Numerical evaluation of the effect of utilizing twisted tape with curved profile as a turbulator on heat transfer enhancement in a pipe

A numerical analysis is performed to investigate the thermal performance of turbulent fluid flow and heat transfer through a circular tube equipped with curved twisted tapes. The considered geometrical parameters are the pitch ratio, height and curvature of the curved twisted tape. Three-dimensional simulations are validated by experimental data available in the literature. The governing equations of turbulent flow are solved by using k - epsilon model for range of Reynolds number between 2500 and 20,000. Due to swirl flow, the effect of two regions, including near wall region and core region, on heat transfer and pressure drop are discussed. The presence of curved profile twisted tape leads to better heat transfer rate. The results show that case with height of curved twisted tape equal to 7 mm has around 35% higher thermal performance than the base case. Also, case with height of curved twisted tape equal to 5 mm has 30% higher thermal performance than the base case. Cases with pitch ratio between 5 and 15 have better thermal performance than normal pipe, but generally case with pitch ratio equal to unity has lower average thermal performance than the normal pipe. The maximum and minimum thermal performance improvement belongs to pitch ratio equal to 5 at Re = 10,000 (around 26%) and pitch ratio equal to unity at Re = 2500 (- 14%). The maximum and minimum thermal performance belongs to curve of curved twisted tape equal to 5 mm and 1.5 mm with 28% (at Re = 20,000) and - 4% (at Re = 2500), respectively.