Effects of operating parameters and fluid properties on the efficiency of a new vacuum evaporation method

¹ Agroscope, Route de Duiller 50, CP. 1012, 1260 Nyon, Switzerland
² ELVAmac SA, Route de Préverenges 10, 1026 Denges, Switzerland
³ Agroscope, Schloss 1, Postfach, 8820 Wädenswil, Switzerland
⁴ hfc Consulting GmbH, Im Bad 1, 8132 Hinteregg, Switzerland

^a Corresponding author: johannes.roesti@agroscope.admin.ch

Abstract

A new process for vacuum evaporation was developed where evaporation takes place near the inner surface of a vortex as produced by a rotor submerged in the liquid. Contrary to the state of the art the new process does not need a vacuum vessel but the rotating liquid creates a geometrically stable low pressure void surrounded by a vortex stabilized by the equilibrium between centrifugal forces and the pressure difference. First tests with water and sugar solutions at concentrations similar to wine must showed evaporation rates in the upper range of thin-film evaporators. A test series was conducted to study the effect of the variation of process parameters. The heating power and thus the fluid temperature has the most important influence on the vaporisation rate. A second test series using sucrose solution of different concentration comes to the conclusion that this method is suitable for aqueous solutions but the vapour production rate drops significantly with increased sugar content using the current rotor design. The simplicity of the construction and the process handling make this new method a promising development for the wine production.