Computational simulation of thermal processes in ncs production plants

Abstract

This paper develops a computational simulation of the fluid dynamics and heat transfer phenomena that occur inside combustion chamber, and flat and semispherical open evaporators used in NCS non-centrifugal sugar industry. The study estimates the effect of primary/secondary air ratio and excess air in the combustion chamber performance resulting in an optimal value of 1.3 for the equivalence ratio in the lower section of combustion chamber. The influence of both mechanisms of heat transfer in the evaporating and concentrating steps of the production process were studied as well as other parameters like geometric configuration, composition of heating gases and flux regimes. To provide a tool for designers, some correlations for Nusselts number were developed. Several assumptions were made to reduce the computers capacity required, like surface at constant temperature, properties of gases modelled by polynomials and negligible radiation at low temperatures. The mechanism of boiling in the liquid that is being heated was not studied. With this model, the authors found that a specific geometric configuration yielded the best results for evaporating and concentrating sugar in the flat-with-fins open evaporator.