Investigation of audible sound waves on the heat transfer characteristics of air-to-air heat exchange systems

To reveal the mechanism of the effect of audible sound waves on the heat transfer process, the flow and heat transfer characteristics of an air-to-air heat exchanger were analyzed by incidence of sound waves with different intensities on its cold, hot, and both sides. The results showed that the sound waves incident on the cold side enhanced the heat exchange between the unstable cold flow and hot surface, which decreased the surface temperature of the latter with an increasing sound pressure level (SPL). In contrast, the sound waves incident on the hot side increased the surface temperature, thereby enhancing the heat transfer performance. When the SPL increased to 140 dB, the average surface heat flux increased by 8.22% and 15.19% under the sound waves incident on the cold and hot sides, respectively, whereas the sound energy efficiency was relatively higher with the sound waves incident on the cold side. Additionally, under the synergetic effect of the incidence of sound waves on both sides on the flow characteristics, the average surface heat flux increased by 25.56%. It was higher than the summation of the corresponding fluxes under the incidence of sound waves on single side, while the sound energy efficiency decreased under high SPL. The results indicated that sound waves incident on both sides can effectively enhance the heat transfer performance. This research is significant for the application of sound waves on the heat transfer process of air-to-air heat exchange systems.