Measurement of mass diffusivity in air using thermal wave interference detection

Abstract

A discussion on the use of the thermal wave interference (TWI) for the monitoring of the transient of hydrocarbon in air is presented. The thermal wave signal was modeled using the logarithm-mixing model for the thermal diffusivity of a two-phase gas system in which the hydrocarbon vapor concentration in the air-filled TWI cell is a varying function of time. The time varying hydrocarbon vapor concentration was described assuming the simple Fick’s model for mass diffusion of the hydrocarbon vapor in the stagnant air column of the TWI cell. The transient TWI signal amplitude data fitting yielded two parameters, namely, the saturation concentration and the characteristic diffusion time. From the corresponding values of the diffusion time the hydrocarbon mass diffusivities were straightforwardly obtained.

Coefficients of Evaporation and Gas Phase Diffusion of Low-Volatility Organic Solvents in Nitrogen from Interferometric Study of Evaporating Droplets

“…For example there are gas chromatographic broadening and flow perturbation techniques, 5 twin-bulb method, Stefan tube method, thermal wave interference, 6 and many others. All these methods are essentially indirect.…”

“…There are also several experimental methods of finding the gas phase diffusion coefficient (see refs and and references therein). For example there are gas chromatographic broadening and flow perturbation techniques, twin-bulb method, Stefan tube method, thermal wave interference, and many others. All these methods are essentially indirect.…”

The role of thermal properties in periodic time-varying phenomena

“…It is a relevant thermophysical parameter for surface heating or cooling processes [2], as well as in the recent developed field of thermal wave interference physics [8][9][10][11][12], where it determines the value of the reflection and transmission coefficients for thermal waves propagating at the interface between two media (it is a measure of the thermal mismatch between them) as will be described later. Part of the objective of this work will be therefore the discussion about its meaning and its role in transient and time-varying heating phenomena.…”

“…When a thermal wave propagates between two media, the thermal effusivity determines the value of the reflection and transmission coefficients at the interface, which are defined in a way analogous to that for electromagnetic waves by substituting the refraction index by the thermal effusivity [1,8]. The wave treatment of heat propagation has been used recently to demonstrate experimentally the occurrence of phenomena that may be regarded as reflection and interference effects in PT experiments [9][10][11][12]. In what follows we will review briefly the fundamental ideas beyond this topic.…”

A simplified model for thermal-wave cavity self-consistent measurement of thermal diffusivity

“…[2][3][4][5][6][7][8] Moreover, the TWC technique was also employed to perform kinetic studies of hydrocarbon vapor diffusion in air 2,9 and thermodynamic studies. 10,11 Additional applications with different experimental systems are described in a comprehensive literature review 12 and in Ref.…”