Determination of the heat transfer coefficients for the combined natural and streaming convection on an ultrasonic transducer

The aim of this study is to determine, using a CFD code, the laminar convective heat transfer on the front side of a spherical-shaped ultrasonic transducer in water. Both the natural convection and the acoustic streaming were considered and modeled. Steady-state simulations were performed for different acoustic intensity values and compared with the particle image velocimetry results for the velocity fields and with thermocouple measurements and infrared pictures for the temperature fields on the front and back sides of the transducer in a water tank. Good agreement between the simulations and the experimental results was found. Correlations for both the steady-state and transient heat transfer conditions were deduced from the simulations and compared with previous studies. The weak influence of the streaming on the heat transfer when compared to natural convection is observed and contributes 5% of the total heat transfer over the involved range [108, 109] of the Rayleigh number.