The paper describes the theory and application of opto-acoustics to determine thermal diffusivities of gases. An experimental device, already described in previous papers of the authors [Internat. J. Thermophys. 19 (1998) 1099; Proc. 2nd European Thermal Science and 14th UIT National Heat Transfer Conf., 1996, pp. 1071-1078] permitted the detection of thermal diffusivities of gases at moderate pressures with an experimental uncertainty of about ±1.25%.Based on the experience gained with this device, a comprehensive error analysis is presented in this paper. It shows how the experimental uncertainties can be considerably reduced to about -0.45 to +0.35%. The parameters for optical cell design are dealt with, as well as the appropriate characteristics, such as frequencies of the modulated laser beam, and the microphone used in the experiment. © 2004 Elsevier SAS. All rights reserved.
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