The effect of the physical properties of the tube wall on the attenuation of sound in evaporating and condensing gas-vapor mixtures

An investigation of sound propagation in an air-water vapor mixture contained in a cylindrical tube with wet walls was recently completed [Hickey et al., J. Acoust. Sec. Am. 107, 1126-1130 (2000)]. A generalization to include the heat flux at the tube wall is presented here. The attenuation of sound in air-water vapor mixtures can be affected by the thermal properties of the tube wall. The controlling parameter is epsilon (s), which is a proportionality constant that relates the heat flux per degree Kelvin for the substrate to that of the gas mixture. For a given amount of heat, provided by expansion and rarefaction of the working fluid, different substrates will undergo different temperature excursions. These temperature swings at the boundary change the vapor pressure of the condensate and thus reduce the diffusion of vapor to and from the boundary resulting in a reduction of the attenuation. (C) 2000 Acoustical Society of America.