E2584 Standard Test Method was developed based on the linear theory of thermal conductivity. After discussions with NIST and ASTM E37-05 subcommittee “Thermophysical Propertiesâ€, we found that the ASTM E2584-14 Standard has a number of problematic questions and deficiencies and needs to be revised. The main task of this paper is to review and to analyze scientific problems which should to be taken into account in the revised version of the Standard.