A step-wise method for measuring thermophysical parameters of materials

Abstract

A version of a transient method for measuring specific heat, thermal diffusivity and thermal conductivity is presented. The dynamic temperature field is generated by the passage of the electrical current through a planar electrical resistance made of thin metallic foil. The heat is produced in the form of a step-wise function. A thermocouple placed apart from the heat source measures the temperature response. The theory of the method, its experimental arrangement and the measuring regime for considering sensitivity coefficients are presented. Experimental data obtained on Perspex are compared with recommended and published data. The data on thermal conductivity agree to within ±0.7% whereas the specific heat is lower on average by 5.2% and the thermal diffusivity is higher by 3.5% when measurements were realized in vacuum. A shift in data of up to 10% was found for measurements made in air.

Using Selected Transient Methods for Measurements of Thermophysical Parameters of Building Materials

“…Then, deviations from ideal models can be characterized by correction factors. The form of correction factors can be obtained by the theoretical analysis of real experimental arrangement (Kubičár et al, 1997). Several corrections have been introduced according to Assael et al (1992) for the heat capacity of the probe, thermal contact resistance between the probe and the test material, the finite dimension of the sample, and the finite dimension of the probe embedded in the sample.…”

Simultaneous Measurement of Thermophysical Properties of Tissue-Mimicking Phantoms for High Intensity Focused Ultrasound (HIFU) Exposures

“…The difference analysis method [11] is based on sequential fitting of Eq. 5 to the measured temperature change curve.…”

“…The transient methods for the determination of thermophysical properties, including the hot-wire method, the hot-strip method, the hot-disk method, the hot-plate method, the pulse transient method, the step-wise transient method, the laser-flash method, etc., can be used to perform measurements during the process of heating [11][12][13][14][15][16][17][18][19]. The relatively short duration of the experiments eliminates unwanted physical or chemical changes of the test sample, and hence reduces the measurement errors caused by time; also, the relatively simple experimental setup makes the measurements cost effective.…”

“…Suppose that the test sample has no heat exchange with the surrounding environment and the thickness of the planar heat source is zero, the measurement principle can be taken as a one-dimensional unsteady state heat conduction problem in semi-infinite solids [11,13]:…”

“…7-11 [11,13], based on the proposed experimental setup and material properties presented in Divkovic and Liebler [9] (ρ = (1045 ± 5) kg · m −3 , k = (0.59 ± 0.06) W · m −1 · • C −1 , and c = (4270 ± 365) J · kg −1 · • C −1 ). As shown in Fig.…”