Efficiency of Heat Transfer Improvement Performed in Circular Tubes Utilizing Various Types of Ring-Shaped Turbulators

Abstract

The enhancement of heat transfer performance by using different types of ring-shaped turbulators equipped in a circular tube was investigated through 3D numerical simulations (CFD) with the finite volume method. Three types of turbulators—orbicular-ring turbulator (ORT), pyramidal-ring turbulator (PRT) and proposed innovative cogwheel-ring turbulator (CRT)—were considered. Air at 300 K was passed through the tube with uniform wall heat flux conditions varying from Reynold’s numbers of 4,000 to 20,000. The standard k-ε turbulence model was used to simulate the flows via the ANSYS FLUENT commercial software. Geometric influences in the heat transfer were investigated in terms of compositing the diameter ratio (DR = 0.5, 0.6 and 0.7), the pitch ratio (PR = 4 and 8) and the number of teeth in the cogwheel-ring turbulator (N = 6, 8 and 10). In conclusion, the heat transfer rate in the tubes fitted with ORT and PRT were in the range of 87, which was 199% higher than that of the tube without a turbulator. The PRT offered a slightly higher heat transfer rate than the ORT. Decreasing the pitch and diameter ratio could increase the heat transfer rate. Moreover, it was demonstrated that the proposed innovative CRT outperformed both the ORT and PRT in terms of heat transfer performance. In the case of CRT, the highest number of teeth (N) offered the lowest friction factor and pressure drop.