Abstract
The liquid-solid mass transfer behaviour of helical tubes was studied by the diffusion controlled dissolution of copper tubes in acidified dichromate. Variables studied were solution velocity, tube diameter, coil diameter and physical properties of the solution. The effect of drag reducing polymers on the rate of mass transfer in the helical tubes was also studied. The blank solution mass transfer data were correlated for the conditions 850 <Sc< 1322: 6000 <Re< 23,400 and 5 <d(c)/d< 25 by the equation.
Sh= 0.107Sc(0.33)Re(0.68)
The mass transfer data obtained were found to be well correlated to 0.25 power of the specific power dissipation, indicating that the Kolmogotoff's theory of isotropic turbulence applies to helical tubes. Polyox WSR-301 drag reducing polymer was found to decrease the rate of mass transfer in helical tubes by a maximum of 21.6%.
Implications of the present results for the design and operation of helical tubes used to conduct liquid-solid diffusion controlled processes such as catalytic reactions and membrane processes were highlighted. Also the importance of the present results for predicting the rate of diffusion controlled corrosion and the use of drag reducing polymers to inhibit erosion-corrosion in helical tubes was noted. (C) 2009 Elsevier B.V. All rights reserved.