Experimental study on the effect of sound waves on the heat transfer characteristics of heated pipes

This study has experimentally investigated the heat transfer characteristics of a heated steel pipe (diameter = 20 mm) placed horizontally in a vertical experimental cylindrical pipe under longitudinal sound waves. The ranges of sound parameters used in this study are as follows: sound frequency f = 210–1000 Hz, and sound pressure level SPL = 125–135 dB. The heat transfer coefficient and Nusselt number of the cross- section of the heated pipe are used to describe the influence of different sound parameters on the heat transfer behavior of the heated pipe. The results show that under the action of low-frequency strong sound wave (f < 230 Hz), the distribution of local Nusselt number of heated pipe decreases (0-90°) at first and then increases (90-180°), while under the action of high-frequency strong sound wave (f > 500 Hz), the distribution of local Nusselt number first increases and then decreases. The relative Nusselt number decreases exponentially with the increase of the Strouhal number. In addition, the oscillating flow induced by sound waves is greatly influenced by the natural convection. The local enhancing or weakening effects of strong sound waves with different parameters on the heat transfer in a hot steel pipe are related to the characteristics of local flow.