A Thermohydraulic Performance of Internal Spiral Finned Tube Based on the Inner Tube Secondary Flow

In this article, the BSL k-omega model was chosen as the turbulence model to simulate the heat transfer and flow characteristics of the proposed tubes inserted with internal spiral fins when the Re was set as 3000 to 17,000. The numerical results agreed well with the empirical formula. The average deviations of Nu and f between the simulation results and empirical formula results were 5.11% and 8.45%, respectively. By means of numerical simulation, the impact of three configurational parameters on the thermal performance was studied, namely the pitch P, the height H, and the number N of the internal spiral fins. The results showed that the Nu and f of the internal spiral finned tube were 1.77-3.74 and 3.04-10.62 times higher than those of smooth tube, respectively. PEC was also taken into account, ranging from 1.038 to 1.652. When the Re was set as 3000, the PEC achieved the peak value of 1.652 under the height H of the fins at 5 mm, the number N was 8, and the pitch P was 75 mm. However, with the increase of Re, the effect of pressure drop on the comprehensive performance in the tube was stronger than that of thermal enhancement. However, the PEC gradually decreased as the Re increased from 3000 to 17,000. In addition, the velocity and temperature fields were obtained to investigate the mechanisms of heat transfer enhancement.