An improved photothermal gas analyser: Monitoring of simultaneous thermal diffusivity and thermal effusivity

摘要

In this paper we describe a new, simple and fast photothermal method for characterizing simultaneously the thermal diffusivity and thermal effusivity. The improved PTGA essentially combines a photoacoustic cell and a thermal wave pyroelectric cell enclosed in a single compact gas analyzer. The photo- acoustic cell is kept filled with nitrogen and sealed. The pyroelectric cell is also filled with nitrogen and after some warm up time, the nitrogen is exchanged to the gas of interest. It is shown that the analysis of the transient and saturation signals of both photoacoustic and pyroelectric cells are capable of measuring the thermal properties with an accuracy of 5%. The measurements were performed for hydrocarbons as ethane and propane, which are combustible gases. Knowing thermal diffusivity and effusivity, others important properties can be determinate: the thermal conductivity and the volumetric thermal capacity.