Experimental and numerical evaluation of heat transfer enhancement by internal flow excitation

Abstract

Many researchers have studied active and passive methods to improve thermal performance and increase heat transfer in internal flows. Various geometries and configurations of turbulators have been proposed to achieve optimal performance in heat exchangers, and these analyses are ongoing. However, limited studies have been conducted on turbulators with equal obstruction inside the tube and turbulator with aerodynamic geometry. In this study, the effect of stimulating the boundary layer of the internal flow is investigated experimentally and numerically on the heat transfer and flow characteristics. For this purpose, a pipe with ring-shaped turbulators and an equal blocking area is used. Air in a range of Reynolds numbers from 6000 to 26,000 is used as the working fluid for the evaluations. According to the results of the study, the ring insert has the most influence in stimulating the flow inside the tube. The highest increase of Nu with the ring, disk, and o-ring is 2.92, 1.8, and 2.19, respectively. The overall performance increases as much as 16.2% at Re = 24,000 by flow excitation.