PLATE EVAPORATOR FOR THICK JUICE - OPERAT ING EXPERIENCES AND STUDIESOF HEAT-TRANSFER

This paper presents operating experiences with a plate evaporator empl oyed for thick juice in the Rethen factory of Zuckerverbund Nord and m easurements of its heat transfer behaviour. At the start of the campai gn, operation was unstable and required changes in management. In the second half of the campaign, an apparent heat transfer coefficient of about 1750 W/(m2 . K) was established for the plate evaporator. By cha nging the management on the juice side it was possible to operate the plate evaporator for short periods under different conditions. The mea surements showed a higher heat transfer with increasing flow velocity. At all settings, a pulsating exit of juice into the vapour space was observed. The plate evaporator investigated required that the heating surfaces be wetted at a rate of about 0.1 m3 per (m2 . h), in terms of the entering volume of juice, in order to achieve adequate operationa l stability.