Method for determining thermo-physical properties of specimens

TLDR: In this article, the square root of the product of thermophysical properties rho, c and k, where rho is density, c is specific heat and k is thermal conductivity, is determined directly on a test specimen such as a wind tunnel model.

Abstract: The square root of the product of thermophysical properties rho , c and k, where rho is density, c is specific heat and k is thermal conductivity, is determined directly on a test specimen such as a wind tunnel model. The test specimen and a reference specimen of known specific heat are positioned a given distance from a heat source. The specimens are provided with a coating, such as a phase change coating, to visually indicate that a given temperature has been reached as well as to ensure that both specimens have the same absorbtivity and thus receive the same heat rate. A shutter interposed between the heat source and the specimens is opened and a motion picture camera is actuated to provide a time record of the heating step. The temperature of the reference specimen is recorded as a function of time. The heat rate to which both the test and reference specimens have been subjected is determined from the temperature time response of the reference specimen by the conventional thin-skin calorimeter equation. This heat rate is then used to determine 2ROOT rho ck of the test specimen from the transient one dimensional heat conduction equation for a semi-infinite solid subjected to a step heat input at a constant heat rate. A model, such as a wind tunnel model, can be tested directly thus eliminating the costly and inaccurate method of making test models solely for the purpose of determining 2ROOT rho ck.