Effects of Cooling Water Flow Rate and Temperature on the Performance of a Multiple-Effect Evaporator

The multiple-effect evaporator is commonly used in the sugar industry. The final effect of the evaporator operates under a vacuum, which is created by the mixing of cooling water and vapor in a condenser. The complete analysis of the multiple-effect evaporator must take into account the interaction between the evaporator and the condenser. To date, coupled models of evaporator and condenser remain unavailable. Although most studies pertaining to multiple-effect evaporators assume that the final vapor pressure leaving the last effect is given, in fact it depends on the operating conditions of the condenser. This article aims at investigating the interaction between multiple-effect evaporator and direct-contact condenser. Coupled models of multiple-effect evaporator and direct-contact condenser are developed. Nonlinear equations resulting from the models are solved by an iterative procedure. Simulation results of a test case indicate quantitatively how the concentration of sugar juice at the exit of the evaporator varies with the cooling water flow rate and temperature.