Express Methods for Determination of Thermophysical Properties of Different Types of Materials within a Temperature Range of –150°C to +1800°C

Abstract

Most of the test methods for determination of thermal conductivity and diffusivity of materials require the steady state temperature field to be established during thermophysical properties measurements or this is required even prior to starting the measurements. For example, the steady state methods widely used for refractories and building materials (ASTM C-210 and ASTM C-202), as well as the transient hot wire method (ASTM C-202), usually take a day or more in order to obtain 1 data point. This circumstance limits the experimental capabilities for collection of data, in particular, at low and at high temperatures. In this paper we present an overview of a variety of express methods developed by the authors for measuring the apparent thermal conductivity, thermal diffusivity, specific heat and thermal emissivity of different solid, powder and liquid materials. The measurements are conducted during monotonous heating/cooling of the samples of different size and geometry, including the plate, cylinder, cubic shapes, and thin coatings. The developed test methods are based on the non-linear theory of thermal conductivity. The main innovation made by the authors of this paper is the development and review of experimental methods and methodology for performing the thermal physical properties testing during phase, chemical, and structural transformations in the different types of materials. Using the developed test methods, a continuous curve of thermophysical properties of the material as function of temperature can be measured within 0.01– 2 hours. The test materials include highly porous insulation, rough industrial refractories and building materials, powders, liquids, suspensions, thin coatings, and metals. The main limitations for our methods are the thermal conductivity above 50 W/mK and the thickness of the thin coatings and films. In these cases, the flash method and the methods of temperature waves can be recommended. Detailed description of the methods developed at ITL Inc. and examples of experimental results will be presented. The developed approached for evaluation of true thermophysical properties that do not depend on the boundary conditions will be briefly discussed. This problem is important when coupled heat and mass transfer phenomena take place in the materials under investigation.