The goal of this numerical study is to investigate the effect of ultrasound waves on the entropy generation aspects
in a water-cooled pin-fin heatsink. The effect of the number and locations of ultrasound transducers (32 different
scenarios), Re number (500–2000) and frequency of ultrasound waves (F = 15–30 kHz) are investigated on the
thermal and frictional entropy generation rates. It was revealed that different configurations with the transducers
on two, three, and four walls entail a low thermal entropy generation rate, however, most of which have a high
frictional entropy generation rate with the exceptions for case#27 and two other scenarios that bring a moderate
frictional entropy generation rate. Therefore, case#27 was selected as the optimum configuration from the
second thermodynamic law points of view. For the studied range of Re, the thermal entropy generation ratefor
the optimum case is 21–47% lower than that for the base case at F = 30 kHz. While the frictional entropy
generation rate for the optimum case escalates to 11–247 folds of the base case for Re numbers of 500–2000. In
addition, the escalation of frequency from 15 to 25 kHz reduced the thermal and frictional entropy generation
rates by 5.31% and 40.22%, respectively.