Apparatus for determining thermophysical properties of test specimens

Abstract

Apparatus for directly measuring the quantity .sqroot..rho.ck of a test specimen such as a wind tunnel model where .rho. is the density, c is the specific heat and k is the thermal conductivity of the specimen. The test specimen and a reference specimen are simultaneously subjected to the heat from a heat source. A thermocouple is attached to the reference specimen for producing a first electrical analog signal proportional to the heat rate Q that the test specimen is subjected to and an infrared radiometer that is aimed at the test specimen produces a second electrical analog signal proportional to the surface temperature T of the test specimen. An analog-to-digital converter converts the first and second electrical analog signals to digital signals. These digital signals are applied to a computer for determining the quantity .sqroot..rho.ck by computing the quantity ##EQU1## WHERE T.sub.i is the initial test specimen temperature and t is the elapsed time from the time that the specimens were first subjected to the heat source.