Using different numbers of helical obstacles for promoting heat transfer in the tubes

This study investigated the enhancement of heat transfer in turbulent air flow within a horizontal circular tube containing helical obstacles by conducting a detailed numerical analysis. Various parameters were explored, including number of helical obstacles; 1, 2, 3 and 4, helix ratio ( y = H/D); 2, 3 and 4. Air was selected as the working fluid with Reynolds number range of 10,000 ≤ Re ≤ 60,000 to assess performance under varying flow velocities under constant heat flux along the tube surface. The cases were designed and solved using ANSYS Fluent, and k- ω turbulence model was used. The achieving results showed increasing in Nusselt number 82 % over that of plain tube. However, this was accompanied by a content raise in the friction factor. Despite this increased flow resistance, all the obtained thermal performance factors from the analyzed scenarios were greater than unity, with the highest being 1.56 achieved at n and y of 4 and 2 respectively. The configuration of four helical obstacles, n = 4, and helix ratio y = 2 showed the highest thermal enhancement at Re = 10,000. These results indicated that multiple helical obstacles, especially in configurations with lower helix ratios, significantly boosted heat transfer efficiency.