Correlations for the Solid-Liquid Mass Transfer

Several correlations for ksL have been reported in the literature. The Froessling type equation developed by Nienow and Miles (1978) based on the theory of slip velocity between the liquid and solid particles namely, 

Experiments show that the measured value of ksL can be significantly different from that estimated with the correlations above (Nienow, 1975). Therefore, for reliable scale-up or design, laboratory- or pilot-plant experimentation to measure the rate of mass transfer is a must for systems where mass transfer is important. 

At impeller speeds corresponding to Njs, the value of ksL is independent of the geometry of the vessel, impeller design, or the specific power consumption (Doraiswamy and Sharma 1984). 

The functional relationship between ksL and the speed of agitation depends on the hydrodynamic regime of agitation. In the turbulent regime, where the impeller Reynolds number is greater than 1000, the value of ksL is independent of particle size and practically independent of the density difference (Doraiswamy and Sharma, 1984). 

At impeller speeds near Njs, the valne of ksL will be a strong function of the density difference between the particle and the Uquid (Doraiswamy and Sharma, 1984). 

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