Numerical study on the heat transfer enhancement outside the pipe bundle under the effect of continuous pressure waves

Abstract

This paper presents a numerical study of the heat transfer enhancement outside the pipe bundle under the effect of continuous pressure waves (PW) stimulated by a vibrating membrane as a PW generator. Model 1 and 2 made of one and two rows of pipe bundles were investigated, respectively. An oscillating wall boundary condition was applied to the vibrating membrane. Based on the RNG k-ε turbulent model and full cavitation model, the computational fluid dynamics (CFD) model was developed. The prediction results of the model were in good agreement with the experimental data of other researchers. The validity of PW was investigated from the viewpoint of the affected scale by comparing the flow and heat transfer with ultrasound and PW. The effect of the frequency and amplitude of the membrane on the heat transfer enhancement was analyzed. The result shows that the continuous PW had significantly larger affected scale than ultrasonic waves, which can cover the whole pipe bundle space and increase the velocity amplitude of the fluid around the bundle. While the affected scale of ultrasonic waves was limited to the center place of the pipe bundle because of the acoustic stream. In addition, the effect of continuous PW on the convective heat transfer increased with increasing the frequency and amplitude of the membrane. The heat transfer was enhanced by 7.01% to 156.22% at a frequency of 20–160 Hz and an amplitude of 2 mm. Considering the benefits and the energy consumed of PW, the optimal frequencies of models 1 and 2 were 110 and 120 Hz, and the heat transfer coefficient were increased by 119.19% and 150.36% compared to the steady-state flow. The results confirm continuous PW has the great potential in enhancing the heat transfer of large-space pipe bundles.