An experimental methodology was developed to evaluate how the overall heat transfer coefficient of an evaporator system varies according to the solute concentration. To illustrate the method, tests were run in an ascending-descending film type evaporator of industrial size, using a sugar cane solution. These tests checked the methodology reliability and also the reproducibility of the results. The proposed methodology can both be applied in industrial equipment or in a pilot installation, without requiring any extra instrumentation or specific control. The proposed methodology can be used as a powerful tool in the elaboration of a plant design or in the revamping of these systems, increasing their reliability.