Experimental Investigation on Active Heat Transfer Improvement in Double-Pipe Heat Exchangers

In this research, the effect of ultrasonic waves (UWs) on the heat transfer rate of a water-to-water double-pipe heat exchanger (DPHX) was investigated. To conduct the experiments, four ultrasonic transducers with similar sound frequencies of 40 kHz and a maximum power of 60 W were utilized. All the transducers were placed on the outer shell of the DPHX. The effects of the hot water flow rate and the temperature level of the hot water inlet, ranging from 40 to 60 degrees C in the central pipe, both in the absence and presence of UWs, were measured under UWs at different powers from 0 to 240 W. The performed experiments show that UWs increase the heat transfer rate, while the highest heat transfer rate improvement of 104% occurs at an inlet temperature of 60 degrees C and ultrasonic power level of 240 W. Given the scarcity of information regarding heat transfer behavior in ultrasonic-assisted DPHXs, these findings could illuminate the path for designing such heat exchangers.