Finned tube preheater’s. In order to achieve the massecuite temperatures required without dissolving any crystal, the water temperature has to be kept down and preferably not higher than the mother liquor saturation temperature. Thus the ∆t is low and the area must be large. This is achieved using fins on tubes in which the heating water circulates. Early designs made use of a greens finned tube economizer, which was subsequently developed by Tate and Lyle for this duty, and became the green – smith repeater