Mathematical modelling of flow and heat transfer in a vertical crystalliser

To operate effectively, a vertical crystalliser ideally requires uniform massecuite flow in the vertical direction, a controlled vertical temperature gradient and a uniform temperature at each vertical level. In this study the velocity and temperature distributions within a vertical crystalliser of simplified geometry under typical operating conditions were determined using computational fluid dynamics (CFD). The simulations revealed that the velocity distributions not uniform and that short circuiting of massecuite between inlet and outlet may occur with the existing cooling pipe arrangement. Additionally, massecuite cooling only occurred in very localised regions around the cooling pipes, leading to a highly non-uniform temperature distribution. Simulations using staggered cooling pipes showed considerable improvements over the aligned cooling pipe arrangement.