Study the effect of innovative active and passive methods on thermal characteristics and turbulent flow behaviour in a heat exchanger pipe

Turbulators are used in oil and gas industries, steel, power plants and air conditioning to improve energy performance. For example, to decrease gas consumption in the heater of the city gas station. So far, few studies have been done on a using of active method and compared with passive method. Therefore, in the present study, the effect of moving turbulators as an innovative subject on thermal characteristics in turbulent flow inside the tube is investigated experimentally and numerically. The numerical solution is performed using Ansys Fluent software in the range of Re = 6000–21000. Then, to deepen the obtained results, experiments were performed. For experiments, a heat exchanger is made in which water flows inside the shell and air inside the tube. Disc turbulator sectors with AR = 0.125, 0.25, 0.375, 0.5, 0.75 from rotational speeds 10–3000 rpm are inserted into the tube. The results show that the thermal efficiency increases by decreasing the angle ratio and increasing the rotation speed of the turbulator. The Nu, f , and η increase compared to smooth pipe, 3.59, 38, and 1.58, respectively. In addition, the maximum thermal efficiency of 1.51 is obtained for the turbulator with AR = 0.125 and PR = 2 at n = 600 rpm and Re = 6000. Under the same conditions, the Nusselt number for the moving turbulator increases by 118% compared to the stationary turbulator. The turbulators with a lower angle ratio are an optimum and cost-efficient selection. Also, rotating turbulators create higher thermal performance than stationary turbulators.