Improving Heat Transfer in Falling Film Evaporators in Food Industries

Falling film evaporators, due to their high heat transfer coefficients, low energy loss, rather a low holdup time, and th ability to handle high capacities have broad applications in food industries. Thus, this kind of evaporator is being used in the production of temperature sensitive compounds such as syrups. In this study, through modelling of the falling film evaporator with the use of Computational Fluid Dynamics (CFD) we have tried to investigate the effect of adding flow turbulator (baffles) on the inner side of the tubes and assess the key parameters for increasing the efficiency of the evaporator. The simulation was conducted using ANSYS FUENT (v 0.16.0). Results indicate that placing baffles would have a significant effect on increasing evaporator efficiency. The results of the parametric study showed that by installing baffles, the amount of juice evaporation rate can be increased, however, both the evaporator length and volume fraction can be reduced. The results showed that the heat transfer coefficient has increased from 10000 W/m2 °C in the case of the typical evaporator to 25000 W/m2 °C in the case of a baffled tube wall.