Heat transfer enhancement in an annulus under ultrasound field: A numerical and experimental study

This paper presents experimental and numerical studies of heat transfer enhancement of water in an annulus under ultrasonic waves and fluid flow. An experimental setup is designed and built from two concentric pipes and a bolted Langevin ultrasonic transducer with a frequency of 25.7 kHz stuck to the inner pipe. Two new solvers are developed in OpenFOAM software and a numerical simulation is carried out to model the effect of both acoustic streaming and fluid flow on heat transfer and flow field. There are good agreements between the experimental and numerical results. Experimental results show that increasing the Reynolds number decreases the effect of acoustic streaming as compared to the effect of fluid flow on heat transfer and flow field. As a result, heat transfer enhances about 87% and 25% for Reynolds numbers of 32 and 674, respectively, at the transmitted acoustic power of 100 W. Numerical simulation is used to find the reason of heat transfer enhancement under ultrasonic waves, and results show that the cross-flow generated by circulations due to acoustic streaming is responsible for heat transfer augmentation.