Experimental research on enhanced heat transfer of double-pipe exchanger with audible acoustic field

Abstract

Acoustic reinforced heat transfer is an active reinforced heat transfer method that has the advantages of having no contacts and being high energy and adjustable. To explore the convective heat transfer characteristics under the audible acoustic field, a convective heat exchange experimental platform was built; the platform was a double-pipe heat exchanger. Comparative experimental research on heat transfer of hot flue gas both with acoustic field and without acoustic field was carried out. The results verified that the heat exchanger with an acoustic field had better heat transfer effect. The effects that parameters (such as sound pressure level, acoustic frequency, and the inlet temperature of the hot flue gas) had on the enhanced heat exchange effect were systematically studied. The influence law of the acoustic field on the convective heat transfer capacity of heat exchanger was obtained. The results show that, with an acoustic field, the temperature of the hot flue gas at the outlet of the heat exchanger decreases significantly, whereas the heat transfer power, convective heat transfer coefficient, and the Nusselt number increased significantly. Within the selected range of experimental parameters, 0.6 kHz is the optimal acoustic frequency for enhanced heat transfer. With an increase in the sound pressure level, the reinforcement efficiency increased. At the same time, increasing the inlet temperature of the hot flue gas helped to enhance the capacity of the sound wave to strengthen the heat transfer. When the temperature of the inlet hot flue gas was 59 °C, the sound pressure level was 145 dB, the acoustic frequency was 0.6 kHz, and the maximum reinforcement efficiency was 76.22%.