Pressure drop correlations for flow through regular helical coil tubes

An attempt has been made to arrive at a better characterizing dimensionless group for steady isothermal flow of Newtonian fluids in helically coiled circular tubes. Pressure drop versus flow rate data has been experimentally obtained for helical coils made from thick-walled polyethylene tubing. Generalized pressure drop correlations have been developed in terms of Euler number, Eu, Reynolds number, Re, and the obtained geometrical group, G_rhc = (d^0.85D_eq^0.15/L_c), where d is the inside diameter of the tube, D_eq is the equivalent diameter which accounts for the torsion effect, and L_c is the length of the coil. The Fanning friction factor for helical coil tube is found to depend on Reynolds number and a geometrical number, d/D_eq, separately both, and not by a dimensionless number obtained by any combination of Reynolds number and some geometrical number as is the case of Dean number, De = Re √(d/D), where D is the diameter of the coil. There exist four regimes of flow for the flow through helical-coiled circular tubes. The obtained pressure drop correlations are simple to use.