Adaptation of the modified pulse method for determination of thermal diffusivity of solids in the vicinity of the second-order phase transition points

Abstract

The paper presents the adaptation of the modified pulse method for investigating temperature characteristics of thermal diffusivity in the vicinity of the second-order phase transition points. The principle of the adaptation consists in the modified in relation to the original method, development of the characteristics of temperature changes between boundary surfaces of a flat-parallel specimen after the laser shot onto its front surface. The application of this adaptation was illustrated with investigation into thermal diffusivity of nickel (99.9% wt) in the temperature range of 20-380◦C. In all cases the measurement error was less than 3%, and the averaging interval for the measured values of thermal diffusivity was not greater than 1.2 K.

A study of thermal diffusivity of carbon-epoxy and glass-epoxy composites using the modified pulse method

“…The values of thermal diffusivity were defined on the basis of the analysis of experimentally determined changes in temperature difference between the extreme surfaces of the adiabatic sample after the laser shot on its front face. Suitable software was used for that purpose [7].…”

“…Then the appropriate program is used to process the resulting course of temperature difference changes, and the end result of this procedure is the sought value of thermal diffusivity. This method has been described in detail in [6,7], and its outline is illustrated in Figs. 1 and 2. The procedure of determining thermal diffusivity a using the modified pulse method is as follows:…”

“…Measurements of thermal diffusivity of selected composite walls were made using the modified pulse method [6,7,8]. Two of the walls chosen for the study were made of carbon-epoxy and glass-epoxy composites, and the third one, the polymer wall constituted the matrix for the two composite walls.…”

“…: a) The principle of temperature Θ2(t) and temperature difference ∆Θ(t) measurements between the extreme surfaces of the same sample: kt -Seebeck constant of thermocouple 'CuNi -material of the sample'; k -known value of the Seebeck constant of thermocouple 'Fe -CuNi'; b) typical plot of changes in temperature on the front Θ(0, l) and rear Θ(l, t) faces of the sample and the difference between these values ∆Θ(t) on the extreme surfaces of the sample after the absorption of radiation energy of the laser pulse on the front face[4][5][6][7], ∆E th -e.m.f. of the differential thermocouple, ∆E th,2 -e.m.f.…”

Determination of the effective thermal conductivity of solid fuels by the laser flash method

“…In 1961, Parker et al [17], for the first time, described a flash method for measuring the thermal diffusivity, heat capacity and thermal conductivity of copper, silver, iron, nickel, aluminium, tin, zinc and some alloys at 22 and 135 o C. The laser flash system allows for the determination of the thermal conductivity of materials between 0.1 and 2000 W/(m K) over the temperature range of -125 to 1100 o C. Easy sample preparation, short measurement times and high accuracy are only some of the advantages of this noncontact, nondestructive method [18]. Nowadays, the laser flash methods are the most commonly used techniques of thermal diffusivity a measurements of the opaque solids, e.g., [19][20][21]. However, to date, there are no experimental data available in the open literature regarding the determination of thermal conductivity of solid fuels using this laser flash system.…”