Enhancement of heat transfer using ultrasonic waves: Experimental investigation and empirical correlations

This work aimed to investigate the effect of ultrasonic waves on heat transfer enhancement under a subcooled pool condition. For this purpose, a cylindrical rod is submerged in distilled water and a 1.7 MHz ultrasonic transducer was utilized to generate ultrasonic waves. Three main parameters were examined including loaded heat flux, water temperature, and heights (distance from ultrasonic transducer). A Particle Image Velocimetry (PIV) is used as a non-intrusive flow visualization system to visualize how ultrasonic waves propagate in a water medium. The results obtained without imposing ultrasonic waves are compared with that of the results where ultrasonic waves are imposed, the average heat transfer rate with imposing ultrasonic waves is increased by 133%, while the increasing in enhancement factor is about 2.4 times at (H = 22 mm). Meanwhile, the increase in water temperature led to decreases in the heat transfer rate, this decreasing in the heat transfer rate is the most with Tw = 50 °C and it's around 46.8%, while it's about 17.2% with Tw = 40 °C under similar conditions. Effect of heated surface height is also investigated and analyzed, the ultrasonic waves are influential in the case of changing height and improved the enhancement factor by 3.52 times at (H = 65 mm). By using the database obtained under test conditions, empirical correlations were proposed to evaluate the real benefits of using ultrasonic waves in heat transfer enhancement.