Mass transfer to local electrodes at wall and wall friction factor in decaying turbulent swirl flow

Abstract

Abstract This paper describes an investigation of mass transfer to local electrodes at the wall and wall friction factor behaviour in decaying swirl flow in a circular duct generated by short helical swirl generators. Five swirl generators with angles between 15–70° to duct axis were employed. The experiments were carried out in a Reynolds number range 8900-27 000 and at a Schmidt number of 1692. The axial distribution of the mass transfer to a circular electrode at the wall were measured using an electrochemical technique and the friction factors at the wall were calculated. Flow visualization experiments showed that no circulation nor dead zone occurs in the system. The local mass transfer data were correlated in the form of Shx = 0.0490 Rex0.817 (1+tan θ0)0.508, Sc 1 3 , for the whole range of swirl generator angles and the following correlations were developed f = 0.2517 Rex−0.263 (1 + tan θ0)0.880 and f = 39.810 Rex−0.642 (1 + tan θ0)0.746 for local friction factor for swirlers of 15–45° and 60 and 70°, respectively.