Numerical study on pressure drop characteristics for turbulent flow in conical spiral tubes

Abstract

The study of pressure drop characteristics in a curved tube is important as it has extensive application in coiled tube heat exchangers, hydraulic and pneumatic systems. The literature review suggests that the pressure drop characteristics at the coil level as well as at local level for the curved tubes with varying curvature i. e. conical spiral tubes require further investigations. The objective of the present work is to investigate the flow resistance characteristics of turbulent fluid flow in conical spiral tubes with uniform wall temperature heating with the numerical simulation approach using ANSYS Fluent. The conical spiral tubes with different curvature and cone taper angle ranging from 10° to 60° were modelled and simulated for the Reynolds number range of 104 to 105. The CFD results reveal that the total pressure drop and the local cross-flow pressure loss coefficient increased with Reynolds number, cone taper angle and curvature ratio. The results also show that the friction factor and the cross-flow coefficient increased significantly in the tube at a cone taper angle of 60° due to an enhancement in the secondary flow and hence the pressure loss. For the given curvature radius and tube diameter of the conical spiral tube there exists an optimum Reynolds number at which the dimensionless cross-flow pressure coefficient has an optimum value. A correlation to predict the friction factor as a function of Reynolds number and cone taper angle is proposed for the turbulent flow in conical spiral tubes. For the usual practically applicable curvature ratio of less than 0.1 in curved tubes, the pressure drop prediction using the proposed correlation is found to be within ±10% of the numerical simulation results.