Dean number only can not determine characteristics of fluid flow and heat transfer in helically coiled tubes with large curvature

Abstract

The majority of reported findings indicate that the fluid flow and heat transfer characteristics within helically coiled tubes (HCTs) with small curvature can be determined solely by Dean number. Due to a scarcity of published investigations pertaining to HCTs with large curvature, the extent to which Dean number can ascertain the attributes of HCTs with large curvature remains uncertain. However, the advancement of technology has enabled the production and utilization of HCTs with large curvature. Consequently, there is a significant demand for understanding the fluid flow and heat transfer characteristics of HCTs with large curvature. The present study employs a numerical approach to investigate the characteristics of laminar fluid flow and heat transfer in HCTs with large curvature, where the ratio of coil radius to tube radius (D/d) is less than 5. The findings indicate that the fluid flow and heat transfer characteristics in HCTs cannot be solely determined by Dean number. In addition to the (D/d)0.5 included in Dean number, the fluid flow friction factor is also influenced by (D/d)−0.1902. When considering uniform wall temperature boundary, Nusselt number is mainly determined by Dean number. However, for uniform wall heat flux boundary, Nusselt number is additionally influenced by (D/d)0.1222.

Keywords

• Helically coiled tube
• Convective heat transfer
• Heat transfer enhancement