Dilatometric determination of thermal diffusivity in low conducting materials

Abstract

Thermal diffusivity of low conducting materials is measured by detecting the thermal expansion of a cylindrical specimen heated at one base, in contact with a copper disc. The simultaneous recording of the temperature of the copper and of the capacitive signal by which one can measure the dilation of the specimen allows the experimental determination of thermal diffusivity without the uncontrolled heat losses which usually occur due to temperature sensors.

A dilatometric method to measure the thermal diffusivity of nonmetallic liquids

“…At the upper base (z=0) the temperature of the liquid at any time is assumed to be the same as the temperature of the copper disk: In fact• the temperature jump through the contact between a metal and a low-conducting medium is negligibly small, as experimentally shown by the authors in previous works [6,7]. Consequently our assumption is valid for all the dielectric liquids but would certainly fail for liquid metals.…”

“…Such a method is based on an original idea already used for solids: The temperature field in the specimen is determined by measuring its thermal expansion [6][7][8]. Through the Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-I0129 Torino, Italy.…”

Measuring the Thermal Diffusivity in a Student Laboratory

“…The solution of the thermal transport is obtained as in Refs. [2][3][4][5][6][7][8][9][10][11][12]. Let us consider a time interval τ small enough.…”

“…This technique reduces the thermal leaks, but, as in the case of dilatometric methods, requires a sophisticate set-up.Aiming to improve a laboratory for students with a measure of the thermal diffusivity, without increasing the overalls cost of the structure, we describe here an experimental procedure based on the use of thermocouples, adapting the numerical methods of determining the thermal field developed in Ref. [2][3][4][5][6][7][8][9][10][11][12]. The method of solution is simplified for undergraduate students.…”

“…Here then, we propose a method that allows the students to have an experimental approach to the problem of thermal transport. Years ago, the author has published some papers [2][3][4][5][6][7][8][9][10][11][12] on new methods to measure the thermal diffusivity. Some measures reported in the references were based on modelling the thermal field inside a specimen after the measure of its thermal expansion.…”