IMPROVED ROBERTS EVAPORATOR PERFORMANCE THROUGH CIRCULATION MODELLING WITH CFD

摘要

The design of Roberts evaporators in the Australian sugar industry is currently based onrnparameters evolved from experience with a limited amount of experimentation intornsome of the critical design criteria. Numerous configurations of juice inlets and outlets,rncalandrias and downcomers exist in the industry. Experimental and computational fluidrndynamics (CFD) modelling studies were undertaken to identify design modifications tornRoberts evaporator vessels that could lead to an increase in throughput capacity.rnResidence time and heat transfer trials were conducted on an existing evaporator set tornprovide data for fluid dynamics modelling. A CFD model of the first vessel of the setrnwas developed. In addition, two alternative evaporator configurations were exploredrnwith CFD. The following conclusions are drawn from the experimental and modellingrnwork. The optimal flow pattern of juice inside an evaporator vessel is plug flow, with norninternal recirculation, stagnant regions or bypassing. The calculated benefits from plugrnflow on the throughput capacity of an effect range from 4% for the No. 1 effect to abovern30% for the final effect. The evaporator vessels, which typically have three peripheralrnjuice inlets and a single central juice outlet, showed significant mixing and recirculationrnof the juice, as well as short-circuiting of juice from the feed inlet to the outlet. This wasrnseen in both the experimental data and the CFD model predictions. CFD modelling ofrnalternative evaporator configurations has indicated that the preferred configuration is arnvessel with fully distributed feed and a single central outlet.