Experimental study on the effects of mechanical vibration on the heat transfer characteristics of tubular laminar flow

In this study, experiments were performed to investigate the effects of sinusoidal vibrations on the heat transfer characteristics of internal flow in a circular heated tube. Water was used as the working fluid with inlet Reynolds numbers varying between 512 and 2047. The frequencies of the mechanical vibration generator varied from 158 to 3000 Hz, and the vibration accelerations were 1.0 g, 3.0 g, and 5.0 g. The time domain acceleration signal was obtained using a vibration accelerometer and then transferred to the frequency domain using the fast Fourier transform method in the experiments. The results demonstrated that mechanical force vibration significantly influences the heat transfer in a heated pipe flow. The Nusselt number increases indistinctively with the vibration acceleration augmentation, while the enhancement in the Nusselt number is weakened as the inlet velocity increases. The Nusselt number increases rapidly when the vibration frequency increases to the resonance frequency value of 400 Hz and then decreases sharply and levels off at the frequency of 1500 Hz. Finally, a new correlation was derived using the key parameters of vibration frequency, vibration acceleration, and Reynolds number.