Investigation of the interaction of velocity and concentration fields by coupling LDV to conductivity probe in a continuous stirred tank reactor (CSTR)

Abstract

Velocity and concentration fields interaction has been experimentally investigated by mixing pure and salty water in a continuous stirred tank reactor. This has been achieved by coupling LDV and conductivity system which led to velocity–concentration correlations and to turbulent diffusivity. The axial velocity–concentration correlation coefficient does not exceed 5% in the turbine plan and below it. The knowledge of both concentration gradient and turbulent flux allowed the determination of turbulent diffusivity. The assumption of turbulence isotropy is discussed. Except in the immediate proximity of the stirrer, the probability density function of either velocities and concentration does not deviate significantly from Gaussian distribution indicating, in agreement with literature, local isotropy conditions particularly in the upper part of the tank with respect to the stirrer. The obtained results will contribute to refined mixing models while improving scale up procedures.